CN109257788B

CN109257788B - Network switching method and device

Info

Publication number: CN109257788B
Application number: CN201810602051.XA
Authority: CN
Inventors: 崇卫微; 吴晓波; 辛阳
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2017-07-14
Filing date: 2017-08-14
Publication date: 2021-06-22
Anticipated expiration: 2037-08-14
Also published as: WO2019011107A1; CN109257780A; CN109257788A; CN109041149A; CN109041149B; CN109257780B

Abstract

The application discloses a network switching method and a network switching device, which are used for solving the problem that terminal equipment cannot perform IMS voice service. The method comprises the following steps: the first access network equipment receives first session management information from a session management network element, wherein the first session management information is used for requesting to establish a user plane tunnel for a voice service of the terminal equipment; the first access network device sends a handover request to a first mobility management network element according to the first session management information and a first condition, where the handover request is used to handover the terminal device from the first network to a second network, and the first condition includes: the first network is not capable of voice traffic. The application is applicable to the technical field of communication.

Description

Network switching method and device

Technical Field

The present application relates to the field of communications technologies, and in particular, to a network switching method and apparatus.

Background

At present, on one hand, many operators do not deploy or intend to deploy an internet protocol multimedia subsystem (IMS) voice service in a fifth generation (5G) wireless communication system, and on the other hand, frequency spectrums in a 5G network are mostly in a high frequency band, a coverage range of a high frequency signal is small, and a coverage range of a signal required by the IMS voice service is large, so that terminal equipment in the 5G network cannot perform the IMS voice service.

Disclosure of Invention

The embodiment of the application provides a network switching method and a network switching device, which are used for solving the problem that terminal equipment cannot perform an IMS voice service.

In order to achieve the above purpose, the embodiments of the present application provide the following technical solutions:

in a first aspect, a network handover method is provided, including: the first access network equipment receives first session management information from a session management network element, wherein the first session management information is used for requesting to establish a user plane tunnel for a voice service of the terminal equipment; the first access network device sends a handover request to a first mobility management network element according to the first session management information and a first condition, where the handover request is used to handover the terminal device from the first network to a second network, and the first condition includes: the first network is not capable of voice traffic.

In the method provided by the first aspect, when the terminal device in the first network performs the voice service, the terminal device may be switched to the second network, so that the terminal device may perform the voice service in the second network, and the problem that the terminal device in the first network cannot perform the voice service is solved.

In one possible design, the first condition further includes: the second network supports voice services, the signal quality of the second network meets at least one of voice service requirements and network equipment of the first network, and the terminal equipment supports handover between the first network and the second network.

In one possible design, the method further includes: the first access network device sends second session management information to the session management network element, where the second session management information includes information that establishment of a user plane tunnel of the voice service is accepted. With this possible design, the network element in the first network may establish a user plane tunnel for the voice service of the terminal device.

In one possible design, before the first access network device sends the second session management information to the session management network element, the method further includes: and the first access network equipment determines not to allocate wireless resources for the user plane tunnel of the voice service according to the first session management information and the first condition. With this possible design, the network element in the first network may establish a user plane tunnel for the voice service of the terminal device.

In one possible design, the method further includes: the first access network device sends third session management information to the session management network element, where the third session management information includes information that establishment of the user plane tunnel of the voice service is denied. With the possible design, after the terminal device completes the handover from the first network to the second network, the network element in the second network may establish a user plane tunnel for the voice service of the terminal device.

In one possible design, the information that establishment of the user plane tunnel for voice traffic is denied includes reason for the denial. With the possible design, after the terminal device completes the handover from the first network to the second network, the network element in the second network may establish a user plane tunnel for the voice service of the terminal device.

In one possible design, the reason information is: the terminal device executes a handover procedure. With the possible design, after the terminal device completes the handover from the first network to the second network, the network element in the second network may establish a user plane tunnel for the voice service of the terminal device.

In one possible design, the first condition further includes: the second network cannot perform voice service, and the method further comprises: the first access network equipment sends fourth session management information to the session management network element, wherein the fourth session management information comprises information that the establishment of the user plane tunnel of the voice service is refused, and the information that the establishment of the user plane tunnel of the voice service is refused comprises the shortage of radio resources. With the possible design, after the terminal device completes the handover from the first network to the second network, the network element in the second network does not establish the user plane tunnel for the voice service of the terminal device.

In a second aspect, a network handover method is provided, including: the session management network element receives third session management information sent by the first access network device, wherein the third session management information comprises the reason information that the establishment of a user plane tunnel of the voice service of the terminal device is rejected; the session management network element determines that the terminal equipment is switched from a first network to a second network; and the session management network element establishes a user plane tunnel for the voice service in the second network according to the reason information.

In the method provided in the second aspect, when the terminal device in the first network is switched from the first network to the second network, the session management network element establishes the user plane tunnel for the voice service in the second network according to the reason information, and if the second network can perform the voice service, the user plane tunnel can be successfully established, so that the terminal device can perform the voice service in the second network, and the problem that the terminal device in the first network cannot perform the voice service is solved.

In one possible design, the reason information is: the terminal device executes a handover procedure.

In one possible design, the session management network element establishes a user plane tunnel for the voice service in the second network according to the reason information, including: and the session management network element establishes a user plane tunnel for the voice service in the second network after a first preset time period according to the reason information and a second condition, wherein the second condition comprises that the second network cannot perform the voice service. The possible design reserves a first preset time period for the terminal equipment to complete the joint registration, and the terminal equipment can send out the CSFB call after completing the joint registration through reasonable setting of the first preset time period, so that the terminal equipment is ensured to successfully send out the CSFB call.

In a possible design, the establishing, by the session management network element, a user plane tunnel for the voice service in the second network after the first preset time period according to the reason information and the second condition includes: and the session management network element sends a tunnel establishment request to a service gateway of the second network after a first preset time period according to the reason information and the second condition, wherein the tunnel establishment request is used for requesting to establish a user plane tunnel of the voice service.

In one possible design, the session management network element, after a first preset time period according to the reason information and a second condition, establishes a user plane tunnel for the voice service in the second network, including: the session management network element sends a tunnel establishment request to a service gateway of the second network according to the reason information, wherein the tunnel establishment request is used for requesting to establish a voice service user plane tunnel; the session management network element receives a tunnel establishment response sent by the service gateway, wherein the tunnel establishment response comprises the refused information of the user plane tunnel establishment of the voice service; and the session management network element sends a first message to the policy function control network element after a first preset time period according to the second condition, wherein the first message is used for indicating that the establishment of the user plane tunnel of the voice service fails.

In a third aspect, a network handover method is provided, including: a second mobility management network element receives a tunnel establishment request sent by a service gateway, wherein the tunnel establishment request is used for requesting to establish a user plane tunnel of a voice service for terminal equipment; and the second mobility management network element sends a tunnel establishment response to the service gateway according to a second condition, wherein the tunnel establishment response comprises the information that the establishment of the user plane tunnel of the voice service of the terminal equipment is rejected, and the second condition comprises that the voice service can not be carried out by the second network.

In the method provided in the third aspect, the second mobility management network element sends a tunnel establishment response to the serving gateway when the second network cannot perform the voice service, so that the serving gateway transmits the information that the establishment of the user plane tunnel is rejected to the IMS network, and thus the IMS network can trigger the CSFB service of the terminal device, and the terminal device performs the CS voice service.

In one possible design, the second condition further includes: the terminal device is a terminal device that is handed over from a first network to a second network.

In one possible design, before the second mobility management network element sends the tunnel establishment response to the serving gateway according to the second condition, the method further includes: and the second mobility management network element determines that the terminal equipment completes the joint registration. This possible design may ensure that the terminal device successfully initiates the CSFB call.

In one possible design, the determining, by the second mobility management network element, that the terminal device completes the joint registration includes: and the second mobility management network element determines that the joint registration completion message from the terminal equipment is received.

In a fourth aspect, a network handover method is provided, including: the second mobility management network element sends a wireless tunnel establishment request to the second access network equipment, wherein the wireless tunnel establishment request is used for requesting the establishment of a user plane tunnel for the voice service of the terminal equipment; the second mobility management network element receives a wireless tunnel establishment response sent by the second access network equipment, wherein the wireless tunnel establishment response comprises information that the establishment of a user plane tunnel of the voice service of the terminal equipment is rejected; and the second mobility management network element sends a tunnel establishment response to the service gateway according to a second condition, wherein the tunnel establishment response comprises the information that the establishment of the user plane tunnel of the voice service of the terminal equipment is rejected, and the second condition comprises that the voice service can not be carried out by the second network.

In the method provided in the fourth aspect, the second mobility management network element sends the information that the establishment of the user plane tunnel is rejected to the serving gateway, so that the serving gateway transmits the information that the establishment of the user plane tunnel is rejected to the IMS network, and thus the IMS network can trigger the CSFB service of the terminal device, and the terminal device performs the CS voice service.

In one possible design, the sending, by the second mobility management network element, the tunnel establishment response to the serving gateway according to the second condition includes: the second mobility management network element determines that a second condition is established and the terminal equipment completes the joint registration; the second mobility management network element sends a tunnel establishment response to the serving gateway. This possible design may ensure that the terminal device successfully initiates the CSFB call.

In one possible design, the determining, by the second mobility management network element, that the terminal device completes the joint registration includes: the second mobility management network element determines that the registration completion message from the terminal device is received.

In a fifth aspect, a network handover method is provided, including: a second mobility management network element receives a tunnel establishment request sent by a service gateway, wherein the tunnel establishment request is used for requesting to establish a user plane tunnel of a voice service for user equipment terminal equipment; if the second condition is established, the second mobility management network element determines that the terminal equipment completes the joint registration, wherein the second condition comprises that the second network cannot perform voice service; the second mobility management network element sends a wireless tunnel establishment request to the second access network equipment, wherein the wireless tunnel establishment request is used for requesting the establishment of a user plane tunnel for the voice service of the terminal equipment; the second mobility management network element receives a wireless tunnel establishment response sent by the second access network equipment, wherein the wireless tunnel establishment response comprises information that the establishment of a user plane tunnel of the voice service of the terminal equipment is rejected; and the second mobility management network element sends a tunnel establishment response to the service gateway according to the wireless tunnel establishment response, wherein the tunnel establishment response comprises the information that the user plane tunnel establishment of the voice service of the terminal equipment is rejected.

In the method provided in the fifth aspect, after determining that the terminal device completes the joint registration, the second mobility management network element sends the information that the establishment of the user plane tunnel is rejected to the serving gateway, so that the serving gateway transmits the information that the establishment of the user plane tunnel is rejected to the IMS network, thereby enabling the IMS network to trigger the CSFB service of the terminal device, further enabling the terminal device to perform the CS voice service, and further ensuring that the terminal device successfully initiates a CSFB call.

In one possible design, the determining, by the second mobility management network element, that the terminal device completes the joint registration includes: and the second mobility management network element determines to receive the registration completion message sent by the terminal equipment.

In a sixth aspect, a network handover method is provided, including: the second access network equipment receives a wireless tunnel establishment request sent by a second mobility management network element, wherein the wireless tunnel establishment request is used for requesting the second access network equipment to establish a user plane tunnel of the voice service for the terminal equipment; and the second access network equipment sends a wireless tunnel establishment response to the second mobility management network element according to a second condition, wherein the wireless tunnel establishment response comprises the information that the establishment of the user plane tunnel of the voice service is rejected, and the second condition comprises that the second network cannot carry out the voice service.

In the method provided in the sixth aspect, the second access network device rejects the allocation of the radio resource to the user plane tunnel when the second network cannot perform the voice service, and carries the rejected information of the establishment of the user plane tunnel of the voice service in the radio tunnel establishment response to send to the second mobility management network element, and the second mobility management network element can transfer the rejected information of the establishment of the user plane tunnel to the IMS network, so that the IMS network triggers the CSFB service of the terminal device, and the terminal device performs the CS voice service.

A seventh aspect provides a network handover method, including: an IMS network element receives a request message for establishing a voice service in a PS domain for terminal equipment; the IMS network element determines that a voice service cannot be established in a PS domain of a first network or a second network; the IMS network element determines that the terminal equipment completes the combined registration; and triggering the CSFB service of the terminal equipment by the IMS network element.

In the method provided in the seventh aspect, when it is determined that the voice service cannot be established in the PS domain of the first network or the second network and the terminal device completes the joint registration, the IMS network element triggers the CSFB service of the terminal device, and since the completion of the joint registration by the terminal device is a necessary condition for the terminal device to initiate a CSFB call, the method provided in the seventh aspect can further ensure that the terminal device successfully initiates a CSFB call, thereby enabling the terminal device to perform a CS voice service.

In one possible design, after the IMS network element receives the request message for establishing the voice service in the PS domain for the terminal device, the method further includes: the IMS network element determines that the terminal equipment is registered in the first network.

In one possible design, the determining, by the IMS network element, that the voice service cannot be established in the PS domain of the first network or the second network includes: the IMS network element acquires voice service establishment failure information from a PS domain of a first network; or the IMS network element acquires the voice service establishment failure information from the PS domain of the second network.

In one possible design, the determining, by the IMS network element, that the terminal device completes the joint registration includes: after the IMS network element determines that the voice service cannot be established in the PS domain of the first network or the second network within a second preset time period, the IMS network element determines that the terminal equipment completes the combined registration; or, the IMS network element determines that the terminal equipment completes the joint registration according to the registration position information of the terminal equipment, which is obtained from the strategy control network element or the home subscriber server.

In a possible design, the terminal device is a calling terminal device of a voice service, and the triggering of the CSFB service by the IMS network element includes: and the IMS network element sends a second message to the calling terminal equipment, wherein the second message is used for triggering the calling terminal equipment to initiate the CSFB calling service.

In a possible design, the terminal device is a called terminal device of a voice service, and the IMS network element triggers a CSFB service of the terminal device, including: the IMS network element sends a third message to the called domain selection device, wherein the third message is used for indicating that the called voice service in the PS domain of the first network or the second network fails to be established, so that the called domain selection device triggers the CSFB called voice service of the called terminal device.

In an eighth aspect, a network handover method is provided, including: the second mobility management network element receives a fourth message sent by the first mobility management network element, wherein the fourth message is used for confirming that the terminal equipment completes relocation; and the second mobility management network element sends a tunnel modification request to the service gateway according to a second condition, wherein the tunnel modification request is used for modifying signaling plane tunnel information of the voice service of the terminal equipment, and the second condition comprises that the second network cannot perform the voice service.

In the method provided by the eighth aspect, when the second network cannot perform the voice service, the second mobility management network element sends a tunnel modification request to the serving gateway, and the serving gateway forwards the tunnel modification request to the session management network element.

In one possible design, the sending, by the second mobility management network element, the tunnel modification request to the serving gateway according to a second condition includes: the second mobility management network element determines that a second condition is established and the UE completes joint registration; the second mobility management network element sends a tunnel modification request to the serving gateway. This possible design may ensure that the terminal device successfully initiates the CSFB call.

In a ninth aspect, a network registration method is provided, which includes: the first mobility management network element receives a registration request from the terminal equipment, wherein the registration request is used for requesting the terminal equipment to be registered in the first network; if the third condition is satisfied, the first mobility management network element sends first indication information to the terminal device, where the first indication information is used to indicate that the voice service in the PS domain is supported, and the third condition includes: the first network supports moving the terminal device to the second network. In the method provided by the ninth aspect, no matter whether the first network supports the voice service of the terminal device, as long as the first network has the capability of dropping the terminal device back to the network capable of providing the voice service through handover or other manners when the terminal device initiates the voice service, when the terminal device registers with the first network, the first mobility management network element indicates that the voice service of the PS domain of the terminal device is supported, so that the terminal device is ensured to register and reside in the first network without reselecting to other networks, network resources are saved, and the terminal device is ensured to normally execute a PS domain voice service registration process and initiate a PS domain voice call process through the first network.

In one possible design, the core networks of the first network and the second network are the same, and the access modes are different; or the core network and the access system of the first network and the second network are different.

In one possible design, the first network supporting movement of the terminal device to the second network includes: the first access network device in the first network supports the terminal device to access the second network when receiving the first session management information from the session management network element, and the first session management information is used for requesting to establish a user plane tunnel for the voice service of the terminal device.

In one possible design, the third condition further includes: the first network supports handover interoperability with the second network, and the second network is capable of supporting at least one of voice services of the PS domain.

In one possible design, a handover interoperability is supported between a first network and a second network, including: a handover interoperation interface exists between the first network and the second network.

In one possible design, before the first mobility management network element sends the first indication information to the terminal device, the method further includes: the first mobility management network element determines that the terminal equipment is the terminal equipment mainly based on the voice service. Since the terminal device based on the data service is not related to the voice service, the optional method can distinguish the terminal type, and the terminal device based on the data service does not need to execute the set of scheme, that is, whether the third condition is satisfied or not does not need to be determined, and the first indication information does not need to be sent.

In a possible design, the registration request carries indication information that the terminal device is a terminal device mainly based on a voice service, and the first mobility management network element determines that the terminal device is a terminal device mainly based on a voice service, including: and the first mobility management network element determines the terminal equipment as the terminal equipment mainly based on the voice service according to the registration request.

In one possible design, before the first mobility management element sends the first indication information to the terminal device, the method further includes the first mobility management element determining that the terminal device supports moving from the first network to the second network in the voice service initiation process and continuing the voice service initiation process through the second network. The method provided by the first aspect can be implemented only when the terminal device supports the process of initiating the voice service by moving from the first network to the second network and continuing the voice service through the second network in the process of initiating the voice service, so that the information can be determined in advance, and the terminal device which cannot support the process of initiating the voice service by moving from the first network to the second network and continuing the voice service through the second network in the process of initiating the voice service can be prevented from being affected.

In a possible design, the registration request further carries indication information that the terminal device supports an initiation process of moving from the first network to the second network and continuing the voice service through the second network in a voice service initiation process, and the determining, by the first mobility management network element, that the terminal device supports an initiation process of moving from the first network to the second network and continuing the voice service through the second network in the voice service initiation process includes: and the first mobility management network element determines that the terminal equipment supports the process of moving from the first network to the second network in the process of initiating the voice service and continuing the process of initiating the voice service through the second network according to the registration request.

In a tenth aspect, a network registration method is provided, which includes: the terminal equipment generates a registration request, wherein the registration request is used for requesting the terminal equipment to be registered in a first network, and the registration request carries indication information of the terminal equipment which is mainly based on voice service; the terminal equipment sends a registration request to the first mobility management network element.

In a possible design, the registration request further includes indication information that the terminal device supports moving from the first network to the second network during the voice service initiation process and continuing the voice service initiation process through the second network.

In an eleventh aspect, a network device is provided, where the network device may be a first access network device, a session management network element, a second mobility management network element, a second access network device, an IMS network element, or a first mobility management network element, and when the network device is the first access network device, the network device has a function of implementing any one of the methods provided in the first aspect; when the network device is a session management network element, the network device has a function of implementing any one of the methods provided in the second aspect; when the network device is a second mobility management network element, the network device has a function of implementing any one of the methods provided in the third aspect, the fourth aspect, the fifth aspect, or the eighth aspect; when the network device is a second access network device, the network device has a function of implementing any one of the methods provided in the sixth aspect; when the network device is an IMS network element, the network device has a function of implementing any one of the methods provided in the seventh aspect; when the network device is the first mobility management network element, the network device has a function of implementing any one of the methods provided in the ninth aspect. The functions realized by the network device can be realized by hardware, and can also be realized by executing corresponding software by hardware. The hardware or software comprises one or more functional units corresponding to the above-described method.

A twelfth aspect provides a terminal device, where the terminal device has a function of implementing any one of the methods provided in the tenth aspect, and the function implemented by the terminal device may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software comprises one or more functional units corresponding to the method of the tenth aspect.

In a thirteenth aspect, a network device is provided, which includes: a memory, a processor, and a communication interface; the memory is configured to store computer execution instructions, and the processor executes the computer execution instructions stored in the memory, and enables the network device to implement the method provided in the foregoing aspect through the communication interface, specifically, the network device may be a first access network device, a session management network element, a second mobility management network element, a second access network device, an IMS network element, or a first mobility management network element, and when the network device is the first access network device, the network device may implement any one of the methods provided in the first aspect; when the network device is a session management network element, the network device may implement any one of the methods provided in the second aspect; when the network device is a second mobility management network element, the network device may implement any one of the methods provided in the third aspect, the fourth aspect, the fifth aspect, or the eighth aspect; when the network device is a second access network device, the network device may implement any one of the methods provided in the sixth aspect; when the network device is an IMS network element, the network device may implement any one of the methods provided in the seventh aspect; when the network device is the first mobility management network element, the network device has a function of implementing any one of the methods provided in the ninth aspect.

In a fourteenth aspect, a terminal device is provided, which includes: a memory, a processor, and a communication interface; the memory is used for storing computer execution instructions, and the processor executes the computer execution instructions stored in the memory and enables the terminal device to realize any one of the methods provided by the tenth aspect through the communication interface.

In a fifteenth aspect, a computer-readable storage medium is provided, comprising instructions which, when executed on a computer, cause the computer to perform any one of the methods provided by the first aspect.

In a sixteenth aspect, there is provided a computer-readable storage medium comprising instructions which, when executed on a computer, cause the computer to perform any one of the methods provided by the second aspect.

In a seventeenth aspect, a computer-readable storage medium is provided, comprising instructions which, when executed on a computer, cause the computer to perform any one of the methods provided by the third aspect.

In an eighteenth aspect, there is provided a computer-readable storage medium comprising instructions which, when executed on a computer, cause the computer to perform any one of the methods provided in the fourth aspect.

In a nineteenth aspect, there is provided a computer-readable storage medium comprising instructions which, when executed on a computer, cause the computer to perform any one of the methods provided by the fifth aspect.

In a twentieth aspect, there is provided a computer-readable storage medium comprising instructions which, when executed on a computer, cause the computer to perform any one of the methods provided in the sixth aspect.

A twenty-first aspect provides a computer-readable storage medium comprising instructions which, when executed on a computer, cause the computer to perform any one of the methods provided in the seventh aspect.

In a twenty-second aspect, there is provided a computer-readable storage medium comprising instructions which, when run on a computer, cause the computer to perform any one of the methods provided in the eighth aspect.

In a twenty-third aspect, there is provided a computer-readable storage medium comprising instructions which, when run on a computer, cause the computer to perform any one of the methods provided in the ninth aspect.

A twenty-fourth aspect provides a computer-readable storage medium comprising instructions which, when run on a computer, cause the computer to perform any one of the methods provided by the tenth aspect.

In a twenty-fifth aspect, there is provided a computer program product containing instructions which, when run on a computer, cause the computer to perform any one of the methods provided in the first aspect.

In a twenty-sixth aspect, there is provided a computer program product containing instructions which, when run on a computer, cause the computer to perform any one of the methods provided by the second aspect.

In a twenty-seventh aspect, there is provided a computer program product comprising instructions which, when run on a computer, cause the computer to perform any one of the methods provided in the third aspect.

In a twenty-eighth aspect, there is provided a computer program product containing instructions which, when run on a computer, cause the computer to perform any of the methods provided in the fourth aspect.

In a twenty-ninth aspect, there is provided a computer program product comprising instructions which, when run on a computer, cause the computer to perform any one of the methods provided in the fifth aspect.

In a thirty-first aspect, there is provided a computer program product comprising instructions which, when run on a computer, cause the computer to perform any one of the methods provided in the sixth aspect.

In a thirty-first aspect, there is provided a computer program product comprising instructions which, when run on a computer, cause the computer to perform any one of the methods provided in the seventh aspect.

In a thirty-second aspect, there is provided a computer program product comprising instructions which, when run on a computer, cause the computer to perform any of the methods provided in the eighth aspect.

In a thirty-third aspect, there is provided a computer program product containing instructions which, when run on a computer, cause the computer to perform any of the methods provided in the ninth aspect.

A thirty-fourth aspect provides a computer program product comprising instructions which, when run on a computer, cause the computer to perform any of the methods provided by the tenth aspect.

The technical effects brought by any one of the design manners in the eleventh aspect to the thirty-fourth aspect can be seen in the technical effects brought by different design manners in the first aspect to the tenth aspect, and are not described herein again.

Drawings

Fig. 1 is a schematic architecture diagram of a 5G network according to an embodiment of the present disclosure;

fig. 1A is a schematic diagram of a terminal device accessing a 5G CN according to an embodiment of the present application;

fig. 2 is a schematic architecture diagram of an EPS network according to an embodiment of the present application;

fig. 3 is a schematic diagram of a network architecture after integration of a 5G network and an EPS network provided in an embodiment of the present application;

fig. 4 is a schematic communication diagram of an EPS network and an IMS network according to an embodiment of the present application;

fig. 5 is a schematic diagram of IMS voice communication between terminal devices according to an embodiment of the present application;

fig. 6 is a schematic composition diagram of a network device according to an embodiment of the present application;

fig. 6A is a schematic composition diagram of a terminal device according to an embodiment of the present application;

fig. 7 is an interaction flowchart of a network switching method according to an embodiment of the present application;

fig. 8 and fig. 9 are flowcharts of a network handover process according to an embodiment of the present application respectively;

fig. 10-12 are schematic diagrams respectively illustrating a process of establishing a user plane tunnel according to an embodiment of the present application;

fig. 13-17 are schematic diagrams respectively illustrating a method for ensuring that a terminal device successfully initiates a CSFB call according to an embodiment of the present application;

fig. 18 to fig. 28 are interaction flowcharts of a network handover method according to an embodiment of the present application, respectively;

fig. 28A is a flowchart of a network registration method according to an embodiment of the present application;

fig. 28B is a flowchart of another network registration method according to an embodiment of the present application;

fig. 29 is a schematic diagram of a network device according to an embodiment of the present application;

fig. 29A is a schematic diagram of a terminal device 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 an OR meaning, for example, A/B may indicate A or B; "and/or" herein is merely an association describing an associated object, and means that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the present application, "a plurality" means two or more than two.

The method provided by the embodiment of the application can be applied to a wireless communication system, for example: global system for mobile communications (GSM) system, Code Division Multiple Access (CDMA) system, Wideband Code Division Multiple Access (WCDMA) system, General Packet Radio Service (GPRS) system, Universal Mobile Telecommunications System (UMTS), EPS network and 5G network, and may also be used in future wireless communication systems.

Specifically, the method provided in the embodiment of the present application may be applied to a 5G network shown in fig. 1, where as shown in fig. 1, the 5G network may include: AN authentication server function (AUSF) network element, AN access and mobility management function (AMF) network element, a Data Network (DN), a Unified Data Management (UDM) network element, a Policy Control Function (PCF) network element, (radio) access network (R) AN) device, a user plane function (user plane function, UPF) network element, a terminal device, AN Application Function (AF) network element, and a Session Management Function (SMF) network element.

The (R) AN device of the 5G network may be a Next Generation (NG) RAN device, or AN evolved universal terrestrial radio access network (E-UTRAN) device, and the 5G network may be connected to the two access network devices at the same time, that is, the 5G network may have two different Radio Access Types (RATs) at the same time. Referring to fig. 1A, a terminal device may access a 5G Core Network (CN) through an E-UTRAN device or an NG RAN device, and the method provided by the embodiment of the present application is exemplarily described in the present application by taking an example that the terminal device registers in the 5G network through the NG RAN and initiates a voice service in an NG RAN access mode.

The Control Plane (CP) functional network element includes: UDM network element, AUSF network element, PCF network element, AMF network element and SMF network element.

Specifically, the (R) AN device main functions include: providing a wireless connection; the main functions of the UPF network element include: enabling a data packet to be routed and forwarded, enabling a mobility anchor point and an uplink classifier to support routing service flow to DN and BP to support multi-homing Packet Data Unit (PDU) conversation and the like; the DN can be served by an operator, Internet access or third-party service; the main functions of the AMF network element comprise user registration management, reachability detection, selection of SMF nodes, mobile state conversion management and the like; the SMF network element has the main functions of: controlling the establishment, modification and deletion of sessions, the selection of user plane nodes and the like; the main functions of the PCF network element include: policy decision points, which provide rules based on service data flow and application detection, gating, quality of service (QoS for short) and flow-based charging control; the main functions of the AF network element include: interacting with a core network of a third generation partnership project (3rd generation partnership project, 3GPP for short) to provide services to influence service flow routing, access network capability opening, policy control and the like; the main functions of the AUSF network element include: providing an authentication service; the main functions of the UDM network element include: and storing the user subscription data.

A terminal device may also be referred to as a User Equipment (UE), an access terminal, a subscriber unit, a subscriber station, a mobile station, a remote terminal, a mobile device, a user terminal, a wireless communication device, a user agent, or a user equipment. The terminal device may also be a Station (ST) in a Wireless Local Area Network (WLAN), which may be a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA) device, a handheld device with a wireless communication function, a computing device, or other processing devices connected to a wireless modem, a vehicle-mounted device, a wearable device (also referred to as a wearable smart device). The terminal device may also be a terminal device in a next-generation communication system, for example, a terminal device in 5G or a terminal device in a Public Land Mobile Network (PLMN) for future evolution, a terminal device in a New Radio (NR) communication system, and the like.

Specifically, the method provided in the embodiment of the present application may also be applied to an Evolved Packet System (EPS) network (generally referred to as a 4G network) shown in fig. 2, where as shown in fig. 2, the EPS network may include the following functional network elements: a terminal device, an E-UTRAN (specifically, an eNodeB), a Serving Gateway (SGW), a packet data gateway (PGW), a Mobility Management Element (MME), a Home Subscriber Server (HSS), a Mobile Switching Center (MSC), and a Policy and Charging Rules Function (PCRF), where the SGW is a service gateway, the MME is a packet data network gateway (PGW).

Under the condition that both the 5G network and the EPS network are deployed, the functional network element in the 5G network and the functional network element in the EPS network may be integrated, so that the 5G network and the EPS network may interact with each other, and referring to fig. 3, the integrated functional network element in the network includes: an HSS + UDM functional network element (which refers to a functional network element having both an HSS function and a UDM function), a PCF + PCRF functional network element (which refers to a functional network element having both a PCF function and a PCRF function), an SMF + PGW-C functional network element (which refers to a functional network element having both an SMF function and a packet data network gateway-control plane (PGW-C) function), an UPF + PGW-U functional network element (which refers to a network element function having both an UPF function and a packet data network gateway-user plane (PGW-U) function), an SGW, an MME, an E-UTRAN, an AMF, an ngn, and a terminal device. In the embodiments of the present application, the HSS + UDM functional network element, the PCF + PCRF functional network element, the SMF + PGW-C functional network element, and the UPF + PGW-U are only examples, and each network element may also be two network elements separated from each other, which is not limited herein.

The current mature voice service schemes include an IMS voice service scheme in an EPS network and a Circuit Switching (CS) voice service scheme in a 2G/3G network. Because the 5G network in the prior art does not support IMS and CS voice services, the embodiment of the present application provides a network switching method, so that a terminal device can switch from the 5G network to an EPS network or a 2G/3G network to perform a voice service when the voice service is required.

Referring to fig. 2, if the IP service of the operator is an IMS voice service, a communication diagram of the EPS network and the IMS network may refer to fig. 4, where the IMS network includes: a Proxy-Call Session Control function (P-CSCF)/Session edge Control (SBC), an inquiry-Call Session Control function (I-CSCF)/service-Call Session Control function (S-CSCF), a Telephony Application Server (TAS), and an IMS media gateway (IMSMGW), wherein a called domain selection function (T-ADS) may be included in the TAS, and thus, the called domain selection device may be referred to as the TAS hereinafter. The TAS may also be a service centralized and continuity application server (SCC AS for short).

When the terminal device performs the IMS voice service, the process of communication between the calling terminal device and the called terminal device may refer to fig. 5, which specifically includes: the calling terminal device sends the information related to the call to the calling access network, the information related to the call reaches the called terminal device after passing through the calling access network, the calling core network, the calling IMS network, the called core network and the called access network, and the information fed back to the calling terminal device by the called terminal device is sent in the opposite direction.

As shown in fig. 6, a schematic hardware structure of a network device 60 provided in the embodiment of the present application includes at least one processor 601, a communication bus 602, a memory 603, and at least one communication interface 604. The network device 60 may be a first access network device, a second access network device, a first mobility management network element, a second mobility management network element, a session management network element, an IMS network element, a user plane gateway, or a serving gateway in this application.

The processor 601 may be a general processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more ics for controlling the execution of programs according to the present disclosure.

The communication bus 602 may include a path that conveys information between the aforementioned components.

The communication interface 604 may be any device, such as a transceiver, for communicating with other devices or communication networks, such as an ethernet, a Radio Access Network (RAN), a Wireless Local Area Network (WLAN), etc.

The memory 603 may be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, a Random Access Memory (RAM) or other types of dynamic storage devices that can store information and instructions, an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compact disc, laser disc, optical disc, digital versatile disc, blu-ray disc, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited to such. The memory may be self-contained and coupled to the processor via a bus. The memory may also be integral to the processor.

The memory 603 is used for storing application program codes for executing the scheme of the application, and the processor 601 controls the execution. The processor 601 is adapted to execute application program code stored in the memory 603 in order to implement the methods described hereinafter.

In particular implementations, processor 601 may include one or more CPUs such as CPU0 and CPU1 in fig. 6 as an example.

In particular implementations, network device 60 may include multiple processors, such as processor 601 and processor 608 of FIG. 6, for example, as an example. Each of these processors may be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. A processor herein may refer to one or more devices, circuits, and/or processing cores for processing data (e.g., computer program instructions).

In one embodiment, the network device 60 may further include an output device 605 and an input device 606. Output device 605 is in communication with processor 601 and may display information in a variety of ways.

As shown in fig. 6A, a schematic diagram of a hardware structure of a terminal device 60A provided in this embodiment of the present application is shown, where the terminal device 60A includes at least one processor 601A, a communication bus 602A, a memory 603A, and at least one communication interface 604A.

In particular implementations, processor 601A may include one or more CPUs, such as CPU0 and CPU1 of FIG. 6A, for example, as an embodiment.

In one implementation, the terminal device 60A may include multiple processors, such as the processor 601A and the processor 608A in fig. 6A, for example.

In a specific implementation, the terminal device 60A may further include an output device 605A and an input device 606A, as an embodiment. The role of the various devices shown in fig. 6A, as well as other descriptions, may be illustratively referred to above.

In this embodiment, the first network and the second network may refer to two networks with different access schemes and different core networks, for example, a 5G network with an NG RAN access scheme and an EPS network with an E-UTRAN access scheme; the network access method can also refer to two networks with different access modes but the same core network, for example, a 5G network with an NG RAN access mode and a 5G network with an E-UTRAN access mode. In the embodiment of the present application, a first network and a second network are taken as two networks with different access schemes and different core networks, which should not be considered as limitations to the protection scope of the present application.

The scheme provided by the embodiment of the present application may be based on a service architecture, and the communication between the network elements may be based on a service interface or a non-service traditional interface, which is not specifically limited by the embodiment of the present application.

An embodiment of the present application provides a network switching method, as shown in fig. 7, the method may include:

701. the first access network device receives first session management information from a Session Management (SM) network element, where the first session management information is used to request establishment of a user plane tunnel for a voice service of the terminal device.

Specifically, the first session management information is used to request establishment of a user plane tunnel for the voice service of the terminal device in the first network. The voice service of the terminal device may be an IMS voice service.

The terminal device may be a calling terminal device of the voice service, and may also be a called terminal device of the voice service. The user plane tunnel may be referred to as QoS flow in a 5G network.

702. The first access network device sends a handover request (handoff required) to the first mobility management network element according to the first session management information and the first condition, where the handover request is used to switch the terminal device from the first network to the second network, and the first condition includes: the first network is not capable of voice traffic.

The first access network device may be an NG RAN, the session management network element may be an SMF + PGW-C functional network element, the first mobility management network element may be an AMF, the first network may be a 5G network, the second network may be an EPS network, and in addition, the first network and the second network may both be 5G networks, which is different in that access systems of the first network and the second network are different.

The first session management information may include QoS parameters of the user plane tunnel of the IMS voice service of the terminal device, for example, parameters such as a 5G QoS indicator (5G QoS indicator, hereinafter referred to as 5QI) ═ 1, an allocation/retention priority (ARP), a Guaranteed Bit Rate (GBR), a Maximum Bit Rate (MBR), and the like, and may further include other information.

The SMF + PGW-C functional network element may carry the first session management information in a session management request (session management with PDU modification command) carrying a PDU modification command, and send the first session management information to the AMF, and the AMF then carries the first session management information in an N2session request (N2session request) and sends the first session management information to the NG RAN.

According to the method provided by the embodiment of the application, when the terminal equipment in the 5G network performs the voice service, the terminal equipment can be switched to the EPS network, so that the terminal equipment can perform the IMS voice service in the EPS network, and the problem that the terminal equipment in the 5G network cannot perform the IMS voice service is solved.

According to the current specification of the 5G network protocol, for a terminal device with voice as a main (voice center), if the network side of the 5G network does not support IMS voice service, the terminal device with voice as a main should not initially select NR to access a 5G core network (5G core network, abbreviated as 5GC), or even if 5GC is accessed, reselect to access an E-UTRAN and an Evolved Packet Core (EPC), and if the 5G network does not support IMS voice service, the terminal device cannot stay in the 5G network and enjoy high-speed data service. In the method provided by the embodiment of the present application, when the 5G network cannot perform the IMS voice service, the NG RAN may send a handover request to the AMF, so that the terminal device in the 5G network is handed over from the 5G network to the EPS network, and the terminal device may perform the IMS voice service in the EPS network, so that the terminal device may first stay in the 5G network to enjoy a high-speed data service, and when the IMS voice service needs to be performed, then switch to the EPS network to perform the IMS voice service.

Further, in order to ensure that the terminal device in the 5G network can smoothly perform the voice service, the embodiment of the present application provides a method for the terminal device to perform network switching in two scenarios.

In scenario one, the first network cannot perform a voice service, and the second network can perform a voice service.

In this scenario, the first condition may further include: the second network supports voice services, the signal quality of the second network meets at least one of voice service requirements and network equipment of the first network, and the terminal equipment supports handover between the first network and the second network.

In this scenario, the terminal device may perform network switching in any one of the following first and second manners.

In the first mode, by notifying the session management network element that the establishment of the user plane tunnel of the voice service is accepted, the network device in the first network establishes the user plane tunnel for the voice service of the terminal device, and in the process that the terminal device is switched from the first network to the second network, the user plane tunnel established by the network device in the first network for the voice service of the terminal device is switched to the user plane tunnel of the voice service in the second network.

Referring to fig. 8, a first mode may specifically include:

s11, the first access network device sends second session management information to the session management network element, where the second session management information includes information that the establishment of the user plane tunnel of the voice service is accepted.

Specifically, the first access network device may carry the second session management information in an N2session response (N2session response) to send to the first mobility management element, and the first mobility management element then carries the second session management information in a session management response (session management with PDU modification command) that carries a PDU session modification command to send to the session management element.

It should be noted that, since the first network cannot perform the voice service, although the second session management information includes information that establishment of the user plane tunnel of the voice service is accepted, the first access network device does not actually allocate a radio resource to the voice service.

Optionally, referring to fig. 8, before step S11, the method may further include: and the first access network equipment determines not to allocate wireless resources for the user plane tunnel of the voice service according to the first session management information and the first condition.

S12, the session management network element receives the second session management information sent by the first access network device, and determines the user plane tunnel related information of the voice service according to the second session management information.

Specifically, the user plane tunnel related information of the voice service of the terminal device may specifically be data detection (packet detection), execution policy (enforcement rule), reporting policy (reporting rule), core network tunnel information (core network tunnel information), and the like related to the user plane tunnel of the voice service.

S13, the session management network element sends the user plane tunnel related information of the voice service to the user plane gateway.

The user plane gateway can be a UPF + PGW-U functional network element.

The SMF + PGW-C functional network element may carry the user plane tunnel related information of the voice service in an N4 session modification request (N4 session modification request) and send the result to the UPF + PGW-U functional network element.

S14, the user plane gateway receives the user plane tunnel related information of the voice service sent by the session management network element, and establishes a user plane tunnel for the voice service according to the user plane tunnel related information of the voice service.

Steps S11-S14 may be executed before step 702, or after step 702 and before the user plane tunnel of the voice service starts to be switched, and the user plane tunnel established by the user plane gateway for the voice service may also be switched to the user plane tunnel of the voice service in the second network by the switching of the user plane tunnel of the voice service, so that the terminal device may perform the voice service in the second network.

And secondly, by notifying the reason information that the establishment of the user plane tunnel of the voice service of the session management network element is rejected, the session management network element reestablishes the user plane tunnel for the voice service of the terminal equipment after the terminal equipment completes the switching from the first network to the second network.

Referring to fig. 9, the second mode may specifically include:

s21, the first access network device sends third session management information to the session management network element, where the third session management information includes the reason information that the establishment of the user plane tunnel of the voice service of the terminal device is rejected.

Specifically, the NG RAN may carry the third session management information in the N2session response to send to the AMF, and the AMF carries the third session management information in the session management response carrying the PDU session modification command to send to the SMF + PGW-C function network element.

Optionally, the reason information of the rejection may be: the terminal device executes a handover procedure.

S22, the session management network element receives the third session management information sent by the first access network device.

S23, the session management network element determines that the terminal device is switched from the first network to the second network.

Step S23 may be implemented in any one of a manner (1) and a manner (2), where in the manner (1) a timer is set in the session management network element, and when the timer expires, it is determined that the terminal device is switched from the first network to the second network, and in the second manner, when a tunnel modification request (modify router request) is received, the session management network element determines that the terminal device is switched from the first network to the second network, and the tunnel modification request is used to modify signaling plane tunnel information of a voice service of the terminal device.

S24, the session management network element establishes a user plane tunnel for the voice service in the second network according to the reason information.

In a specific implementation of step S24, when the session management network element determines that the third session management information is the reason information or the reason information is that the terminal device is executing a handover procedure, a user plane tunnel may be established for the voice service in the second network after the terminal device is handed over from the first network to the second network.

In the second mode, although the network device in the first network does not establish the user plane tunnel for the voice service, the session management network element establishes the user plane tunnel for the voice service of the terminal device in the second network after determining that the terminal device is switched from the first network to the second network, so that the terminal device can perform the voice service in the second network.

The second mode provides a method for switching networks by the terminal device in the scene that the first network can not carry out voice service but the second network can carry out voice service, when the first access network device receives the first session management information, the terminal device in the first network can be switched to the second network in time, so that the terminal device in the first network continues to perform the voice call setup procedure in the second network, meanwhile, the first access network equipment rejects the establishment of the user plane tunnel of the voice service by using the reason that the terminal equipment executes the switching process as the reason information, and triggering the user plane gateway to reestablish the user plane tunnel of the voice service after the terminal device is successfully switched to the second network (because the second network can perform the voice session in the scene, the user plane tunnel can be successfully established), so that the terminal device performs the voice service in the second network.

And in the second scenario, the first network and the second network cannot perform voice service.

In this scenario, the first condition may further include: the second network is not capable of voice traffic.

In this scenario, the terminal device may perform network switching in any one of the following three and four ways.

And thirdly, by notifying the reason information that the establishment of the user plane tunnel of the voice service of the session management network element is rejected, the session management network element reestablishes the user plane tunnel for the voice service of the terminal equipment after the terminal equipment completes the switching from the first network to the second network, and when the establishment of the user plane tunnel is unsuccessful, the terminal equipment falls back to the 2G/3G network for the voice service.

The third mode may specifically include:

S31-S34。

steps S31-S34 correspond to steps S21-S24, respectively, i.e., step S31 is the same as step S21, step S32 is the same as step S22, step S33 is the same as step S23, and step S34 is the same as step S24. See in particular fig. 9.

When the step S34 is implemented specifically, the process of establishing the user plane tunnel may be implemented specifically by any one of the following processes P1 to P4.

Referring to fig. 10, process P1 may include:

(11) and the service gateway sends a tunnel establishment request (create bearer request) to the second mobility management network element, wherein the tunnel establishment request is used for requesting to establish a user plane tunnel of the voice service for the terminal equipment.

The serving gateway may be an SGW, the second mobility management network element may be an MME, and the user plane tunnel of the voice service may be a dedicated bearer having a QCI of 1(QCI refers to a service quality class identifier, and is referred to as qos class identifier in english).

(12) And the second mobility management network element receives the tunnel establishment request sent by the service gateway and sends a tunnel establishment response (create bearer response) to the service gateway according to the second condition.

The tunnel establishment response comprises information that the user plane tunnel establishment of the voice service of the terminal equipment is refused.

The second condition may include the second network not being capable of voice traffic, and the second condition may further include the terminal device being a terminal device that is handed over from the first network to the second network.

Specifically, when the second mobility management element determines that the second condition is met, the second mobility management element rejects establishment of a user plane tunnel for the voice service, and includes the information in a tunnel establishment response and sends the information to the serving gateway.

After the step (12), the serving gateway may notify the IMS network element of the rejected information of the user plane tunnel establishment of the voice service through the session management network element and the policy control function network element, so that the IMS network element triggers a Circuit Switched Fallback (CSFB) service of the terminal device. The IMS network element may be a P-CSCF.

Referring to fig. 11, process P2 may include:

(21) and the service gateway sends a tunnel establishment request to the second mobility management network element, wherein the tunnel establishment request is used for requesting to establish a user plane tunnel of the voice service for the terminal equipment.

(22) And the second mobility management network element sends a radio tunnel establishment request (bearer setup request) to the second access network device, wherein the radio tunnel establishment request is used for requesting to establish a user plane tunnel for the voice service of the terminal device.

The second access network device may be an eNB, and the user plane tunnel for the voice service may be a dedicated bearer with QCI ═ 1.

(23) And the second access network equipment receives the wireless tunnel establishment request sent by the second mobility management network element and sends a wireless tunnel establishment response (bearer setup response) to the second mobility management network element according to the second condition.

Wherein the wireless tunnel establishment response includes information that the user plane tunnel establishment of the voice service is rejected. The second condition may include the second network not being capable of voice traffic, and the second condition may further include the terminal device being a terminal device that is handed over from the first network to the second network.

Specifically, when the second access network device determines that the second condition is met, the second access network device rejects establishment of a user plane tunnel for the voice service, and includes the information in a radio tunnel establishment response and sends the information to the second mobility management network element.

(24) And the second mobility management network element receives the wireless tunnel establishment response sent by the second access network equipment and sends the tunnel establishment response to the service gateway according to the second condition.

After the step (24), the serving gateway may notify the IMS network element of the information that the establishment of the user plane tunnel of the voice service is rejected through the session management network element and the policy control function network element, so that the IMS network element triggers the CSFB service of the terminal device.

The policy control function network element may be a PCF + PCRF function network element.

Referring to fig. 12, process P3 may include:

(31) and the service gateway sends a tunnel establishment request to the second mobility management network element, wherein the tunnel establishment request is used for requesting to establish a user plane tunnel of the voice service for the terminal equipment.

(32) And the second mobility management network element receives the tunnel establishment request sent by the service gateway and sends a wireless tunnel establishment request to the second access network equipment, wherein the wireless tunnel establishment request is used for requesting the establishment of a user plane tunnel for the voice service of the terminal equipment.

(33) And the second access network equipment receives the wireless tunnel establishment request sent by the second mobility management network element and sends a wireless tunnel establishment response to the second mobility management network element according to the second condition.

(34) And the second mobility management network element receives the wireless tunnel establishment response sent by the second access network equipment and sends the tunnel establishment response to the service gateway according to the wireless tunnel establishment response.

The wireless tunnel establishment response comprises information that the establishment of the user plane tunnel of the voice service of the terminal equipment is rejected, and the tunnel establishment response comprises information that the establishment of the user plane tunnel of the voice service of the terminal equipment is rejected.

After the step (34), the serving gateway may notify the IMS network element of the information that the establishment of the user plane tunnel of the voice service is rejected through the session management network element and the policy control function network element, so that the IMS network element triggers the CSFB service of the terminal device.

In this scenario, the second network cannot perform a voice session, and therefore, a user plane tunnel of a voice service cannot be established successfully. In this case, the terminal device may fall back to the 2G/3G network to perform the voice service, and the terminal device is required to perform the CSFB service, and the joint registration is a necessary precondition for the terminal device to subsequently initiate a CSFB call, and the terminal device completing the joint registration means that the terminal device completes a joint registration procedure of the EPS and CS domains. Therefore, in order to ensure that the terminal device successfully initiates the CSFB call, it is necessary to trigger the CSFB service of the terminal device after the terminal device completes the joint registration, and the CSFB service may be specifically implemented in any one of the following four ways, W1 to W4.

Mode W1:

referring to fig. 10, in process P1, the second mobility management element determines that the terminal device completes the joint registration, and then performs step (12), specifically, when the second mobility management element determines that a joint registration completion message from the terminal device is received, the joint registration completion message may specifically be a tracking area update completion (tracking area update complete) message, and the second mobility management element determines that the terminal device completes the joint registration.

Referring to fig. 11, in procedure P2, in step (24), after the second mobility management element determines that the second condition is satisfied and the terminal device completes the joint registration, the second mobility management element sends a tunnel establishment response to the serving gateway. Specifically, when the second mobility management network element determines that the joint registration completion message from the terminal device is received, the second mobility management network element determines that the terminal device completes the joint registration.

Referring to fig. 12, in process P3, if the second condition is met, the second mobility management element performs step (32) after determining that the terminal device completes the joint registration. Specifically, when the second mobility management network element determines that the joint registration completion message from the terminal device is received, the second mobility management network element determines that the terminal device completes the joint registration.

In this way, since the IMS network element triggers the CSFB service of the terminal device after receiving the information that the user plane tunnel establishment of the voice service is rejected, the second mobility management network element sends a tunnel establishment response to the serving gateway after determining that the terminal device completes the joint registration, so that the IMS network element triggers the CSFB service of the terminal device after the terminal device completes the joint registration, thereby ensuring that the terminal device successfully initiates a CSFB call.

Mode W2:

in step S34, when the session management network element is implemented specifically, the session management network element establishes a user plane tunnel for the voice service in the second network after the first preset time period according to the reason information and the second condition.

The mode m1 and the mode m2 can be specifically realized.

Mode m1 is: and the session management network element sends a tunnel establishment request to a service gateway of the second network after a first preset time period according to the reason information and the second condition, wherein the tunnel establishment request is used for requesting to establish a user plane tunnel of the voice service.

Specifically, the starting time point of the first preset time period may be a time point at which the reason information is received.

Mode m2 is: the session management network element sends a tunnel establishment request to a service gateway of the second network according to the reason information, wherein the tunnel establishment request is used for requesting to establish a voice service user plane tunnel; the session management network element receives a tunnel establishment response sent by the service gateway, wherein the tunnel establishment response comprises the refused information of the user plane tunnel establishment of the voice service; and the session management network element sends a first message to the policy function control network element after a first preset time period according to the second condition, wherein the first message is used for indicating that the establishment of the user plane tunnel of the voice service fails. The first message may be a credit control request (CCR for short), and the information that the user plane tunnel establishment fails may be included in the CCR.

In this manner, when it is considered that the IMS network element delays triggering of the CSFB service of the terminal device for the first preset time period, the terminal device has already completed the joint registration, and specifically, the session management network element may delay sending of the tunnel establishment request or the first message for the first preset time period by the session management network element so as to delay triggering of the CSFB service of the terminal device for the first preset time period, thereby ensuring that the terminal device successfully initiates the CSFB call.

Mode W3:

referring to fig. 13, the mode W3 may include:

the W3-1 and the IMS network element receive a request message for establishing a voice service in a Packet Switching (PS) domain for a terminal device.

The request message may specifically be an invite (invite) message.

W3-2, IMS network element determines that it can not establish voice service in PS domain of the first network or the second network.

And the W3-3 and the IMS network element determine that the terminal equipment completes the joint registration.

W3-4, the IMS network element triggers the CSFB service of the terminal equipment.

In this way, after the IMS network element determines that the terminal device completes the joint registration, the CSFB service of the terminal device is triggered, thereby ensuring that the terminal device successfully initiates a CSFB call.

Optionally, after the step W3-1, the method may further include: the IMS network element determines that the terminal equipment is registered in the first network according to the request message for establishing the voice service in the packet switching domain, and further determines that the request message is received in the first network.

Optionally, W3-2 may specifically include: the method comprises the steps that an IMS network element obtains voice service establishment failure information from a PS (packet switched) domain of a first network, and specifically, when the IMS network element receives the user plane tunnel establishment failure information of the voice service, the IMS network element judges that the user plane tunnel establishment failure information of the voice service is the PS domain from the first network by determining that a terminal device is registered in the first network; or, the IMS network element obtains the voice service establishment failure information from the PS domain of the second network, and specifically, when receiving the user plane tunnel establishment failure information of the voice service, the IMS network element determines that the user plane tunnel establishment failure information of the voice service is from the PS domain of the second network by determining that the terminal device is registered in the second network.

The voice service establishment failure information can be reported to the IMS network element by other network devices.

Optionally, W3-3 may specifically include: after the IMS network element determines that the voice service cannot be established in the PS domain of the first network or the second network within a second preset time period, the IMS network element determines that the terminal equipment completes the combined registration; or, the IMS network element determines that the terminal device completes the joint registration according to the registration location information of the terminal device obtained from the policy control network element or the home subscriber server (HSS for short).

Specifically, the policy control network element or the home subscriber server may actively report the registration location information of the terminal device to the IMS network element, or the IMS network element may query the registration location information from the policy control network element or the home subscriber server.

When the terminal device is a calling terminal device of a voice service, the W3-4 may specifically include: and the IMS network element sends a second message to the calling terminal equipment, wherein the second message is used for triggering the calling terminal equipment to initiate the CSFB calling voice service.

When the terminal device is a called terminal device of a voice service, the W3-4 may specifically include: the IMS network element sends a third message to the called domain selection device, wherein the third message is used for indicating that the called voice service in the PS domain of the first network or the second network fails to be established, so that the called domain selection device triggers the CSFB called voice service of the called terminal device.

The second message and the third message may be a 500 response message or a 380 response message or a 503 response message.

And if the rejected information includes insufficient radio resources (or failure in resource allocation), the session management network element does not establish the user plane tunnel for the voice service of the terminal device after the terminal device completes switching from the first network to the second network, and the unsuccessful user plane tunnel establishment information is transmitted to the IMS network through the first network, so that the IMS network triggers the CSFB service of the terminal device.

The fourth mode specifically includes: the first access network equipment sends fourth session management information to the session management network element, wherein the fourth session management information comprises information that the establishment of the user plane tunnel of the voice service is refused, and the information that the establishment of the user plane tunnel of the voice service is refused comprises the shortage of radio resources.

In this manner, after the terminal device is switched from the first network to the second network, the session management network element does not re-establish the user plane tunnel for the voice service of the terminal device, but improves the switching process, so as to ensure that the terminal device successfully initiates the CSFB call, which may specifically be implemented by any one of the above-mentioned W3 and the following manners W4 to W8, where W5 and W6 are directed to a case where the terminal device is a calling terminal device.

Mode W4:

referring to fig. 14, the mode W4 includes:

and the W4-1 and the second mobility management network element receive a fourth message sent by the first mobility management network element, wherein the fourth message is used for confirming that the terminal equipment completes relocation.

The fourth message may specifically be a relocation request complete response (relocation request acknowledge) message, where relocation refers to that a mobility management network element corresponding to the terminal device is relocated in a process of switching the terminal device from the first network to the second network, and the relocation is performed from the first mobility management network element to the second mobility management network element.

And W4-2, the second mobility management network element determines that the second condition is established and the terminal equipment completes the joint registration.

And W4-3, the second mobility management network element sends a tunnel modification request to the service gateway, wherein the tunnel modification request is used for requesting to modify the signaling plane tunnel information of the voice service of the terminal equipment.

And after receiving the tunnel modification request, the service gateway sends the tunnel modification request to the session management network element, and the session management network element further sends the tunnel modification request to the user plane gateway, so that the user plane gateway establishes a corresponding signaling plane tunnel of the voice service according to the signaling plane tunnel information of the voice service. The signaling plane tunnel of the voice service may specifically be a dedicated bearer with QCI ═ 5.

It should be noted that, after learning that the user plane tunnel is failed to be established, the IMS network element may send a second message to the terminal device (the meaning of the second message is the same as that mentioned above), where the second message needs to be transmitted to the terminal device through a signaling plane tunnel of the voice service (i.e., a dedicated bearer with QCI ═ 5), and the user plane gateway sends the second message to the terminal device through the signaling plane tunnel after receiving the tunnel modification request and completing the establishment of the signaling plane tunnel of the voice service. In this way, the second mobility management network element sends a tunnel modification request to the serving gateway after determining that the terminal device completes the joint registration, thereby ensuring that the terminal device successfully initiates the CSFB call.

Mode W5:

referring to fig. 15, the mode W5 includes:

w5-1, MME determines that the terminal equipment completes the joint registration.

W5-2, IMS network element determines that it can not establish voice service in PS domain of the first network or the second network.

And W5-3, the IMS network element sends a second message to the terminal equipment.

The implementation method of each step in the mode W5 can be referred to above, and is not described here.

In this way, after the MME determines that the terminal device completes the joint registration, the IMS network element sends the second message to the terminal device, so that it can be ensured that the terminal device successfully initiates the CSFB call.

Mode W6:

referring to fig. 16, the mode W6 includes:

w6-1, IMS network element determines that it can not establish voice service in PS domain of the first network or the second network.

And W6-2, the IMS network element sends a second message to the user plane gateway.

W6-3, the user plane gateway, buffers the second message.

W6-4, MME determines that the terminal equipment completes the joint registration.

W6-5, MME sends a tunnel modification request to the user plane gateway.

And W6-6, the user plane gateway sends a second message to the terminal equipment after receiving the tunnel modification request.

The implementation methods of the steps in the method W6 and the meanings of the related terms may be referred to above, and are not described herein again.

In this way, the user plane gateway first caches the second message sent by the IMS network element, and sends the second message to the terminal device after receiving the tunnel modification request, and since the tunnel modification request is sent to the user plane gateway after the MME determines that the terminal device completes the joint registration, it can be ensured that the terminal device successfully initiates the CSFB call.

Mode W7:

referring to fig. 17, the mode W7 includes:

w7-1, IMS network element determines that the voice service can not be established in PS domain of the first network or the second network.

W7-2, when the terminal equipment is the calling terminal equipment, the IMS network element delays a second preset time period to send a second message to the terminal equipment; and when the terminal equipment is called terminal equipment, the IMS network element delays a second preset time period to send a third message to the called domain selection equipment.

The implementation methods of the steps in the method W7 and the meanings of the related terms may be referred to above, and are not described herein again.

In this way, when the IMS network element delays the triggering of the CSFB service of the terminal device for the second preset time period, the terminal device has already completed the joint registration, thereby ensuring that the terminal device successfully initiates the CSFB call.

The first preset time period and the second preset time period may be preset according to an actual network condition, and the first preset time period and the second preset time period may be the same or different, for example, the first preset time period may be 500ms, and the second preset time period may be 100 ms.

It should be noted that, the 5G network does not deploy a special CS domain as the 2G/3G network, so that a CS voice service similar to the conventional voice cannot be provided for the terminal device, and through the third and fourth modes, the method provided in the embodiment of the present application can also enable the terminal device to perform the CS voice service under the condition that the terminal device cannot perform the IMS voice service.

The present application further provides the following 4 embodiments for exemplarily explaining the method, where both application scenarios of the embodiments (1) and (2) are scenarios in which the 5G network cannot perform the IMS voice service but the EPS network can perform the IMS voice service, and both application scenarios of the embodiments (3) and (4) are scenarios in which the 5G network cannot perform the IMS voice service and the EPS network cannot perform the IMS voice service. In each embodiment, the UE and each network element in the method for describing the calling side may be divided into a calling side and a called side, and if no specific description is provided, the UE and each network element in the method for describing the calling side refer to the UE and the network element of the calling side, and the UE and each network element in the method for describing the called side refer to the UE and the network element of the called side.

Example (1)

The embodiment provides a method for performing network handover by a calling UE, and referring to fig. 18, the method includes:

1801. and the UE sends an invitation message to the P-CSCF, wherein the invitation message is used for requesting to establish the IMS voice service.

The UE is a UE in the 5G network, and the invite message is a message for requesting to establish a voice service in the PS domain for the UE of the 5G network.

1802. And the P-CSCF establishes the IMS voice session for the UE according to the received invitation message sent by the UE.

The P-CSCF may also send the invite message to subsequent nodes in the calling IMS network (e.g., IMS nodes such as S-CSCF and TAS), where the subsequent nodes in the IMS network start processing the received invite message, and the called UE may receive the invite message of the calling UE forwarded by the called IMS network.

1803. The P-CSCF sends an authentication authorization request (AAR for short) to the PCF + PCRF to trigger establishment of a user plane tunnel for IMS voice traffic of the UE.

The AAR may carry a user identifier of the UE, an IMS application layer charging identifier, media description information of the IMS voice service, and the like, and the media description information may include at least one of the following information: classifier identification, bandwidth requirement description information, media type description information, and QoS parameters.

It should be noted that the P-CSCF may directly send the AAR to the PCF + PCRF, or may send the AAR to the PCF + PCRF after receiving the 183 response message sent by the S-CSCF in the IMS network.

1804. And the PCF + PCRF sends a packet data unit-connection access network (PDU-CAN for short) session modification (session modification) flow request to the SMF + PGW-C according to the media description information carried in the AAR sent by the P-CSCF so as to trigger a network element in the 5G network to establish a user plane tunnel for the IMS voice service of the UE.

The PDU-CAN session modification carries QoS rules (rules) including QoS parameter sets (profiles) which are generally composed of one or more of the following QoS key parameters, and packet filters (packet filters), etc.: GBR, ARP, 5QI, MBR, etc.

Generally, a user plane tunnel in a 5G network generally refers to a QoS flow for transmitting user plane data, and a 5QI of the user plane tunnel of the IMS voice service may be equal to 1, or may be another value.

1805. After receiving a PDU-CAN session modification flow request sent by a PCF + PCRF network element, an SMF + PGW-C sends a session management request carrying a PDU session modification command to an AMF, where the request includes first SM information, where the first SM information is SM information related to a user plane tunnel of an IMS voice service of a UE, the first SM information may include QoS parameters of the user plane tunnel, for example, 5QI ═ 1, and parameters such as ARP, GBR, and MBR, and the first SM information may further include other information.

1806. And the AMF sends an N2session request to the NG RAN according to the received first SM information sent by the SMF + PGW-C, wherein the first SM information is transmitted to the NG RAN in a transparent mode, so that the NG RAN allocates corresponding radio resources for the user plane tunnel with the 5QI being 1 according to the first SM information.

1807. And the NG RAN determines not to allocate radio resources for the user plane tunnel of the IMS voice service of the UE according to the first SM information and the first condition.

It should be noted that step 1807 may or may not be executed, and this is not specifically limited in this embodiment of the application.

The first condition may include the following conditions: (1) the 5G network can not carry out IMS voice service, the condition indicates that the 5G network does not deploy IMS voice service, or the signal coverage of the current 5G network is not enough to meet the requirement of the IMS voice service; (2) the EPS network supports voice traffic, which condition can be configured on the NG RAN by the operator as a local policy; (3) the signal quality of the EPS network meets the voice service requirement, and the NGRAN can determine whether the signal quality of the EPS network meets the voice service requirement or not by indicating the UE to measure and report the signal quality of the peripheral EPS cells; (4) the network equipment (AMF, NG RAN, etc.) and the UE of the 5G network support the switching between the 5G network and the EPS network, wherein whether the UE and the AMF support the switching between the 5G network and the EPS network or not can be informed to the NG RAN by the AMF through an N2 message when the UE is changed from an idle (idle) state to a connected (connected) state.

1808. The NG RAN sends an N2session response (N2session response) to the AMF.

The N2session response includes second SM information, which includes information that establishment of the user plane tunnel of the IMS voice service of the UE is accepted.

1809. And the AMF sends a session management response carrying the PDU session modification command to the SMF + PGW-C according to the received N2session response, wherein the second SM information is transmitted to the SMF + PGW-C.

1810. And the SMF + PGW-C sends an N4 session modification request to the UPF + PGW-U according to the received session management response carrying the PDU session modification command sent by the AMF. The N4 here means that an N4 interface is between the SMF + PGW-C and the UPF + PGW-U, but the embodiment of the present application does not limit the interface name, that is, the message name is not limited to the N4 session modification request.

The N4 session modification request carries data detection (packet detection), execution policy (enforcement rule), reporting policy (reporting rule), core network tunnel information (CN tunnel information) related to the user plane tunnel with 5QI ═ 1, so that the UPF + PGW-U can establish a corresponding core network tunnel for the user plane tunnel with 5QI ═ 1.

1811. And the UPF + PGW-U receives the N4 session modification request sent by the SMF + PGW-C, and establishes a corresponding core network tunnel for the user plane tunnel with the 5QI being 1 according to the N4 session modification request.

It should be noted that the user plane tunnel in the 5G network generally refers to QoS flow for transmitting user plane data, and the user plane tunnel in the EPS network generally refers to bearer (bearer) for transmitting user plane data. After the UPF + PGW-U establishes a corresponding user plane tunnel for the user plane tunnel with 5QI ═ 1, in the process of switching the UE from the 5G network to the EPS network, the user plane tunnel is also switched, that is, the QoS flow with 5QI ═ 1 is switched to the dedicated bearer with QCI ═ 1. Specifically, the SMF + PGW-C may determine, through the received tunnel modification request sent by the SGW, that the user plane tunnel with 5QI ═ 1 of the UE has been switched from the 5G network to the user plane tunnel with QCI ═ 1 of the EPS network, and that the user plane tunnel with QCI ═ 1 has been successfully established. After the UE is switched to the EPS network from the 5G network, the UE continues the subsequent IMS voice call establishment flow in the EPS network after receiving the related signaling of the IMS voice service forwarded by the EPS network, thereby completely establishing the IMS voice session.

After step 1811, the UPF + PGW-U also sends N4 session modification response to the SMF + PGW-C, the SMF + PGW-C sends PDU-CAN session modification to the PCF + PCRF, the PCF + PCRF sends Re-authentication Request (RAR) to the P-CSCF, and the P-CSCF sends credit Re-authentication answer (RAA) to the PCF + PCRF, so that the P-CSCF CAN know that the user plane tunnel of the IMS voice service is successfully established.

1812. And the NG RAN sends a switching request to the AMF according to the received first SM information and the first condition so as to trigger the UE to be switched from the 5G network to the EPS network.

Specifically, when the first condition is met, the NG RAN may send a handover request to the AMF when it determines that a user plane tunnel with a 5QI of 1 needs to be established according to the first SM information.

The handover procedure of the UE from the 5G network to the EPS network may refer to a standard protocol, which is not described herein again. After the UE is switched to the EPS network from the 5G network, the UE continues the subsequent IMS voice call establishment flow in the EPS network after receiving the related signaling of the IMS voice service forwarded by the EPS network, thereby completely establishing the IMS voice session.

The embodiment also provides a method for network handover of a called UE, referring to fig. 19, the method includes:

1901. and the P-CSCF receives the invitation message sent by the S-CSCF and establishes the IMS voice session for the UE according to the invitation message.

The invite message is a message for requesting setup of a voice service in the PS domain for the UE of the 5G network.

1902. The P-CSCF sends an invite message to the UE.

1903. The UE receives the invite message sent by the P-CSCF and replies 183 to the P-CSCF with a response message.

1904. And the P-CSCF receives the 183 response message sent by the UE and sends the 183 response message to the S-CSCF.

The S-CSCF can further send 183 response message to the calling party S-CSCF, the calling party S-CSCF further sends 183 response message to the calling party P-CSCF, and the calling party P-CSCF can forward 183 response message to the calling UE if the calling party P-CSCF receives the 183 response message sent by the calling party S-CSCF.

1905-1914。

Step 1905-.

The above embodiment (1) provides a method for switching a network by a terminal device in a scenario where a 5G network cannot perform an IMS voice service but an EPS network can perform the IMS voice service, where the NG RAN can switch the 5G terminal to the EPS network in time when receiving a user plane tunnel establishment request with a 5QI of 1, so that the terminal device in the 5G network continues to execute an IMS voice call establishment procedure in the EPS network.

Example (2)

The embodiment provides a method for performing network handover by a calling UE, and referring to fig. 20, the method includes:

2001-2006。

the steps 2001 + 2006 correspond to the steps 1801 + 1806 respectively.

2007. The NG RAN sends an N2session response to the AMF according to the first SM information and the first condition.

The NG RAN may determine, according to the first SM information, that the user plane tunnel requested to be established is the IMS voice service, specifically, the user plane tunnel with 5QI ═ 1.

The N2session response includes third SM information, where the third SM information may include SM information indicating that the NG RAN rejects allocation of radio resources to the user plane tunnel with 5QI ═ 1, and carries rejected reason information, and the reason information is that the UE is performing a handover procedure, and further, the reason information may be that the UE is performing a handover from the 5G network to the EPS network, so that the SMF + PGW-C determines, according to the reason information, that the establishment of the user plane tunnel of the IMS voice service of the UE is re-initiated after the handover procedure of the UE is completed.

The first condition may include the following conditions: (1) the 5G network can not carry out IMS voice service, the condition indicates that the 5G network does not deploy IMS voice service, or the signal coverage of the current 5G network is not enough to meet the requirement of the IMS voice service; (2) the EPS network supports voice traffic, which condition can be configured on the NG RAN by the operator as a local policy; (3) the signal quality of the EPS network meets the voice service requirement, and the NGRAN can determine whether the signal quality of the EPS network meets the voice service requirement or not by indicating the UE to measure and report the signal quality of the peripheral EPS cells; (4) the network equipment (AMF, NG RAN, etc.) and the UE of the 5G network support the switching between the 5G network and the EPS network, wherein whether the UE and the AMF support the switching between the 5G network and the EPS network or not can be informed to the NG RAN through an N2 message when the UE is changed from an idle state to a connected state by the AMF.

2008. And the AMF sends a session management request carrying the PDU session modification command to the SMF + PGW-C according to the received N2session response, wherein the third SM information is transmitted to the SMF + PGW-C.

2009. And the SMF + PGW-C determines to establish a user plane tunnel for the IMS voice service of the UE again in the EPS network after the UE is switched from the 5G network to the EPS network according to the received third SM information in the session management request which is sent by the AMF and carries the PDU session modification command.

It should be noted that reestablishing the user plane tunnel for the IMS voice service of the UE in the EPS network refers to establishing the user plane tunnel with QCI ═ 1.

In the process of switching the UE from the 5G network to the EPS network, the SMF + PGW-C may determine, through the received tunnel modification request sent by the SGW, that the UE has successfully switched from the 5G network to the EPS network. In addition, the SMF + PGW-C may also trigger the timer to count time from receiving the third SM information by setting the timer, and determine that the UE has successfully switched from the 5G network to the EPS network when the timer count time ends.

2010. And the NG RAN sends a switching request to the AMF according to the received first SM information and the first condition so as to trigger the UE to be switched from the 5G network to the EPS network.

The handover procedure of the UE from the 5G network to the EPS network may refer to a standard protocol, which is not described herein again.

2011. After the UE completes handover, the SMF + PGW-C sends a tunnel establishment request (create bearer request) to the SGW to trigger establishment of a user plane tunnel with QCI of 1.

Subsequently, the user plane tunnel with QCI ═ 1 is successfully established in the EPS network, and the EPS network feeds back the user plane tunnel establishment success of the IMS voice service to the IMS network, and the user plane tunnel establishment procedure with QCI ═ 1 and the establishment procedure of the IMS voice session in the EPS network specifically see the standard protocol, which is not described herein again.

The embodiment also provides a method for network handover of a called UE, referring to fig. 21, the method includes:

2101-2113。

wherein, the steps 2101 and 2104 and 1901 and 1904 are respectively the same, and the steps 2105 and 2113 and 2003 and 2111 are respectively the same.

The above embodiment (2) provides a method for switching a network by a terminal device in a scenario where a 5G network cannot perform an IMS voice service but an EPS network can perform the IMS voice service, where the NG RAN can switch the 5G terminal to the EPS network in time when receiving a request for establishing a user plane tunnel with a 5QI of 1, so that the terminal device in the 5G network continues to execute an IMS voice call establishment procedure in the EPS network, and meanwhile, the NG RAN rejects the establishment of the user plane tunnel with the 5QI of 1 based on information that the switching is being performed, so as to trigger a core network gateway to reestablish the user plane tunnel with a QCI of 1 after the UE is successfully switched to the EPS network.

Example (3)

The embodiment provides a method for performing network handover by a calling UE, and referring to fig. 22, the method includes:

2201-2210。

steps 2201-2210 correspond to steps 2001-2010, respectively.

2211. After the UE completes handover, the SMF + PGW-C sends a tunnel establishment request to the SGW to trigger establishment of a user plane tunnel with QCI ═ 1.

2212. The SGW forwards the tunnel establishment request to the MME.

After step 2212, the MME receives the tunnel establishment request and performs any one of procedure one (including a1), procedure two (including b1-b4), and procedure three (including c1-c4) among the following procedures.

The first process is as follows:

a1, MME sends a tunnel establishment response to SGW according to the second condition, the tunnel establishment response includes the information that the user plane tunnel establishment of the voice service of UE is refused.

In the first process, the second condition may include that the second network cannot perform the voice service, and may further include that the UE completes at least one of the joint registration for the UE switched from the 5G network to the EPS network and the UE, where the failure of the voice service by the second network specifically may mean that the IMS voice service cannot be performed, and the completion of the joint registration by the UE means that the UE completes the joint registration procedure of the EPS and CS domains.

Specifically, the MME may determine that the UE completes the joint registration according to the received registration completion message sent by the UE.

Before a1, the MME may or may not send a radio tunnel setup request and receive a response message to the eNB for the IMS voice service, which is not limited herein.

And a second process:

b1, the MME sends a wireless tunnel establishment request to the eNB, where the wireless tunnel establishment request is used to request establishment of a user plane tunnel for the IMS voice service of the UE, and specifically, the user plane tunnel for the IMS voice service may refer to a dedicated bearer with QCI ═ 1.

b2, the eNB receives the request for establishing the wireless tunnel, and sends a response for establishing the wireless tunnel to the MME according to the second condition, wherein the response for establishing the wireless tunnel comprises the information that the establishment of the user plane tunnel of the IMS voice service of the UE is refused.

In the second process, the second condition includes that the second network cannot perform the IMS voice service, and the UE may be a UE that is switched from the 5G network to the EPS network.

b3, the MME receives a wireless tunnel establishment response sent by the eNB, and if the second condition is satisfied, the MME determines that the UE completes the joint registration.

The wireless tunnel establishment response includes information that the user plane tunnel establishment of the IMS voice service of the UE is rejected.

Specifically, in step b3, when the MME determines that the registration completion message sent by the UE is received, the MME determines that the UE completes the joint registration.

b4, MME sends a tunnel establishment response to SGW, the tunnel establishment response includes the information that the user plane tunnel establishment of the IMS voice service of the UE is refused.

The third process:

c1, if the second condition is true, the MME determines that the UE completes the joint registration.

Specifically, in step c1, when the MME determines that the registration completion message sent by the UE is received, the MME determines that the UE completes the joint registration.

In the third process, the second condition includes that the second network cannot perform the IMS voice service, and may also include that the UE is a UE that is switched from the 5G network to the EPS network.

c2, MME sends a wireless tunnel establishment request to eNB, and the wireless tunnel establishment request is used for requesting the establishment of a user plane tunnel for the IMS voice service of UE.

c3, the eNB receives the wireless tunnel establishment request sent by the MME, and sends a wireless tunnel establishment response to the MME according to the second condition, wherein the wireless tunnel establishment response comprises the information that the user plane tunnel establishment of the IMS voice service of the UE is refused.

c4, MME receives the wireless tunnel establishment response sent by eNB, and sends the tunnel establishment response to SGW according to the wireless tunnel establishment response, wherein the tunnel establishment response comprises the information that the user plane tunnel establishment of the IMS voice service of UE is refused.

2213. And the SGW receives the tunnel establishment response sent by the MME and sends the tunnel establishment response to the SMF + PGW-C.

2214. And the SMF + PGW-C sends the CCR to the PCF + PCRF.

The CCR carries an indication for explaining that the user plane tunnel establishment fails with QCI ═ 1, and may also carry cause information of the tunnel establishment failure, where the cause information is specifically set with reference to the cause information carried in the tunnel establishment response sent by the SGW. Here, CCR may also be replaced by messages with other names, such as, but not limited to, IP-CAN session modification request.

2215. PCF + PCRF sends credit control answer (CCA for short) to SMF + PGW-C.

2216. PCF + PCRF sends RAR to P-CSCF according to CCR, RAR can carry the indicating information used for pointing out the radio resource is not enough (or used for pointing out the indicating information of the failure of resource allocation).

2217. And the P-CSCF sends RAA to the PCF + PCRF.

2218. And the P-CSCF determines that the IMS voice service of the UE cannot be established in the PS domain after the obtained indication information of the insufficient wireless resources (or the indication information of the failure of resource allocation).

2219. The P-CSCF sends a 500 response message to the UE.

After step 2219, after receiving the 500 response message sent by the P-CSCF, the UE may select and initiate a CSFB call by the calling domain again, and the UE side and the network side cooperate to execute a CSFB procedure, and finally may establish a voice call in the CS domain.

After step 2219, if the P-CSCF has received the 183 response message, the P-CSCF may send a cancel (cancel) message to a node in the IMS network, such as the S-CSCF, to cancel the requested IMS voice service related call.

It should be noted that, in the process of switching the UE from the 5G network to the EPS network, the mobility management network element serving the UE is converted from the AMF to the MME, and therefore, the MME allocates a new Globally Unique Temporary Identity (GUTI) to the UE. Referring to fig. 22, after the handover procedure, the UE sends a Tracking Area Update (TAU) request to the MME, and when the MME receives the TAU request sent by the NG RAN, the MME brings the allocated new GUTI to the UE through a TAU accept message, so that the UE replies a TAU complete message (i.e., a joint registration complete message) to the MME after receiving the TAU accept message carrying the new GUTI.

In the foregoing description of this embodiment, the purpose of the MME sending the tunnel establishment response to the SGW after determining that the UE completes the joint registration procedure of the EPS and CS domains is to ensure that the message with the QCI ═ 1 that the user plane tunnel establishment is unsuccessful arrives at the IMS network after the UE completes the joint registration procedure of the EPS and CS domains, so that the 500 response message sent by the IMS network may arrive at the UE after the UE completes the joint registration procedure of the EPS and CS domains, and finally, the UE is ensured to successfully initiate the CSFB call.

In order to ensure that the 500 response message sent by the IMS network may reach the UE after the UE completes the joint registration procedure of the EPS and CS domains, in addition to enabling the MME to send the tunnel establishment response to the SGW after determining that the UE completes the joint registration procedure of the EPS and CS domains, the method may be implemented in any one of the following manners 1 to 5.

In the mode 1, the SMF + PGW-C delays to send a tunnel establishment request to the SGW according to a second condition for a first preset time period.

In the method 1, the second condition includes that the EPS network cannot perform the IMS voice service.

In the mode 2, the SMF + PGW-C delays the first preset time period to send the CCR to the PCF + PCRF.

In the mode 3, after acquiring the indication information of insufficient radio resources or the indication information of resource allocation failure, the P-CSCF delays to send 500 the response message to the UE for a second preset time period.

In the mode 4, after the SMF + PGW-C sends the CCR to the PCF + PCRF, the SMF + PGW-C instructs the UPF + PGW-U to cache data on the user plane tunnel with QCI ═ 5 sent to the UE for a first preset time period, and after the first preset time period elapses, the UPF + PGW-U may continue to send the data to the UE.

Mode 5, the P-CSCF sends 500 a response message to the UE after determining that the UE completes the joint registration.

Mode 5, when implemented, may include: after the P-CSCF determines that the voice service cannot be established in the PS domain of the 5G network or the EPS network within a second preset time period, the P-CSCF determines that the terminal equipment completes the joint registration; or, the P-CSCF determines that the terminal device completes the joint registration according to the registration location information of the terminal device obtained from the HSS/home location register (HLR for short).

The first preset time period and the second preset time period may be set according to actual network communication conditions, for example, both the first preset time period and the second preset time period may be 500 ms.

The embodiment also provides a method for network handover of a called UE, referring to fig. 23, the method includes:

2301-2304。

the steps 2301 and 2304 are respectively the same as the steps 1901 and 1904.

2305-2320。

The steps 2305 and 2320 correspond to the steps 2203 and 2218, respectively.

2321. And the P-CSCF sends 500 response messages to the TAS in the IMS network through the S-CSCF after the P-CSCF receives the acquired indication information of the insufficient wireless resources (or the indication information of the failure of resource allocation), wherein the 500 response messages are specifically sent to a called domain selection function module T-ADS in the TAS.

2322. And after acquiring the indication information of insufficient radio resources (or the indication information of resource allocation failure), the P-CSCF sends a cancellation message to the UE to cancel the requested IMS voice service related session.

Step 2321 and step 2322 do not define a precedence relationship.

After step 2322, the TAS in the IMS network selects a called session relocation domain to the CS domain, and initiates a call to a CS domain call control device (e.g., a Mobile Switching Center (MSC)) through a device such as an S-CSCF, the CS domain call control device initiates a call to the MME through an SGs interface, the MME triggers a CSFB procedure of the UE, and the UE may finally establish a voice session in the CS domain through the CSFB procedure of the UE. The details of the specific flow are described in 3GPP TS 23.272. And will not be described in detail herein.

In the foregoing description of this embodiment, the MME sends the tunnel establishment response to the SGW after determining that the UE completes the joint registration procedure of the EPS and CS domains, so as to ensure that the message with the QCI ═ 1 that the user plane tunnel establishment is unsuccessful reaches the IMS network after the UE completes the joint registration procedure of the EPS and CS domains, so that the 500 response message sent by the IMS network may reach the TAS after the UE completes the joint registration procedure of the EPS and CS domains, and finally ensure that the IMS callee can be converted into a CSFB callee to reach the UE.

In order to ensure that the 500 response message sent by the IMS network may reach the TAS after the UE completes the joint registration procedure of the EPS and CS domains, in addition to enabling the MME to send the tunnel establishment response to the SGW after determining that the UE completes the joint registration procedure of the EPS and CS domains, the method may be implemented in any one of the following modes 1 to 5.

In the method 3, after acquiring the indication information of insufficient radio resources (or the indication information of resource allocation failure), the P-CSCF delays to send 500 the response message to the TAS for a second preset time period.

In the method 4, after the SMF + PGW-C sends the CCR to the PCF + PCRF, the SMF + PGW-C instructs the UPF + PGW-U to cache data (which may be a cancellation message) on the user plane tunnel with QCI ═ 5 sent to the UE for a first preset time period, and after the first preset time period elapses, the UPF + PGW-U may continue to send the data to the UE.

Mode 5, the P-CSCF sends 500 a response message to the TAS after determining that the UE completes the joint registration.

Mode 5, when implemented, may include: after the P-CSCF determines that the voice service cannot be established in the PS domain of the 5G network or the EPS network within a second preset time period, the P-CSCF determines that the terminal equipment completes the joint registration; or the P-CSCF determines that the terminal equipment completes the joint registration according to the registration position information of the terminal equipment obtained from the HSS/HLR.

Example (4)

The embodiment provides a method for a calling UE to perform network handover, referring to fig. 24, 25, 26 and 27, the method includes:

2401-2406。

the steps 2401 and 2406 are the same as the steps 1801 and 1806, respectively.

Since the scenario applied in this embodiment is a scenario in which the 5G network cannot perform the IMS voice service and the EPS network cannot perform the IMS voice service, in order to ensure that the UE successfully initiates the CSFB call, the 500 response message sent by the IMS network needs to reach the UE after the UE completes the joint registration procedure between the EPS and the CS domain.

In order to ensure that the UE successfully initiates the CSFB call, after step 2406, the network handover of the UE may be completed through any one of the following procedure 1 (see fig. 24), procedure 2 (see fig. 25), procedure 3 (see fig. 26), and procedure 4 (see fig. 27).

Process 1:

a1, NG RAN sends a switching request to AMF according to the received first SM information and the first condition to trigger UE to switch from the 5G network to the EPS network.

In this case, the first condition may include the following conditions: (1) the 5G network can not carry out IMS voice service, the condition indicates that the 5G network does not deploy IMS voice service, or the signal coverage of the current 5G network is not enough to meet the requirement of the IMS voice service; (2) the network equipment (AMF, NG RAN, etc.) and the UE of the 5G network support the switching between the 5G network and the EPS network, wherein whether the UE and the AMF support the switching between the 5G network and the EPS network or not can be informed to the NG RAN through an N2 message when the UE is changed from an idle state to a connected state by the AMF. (3) The EPS network does not support voice services, and this condition may be configured on the NG RAN by the operator as a local policy; (4) the signal quality of the EPS network does not meet the voice service requirement, and the NG RAN can determine whether the signal quality of the EPS network meets the voice service requirement or not by indicating the UE to measure and report the signal quality of the peripheral EPS cells.

A2, in the process of switching the UE from the 5G network to the EPS network, the process of preparing for switching is ended, and the NG RAN sends a switching command (handover command) to the UE.

A3, NG RAN sends N2session response to AMF according to the first condition, the N2session response carries fourth SM information, the fourth SM information comprises information that the establishment of the user plane tunnel of the IMS voice service is refused, and the information that the establishment of the user plane tunnel of the IMS voice service is refused comprises the lack of radio resources (or the failure of resource allocation).

A4, AMF sends a session management response carrying the PDU session modification command to SMF + PGW-C according to the received N2session response, wherein the fourth SM information is transmitted to SMF + PGW-C.

And after the A5 and the SMF + PGW-C analyze the fourth SM information, sending a PDU-CAN session modification message to the PCF + PCRF.

The PDU-CAN session modification message includes information for indicating that the user plane tunnel of the IMS voice service is failed to be established, where the indication information may be indication information of insufficient radio resources (or indication information of failure in resource allocation).

A6, PCF + PCRF sends RAR to P-CSCF, which can carry information for indicating the failure of establishing user plane tunnel of IMS voice service.

And the A7 and the P-CSCF determine that the IMS voice service can not be established in the PS domain according to the received information for indicating the failure of establishing the user plane tunnel.

The A8, P-CSCF sends 500 a response message to the UE, which reaches the UPF + PGW-U.

Wherein the 500 response message is transmitted to the UE via a tunnel (specifically a certain QoS flow) of the 5G network.

A9, in the process of switching the UE from the 5G network to the EPS network, the MME determines that the UE completes the joint registration.

A10, the MME sends a tunnel modification request of the QCI-5 user plane tunnel to the SMF + PGW-C through the SGW, for indicating the downward SGW user plane address and tunnel information of the QCI-5 dedicated bearer to the SMF + PGW-C.

A11 and SMF + PGW-C send a tunnel modification request to UPF + PGW-U, and indicate the downstream SGW user plane address and tunnel information of QCI-5 special load to UPF + PGW-U. And then the SMF + PGW-C feeds back a tunnel modification response to the MME through the SGW.

A12, UPF + PGW-U forwards user plane data on QCI ═ 5 dedicated bearer to the UE, i.e. a 500 response message is sent to the UE.

After step a12, the UE initiates a CSFB calling voice service, and the UE side and the network side cooperate to execute a CSFB procedure, and finally a voice call may be established in the CS domain.

Since the UE has left the 5G network and accesses the EPS network at this time, after the 500 response message reaches the UPF + PGW-U, the UE will be sent by the UPF + PGW-U through an IMS signaling tunnel (user plane tunnel with QCI ═ 5) of the EPS network. If the P-CSCF has received the 183 response message, the P-CSCF may send a cancel message to a node in the IMS network, such as the S-CSCF, to cancel the call related to the requested IMS voice service.

In the process 1, because the UPF + PGW-U sends the 500 response message to the UE after receiving the tunnel modification request, the MME sends the tunnel modification request of the user plane tunnel with QCI ═ 5 to the SMF + PGW-C and then to the UPF + PGW-U after determining that the UE completes the joint registration, so that the 500 response message sent by the IMS network reaches the UE after the UE completes the joint registration procedure of the EPS and CS domains, thereby providing a guarantee for the UE to successfully initiate the CSFB call.

And (2) a process:

b1, NG RAN sends N2session response to AMF according to the first condition, N2session response carries fourth SM information, the fourth SM information comprises information that the establishment of the user plane tunnel of the IMS voice service is refused, and the information that the establishment of the user plane tunnel of the IMS voice service is refused comprises the lack of radio resources (or the failure of resource allocation).

Specifically, the NG RAN may determine the fourth SM information according to the first condition.

In this case, the first condition may include the following conditions: (1) the 5G network can not carry out IMS voice service, the condition indicates that the 5G network does not deploy IMS voice service, or the signal coverage of the current 5G network is not enough to meet the requirement of the IMS voice service; (2) the network equipment (AMF, NG RAN and the like) and the UE of the 5G network support the switching between the 5G network and the EPS network, wherein whether the UE and the AMF support the switching between the 5G network and the EPS network or not can be informed to the NG RAN through an N2 message when the UE is changed from an idle state to a connected state by the AMF; (3) the EPS network does not support voice services, and this condition may be configured on the NG RAN by the operator as a local policy; (4) the signal quality of the EPS network does not meet the voice service requirement, and the NG RAN can determine whether the signal quality of the EPS network meets the voice service requirement or not by indicating the UE to measure and report the signal quality of the peripheral EPS cells.

And B2, the AMF sends a session management response carrying the PDU session modification command to the SMF + PGW-C according to the received N2session response, wherein the fourth SM information is transmitted to the SMF + PGW-C in a transparent mode.

B3, SMF + PGW-C determines to keep notifying PCF + PCRF, namely suspend notifying PCF + PCRF of the information that the establishment of the user plane tunnel of the voice service is refused.

B4, the NG RAN sends a handover request to the AMF according to the first condition and the first SM information.

B5, in the switching process, the MME determines that the UE completes the joint registration.

B6, the MME sends a tunnel modification request of the user plane tunnel with QCI-5 to the SMF + PGW-C through the SGW, for indicating the downlink SGW user plane address and tunnel information to the SMF + PGW-C.

B7, SMF + PGW-C sends a tunnel modification request to UPF + PGW-U, and indicates, to UPF + PGW-U, a downlink SGW user plane address and tunnel information, which are exclusively carried by QCI ═ 5. And then the SMF + PGW-C feeds back a tunnel modification response to the MME through the SGW.

B8, SMF + PGW-C sends IP CAN conversation modifying information to PCF + PCRF.

The IP CAN session modification message carries information for indicating that the user plane tunnel of the IMS voice service has failed to be established, and the indication information may be indication information of insufficient radio resources (or indication information of failure in resource allocation). In this embodiment, the message name is not limited to the IP-CAN session modification message, and may be other message names, such as CCR.

B9, PCF + PCRF sends RAR to P-CSCF, the RAR carries the information used for indicating the failure of establishing the user plane tunnel of IMS voice service.

And B10, the P-CSCF determines that the IMS voice service can not be established in the PS domain according to the received information for indicating the failure of establishing the user plane tunnel.

The B11, P-CSCF sends 500 a response message to the UE.

After step B11, the UE initiates a CSFB calling voice service, and the UE side and the network side cooperate to execute a CSFB procedure, and finally a voice call may be established in the CS domain.

In the process 2, the P-CSCF sends the 500 response message to the UE after determining that the user plane tunnel of the IMS voice service fails to be established, and the PCF + PCRF sends the information indicating that the user plane tunnel of the IMS voice service fails to be established to the P-CSCF after the MME determines that the UE completes the joint registration, so that the 500 response message sent by the IMS network reaches the UE after the UE completes the joint registration procedure of the EPS and CS domains, thereby providing a guarantee for the UE to successfully initiate the CSFB call.

And 3, process:

and C1, the NG RAN sends an N2session response to the AMF according to the first condition, the N2session response carries fourth SM information, the fourth SM information comprises information that the establishment of the user plane tunnel of the IMS voice service is refused, and the information that the establishment of the user plane tunnel of the IMS voice service is refused comprises insufficient radio resources (or resource allocation failure).

And C2, the AMF sends a session management response carrying the PDU session modification command to the SMF + PGW-C according to the received N2session response, wherein the fourth SM information is transmitted to the SMF + PGW-C in a transparent mode.

And the C3 and the SMF + PGW-C send an N4 session modification request to the UPF + PGW-U according to the received session management response carrying the PDU session modification command sent by the AMF.

The N4 session modification request includes a first command instructing the UPF + PGW-U to cache data on the user plane tunnel with 5QI ═ 5.

And C4, the UPF + PGW-U feeds back an N4 session modification response to the SMF + PGW-C according to the received N4 session modification request.

C5, SMF + PGW-C sends PDU CAN conversation amending message to PCF + PCRF.

The PDU CAN session modification message carries information for indicating that the user plane tunnel of the IMS voice service is failed to be established, and the indication information may be indication information of insufficient radio resources (or indication information of failure in resource allocation). In this embodiment, the message name is not limited to the IP-CAN session modification message, and may be other message names, such as CCR.

C6, PCF + PCRF sends RAR to P-CSCF, RAR carries the information used for pointing out the user plane tunnel of IMS voice service is set up and failed.

And C7, P-CSCF feeds back RAA to PCF + PCRF.

And C8, the P-CSCF determines that the IMS voice service can not be established in the PS domain according to the received information for indicating the failure of establishing the user plane tunnel.

The C9, P-CSCF sends 500 a response message to the UE, which reaches the UPF + PGW-U.

C10 and UPF + PGW-U buffer data on the 5QI ═ 5 user plane tunnel.

The data on the 5 QI-5 user plane tunnel may include a 500 response message.

C11, the NG RAN sends a handover request to the AMF according to the first condition and the first SM information.

C12, MME determines that UE completes the joint registration.

C13, the MME sends, to the SMF + PGW-C, a tunnel modification request (modify bearer request) of the user plane tunnel with QCI ═ 5 through the SGW, so as to indicate the downlink SGW user plane address and tunnel information to the SMF + PGW-C.

C14, SMF + PGW-C sends a tunnel modification request to UPF + PGW-U, where the tunnel modification request includes a second command, and the second command is used to instruct UPF + PGW-U to stop buffering information of data on QCI ═ 1.

After step C14, the UPF + PGW-U will send a 500 response message to the UE, the UE initiates the CSFB calling voice service, the UE side and the network side cooperate to execute the CSFB procedure, and finally, the voice call may be established in the CS domain.

In the process 3, the 500 response message sent by the P-CSCF is cached in the UPF + PGW-U through the first command, and after the MME determines that the UE completes the joint registration, the P-CSCF sends the 500 response message to the terminal device through the second command, so that the 500 response message sent by the IMS network reaches the UE after the UE completes the joint registration procedure of the EPS and CS domains, thereby providing a guarantee for the UE to successfully initiate a CSFB call.

And 4, process:

d1, NG RAN sends N2session response to AMF according to the first condition, N2session response carries fourth SM information, the fourth SM information includes information that the establishment of the user plane tunnel of the IMS voice service is refused, and the information that the establishment of the user plane tunnel of the IMS voice service is refused includes that the radio resources are insufficient (or the resource allocation is failed).

D2, the AMF sends a session management response carrying the PDU session modification command to the SMF + PGW-C according to the received N2session response, wherein the fourth SM information is transmitted to the SMF + PGW-C.

D3, SMF + PGW-C sends PDU CAN conversation amending message to PCF + PCRF. In this embodiment, the message name is not limited to the IP-CAN session modification message, and may be other message names, such as CCR.

The PDU CAN session modification message carries information for indicating that the user plane tunnel of the IMS voice service is failed to be established, and the indication information may be indication information of insufficient radio resources (or indication information of failure in resource allocation).

D4, PCF + PCRF sends RAR to P-CSCF, RAR carries the information used for pointing out the user plane tunnel of IMS voice service is set up and failed.

D5, P-CSCF according to received information used for indicating user plane tunnel establishment failure, determines that IMS voice service can not be established in PS domain.

And D6, P-CSCF feeds back RAA message to PCF + PCRF.

The D7, P-CSCF determines to delay sending 500 the response message for a second preset time period.

And D8, the NG RAN sends a switching request to the AMF according to the received first SM information and the first condition to trigger the UE to be switched from the 5G network to the EPS network.

After step D8, the UE executes the handover procedure, and after the handover procedure is finished, the P-CSCF sends 500 a response message to the UE, the UE initiates the CSFB call voice service, and the UE side and the network side cooperate to execute the CSFB procedure, and finally, a voice call may be established in the CS domain.

In the process 4, the P-CSCF delays the sending of the 500 response message for the second preset time period, so that the 500 response message sent by the IMS network reaches the UE after the UE completes the joint registration procedure of the EPS and CS domains, thereby providing a guarantee for the UE to successfully initiate the CSFB call.

Since the scenario applied in this embodiment is that the 5G network cannot perform the IMS voice service and the EPS network cannot perform the IMS voice service, in order to ensure that the UE successfully initiates the CSFB call, the 500 response message sent by the IMS network needs to reach the TAS after the UE completes the joint registration procedure between the EPS and the CS domain, so that the TAS can select the UE to the CS domain again, thereby ensuring that the CSFB call is successful. Referring to fig. 28, the method includes:

2801-2808。

the steps 2801 and 2808 are the same as the steps 1901 and 1908, respectively.

2809-2814。

Steps 2809-2814 are the same as steps D1-D6, respectively.

2815. The P-CSCF delays sending 500 the response message to the TAS for a second preset time period. The 500 response message is specifically sent to the called domain selection function module T-ADS in the TAS.

And the P-CSCF delays the second preset time period to send the 500 response message, so that the 500 response message sent by the P-CSCF reaches the TAS after the UE completes the joint registration process of the EPS and the CS domains, and the CSFB call is ensured to be successful.

The network handover methods provided in embodiments (3) and (4) can enable the 5G terminal device to handover to the EPS network in the IMS voice session establishment phase, and then enable the UE to fall back to the 2G/3G network by using the CSFB technique in the EPS network, and finally initiate a voice call in the CS domain of the 2G/3G network. The method for performing the voice service under the scene that the IMS voice service can not be performed in both the 5G network and the EPS network is provided for the terminal equipment in the 5G network by using the EPS network as the springboard and reusing the traditional 2G/3G network architecture.

The 500 response message in the above embodiments (1) to (4) may also be a 380 response message or a 503 response message, and the RAR message may also be a session termination request (ASR) message, in which case the RAA message may be an abort response to session (ASA) message.

An embodiment of the present application further provides a network registration method, as shown in fig. 28A, the method includes:

2801A, the first mobility management network element receives a registration request (registration request) from the terminal device, the registration request being for requesting that the terminal device be registered with the first network.

The first mobility management network element may be an AMF, and the first network may be a 5G network.

2802A, if the third condition is met, the first mobility management network element sends first indication information to the terminal device, where the first indication information is used to indicate that the voice service in the PS domain is supported.

Wherein the third condition may include: the first network supports moving the terminal device to the second network. The first network supporting movement of the terminal device to the second network may refer to the first network supporting movement of the terminal device to the second network through handover or redirection or other means.

Optionally, the moving the terminal device to the second network supported by the first network may include: the first access network device in the first network supports the terminal device to access the second network when receiving the first session management information from the session management network element, and the first session management information is used for requesting to establish a user plane tunnel for the voice service of the terminal device. The first access network device may be an NG RAN, and the session management network element may be an SMF + PGW-C functional network element.

For example, the first indication information may be carried in a registration acceptance message, the voice service may be an IMS voice service, and the terminal device may specifically be a terminal device that initiates a calling or called voice service.

Specifically, the first mobility management network element may determine whether the third condition is satisfied by any one of the following manners or other manners:

(1) in the process that the terminal device is registered in the first network, the first mobility management network element determines whether the third condition is satisfied by acquiring whether the access network device and/or the core network element device where the current terminal device is located has the capability of moving the terminal device to the second network.

(2) The first mobility management network element determines whether the third condition is satisfied according to a configuration condition of the first mobility management network element, where the configuration condition configures whether the access network device and/or the core network element device where the terminal device is located can move the terminal device to the second network.

Optionally, the core networks of the first network and the second network are the same, and the access modes are different; or the core network and the access system of the first network and the second network are different.

The second network may be an EPS network when the core networks and the access systems of the first network and the second network are different, and the first network and the second network may be both 5G networks when the core networks and the access systems of the first network and the second network are the same and different, except that the access systems of the first network and the second network are different.

Specifically, the first access network device may access the terminal device to the second network by sending a handover request for handover of the terminal device from the first network to the second network to the first mobility management network element. It should be noted that, when the terminal device initiates the PS domain voice service, the first access network device accesses the terminal device to the second network, and the terminal device may be a terminal device that initiates the calling PS domain voice service or a terminal device that initiates the called PS domain voice service.

Optionally, the third condition may further include: handover interoperability is supported between the first network and the second network. In this case, the first network supports moving the terminal device to the second network by handover.

Optionally, the supporting, switching and interoperating between the first network and the second network includes: a handover interoperation interface exists between the first network and the second network. Illustratively, the switching interoperation interface may be specifically an N26 interface.

Optionally, the second network may support a PS domain voice service, or may not support a PS domain voice service. If the second network is defined to support PS domain voice service, the third condition may further include: the second network is capable of supporting PS domain voice services.

Optionally, before step 2803A, the method may further comprise: the first mobility management network element determines that the terminal equipment is the terminal equipment mainly based on the voice service. Since the terminal device based on the data service is not related to the voice service, the optional method can distinguish the terminal type, and the terminal device based on the data service does not need to execute the set of scheme, that is, whether the third condition is satisfied or not does not need to be determined, and the first indication information does not need to be sent.

Optionally, the method may further include: the terminal equipment generates a registration request, and the registration request carries indication information of the terminal equipment which is mainly based on voice service; the terminal equipment sends a registration request to a first mobility management network element; in this case, the determining, by the first mobility management network element, that the terminal device is a terminal device mainly based on the voice service includes: and the first mobility management network element determines the terminal equipment as the terminal equipment mainly based on the voice service according to the registration request.

In this case, the terminal device carries the indication information that the terminal device is a terminal device mainly based on the voice service through the registration request, so that the first mobility management network element does not need to send a signaling separately to inform the indication information, and signaling overhead can be saved.

Optionally, before step 2803A, the method may further comprise: the first mobility management network element determines that the terminal equipment supports moving from the first network to the second network in the voice service initiating process and continues the voice service initiating process through the second network. The method can be implemented only when the terminal device supports the process of moving from the first network to the second network and continuing the voice service initiation process through the second network in the voice service initiation process, so that the information can be determined in advance, and the influence on the terminal device which cannot support the process of moving from the first network to the second network and continuing the voice service initiation process through the second network in the voice service initiation process is avoided.

Optionally, the registration request further carries indication information that the terminal device supports an initiation process of moving from the first network to the second network and continuing the voice service through the second network in the voice service initiation process, and the first mobility management network element determines that the terminal device supports an initiation process of moving from the first network to the second network and continuing the voice service through the second network in the voice service initiation process, including: and the first mobility management network element determines that the terminal equipment supports the process of moving from the first network to the second network in the process of initiating the voice service and continuing the process of initiating the voice service through the second network according to the registration request.

In this case, the terminal device supports, through the registration request, the indication information that the terminal device moves from the first network to the second network in the voice service initiation process and continues the voice service initiation process through the second network, so that the terminal device does not need to separately send a signaling to inform the first mobility management network element of the indication information, and signaling overhead can be saved.

It should be noted that the method provided in this embodiment may be performed before any one of the methods described before fig. 28. In addition, the first mobility management element may also send the first indication information to the terminal device not in the third condition but in other conditions.

In the method provided by this embodiment, no matter whether the first network supports the voice service of the terminal device, as long as the first network has the capability of dropping the terminal device back to the network capable of providing the voice service through handover or other manners when the terminal device initiates the voice service, when the terminal device registers with the first network, the first mobility management network element indicates that the voice service of the PS domain of the terminal device is supported, so as to ensure that the terminal device registers and resides in the first network without reselecting to other networks, save network resources, and ensure that the terminal device normally executes a PS domain voice service registration procedure and initiates a PS domain voice call procedure through the first network.

An embodiment of the present application further provides a network registration method, as shown in fig. 28B, for specifically describing the method shown in fig. 28A, where the method includes:

2801B, UE sends a registration request to the AMF.

Specifically, the registration request is for requesting that the UE be registered with the first network, and the UE may send the registration request to the NG RAN, which forwards the registration request to the AMF.

The registration request may carry indication information that the UE is a UE that mainly uses a voice service and indication information that the UE supports an initiation process of moving from a first network to a second network and continuing the voice service through the second network in the initiation process of the voice service.

2802B, AMF receives a registration request from the UE.

2803B, AMF determines from the registration request that the UE supports movement from the first network to the second network during initiation of the voice service and continues the initiation of the voice service through the second network.

2804B, AMF determines that the UE is mainly voice service according to the registration request.

The execution sequence of step 2803B and step 2804B is not sequential.

2805B, AMF determines if the third condition holds.

If so, go to step 2806B. Wherein the third condition includes: the first network supports moving the UE to the second network, which is capable of supporting voice services in the PS domain. Fig. 28B is drawn by taking the case where the third condition is determined by AMF as an example.

2806B, AMF transmits first indication information to the UE, the first indication information indicating that voice service of the PS domain is supported.

The first indication information may be carried in the registration acceptance message.

After step 2806B, the UE continues with the subsequent procedure.

The above-mentioned scheme provided by the embodiment of the present application is introduced mainly from the perspective of interaction between network elements. It is understood that each network device described above, in order to implement the above functions, includes a corresponding hardware structure and/or software module for performing each function. Those of skill in the art would readily appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as hardware or combinations of hardware and computer software. Whether a function is performed as hardware or computer software drives hardware depends upon the particular application and design constraints imposed on the solution. 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.

In the embodiment of the present application, functional modules may be divided according to the above method examples for each network device, for example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. It should be noted that, in the embodiment of the present application, the division of the module is schematic, and is only one logic function division, and there may be another division manner in actual implementation.

The following is an exemplary embodiment of a functional module division manner of a network device provided in the embodiments of the present application.

The embodiment of the present application further provides a network device 290, see fig. 29, including a processing unit 2901 and a transceiving unit 2902.

The network device may be a first access network device, a session management network element, a second mobility management network element, a second access network device, an IMS network element, or a first mobility management network element.

Specifically, when fig. 29 is a schematic diagram of a first access network device, the processing unit 2901 is configured to receive, through the transceiving unit 2902, first session management information from a session management network element, where the first session management information is used to request to establish a user plane tunnel for a voice service of a terminal device; sending, by the transceiving unit 2902, a handover request to the first mobility management network element according to the first session management information and a first condition, the handover request being used for handing over the terminal device from the first network to the second network, the first condition including: the first network is not capable of voice traffic.

Optionally, the first condition further includes: the second network supports voice services, the signal quality of the second network meets at least one of voice service requirements and network equipment of the first network, and the terminal equipment supports handover between the first network and the second network.

Optionally, the processing unit 2901 is further configured to send, by the transceiving unit 2902, second session management information to the session management network element, where the second session management information includes information that establishment of a user plane tunnel of the voice service is accepted.

Optionally, the processing unit 2901 is further configured to determine, according to the first session management information and the first condition, that no radio resource is allocated for the user plane tunnel of the voice service.

Optionally, the processing unit 2901 is further configured to send, by the transceiving unit 2902, third session management information to the session management network element, where the third session management information includes information that establishment of the user plane tunnel of the voice service is rejected.

Optionally, the information that the establishment of the user plane tunnel of the voice service is rejected includes reason information of the rejection.

Optionally, the reason information is that the terminal device is executing a handover procedure.

Optionally, the first condition further includes: the second network cannot perform the voice service, and the processing unit 2901 is further configured to send fourth session management information to the session management network element through the transceiving unit 2902, where the fourth session management information includes information that the establishment of the user plane tunnel of the voice service is rejected, and the information that the establishment of the user plane tunnel of the voice service is rejected includes that the radio resource is insufficient.

When the terminal device in the first network performs the voice service, the network device 290 may switch the terminal device to the second network, so that the terminal device may perform the voice service in the second network, and the problem that the terminal device in the first network cannot perform the voice service is solved.

When fig. 29 is a schematic diagram of a session management network element, the processing unit 2901 is configured to receive, through the transceiving unit 2902, third session management information sent by the first access network device, where the third session management information includes information of a reason why the establishment of the user plane tunnel of the voice service of the terminal device is rejected; determining that the terminal device is switched from a first network to a second network; and establishing a user plane tunnel for the voice service in the second network according to the reason information.

Optionally, the processing unit 2901 is specifically configured to establish a user plane tunnel for the voice service in the second network after a first preset time period according to the reason information and a second condition, where the second condition includes that the voice service cannot be performed by the second network.

Optionally, the processing unit 2901 is specifically configured to send, by the transceiving unit 2902, a tunnel establishment request to the service gateway of the second network after the first preset time period according to the reason information and the second condition, where the tunnel establishment request is used to request to establish a user plane tunnel of the voice service.

Optionally, the processing unit 2901 is specifically configured to send, by the transceiving unit 2902, a tunnel establishment request to the service gateway of the second network according to the reason information, where the tunnel establishment request is used to request establishment of a voice service user plane tunnel; receiving, by the transceiver 2902, a tunnel establishment response sent by the serving gateway, where the tunnel establishment response includes information that establishment of a user plane tunnel of the voice service is denied; sending, by the transceiving unit 2902, a first message to a policy function control network element after the first preset time period according to the second condition, where the first message is used to indicate that the establishment of the user plane tunnel of the voice service fails.

When the terminal device in the first network is switched from the first network to the second network, the network device 290 establishes a user plane tunnel for the voice service in the second network according to the reason information, and if the second network can perform the voice service, the user plane tunnel can be successfully established, so that the terminal device can perform the voice service in the second network, and the problem that the terminal device in the first network cannot perform the voice service is solved.

When the schematic diagram of the second mobility management element is shown in fig. 29, the network device 290 may perform the following action one, action two, action three, or action four.

Action one, the processing unit 2901 is configured to receive a tunnel establishment request sent by a service gateway through the transceiving unit 2902, where the tunnel establishment request is used to request to establish a user plane tunnel for a voice service for a terminal device; sending, by the transceiving unit 2902, a tunnel establishment response to the serving gateway according to a second condition, where the tunnel establishment response includes information that establishment of a user plane tunnel of the voice service of the terminal device is rejected, and the second condition includes that the voice service cannot be performed by a second network.

Optionally, the second condition further includes: the terminal device is a terminal device that is switched from a first network to the second network.

Optionally, the processing unit 2901 is further configured to determine that the terminal device has completed joint registration.

The processing unit 2901 is specifically configured to determine that a joint registration completion message is received from the terminal device.

Network device 290 sends a tunnel establishment response to the serving gateway when the second network cannot perform the voice service, so that the serving gateway transmits the information that the establishment of the user plane tunnel is rejected to the IMS network, thereby enabling the IMS network to trigger the CSFB service of the terminal device, and further enabling the terminal device to perform the CS voice service.

Action two, the processing unit 2901 is configured to send a wireless tunnel establishment request to the second access network device through the transceiving unit 2902, where the wireless tunnel establishment request is used to request to establish a user plane tunnel for the voice service of the terminal device; receiving, by the transceiving unit 2902, a radio tunnel establishment response sent by the second access network device, where the radio tunnel establishment response includes information that establishment of a user plane tunnel of the voice service of the terminal device is rejected; sending, by the transceiving unit 2902, a tunnel establishment response to the serving gateway according to a second condition, where the tunnel establishment response includes information that the user plane tunnel establishment of the voice service of the terminal device is rejected, and the second condition includes that the voice service cannot be performed by the second network.

Optionally, the processing unit 2901 is specifically configured to determine that the second condition is satisfied and that the terminal device completes joint registration; a tunnel establishment response is sent to the serving gateway through the transceiving unit 2902.

Optionally, the processing unit 2901 is specifically configured to determine that a registration completion message from the terminal device is received.

The network device 290 sends the information that the establishment of the user plane tunnel is rejected to the serving gateway, so that the serving gateway transmits the information that the establishment of the user plane tunnel is rejected to the IMS network, so that the IMS network triggers the CSFB service of the terminal device, and the terminal device performs the CS voice service.

Action three, the processing unit 2901 is configured to receive, through the transceiving unit 2902, a tunnel establishment request sent by the service gateway, where the tunnel establishment request is used to request establishment of a user plane tunnel of a voice service for the user equipment terminal device; if a second condition is established, determining that the terminal equipment completes joint registration, wherein the second condition comprises that a second network cannot perform the voice service; sending a wireless tunnel establishment request to a second access network device through the transceiving unit 2902, where the wireless tunnel establishment request is used to request establishment of a user plane tunnel for a voice service of the terminal device; receiving, by the transceiving unit 2902, a radio tunnel establishment response sent by the second access network device, where the radio tunnel establishment response includes information that establishment of a user plane tunnel of the voice service of the terminal device is rejected; sending, by the transceiving unit 2902, a tunnel establishment response to the serving gateway according to the wireless tunnel establishment response, where the tunnel establishment response includes information that establishment of a user plane tunnel of the voice service of the terminal device is rejected.

Optionally, the processing unit 2901 is specifically configured to determine that the registration completion message sent by the terminal device is received.

After determining that the terminal device completes the joint registration, the network device 290 sends the information that the establishment of the user plane tunnel is rejected to the serving gateway, so that the serving gateway transmits the information that the establishment of the user plane tunnel is rejected to the IMS network, thereby enabling the IMS network to trigger the CSFB service of the terminal device, further enabling the terminal device to perform the CS voice service, and further ensuring that the terminal device successfully initiates a CSFB call.

Action four, the processing unit 2901 is configured to receive, through the transceiving unit 2902, a fourth message sent by the first mobility management network element, where the fourth message is used to confirm that the terminal device completes relocation; sending, by the transceiving unit 2902, a tunnel modification request to a serving gateway according to a second condition, where the tunnel modification request is used to modify signaling plane tunnel information of the voice service of the terminal device, and the second condition includes that the voice service cannot be performed by a second network.

Optionally, the processing unit 2901 is specifically configured to determine that the second condition is satisfied and that the UE completes joint registration; the tunnel modification request is sent to the service gateway through the transceiving unit 2902.

When the second network cannot perform the voice service, the network device 290 sends a tunnel modification request to the serving gateway, and the serving gateway forwards the tunnel modification request to the session management network element, and since the session management network element sends a message (i.e., the second message in the foregoing) for triggering the terminal device to initiate a CSFB call to the terminal device after receiving the tunnel modification request, the network device 290 may trigger the terminal device to initiate a CSFB call when the second network cannot perform the voice service, so that the terminal device performs the CS voice service.

When fig. 29 is a schematic diagram of a second access network device, a processing unit 2901 is configured to receive, through a transceiving unit 2902, a radio tunnel establishment request sent by a second mobility management network element, where the radio tunnel establishment request is used to request the second access network device to establish a user plane tunnel for a voice service for a terminal device; sending, by the transceiving unit 2902, a radio tunnel establishment response to the second mobility management network element according to a second condition, where the radio tunnel establishment response includes information that establishment of a user plane tunnel of the voice service is rejected, and the second condition includes that the voice service cannot be performed by the second network.

The network device 290 rejects allocating the radio resource to the user plane tunnel when the second network cannot perform the voice service, and carries the rejected information of the user plane tunnel establishment of the voice service in the radio tunnel establishment response to send to the second mobility management network element, and the second mobility management network element may transfer the rejected information of the user plane tunnel establishment to the IMS network, so that the IMS network triggers the CSFB service of the terminal device, and the terminal device performs the CS voice service.

When fig. 29 shows a schematic diagram of an IMS network element, the processing unit 2901 is configured to receive a request message for establishing a voice service in a packet switched PS domain for a terminal device through the transceiving unit 2902; determining that the voice service cannot be established in a PS domain of the first network or the second network; determining that the terminal equipment completes joint registration; and triggering the circuit switched fallback CSFB service of the terminal equipment.

Optionally, the processing unit 2901 is further configured to determine that the terminal device is registered in the first network.

Optionally, the processing unit 2901 is specifically configured to acquire the voice service establishment failure information from the first network PS domain; or, acquiring the voice service establishment failure information from the second network PS domain.

Optionally, the processing unit 2901 is specifically configured to determine that the terminal device completes the joint registration after determining that the voice service cannot be established in the PS domain of the first network or the second network for a second preset time period; or, determining that the terminal device completes the joint registration according to the registration location information of the terminal device obtained from the policy control network element or the home subscriber server.

Optionally, the terminal device is a calling terminal device of the voice service, and the processing unit 2901 is specifically configured to send a second message to the calling terminal device through the transceiving unit 2902, where the second message is used to trigger the calling terminal device to initiate a CSFB calling service.

Optionally, the terminal device is a called terminal device of the voice service, and the processing unit 2901 is specifically configured to send a third message to a called domain selection device through the transceiving unit 2902, where the third message is used to indicate that the called voice service in the PS domain of the first network or the second network fails to be established, so that the called domain selection device triggers the CSFB called voice service of the called terminal device.

The network device 290 triggers the CSFB service of the terminal device when determining that the voice service cannot be established in the PS domain of the first network or the second network and the terminal device completes the joint registration, and since the terminal device completes the joint registration is a necessary condition for the terminal device to initiate a CSFB call, it can be ensured that the terminal device successfully initiates the CSFB call, thereby enabling the terminal device to perform the CS voice service.

When fig. 29 shows a schematic diagram of a first mobility management network element, the processing unit 2901 is configured to receive a registration request from a terminal device through the transceiving unit 2902, where the registration request is used to request that the terminal device be registered in a first network; the processing unit 2901 is further configured to determine that a third condition holds, the third condition comprising: the first network supports moving the terminal equipment to the second network, and the second network can support the voice service of the PS domain; the processing unit 2901 is further configured to send, to the terminal device through the transceiving unit 2902, first indication information for indicating that the voice service of the PS domain is supported.

Optionally, the moving the terminal device to the second network is supported by the first network, including: the first access network device in the first network supports the terminal device to access the second network when receiving the first session management information from the session management network element, and the first session management information is used for requesting to establish a user plane tunnel for the voice service of the terminal device.

Optionally, the third condition further includes: handover interoperability is supported between the first network and the second network.

Optionally, the supporting, switching and interoperating between the first network and the second network includes: a handover interoperation interface exists between the first network and the second network.

Optionally, the processing unit 2901 is further configured to determine that the terminal device is a terminal device mainly based on a voice service.

Optionally, the registration request carries indication information that the terminal device is a terminal device mainly based on a voice service, and the processing unit 2901 is specifically configured to determine that the terminal device is a terminal device mainly based on a voice service according to the registration request.

Optionally, the processing unit 2901 is further configured to determine that the terminal device supports moving from the first network to the second network in the voice service initiating process and continuing the voice service initiating process through the second network.

Optionally, the registration request further carries indication information that the terminal device supports an initiation process of moving from the first network to the second network and continuing the voice service through the second network in the voice service initiation process, and the processing unit 2901 is specifically configured to determine, according to the registration request, that the terminal device supports an initiation process of moving from the first network to the second network and continuing the voice service through the second network in the voice service initiation process.

No matter whether the first network supports the voice service of the terminal device, as long as the first network has the capability of dropping the terminal device back to the network capable of providing the voice service through switching or other ways when the terminal device initiates the voice service, when the terminal device registers to the first network, the first mobility management network element indicates that the voice service of the PS domain of the terminal device is supported, so that the terminal device is ensured to register and reside in the first network without reselecting to other networks, network resources are saved, and the terminal device is ensured to normally execute a PS domain voice service registration process and initiate a PS domain voice call process through the first network.

The embodiment of the present application further provides a terminal device 290A, see fig. 29A, including a processing unit 2901A and a transceiving unit 2902A. The processing unit 2901A is configured to generate a registration request, where the registration request is used to request to register the terminal device in the first network, and the registration request carries indication information that the terminal device is a terminal device mainly using a voice service; the processing unit 2901A is further configured to send a registration request to the first mobility management network element through the transceiving unit 2902A.

Optionally, the registration request further includes indication information that the terminal device supports moving from the first network to the second network during the voice service initiation process and continuing the voice service initiation process through the second network.

When the first network has the capability of dropping the terminal device back to the network capable of providing the voice service through switching or other ways when the terminal device initiates the voice service, the terminal device registers and resides in the first network without reselecting to other networks according to the received first indication information sent by the first mobility management network element, so that network resources are saved, and the terminal device is ensured to normally execute a PS domain voice service registration process and initiate a PS domain voice call process through the first network.

An embodiment of the present application further provides a network device, including: a memory, a processor, and a communication interface; the memory is used for storing computer execution instructions, and the processor executes the computer execution instructions stored in the memory and enables the network equipment to realize a method corresponding to the instructions through the communication interface. A schematic diagram of the network device can be seen in fig. 6.

The network device may be a first access network device, a session management network element, a second mobility management network element, a second access network device, an IMS network element, or a first mobility management network element. Specifically, when fig. 6 and fig. 29 are schematic diagrams of a first access network device, the processing unit 2901 may be the processor 601, and the transceiving unit 2902 may be the communication interface 604; when fig. 6 and 29 are schematic diagrams of a session management network element, the processing unit 2901 may be the processor 601, and the transceiving unit 2902 may be the communication interface 604; when fig. 6 and fig. 29 are schematic diagrams of a second mobility management network element, the processing unit 2901 may be the processor 601, and the transceiving unit 2902 may be the communication interface 604; when fig. 6 and 29 are schematic diagrams of a second access network device, the processing unit 2901 may be the processor 601, and the transceiving unit 2902 may be the communication interface 604; when fig. 6 and fig. 29 are schematic diagrams of an IMS network element, the processing unit 2901 may be the processor 601, and the transceiving unit 2902 may be the communication interface 604; when fig. 6 and fig. 29 are schematic diagrams of a first mobility management network element, the processing unit 2901 may be the processor 601, and the transceiving unit 2902 may be the communication interface 604.

An embodiment of the present application further provides a terminal device, including: a memory, a processor, and a communication interface; the memory is used for storing computer execution instructions, and the processor executes the computer execution instructions stored in the memory and enables the terminal equipment to realize a method corresponding to the instructions through the communication interface. The schematic structure of the terminal device can be seen in fig. 6A. The processing unit 2901A may be the processor 601A, and the transceiving unit 2902A may be the communication interface 604A.

Embodiments of the present application also provide a computer-readable storage medium, which includes instructions that, when executed on a computer, cause the computer to perform the above-mentioned method.

Embodiments of the present application also provide a computer program product containing instructions which, when run on a computer, cause the computer to perform the above method.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented using a software program, 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. The procedures or functions described in accordance with the embodiments of the present application are all or partially generated upon loading and execution of computer program instructions on a computer. 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 on a computer readable storage medium or transmitted from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wire (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)), or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or can comprise one or more data storage devices, such as a server, a data center, etc., that can be integrated with the medium. 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.

While the present application has been described in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a review of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Although the present application has been described in conjunction with specific features and embodiments thereof, it will be evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the application. Accordingly, the specification and figures are merely exemplary of the present application as defined in the appended claims and are intended to cover any and all modifications, variations, combinations, or equivalents within the scope of the present application. It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

1. A method for network handover, comprising:

a session management network element sends session management information to access network equipment in a first network, wherein the session management information sent by the session management network element is used for requesting to establish a user plane tunnel for a voice service of terminal equipment;

the session management network element receives session management information sent by the access network equipment, wherein the session management information sent by the access network equipment comprises the reason information that the establishment of a user plane tunnel of the voice service of the terminal equipment is rejected;

the session management network element determines that the terminal equipment is switched from the first network to a second network;

and after the terminal equipment is switched from the first network to the second network, the session management network element establishes a user plane tunnel for the voice service in the second network according to the reason information.

2. The method of claim 1, wherein the reason information is: the terminal device executes a handover procedure.

3. The method of claim 1, wherein the determining, by the session management network element, that the terminal device is handed over from the first network to the second network comprises:

the session management network element triggers a timer to time when receiving the session management information sent by the access network equipment;

and if the timer finishes timing, the session management network element determines that the terminal equipment is switched from the first network to the second network.

4. The method of claim 1, wherein the determining, by the session management network element, that the terminal device is handed over from the first network to the second network comprises:

the session management network element receives a tunnel modification request from a service gateway in the second network;

and the session management network element determines that the terminal equipment is switched from the first network to the second network according to the tunnel modification request.

5. The method of claim 1, wherein the user plane tunnel is a quality of service flow.

6. The method of claim 1, wherein the session management network element establishing a user plane tunnel for voice traffic in the second network comprises:

and the session management network element sends a tunnel establishment request to a service gateway of the second network, wherein the tunnel establishment request is used for requesting to establish a user plane tunnel of the voice service.

7. The method according to any of claims 1-6, wherein the session management network element is a network element having a packet data network gateway-control plane and session management functions.

8. The method according to any of claims 1-6, wherein the first network is a 5G network and the second network is a 4G network.

9. The method according to any one of claims 1-6, wherein the core networks of the first network and the second network are the same, and the access systems are different; or the core networks and the access modes of the first network and the second network are different.

10. A network device, comprising:

a memory for storing computer execution instructions;

a processor to execute memory-stored computer-executable instructions to cause the network device to perform the method of any of claims 1 to 9.

11. A computer-readable storage medium comprising instructions that, when executed on a computer, cause the computer to perform the method of any of claims 1 to 9.

12. A communication system, comprising:

a session management network element for performing the method of any one of claims 1-9; and

and the access network equipment is used for sending session management information to the session management network element, wherein the session management information comprises the reason information that the establishment of the user plane tunnel of the voice service of the terminal equipment is rejected.