CN114071620B

CN114071620B - Communication method, device and system

Info

Publication number: CN114071620B
Application number: CN202010918194.9A
Authority: CN
Inventors: 陶振宇; 林玮健; 姜传奎
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-08-05
Filing date: 2020-09-03
Publication date: 2024-03-26
Anticipated expiration: 2040-09-03
Also published as: CN114071620A

Abstract

The application discloses a communication method, a device and a system, which relate to the technical field of communication and can reduce the probability of terminal service interruption in an EPS fallback scene. The method is applied to the movement of the terminal from a first preset area of a first network to a second preset area of a second network, wherein the Radio Access Technology (RAT) of the first network is different from the RAT of the second network, and the method comprises the following steps: the method comprises the steps that first core network equipment of a first network determines that an Evolved Packet System (EPS) fallback of a terminal is triggered, and first information is sent to second core network equipment of a second network, wherein the first information comprises a first identifier or first indication information; the first identifier is used for identifying a first proprietary bearer corresponding to the terminal, wherein the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer; the first indication information is used for indicating the terminal to fall back to the second network through the EPS fall-back flow.

Description

Communication method, device and system

The present application claims priority from the chinese patent application filed on month 05 of 2020, filed on the national intellectual property agency, application number 202010780286.5, entitled "communication method, apparatus and system", the entire contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates to the field of communications technologies, and in particular, to a communications method, apparatus, and system.

Background

With the advance of the fifth generation (5th generation,5G) network deployment, users can perform voice services through 5G. When a User Equipment (UE) initiates a voice call or is called in a 5G network, in one possible implementation, the 5G network initiates an evolved packet system fallback (evolved packet system Fallback, EPS FB) procedure, and the UE is fallback from the 5G network to a fourth generation (4th generation,4G) network, for example, a long term evolution (long term evolution, LTE) system, and uses a long term evolution-voice-over-period (VoLTE) technology to provide voice services for a user. That is, during EPS fallback, the UE may switch from the 5G network coverage area to the LTE network coverage area. According to the rules of part of operators, if the UE has a cross-zone, the core network mobility management element needs to delete the protocol data unit (protocol data unit, PDU) session (session) or the packet data network (packet data network, PDN) connection (connection) of the UE, and then instruct the UE to reestablish the PDU session (or PDN connection), so as to achieve the purpose that the designated area uses the designated user plane internet protocol (internet protocol, IP) address.

However, deleting the PDU session (or PDN connection) may result in a voice call flow interruption for the UE using EPS FB.

Disclosure of Invention

The application provides a communication method, a communication device and a communication system, which can reduce the probability of terminal service interruption in an EPS fallback scene.

In order to achieve the above purpose, the embodiment of the application adopts the following technical scheme:

in a first aspect, a communication method is provided, which may be performed by a first core network device or an apparatus supporting a function of the first core network device (such as a chip system of the first core network device). The method is applied to a terminal moving from a first preset area of a first network to a second preset area of a second network, wherein the Radio Access Technology (RAT) of the first network is different from the RAT of the second network. The method comprises the following steps: the first core network equipment of the first network determines that the EPS fallback of the terminal is triggered, and sends first information to the second core network equipment of the second network.

Wherein the first information comprises a first identifier or first indication information; the first identifier is used for identifying a first proprietary bearer corresponding to the terminal, wherein the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer; the first indication information is used for indicating the terminal to fall back to the second network through the EPS fall-back flow.

According to the communication method provided by the embodiment of the application, the first core network equipment of the first network can sense that the EPS fallback is triggered, and send the first information to the second core network equipment of the second network. In this way, the second core network device can learn that the EPS fallback is triggered. Therefore, even in a terminal cross-region scene, the second core network equipment cannot delete the audio and video PDN connection of the terminal, namely IMS PDN connection, so that the probability of interruption of the audio and video service when the terminal cross-region occurs is reduced.

In one possible design, the first core network device is an access and mobility management function AMF or a session management function SMF, and the second core network device is a mobility management entity MME.

In one possible design, the method further comprises:

the first core network device obtains information of a first proprietary bearer, where the information of the first proprietary bearer includes: the EPS bearing identifier EBI and the first identifier of the first proprietary bearing.

In one possible design, the first core network device is an SMF, and the first core network device obtains information of a first proprietary bearer, including:

the first core network device sends a first message to the AMF, wherein the first message is used for requesting the AMF to allocate an EBI for a first exclusive bearer;

The first core network device receives the EBI from the AMF.

In one possible design, the first core network device is an SMF, and the method further includes:

the first core network device sends a second message to the second core network device, wherein the second message is used for requesting to delete the first proprietary bearer;

the first core network device receives a response to the second message from the second core network device, the response of the second message indicating that the first proprietary bearer has been deleted.

In this way, the second core network device can release the resources related to the first dedicated bearer.

In one possible design, the first core network device is an SMF, and the first core network device sends first information to a second core network device of the second network, including:

the first core network device sends a session context to the AMF, the session context including a first identification or first indication information.

In one possible design, the first core network device is an AMF, and the first core network device sends first information to a second core network device of the second network, including:

the first core network equipment sends a user context of the terminal to the second core network equipment, wherein the user context comprises a first identifier or first indication information; or, the first core network device sends the session context of the terminal to the second core network device, where the session context includes the first identifier or the first indication information.

The user context includes session context, mobility management context, security context, etc.

In a second aspect, a communication method is provided, which may be performed by a second core network device or an apparatus supporting the functionality of the second core network device (such as a chip system of the second core network device). The method is applied to a terminal moving from a first preset area of a first network to a second preset area of a second network, wherein the Radio Access Technology (RAT) of the first network is different from the RAT of the second network. The method comprises the following steps: the second core network equipment of the second network receives the first information from the first core network equipment of the first network, and reserves the PDN connection of the packet data network corresponding to the terminal according to the first information.

The first information comprises a first identifier or first indication information, the first identifier is used for identifying a first proprietary bearer corresponding to the terminal, and the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer; the first indication information is used for indicating the terminal to fall back to the EPS through the EPS fall-back process.

In one possible design, the first core network device comprises a session management function SMF network element or an access and mobility management function AMF network element, and the second core network device is a mobility management entity MME.

In one possible design, the method further comprises:

the second core network equipment sends information of a first proprietary bearer to the terminal; the information of the first proprietary bearer includes: the EPS bearing identifier EBI and the first identifier of the first proprietary bearing.

In the method, the network side transmits voice and/or video service data of the terminal through a first proprietary bearer.

In one possible design, the first core network device is an AMF, the second core network device receives a first identification from a first core network device of the first network, comprising:

the second core network device receives a user context of the terminal from the first core network device, wherein the user context comprises information of a first special bearer, and the information of the first special bearer comprises a first identifier; or, the second core network device receives a session context of the terminal from the first core network device, where the session context includes information of a first proprietary bearer, and the information of the first proprietary bearer includes a first identifier.

In one possible design, the first core network device is an AMF, and the second core network device receives first indication information from the first core network device of the first network, including:

the second core network device receives a user context of the terminal from the first core network device, wherein the user context comprises first indication information; or, the second core network device receives a session context of the terminal from the first core network device, where the session context includes the first indication information.

the second core network device receives a second message from the first core network device, the second message being for requesting deletion of the first dedicated bearer;

the second core network device sends a response to the second message to the first core network device, the response of the second message indicating that the first proprietary bearer has been deleted.

In one possible design, the method further comprises:

the second core network device sends a third message to the access network device of the second network, wherein the third message is used for requesting to delete the first proprietary bearer;

the second core network device receives a response to the third message from the access network device, the response of the third message indicating that the first proprietary bearer has been deleted.

In this way, the access network device can release the first dedicated bearer related resources.

In a third aspect, a communication apparatus is provided, which may be a first core network device or an apparatus supporting a function of the first core network device (such as a chip system of the first core network device). The apparatus is located in a first network. The device comprises:

the processor determines that the EPS fallback of the evolution packet system of the terminal is triggered; the terminal moves from a first preset area of the first network to a second preset area of a second network, wherein the Radio Access Technology (RAT) of the first network is different from the RAT of the second network;

The communication interface is used for sending first information to second core network equipment of the second network, wherein the first information comprises a first identifier or first indication information;

the first identifier is used for identifying a first proprietary bearer corresponding to the terminal, wherein the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer; the first indication information is used for indicating the terminal to fall back to the second network through the EPS fall-back flow, and the Radio Access Technology (RAT) of the first network is different from the RAT of the second network.

In one possible design, the apparatus is an access and mobility management function AMF or a session management function SMF, and the second core network device is a mobility management entity MME.

In one possible design, the processor is further configured to obtain information of a first proprietary bearer, the information of the first proprietary bearer including: the EPS bearing identifier EBI and the first identifier of the first proprietary bearing.

In one possible design, the apparatus is an SMF, and the processor is configured to obtain information of a first proprietary bearer, including:

the method comprises the steps that a communication interface is controlled to send a first message to an AMF, wherein the first message is used for requesting the AMF to allocate an EBI for a first exclusive bearer; the control communication interface receives the EBI from the AMF.

In one possible design, the apparatus is an SMF, the communication interface is further configured to send a second message to the second core network device, the second message being configured to request deletion of the first dedicated bearer; a response to the second message is received from the second core network device, the response to the second message indicating that the first proprietary bearer has been deleted.

In one possible design, the apparatus is an SMF, a communication interface configured to send first information to a second core network device of a second network, including:

for sending a session context to the AMF, the session context comprising a first identification or first indication information.

In one possible design, the apparatus is an AMF, a communication interface configured to send first information to a second core network device of a second network, including:

the user context is used for sending the user context of the terminal to the second core network equipment, and the user context comprises a first identifier or first indication information; or, sending the session context of the terminal to the second core network device, wherein the session context comprises the first identification or the first indication information.

In a fourth aspect, a communication apparatus is provided, which may be a second core network device or an apparatus supporting functionality of a second core network device (such as a chip system of a second core network device). The device is located in a second network. The device comprises:

a communication interface for receiving first information from a first core network device of a first network; the first information comprises a first identifier or first indication information, the first identifier is used for identifying a first proprietary bearer corresponding to the terminal, and the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer; the first indication information is used for indicating the terminal to fall back to the EPS through the EPS fall-back process; the terminal moves from a first preset area of the first network to a second preset area of the second network, wherein the Radio Access Technology (RAT) of the first network is different from the RAT of the second network;

And the processor is used for reserving the PDN connection of the packet data network corresponding to the terminal according to the first information.

In one possible design, the apparatus is a mobility management entity MME, and the first core network device includes a session management function SMF network element or an access and mobility management function AMF network element.

In one possible design, the communication interface is further configured to send information of the first proprietary bearer to the terminal; the information of the first proprietary bearer includes: the EPS bearing identifier EBI and the first identifier of the first proprietary bearing.

In one possible design, the first core network device is an AMF, and the communication interface is configured to receive a first identifier from the first core network device of the first network, including:

the method comprises the steps of receiving a user context of a terminal from a first core network device, the user context comprising information of a first proprietary bearer, the information of the first proprietary bearer comprising a first identity; or, receiving a session context of the terminal from the first core network device, where the session context includes information of a first proprietary bearer, and the information of the first proprietary bearer includes a first identifier.

In one possible design, the first core network device is an AMF, and the communication interface is configured to receive first indication information from the first core network device of the first network, including:

The method comprises the steps of receiving a user context of a terminal from a first core network device, wherein the user context comprises first indication information; or, receiving a session context of the terminal from the first core network device, wherein the session context comprises the first indication information.

In one possible design, the first core network device is an SMF, the communication interface is further configured to receive a second message from the first core network device, the second message being configured to request deletion of the first dedicated bearer; a response to the second message is sent to the first core network device, the response of the second message indicating that the first proprietary bearer has been deleted.

In one possible design, the communication interface is further configured to send a third message to the access network device of the second network, the third message being configured to request deletion of the first dedicated bearer; a response to the third message is received from the access network device, the response to the third message indicating that the first proprietary bearer has been deleted.

In a fifth aspect, the present application provides a communication apparatus configured to implement a function of the first core network device in any one of the above aspects, or configured to implement a function of the second core network device in any one of the above aspects.

In a sixth aspect, the present application provides a communication device having a function of implementing the communication method of any one of the above aspects. The functions can be realized by hardware, and can also be realized by executing corresponding software by hardware. The hardware or software includes one or more modules corresponding to the functions described above.

In a seventh aspect, there is provided a communication apparatus comprising: a processor and a memory; the memory is configured to store computer-executable instructions that, when executed by the communication device, cause the communication device to perform a communication method as in any of the above aspects.

An eighth aspect provides a communication apparatus, comprising: a processor; the processor is configured to perform the communication method according to any one of the above aspects according to the instructions after being coupled to the memory and reading the instructions in the memory.

In a ninth aspect, embodiments of the present application provide a communication apparatus, including: a processor and interface circuit; the interface circuit is used for receiving the code instruction and transmitting the code instruction to the processor; a processor for executing code instructions to perform the communication method of any of the above aspects.

In a tenth aspect, embodiments of the present application provide a communications device, which may be a chip system including a processor, and optionally a memory, for implementing the functions of the method described in any of the above aspects. The chip system may be formed of a chip or may include a chip and other discrete devices.

In an eleventh aspect, there is provided a communication device, which may be circuitry, the circuitry comprising processing circuitry configured to perform the communication method of any of the above aspects.

In a twelfth aspect, embodiments of the present application also provide a computer-readable storage medium comprising instructions that, when run on a computer, cause the computer to perform the method of any of the above aspects.

In a thirteenth aspect, there is also provided in an embodiment of the application a computer program product comprising instructions which, when run on a computer, cause the computer to perform the method of any of the above aspects.

In a fourteenth aspect, an embodiment of the present application provides a system, where the system includes the first core network device and the second core network device in any one of the above aspects.

In a fifteenth aspect, embodiments of the present application provide a communication method that may be performed by a third core network device or an apparatus supporting a function of the third core network device (such as a chip system of the third core network device). The method is applied to a terminal moving from a first tracking area TA of a third network to a second TA of a fourth network, the radio access technology RAT of the third network being different from the RAT of the fourth network, the method comprising:

And the third core network equipment acquires the information of the first TA and the information of the second TA, and reserves or deletes the PDN connection of the packet data network corresponding to the terminal according to the information of the second TA and the information of the first TA.

According to the communication method provided by the embodiment of the application, the third core network equipment of the third network can acquire the information of the first TA and the information of the second TA. That is, the third core network device can know the location information of the terminal in the third network and the location information of the terminal in the fourth network. In this way, the third core network device can determine to reserve or delete the PDN connection corresponding to the terminal according to the information of the first TA and the information of the second TA, so as to reduce the probability that the core network device erroneously deletes the PDN connection corresponding to the terminal, resulting in interruption of the call service of the terminal.

In one possible design, the third core network device is a session management function SMF, or an access and mobility management function AMF; or a mobility management entity MME.

In one possible design, the third core network device reserves a PDN connection of the packet data network corresponding to the terminal according to the information of the second TA and the information of the first TA, including:

If the first TA and the second TA both belong to a third preset area, the third core network device reserves PDN connection corresponding to the terminal;

or if the second TA belongs to the third preset area, the first TA does not belong to the third preset area, and EPS fallback of the terminal is triggered, the third core network device reserves PDN connection corresponding to the terminal;

or if the second TA does not belong to the third preset area, the first TA belongs to the third preset area, and the EPS fallback of the terminal is triggered, the third core network device reserves PDN connection corresponding to the terminal.

In one possible design, the deleting the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA includes:

if the second TA belongs to a third preset area, the first TA does not belong to the third preset area, and the terminal performs a non-voice service, the third core network device deletes the PDN connection corresponding to the terminal;

or if the second TA does not belong to the third preset area, the first TA belongs to the third preset area, and the terminal performs the non-voice service, the third core network device deletes the PDN connection corresponding to the terminal.

In one possible design, the third core network device is preconfigured with information of the third preset area, the third preset area including at least one TA of the third network and/or at least one TA of the fourth network. In this way, it can be ensured that the third core network device can recognize the TAI of the first network and the TAI of the second network.

In one possible design, the obtaining, by the third core network device, information of the first TA includes:

the third core network device receives the information of the first TA from a fourth core network device, where the fourth core network device belongs to the third network.

In a sixteenth aspect, the present application provides a communication device belonging to a fourth network, the communication device comprising:

the communication interface is used for acquiring the information of the first TA and the information of the second TA;

and the processor is used for reserving or deleting the PDN connection of the packet data network corresponding to the terminal according to the information of the second TA and the information of the first TA.

In one possible design, the device is a session management function SMF, or an access and mobility management function AMF; or a mobility management entity MME.

In one possible design, the processor is configured to reserve a PDN connection of the packet data network corresponding to the terminal according to the information of the second TA and the information of the first TA, and includes:

if the first TA and the second TA both belong to a third preset area, reserving PDN connection corresponding to the terminal;

or if the second TA belongs to the third preset area, the first TA does not belong to the third preset area, and EPS fallback of the terminal is triggered, reserving PDN connection corresponding to the terminal;

or if the second TA does not belong to the third preset area, the first TA belongs to the third preset area, and the EPS fallback of the terminal is triggered, reserving the PDN connection corresponding to the terminal.

In one possible design, the processor is configured to delete a PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA, and includes:

if the second TA belongs to a third preset area, the first TA does not belong to the third preset area, and the terminal performs a non-voice service, deleting a PDN connection corresponding to the terminal;

or if the second TA does not belong to the third preset area, the first TA belongs to the third preset area, and the terminal performs the non-voice service, deleting the PDN connection corresponding to the terminal.

In one possible design, the device is preconfigured with information of the third preset zone, the third preset zone including at least one TA of the third network and/or at least one TA of the fourth network.

In one possible design, the communication interface is configured to obtain information of the first TA, and includes:

and the fourth core network device is used for receiving the information of the first TA from the fourth core network device, and the fourth core network device belongs to the third network.

In a seventeenth aspect, the present application provides a communication device for implementing the functions of the communication device in the sixteenth aspect.

In an eighteenth aspect, the present application provides a communication device having a function of implementing the communication method of any one of the fifteenth aspects described above. The functions can be realized by hardware, and can also be realized by executing corresponding software by hardware. The hardware or software includes one or more modules corresponding to the functions described above.

In a nineteenth aspect, there is provided a communication apparatus comprising: a processor and a memory; the memory is configured to store computer-executable instructions that, when executed by the communication device, cause the communication device to perform the communication method of any of the fifteenth aspects described above.

In a twentieth aspect, there is provided a communication device comprising: a processor; the processor is configured to execute the communication method according to any one of the fifteenth aspect described above according to the instruction after being coupled to the memory and reading the instruction in the memory.

In a twenty-first aspect, an embodiment of the present application provides a communication apparatus, including: a processor and interface circuit; the interface circuit is used for receiving the code instruction and transmitting the code instruction to the processor; a processor for executing code instructions to perform the communication method as in any of the fifteenth aspects above.

In a twenty-second aspect, embodiments of the present application provide a communications device, which may be a chip system including a processor, and optionally a memory, for implementing the functions of the method described in the fifteenth aspect. The chip system may be formed of a chip or may include a chip and other discrete devices.

In a twenty-third aspect, a communication device is provided, which may be circuitry comprising processing circuitry configured to perform the communication method of any of the fifteenth aspects described above.

In a twenty-fourth aspect, there is also provided in an embodiment of the present application a computer-readable storage medium comprising instructions that, when run on a computer, cause the computer to perform the method of the fifteenth aspect described above.

In a twenty-fifth aspect, there is also provided in an embodiment of the present application a computer program product comprising instructions which, when run on a computer, cause the computer to perform the method of the fifteenth aspect described above.

Drawings

Fig. 1 is a schematic view of a scenario of address partition management provided in an embodiment of the present application;

fig. 2 is a schematic diagram of an EPS fallback scenario provided in the embodiment of the present application;

fig. 3 to fig. 5 are schematic diagrams of an architecture of a communication system according to an embodiment of the present application;

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

fig. 7 to 11 are schematic flow diagrams of a communication method according to an embodiment of the present application;

fig. 12 is a schematic structural diagram of a communication device according to an embodiment of the present application;

fig. 13 is a schematic flow chart of a communication method according to an embodiment of the present application;

fig. 14 is a schematic view of an application scenario provided in an embodiment of the present application;

fig. 15 to 17 are schematic flow diagrams of a communication method according to an embodiment of the present application;

fig. 18 is a schematic view of an application scenario provided in an embodiment of the present application;

fig. 19 to 27 are schematic flow diagrams of a communication method according to an embodiment of the present application;

fig. 28 is a schematic structural diagram of a communication device according to an embodiment of the present application.

Detailed Description

The terms "first" and "second" and the like in the description and in the drawings are used for distinguishing between different objects or for distinguishing between different processes of the same object and not for describing a particular sequential order of objects.

"at least one" means one or more.

"plurality" means two or more.

"and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a alone, a and B together, and B alone, wherein a, B may be singular or plural.

The character "/" generally indicates that the context associated object is an "or" relationship, e.g., a/B may represent a or B.

Furthermore, references to the terms "comprising" and "having" and any variations thereof in the description of the present application are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed but may optionally include other steps or elements not listed or inherent to such process, method, article, or apparatus.

It should be noted that, in the embodiments of the present application, words such as "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.

In the description of the present application and in the drawings, "of", the corresponding "and" corresponding "may sometimes be used in combination, and it should be noted that the meaning to be expressed is consistent when the distinction is not emphasized.

The network element a sends a message to the network element B, which may be that the network element a directly sends a message to the network element B or that the network element a sends a message to the network element B via other intermediate network elements.

First, technical terms related to embodiments of the present application will be described:

1. user plane IP address allocation in 5G

After registering to the 5G core network (5th generation core,5GC), the terminal needs to acquire the user plane IP address through a packet data unit session (packet data unit session, PDU session) establishment procedure, so as to establish a communication route between the Data Network (DN).

2. User plane IP address allocation in 4G

In LTE, after a UE registers with an evolved packet core (evolved packet core, EPC), a user plane internet protocol (internet protocol, IP) address needs to be acquired through a packet data network connection (packet data network connection, PDN connection) establishment procedure in order to establish a communication route between a Data Network (DN).

It should be noted that PDN connection of EPC and PDU session of 5GC can be understood as the same concept, and the functions of both are the same.

3. Area-based user plane IP address allocation and updating

In LTE deployment, the EPC is required to be able to allocate a user plane IP address for a UE based on region. Different areas may be assigned different user IP addresses. As shown in fig. 1, the operator divides the network into a plurality of areas, and different areas allocate different user plane IP address resource pools. The EPC can reassign user plane IP addresses to UEs as they move between different areas. The process of reassigning the user plane IP address includes: the EPC deletes the current PDN connection of the UE, then instructs the UE to reestablish the PDN connection, and distributes a new user plane IP address for the UE through the flow of reestablishing the PDN connection.

Currently, the network side may configure an IP management and control area (abbreviated as a management and control area), and when the terminal moves into the IP management and control area, the terminal needs to be re-registered to the core network device, or the PDU session of the terminal is deleted by the core network device, and the core network device instructs the terminal to re-establish the PDU session. Optionally, the core network device may reassign the IP address to the terminal by reestablishing the PDU session procedure, so as to limit the network access rights of the terminal.

The IP management area may include a partial area in a Tracking Area (TA) or may include one or more TAs. Illustratively, the regulatory region 4 as shown in FIG. 1 includes two TAs. The regulatory domain 1 is in a certain TA included in TA list1 (list 1). When the UE moves 1 or 2 or 3 or 4 as shown in fig. 1, the UE may cross-zone, and then the 5G network device reassigns the IP address to the UE when the UE has cross-zone. For another example, in fig. 1, when the terminal enters the management and control area 2, the core network element used for serving the management and control area 2 deletes to reassign the IP address to the terminal. For another example, the terminal moves from the management and control area 3 to the management and control area 4, and the core network element serving the management and control area 4 reallocates the IP address to the terminal.

Similarly, in deployment of 5G networks, there is also a need to support functions of assigning user plane IP addresses by area and updating user plane IP addresses by UE cross-area (i.e., moving out of a certain regulatory domain or into a certain regulatory domain).

The user may move from one designated area a to another designated area B, and may refer to a movement in a physical position or a movement in a non-physical position. For example, the terminal may be located in a location where both a 4G network and a 5G network are deployed. The location of the terminal may be fixed and the terminal may fall back from the 5G provided service to the 4G network provided service. The fallback may be triggered by voice traffic.

In conventional cellular networks, in order to determine that a terminal is reachable at any time, a TA-based mechanism is introduced. The core network device sends a tracking area list (Tracking Area list, TA list) to the terminal when the terminal performs registration or tracking area update (Tracking Area update, TAU). Typically, one TA list comprises one or more TAs, each TA comprising a plurality of cells. Subsequently, if the terminal moves in the cell included in the TA list, the terminal does not need to execute TAU, and after the terminal has service, the core network device pages the terminal in the TA list area. Otherwise, if the terminal moves out of the cell included in the TA list, the terminal needs to execute the TAU, so that the core network device knows the TA where the terminal is currently located.

4. Voice scheme in 5G network

New wireless based voice (voice over new radio, VONR): and providing audio and video call service through the 5G network. In this implementation, a series of parameter tuning is required.

EPS fallback: in one possible implementation, the 5G network provides voice services to the user through the EPS fallback mode. EPS fallback requires interoperability between 5G networks and 4G networks to complete voice traffic. Specifically, the UE may reside in a 5G network after powering on, the UE may register with an IP multimedia system (IP multimedia subsystem, IMS) network, register with the 5G network, and initiate a voice call with a 5G access network device. When the EPS fallback mode is adopted to provide the voice service, the 5G access network equipment refuses the voice bearing establishment request, and initiates a 5G to 4G Handover (HO) or redirection (redirection) process, so that the UE falls back to the EPS. And establishes a voice-specific bearer over the EPC over which voice and/or video traffic data is transmitted.

In the initial stage of 5G network construction, in order to maximally reuse the existing LTE network and protect the existing investment, the 5GC network construction can be accelerated, and operators generally adopt an EPS fallback technology to provide audio and video call services for the 5G terminal.

As shown in fig. 2, in the process that the terminal moves from the 5G coverage area to the 4G coverage area, due to the occurrence of the cross-zone of the UE, the network side deletes the PDU session when the UE is in the 5G coverage area, so as to release the current user plane IP address resource of the UE, and create a PDN connection in the 4G coverage area for the UE, so that in the PDN connection establishment process, a new user plane IP address is allocated for the UE. Meanwhile, if the UE initiates a call or is called, the audio and video (i.e. voice and/or video) service can be normally performed after the PDN connection is established, and a certain time is required for deleting the original PDU session, establishing the PDN connection, and the like, so that the audio and video service of the user may be interrupted. For example, the call signal can be received after a certain time delay, or the called party can be dialed after a certain time delay, and for example, the video can be downloaded or uploaded after a certain time delay.

In order to solve the above technical problems, an embodiment of the present application provides a communication method, which is applied to IP address partition management, where a terminal moves from a first preset area of a first network to a second preset area (the second preset area is a management and control area) of a second network. Fig. 3 is an exemplary network architecture provided in an embodiment of the present application. As shown in fig. 3, the network architecture according to the embodiment of the present application includes an existing fifth-generation communication system (5th generation system,5GS). The 5GS includes an access and mobility management function (access and mobility management function, AMF) network element, a session management function (session management function, SMF) network element, a user plane function (user plane function, UPF) network element, a unified data management (unified data management, UDM) network element, a policy control function (policy control function, PCF) network element, an authentication server function (authentication server function, AUSF) network element, a network opening function (network exposure function, NEF) network element, and some network elements not shown, such as a network function storage function (network function repository function, NRF) network element, which are not specifically limited in this embodiment of the present application.

In this embodiment of the present application, as shown in fig. 3, a terminal accesses 5GS through an access network device, the terminal communicates with an AMF network element through a Next generation network (N1) interface (N1), the access network device communicates with an AMF network element through an N2 interface (N2), the access network device communicates with a UPF network element through an N3 interface (N3), the AMF network element communicates with an SMF network element through an N11 interface (N11), the AMF network element communicates with a UDM network element through an N8 interface (N8), the AMF network element communicates with an AUSF network element through an N12 interface (N12), the AMF network element communicates with a PCF network element through an N15 interface (N15), the SMF network element communicates with a PCF network element through an N7 interface (N7), the SMF network element communicates with a UPF network element through an N4 interface (N29), and the NEF network element communicates with an SMF network element through an N29 interface (N29) interface (N6) access data network. The data network may refer to the Internet, private networks of enterprises, etc. that provide specific services.

In addition, as shown in fig. 3, in order to implement interworking (or interoperability) between the 5GS and the EPS, a network architecture according to an embodiment of the present application may further include a mobility management entity (mobility management entity, MME) in the EPS, where the MME communicates with the SMF network element through an N26 interface (abbreviated as N26). Of course, other network elements in EPS may also be included in the network architecture according to the embodiments of the present application, such as evolved universal mobile telecommunications system (universal mobile telecommunications system, UMTS) terrestrial radio access network (evolved UMTS territorial radio access network, E-UTRAN) equipment, packet data network (packet data network, PDN) gateway user plane function (PDN gateway user plane function, PGW-U) network elements, PDN gateway control plane function (PDN gateway control plane function, PGW-C) network elements, policy and charging rules function (policy and charging rules function, PCRF) network elements, home subscriber server (home subscriber server, HSS) network elements or equipment, and the embodiments of the present application are not limited in this regard.

In one possible implementation, some network elements in the 5GS and EPS interworking architecture may be deployed in one. For example, as shown in fig. 4, a schematic diagram of an existing interworking architecture between 5GS and EPS is shown. Wherein 5GS and EPS share UPF network element+PGW-U network element, SMF network element+PGW-C network element, PCF network element+PCRF network element, UDM network element+HSS. Here "+" indicates a combination, the UPF is a user plane function in 5GS, the PGW-U is a gateway user plane function in EPS corresponding to the UPF, the SMF is a session management function in 5GS, the PGW-C is a gateway control plane function in EPS corresponding to the SMF, the PCF is a policy control function in 5GS, and the PCRF is a policy charging rule function in EPS corresponding to the PCF.

In addition, as shown in fig. 4, the 5GS and EPS interworking architecture may further include an MME and a Serving Gateway (SGW) in the EPS. Optionally, the 5GS and EPS interworking architecture may further include a network slice selection function (network slice selection function, NSSF) network element and some network elements, which are not shown, such as a NEF network element, which is not specifically limited in the embodiments of the present application.

In this embodiment, as shown in fig. 4, the terminal accesses EPS through the E-UTRAN device, and the terminal accesses 5GS through the next generation radio access network (next generation radio access network, NG-RAN) device. E-UTRAN equipment communicates with MME through S1-MME interface, E-UTRAN equipment communicates with SGW through S1-U interface, MME communicates with SGW through S11 interface, MME communicates with UDM network element+HSS through S6a interface, MME communicates with AMF network element through N26 interface, SGW communicates with UPF network element+PGW-U network element through S5-U interface, SGW communicates with SMF network element+PGW-C network element through S5-C interface, UPF network element+PGW-U network element communicates with NG-RAN equipment through N3 interface, UPF network element+PGW-U network element communicates with SMF network element+PGW-C network element through N4 interface, SMF network element+PGW-C network element communicates with PCRF network element through N7 interface, UDM network element+HSS communicates with SMF network element+PGW-C network element through N8 interface, UDM network element+HSS communicates with AMF network element through N8 interface, AMF network element communicates with AMF network element through N15 interface and AMF network element through AMF-C interface, AMF network element communicates with AMF terminal through AMF-C interface through N11 interface.

It should be noted that fig. 4 is only a schematic diagram of an existing interworking architecture between 5GS and EPS, and of course, the interworking architecture between 5GS and EPS may be other, which is not limited in this embodiment.

It should be noted that the names of the network elements and the interfaces between the network elements in fig. 3 or fig. 4 are only an example, and the names of the network elements and the interfaces between the network elements may be other in the specific implementation, which is not specifically limited in the embodiments of the present application.

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.

The network architecture and the service scenario described in the embodiments of the present application are for more clearly describing the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. As can be known to those skilled in the art, with the evolution of the network architecture and the appearance of new service scenarios, the technical solution provided in the embodiments of the present application is also applicable to similar technical problems.

As shown in fig. 5, a communication system 30 according to an embodiment of the present application is provided, where the communication system 30 includes a first core network device 301 and a second core network device 302.

Wherein the first core network device 301 is located in the first network. The first network may be, for example, a 5GS or other network. The first core network device 301 is configured to determine that an EPS fallback of the evolved packet system of the terminal is triggered, and send first information to a second core network device of the second network, where the first information includes a first identifier or first indication information; the first identifier is used for identifying a first proprietary bearer, and the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer; the first indication information is used for indicating that the terminal falls back to the second network through an EPS fall-back procedure, and the radio access technology (radio access technology, RAT) of the first network is different from the RAT of the second network.

The second core network device 302 is configured to receive the first information from the first core network device of the first network, and reserve a PDN connection of the packet data network corresponding to the terminal according to the first information.

Optionally, the evolved packet system fallback system provided in the embodiment of the present application may be applied to a network architecture as shown in fig. 3 or fig. 4, or may be applied to a network architecture for partition management of other IP addresses, which is not specifically limited in the embodiment of the present application.

For example, if the evolved packet system fallback system provided in the embodiment of the present application is applied to a network architecture as shown in fig. 3 or fig. 4, the network element or entity corresponding to the first core network device may be the SMF or AMF network element, and the network element or entity corresponding to the second core network device may be the MME network element. The connection relationship between SMF, AMF, MME can be seen in fig. 3 or fig. 4.

Alternatively, the terminal (terminal) referred to in the embodiments of the present application may include various handheld devices, vehicle-mounted devices, wearable devices, computing devices, or other processing devices connected to a wireless modem, which have wireless communication functions; and may also include a subscriber unit (subscriber unit), a cellular phone (cellular phone), a smart phone (smart phone), a wireless data card, a personal digital assistant (personal digital assistant, PDA) computer, a tablet computer, a wireless modem (modem), a hand-held device (handheld), a laptop computer (laptop), a cordless phone (cord) or a wireless local loop (wireless local loop, WLL) station, a machine type communication (machine type communication, MTC) terminal, a UE, a Mobile Station (MS), a terminal device (terminal device) or a relay user device, etc. The relay user equipment may be, for example, a 5G home gateway (residential gateway, RG). For convenience of description, the above-mentioned devices are collectively referred to as a terminal in this application.

Optionally, the access network device referred to in the embodiments of the present application refers to a device accessing the core network, which may be, for example, NG-RAN device, E-UTRAN device, base station, broadband network service gateway (broadband network gateway, BNG), aggregation switch, non-third generation partnership project (3rd generation partnership project,3GPP) access network device, and so on. The base station may include various forms of base stations, such as: macro base stations, micro base stations (also referred to as small stations), relay stations, access points, and the like.

Optionally, the first core network device and the second core network device in the embodiments of the present application may be implemented by one device, or may be implemented by multiple devices together, or may be implemented as functional modules in one or multiple devices, which is not specifically limited in the embodiments of the present application. It will be appreciated that the above described functionality may be either a network element in a hardware device, a software function running on dedicated hardware, or a virtualized function instantiated on a platform (e.g., a cloud platform).

For example, the first core network device and the second core network device in the embodiments of the present application may be implemented by the communication device in fig. 6. Fig. 6 is a schematic structural diagram of a communication device according to an embodiment of the present application. The communication device 400 comprises at least one processor 401, a memory 403 and at least one communication interface 404.

The processor 401 may be a general purpose central processing unit (central processing unit, CPU), microprocessor, application Specific Integrated Circuit (ASIC), or one or more integrated circuits for controlling the execution of the programs of the present application.

A pathway may be included between each component to transfer information between the components.

The communication interface 404 uses any transceiver-like device for communicating with other devices or communication networks, such as ethernet, radio access network (radio access network, RAN), wireless local area network (wireless local area networks, WLAN), etc.

The memory 403 may be, but is not limited to, a read-only memory (ROM) or other type of static storage device that can store static information and instructions, a random access memory (random access memory, RAM) or other type of dynamic storage device that can store information and instructions, or an electrically erasable programmable read-only memory (electrically erasable programmable read-only memory, EEPROM), a compact disc read-only memory (compact disc read-only memory) or other optical disc storage, a compact disc storage (including compact disc, laser disc, optical disc, digital versatile disc, blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, 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. The memory may be stand alone and be coupled to the processor via a communication line. The memory may also be integrated with the processor.

The memory 403 is used for storing computer-executable instructions for executing the embodiments of the present application, and is controlled by the processor 401 to execute the instructions. The processor 401 is configured to execute computer-executable instructions stored in the memory 403, thereby implementing a communication method provided in the following embodiments of the present application.

Alternatively, the computer-executable instructions in the embodiments of the present application may be referred to as application program codes, which are not specifically limited in the embodiments of the present application.

In a particular implementation, as one embodiment, processor 401 may include one or more CPUs, such as CPU0 and CPU1 in FIG. 6.

In a particular implementation, as one embodiment, the communication device 400 may include multiple processors, such as the processor 401 and the processor 408 in fig. 6. Each of these processors may be a single-core (single-CPU) processor or may be 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).

The communication device 400 may be a general purpose device or a special purpose device. In a specific implementation, the communication device 400 may be any device having a similar structure as in fig. 6. The embodiments of the present application are not limited to the type of communication device 400.

The communication method provided in the embodiment of the present application will be specifically described below with reference to fig. 1 to 6.

It should be noted that, in the embodiments described below, the names of the messages between the network elements or the names of the parameters in the messages are only an example, and may be other names in specific implementations, which are not limited in the embodiments of the present application.

First, the evolved packet system fallback system shown in fig. 5 is applied to the network architecture shown in fig. 3 or fig. 4, and the terminal initiates a voice call, as shown in fig. 7, the communication method provided in the embodiment of the present application includes the following steps:

s701, the terminal initiates a service request to the IMS, and the IMS triggers a special bearing establishment flow.

The communication method provided by the embodiment of the invention is applied to the situation that the terminal moves from the first preset area of the first network to the second preset area of the second network. The first preset area may be a regulatory area or a non-regulatory area. The second preset area is a control area.

The first network, such as but not limited to a 5G network, may be a regulatory domain, i.e. when a terminal enters the first regulatory domain of the first network, the terminal needs to re-register to the core network device, or the PDU session of the terminal is deleted by the core network device, which instructs the terminal to re-establish the PDU session. For example, in fig. 1, the terminal enters a preset area 2, the terminal needs to re-register to the core network device, or the PDU session of the terminal is deleted by the core network device, and the core network device instructs the terminal to re-establish the PDU session, and may allocate an IP address to the terminal. The entering of the preset area 2 may be performed through step 3 of fig. 1, i.e. the preset area 2 is not entered from another preset area. Alternatively, the predetermined area 2 may be accessed from another predetermined area, for example, the predetermined area 1 may be accessed from the predetermined area 2.

In other embodiments, the first predetermined area may not be a management area. That is, when the terminal enters the first preset area of the first network, the terminal does not need to be re-registered to the core network device, or the PDU session of the terminal is not deleted by the core network device.

The second network is, for example but not limited to, a 4G network. In some embodiments, the second preset area is a management and control area, that is, when the terminal enters into the second management and control area of the second network, the terminal needs to be re-registered to the core network device, or the PDN connection corresponding to the terminal is deleted by the core network device, and the core network device instructs the terminal to re-establish the PDN connection.

As shown in fig. 2, the following embodiments mainly take a terminal entering a 4G coverage area (i.e., a second preset area, for example, a management area) from a 5G coverage area (i.e., a first preset area, for example, a non-management area or a management area) as an example, and the following embodiments describe a communication method of the embodiments of the present application in a unified manner.

The service request may be an audio video service request. For example, it may be a caller request in voice service.

It is easily understood that the terminal may reside in the 5G network after power-on, and may establish a PDU session through the 5GC in order to transmit service data through the PDU session. When the IMS receives the service request of the terminal, the IMS recognizes that the user calls the telephone, and triggers the IMS to establish a special load flow. Specifically, the IMS interacts with the 5G network in which the terminal is located, so as to inform network elements in the 5G network to establish a quality of service Flow (quality of service Flow, qoS Flow) for the terminal for carrying service data.

In a 5G network, one PDU session may be associated with one or more QoS flows. Each QoS Flow corresponds to a quality of service class identifier (QoS Class Identifier, QCI). The QCI corresponding to a QoS Flow is related to factors such as QoS requirements of the QoS Flow. For example, the QCI corresponding to the QoS Flow for carrying voice traffic data is 1, and the QCI corresponding to the QoS Flow for carrying video traffic data is 2.

The specific signaling flow between the IMS system and the 5G network element in S701 and the signaling flow between the 5G network element can be referred to the prior art, and will not be described herein. For example, the IMS system may send a fourth message to the PCF, which sends a fifth message to the SMF, which triggers the dedicated bearer establishment procedure. The SMF may be a converged SMF, supporting interoperability with EPS, anchor point unchanged.

Taking the terminal to initiate the voice service as an example, S701 may include the following steps:

1. the PCF sends a session policy control update notification request (npcf_smpoliccontrol_ UpdateNotify Request) to the SMF to notify the SMF to create a QoS Flow for carrying voice traffic data.

2. The SMF invokes a session policy control update notification response (npcf_smpolicy control_ UpdateNotify Response) service, feeding back a response message to the PCF.

3. The SMF invokes an N1/N2 Communication messaging (namf_communication_n1n2message transfer) service, sending a message to the AMF carrying session management (session management, SM) information.

4. The AMF sends an N1/N2 Communication message transfer response (Namf_communication_N1N Message Transfer Response) to the SMF.

5. The AMF sends an N2 session request (N2 PDU session Request) message to the NG RAN device to inform the NG RAN to allocate resources for QoS flows.

6. The NG RAN device refuses the voice QoS Flow and feeds back an N2 session Response (N2 session Response) to the AMF.

It should be appreciated that the NG-RAN decides not to provide voice services to the terminal through the VoNR but through the EPS FB, and then the NG-RAN refuses to establish the QoS Flow.

The N2 session Response message carries the cause value of the IMS voice EPS fallback or radio access technology fallback triggered (IMS Voice EPS Fallback or RAT Fallback Triggered).

7. The AMF sends an update session context request (nsmf_pdu use_ UpdateSMContext Request) message to the SMF.

The message carries IMS Voice EPS Fallback or RAT Fallback Triggered cause value (which may be referred to simply as a first cause value).

S702, the first core network device determines that EPS fallback of the terminal is triggered.

Wherein the first core network device is located in the first network. The first network may be, for example, but not limited to, 5GS. The RAT of the first network is, for example but not limited to, new Radio (NR).

As a possible implementation, the first core network device is the SMF shown in fig. 3 or fig. 4. Then, as a possible implementation manner, S702 is specifically implemented as: the SMF determines whether the EPS fallback of the terminal is triggered according to the nsmf_pdu use_ UpdateSMContext Request message received from the AMF in S701. If the nsmf_pdu use_ UpdateSMContext Request message carries a cause value of "IMS voice EPS fallback or RAT fallback triggered", the SMF determines that EPS fallback is triggered, and the NG-RAN device will initiate an EPS fallback procedure.

As a possible implementation, the first core network device is an AMF shown in fig. 3 or fig. 4. Then, as a possible implementation, S702 is implemented as: the AMF parses the N2 session Response message received from the NG-RAN device in S701, and determines whether the EPS fallback of the terminal is triggered according to the parsing result. If the N2 session Response message carries a cause value of "IMS voice EPS fallback or RAT fallback triggered", the AMF determines that the EPS fallback is triggered.

S703, the first core network device sends first information to the second core network device.

Accordingly, the second core network device receives the first information from the first core network device.

The second core network device is located in the second network. The second network may be, for example, but not limited to, EPS. The second core network device may be, for example, but not limited to, an MME as shown in fig. 3 or fig. 4.

The RAT of the first network is different from the RAT of the second network. The RAT of the second network is, for example but not limited to.

Wherein the first information includes a first identification or first indication information.

The first identifier is used for identifying a first proprietary bearer corresponding to the terminal, and the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer. In a network architecture supporting interworking between the 5GS and the EPS, a PDU session in the 5GS may be migrated to the EPS, i.e. a PDN connection corresponding to the PDU session may be established in the EPS. Accordingly, qoS flows in PDU sessions will map to one EPS bearer (EPS bearer) in the PDN connection. The voice-specific bearer refers to an EPS-specific bearer. The SMF may create a QoS Flow and map the QoS Flow in 5GS to the first proprietary bearer in EPS.

The first indication information is used for indicating the terminal to fall back to the second network through the EPS fall-back flow. The RAT of the first network is different from the RAT of the second network. The first identity may be, for example but not limited to, a QCI of the first proprietary bearer. Optionally, the first indication information is denoted as EPS fallback indication (EPS Fallback Indicator). The EPS Fallback Indicator may be a flag bit, a cause value, or other forms, which are not limited in the embodiments of the present application.

In this embodiment of the present application, the first core network device may indicate to the second core network device that EPS fallback of the terminal is triggered through the first information. Wherein the first information may be a first identification or first indication information. That is, the embodiments of the present application provide at least two ways to indicate that EPS fallback of a terminal is triggered. These two ways are described separately below.

Mode 1: the first core network device (AMF or SMF) sends a first identifier to the second core network device (MME) in order to implicitly indicate that the terminal falls back to the second network (e.g. EPS) through an EPS fallback procedure.

In one possible implementation, in S702, it is determined by the AMF that EPS fallback of the terminal is triggered. And, the AMF obtains information of a first dedicated bearer (dedicated bearer).

The information of the first proprietary bearer includes, but is not limited to, EPS Bearer Identification (EBI) of the first proprietary bearer and the first identification described above. Taking the example that the first proprietary bearer includes a voice proprietary bearer and a video proprietary bearer, the information of the first proprietary bearer includes EBI of the voice proprietary bearer, EBI of the video proprietary bearer, QCI of the voice proprietary bearer (typically 1), QCI of the video proprietary bearer (typically 2).

It should be noted that, the AMF may obtain the information of the first proprietary bearer, which may be locally generated by the AMF. The SMF may generate the information of the first dedicated bearer, and the AMF obtains the information of the first dedicated bearer from the SMF. After that, in S703, the AMF sends the first identity to the MME. For example, taking the example that the first proprietary bearer includes a voice proprietary bearer and a video proprietary bearer, the first identifier is qci=1 for identifying the voice proprietary bearer and qci=2 for identifying the video proprietary bearer. In this way, the AMF can implicitly notify the MME through the first identifier, that the terminal is falling back to the EPS through the EPS fallback procedure. Thus, the MME does not delete the current PDN connection of the terminal so as to avoid causing call interruption of the terminal.

Optionally, the AMF sends the first identifier to the MME, which may be implemented as: the AMF sends a user context of the terminal to the MME, the user context including the first identity.

Or, as a possible implementation manner, the AMF sends the first identifier to the MME, which may be implemented as: the AMF sends a session context of the terminal to the MME, the session context including the first identity.

In yet another possible implementation, in S702, it is determined by the SMF that EPS fallback of the terminal is triggered. And, the SMF obtains information of a first dedicated bearer (dedicated bearer). As a possible implementation manner, the SMF obtains the information of the first proprietary bearer, specifically implemented as: the SMF generates information of the first proprietary bearer. After that, in S703, the SMF sends the first identity to the MME.

Optionally, the SMF sends the first identifier to the MME, which may be specifically implemented as: the SMF sends a session context (session management context, SM context) to the AMF, the session context comprising a first identity. And then the AMF sends the first identification to the MME.

Among other things, user contexts include session context, mobility management context (mobility management context, MM context), security context, etc.

Alternatively, in 5GS, MM contexts are responsible for allocation and saving by the AMF. Including an identification of the terminal, such as a subscriber permanent identification (subscription permanent identifier, SUPI), a general public subscriber identification (generic public subscription identifier, GPSI).

In EPS, MM contexts are assigned and saved by MME in charge. Including an identification of the terminal, such as an international mobile subscriber identity (international mobile subscriber identity, IMSI) (corresponding to 5G SUPI), a mobile subscriber number (mobile subscriber international integrated service digital network/pstn number, MSISDN) (corresponding to 5G GPSI, i.e. a handset number).

Thus, the AMF will pass the user identity to the MME, but in the mobility management context instead of the session management context.

Optionally, the SMF obtains the information of the first dedicated bearer, which may be that the SMF obtains the information of the first dedicated bearer based on information obtained from other network elements and/or local information.

Optionally, the SMF obtains an identification (such as QCI) of the information of the first proprietary bearer based on some information and/or local information obtained from the PCF.

Optionally, the SMF obtains the EBI comprised by the information of the first proprietary bearer based on some information and/or local information obtained from the AMF. Specifically, the SMF may send a first message to the AMF, where the first message is used to request the AMF to allocate EBI for the first dedicated bearer; and receives EBI from the AMF. In this way, after receiving EBI allocated by the AMF for the first dedicated bearer, for example, ebi=7 allocated for the voice dedicated bearer, and ebi=9 allocated for the video dedicated bearer, the SMF generates the information of the first dedicated bearer. For example, generating the information of the first proprietary bearer includes: ebi=7 for voice-specific bearers, ebi=9 for video-specific bearers, qci=1 for voice-specific bearers, qci=2 for video-specific bearers.

Alternatively, the SMF may send the second message to the MME and receive a response to the second message from the MME. The second message is used for requesting to delete the first proprietary bearer; the response of the second message is used to indicate that the first proprietary bearer has been deleted. In this way, the MME may release the first dedicated bearer related resources.

Mode 2: the first core network device (SMF or AMF) sends first indication information to the second core network device (MME), wherein the first indication information is used for explicitly indicating the terminal to fall back to the second network through an EPS fall-back process.

In one possible implementation, in S702, it is determined by the AMF that EPS fallback of the terminal is triggered. Then S703 may be implemented as: the AMF sends first indication information to the MME. For example, the AMF sends an identification bit to the MME for indicating that the terminal falls back to the second network through the EPS fallback procedure.

Optionally, the AMF sends the first indication information to the MME, which may be implemented as: the AMF sends a user context of the terminal to the MME, wherein the user context comprises first indication information.

Or, alternatively, the AMF sends the first identifier to the MME, which may be implemented as: the AMF sends a session context of the terminal to the MME, wherein the session context comprises first indication information.

In yet another possible implementation, in S702, it is determined by the SMF that EPS fallback of the terminal is triggered. Then S703 may be implemented as: the SMF may send the first indication information to the MME through the AMF. That is, the SMF sends the first indication information to the AMF first, and then the AMF sends the first indication information to the MME.

Optionally, the SMF sends the first indication information to the MME, which may be specifically implemented as: the SMF sends a session context to the AMF, the session context including first indication information. And then the AMF sends the first indication information to the MME.

And S704, the second core network equipment reserves the PDN connection of the packet data network corresponding to the terminal according to the first information.

Corresponding to the above mode 1, the MME can infer that the EPS fallback of the terminal is triggered based on the first identifier obtained from the AMF, that is, the identifier of the first proprietary bearer, so, in order to avoid interruption of the audio and video service of the terminal, the MME reserves the PDN connection corresponding to the terminal, so that the voice and/or video proprietary bearer can be established on the reserved PDN connection, so as to carry the voice and/or video service data of the terminal.

Corresponding to the above mode 2, the MME can know that the EPS fallback of the terminal is triggered based on the first indication information obtained from the AMF, and then the MME reserves the PDN connection corresponding to the terminal, so as to be capable of establishing a voice and/or video dedicated bearer on the reserved PDN connection to carry voice and/or video service data of the terminal.

In comparison with the prior art, when a terminal is subjected to cross-region, for example, enters a second preset region, an MME deletes the current PDN connection of the terminal and reestablishes the PDN connection for the terminal, so that the terminal is subjected to transient disconnection. In this way, the second core network device can learn that the EPS fallback is triggered. In this way, even in a scenario in which the terminal moves from the first preset area of the first network to the second preset area of the second network (the second preset area is, for example, a management area), the second core network device will not delete the audio/video PDN connection of the terminal, that is, IMS PDN connection, so as to reduce the probability of interruption of the audio/video service when the terminal spans the area.

The communication method of the embodiment of the present application is described in detail in connection with a specific scenario as follows.

In some embodiments, the terminal drops back to the EPS from 5GS through a handover. And determining whether the EPS of the terminal is triggered or not by the SMF, and sending a first identification to the MME by the SMF through the AMF so as to implicitly indicate the terminal to fall back to the EPS through an EPS fall-back flow. The MME establishes a second dedicated bearer for carrying traffic data. In this case, referring to fig. 8 (a), the communication method in the embodiment of the present application specifically includes:

S801a, a terminal initiates a service request to an IMS, and the IMS triggers a special bearing establishment flow.

Specific implementation of S801a can be seen in S701 described above.

S802a, SMF determines that EPS fallback of the terminal is triggered.

Specific implementation of S802a can be seen from S702 above.

S803a, SMF obtains the information of the first proprietary bearer.

Specifically, the SMF creates a QoS Flow, which can be mapped to a first dedicated bearer in the EPS, and obtains information of the first dedicated bearer.

The information carried by the first proprietary includes a combination of one or more of the following: EPS bearer identity (EPS bearer ID), first identity (e.g. QCI of voice specific bearer and/or QCI of video specific bearer), EPS bearer granularity traffic flow template (EPS bearer traffic flow template), serving gateway S1 interface user plane IP address and tunnel identity (SGW S1 IP address and TEID for user plane), packet data network gateway S5 interface user plane IP address and tunnel identity (PGW S5 IP Address and TEID for user plane), allocation reservation priority (Allocation/Retention Priority), uplink maximum rate (Maximum bit rate for uplink), downlink maximum rate (Maximum bit rate for downlink), uplink maximum guaranteed rate (Guaranteed bit rate for uplink), downlink maximum guaranteed rate (Guaranteed bit rate for downlink).

As a possible implementation manner, in the above procedure, the SMF obtains some information from other network elements, and generates the information of the first proprietary bearer in combination with the local information. For example, the SMF generates partial information of the first proprietary bearer, such as QCI, based on some information received from the PCF and the local information. The SMF generates partial information of the first proprietary bearer, such as EBI, based on some information received from the AMF and the local information.

Optionally, S803a may include the following steps S803a1 and S803a2:

s803a1, SMF sends a first message to AMF.

Accordingly, the AMF receives the first message from the SMF.

The first message is for requesting the AMF to allocate EBI for the first dedicated bearer.

As one possible implementation, the SMF invokes an EBI allocation request (namf_communication_ EBIAssignment Request) service to send a first message to the AMF.

S803a2, AMF sends a response of the first message to SMF.

Accordingly, the SMF receives a response of the first message from the AMF.

As one possible implementation, the AMF returns a response to the EBI allocation response (namf_communication_ EBIAssignment Response) to send the first message to the SMF. The response to the first message includes the EBI of the first proprietary bearer.

Illustratively, the AMF allocates ebi=7 for the first proprietary bearer and sends the EBI to the SMF.

Typically, in the prior art, after receiving the first cause value, the SMF does not create a QoS Flow, and does not map the QoS Flow in 5GS to the first proprietary bearer in the EPS. According to the communication method provided by the embodiment of the application, the SMF can acquire the information of the first proprietary bearer, and the information of the first proprietary bearer comprises the first identifier. In this way, in the subsequent flow, the MME can acquire the first identifier from the SMF, so as to learn that the terminal falls back to the EPS through the EPS fallback flow, so that in order to avoid affecting the terminal service, the MME reserves the PDN connection corresponding to the terminal.

S804a, NG-RAN device sends a handover request to AMF (Handover Required).

Accordingly, the AMF receives a handover request from the NG-RAN device.

It should be appreciated that the NG-RAN device may be configured with an identity of a neighboring EPS access network device (e.g., eNB) and a tracking area identity of the neighboring EPS access network device.

The NG-RAN equipment initiates a 5 GS-EPS switching flow, and the switching request carries a switching Type (Handover Type) target area identifier and a target access network equipment identifier. Wherein the switching type is 5GStoEPS. The target area identifier refers to a target tracking area identifier (target tracking area identity, target TAI) of an area to which the terminal is to be switched, and is 4G TAI if the target area identifier is an EPS Fallback procedure. target TAI may be used to query and select MME. The target access network device identifier refers to an identifier of an access network device (such as a 4G base station) to which the terminal is to be switched. If the Target access network equipment identifier is EPS Fallback, the Target access network equipment identifier is Target eNodeB ID.

Through the switching flow, the terminal falls back from 5GS to EPS, so as to carry out voice service in the 4G network.

S805a, the AMF sends a session context request to the SMF.

Accordingly, the SMF receives a session context request from the AMF.

Optionally, the session context request includes an identification of the session, e.g. EBI, associated EPS bearer identification (linked EPS bearer ID, LBI). The EBI is used to identify the bearer and the LBI is used to identify the PDN connection.

In general, if ebi=lbi, this is interpreted as the default bearer for the PDN connection, and one PDN connection has only one default bearer, so LBI can be considered to identify a certain PDN connection.

It should be understood that after the AMF receives the handover request from the NG-RAN device, it determines that the terminal needs to be handed over to the 4G network according to the handover type in the handover request, and then the AMF sends a session context request to the SMF so as to request the SMF to feed back the session context of the terminal.

As one possible implementation, the AMF invokes a context request (nsmf_pdu use_contenxtrequest) service of the SMF to send a session context request to the SMF.

S806a, SMF sends a session context response to AMF.

Accordingly, the AMF receives the session context response from the SMF.

The session context response includes a session context of the terminal, the session context including information of a first proprietary bearer, the information of the first proprietary bearer including a first identification. For example, the session context includes an identification qci=1 of the voice-specific bearer.

As one possible implementation, the SMF feeds back a Context Response (nsmf_pduse_context Response).

S807a, AMF sends the first identity to MME.

Accordingly, the MME receives the first identity from the AMF.

The AMF selects an MME by querying a domain name server (domain name server, DNS) according to the target area identifier in the handover request acquired in the step, and sends a forward redirection (Forward Relocation Request) message to the selected MME, wherein the message carries the user context of the terminal, the user context comprises information of a first proprietary bearer, and the information of the first proprietary bearer comprises the first identifier. For example, the user context includes qci=1 for voice-specific bearers. The user context may be a session context, or other types of contexts, such as an MM context, security context, etc.

Optionally, the user context further includes a target access network device identifier, such as an eNB ID to which the terminal is handed over. So that the MME knows which 4G eNB the terminal is about to access. The MME may send a Handover Request to the eNB requesting the eNB to allocate resources for the terminal in advance.

(optional) S808a, MME assigning the terminal with the second indication information based on the first identity.

The second indication information is used for indicating that the terminal falls back to the EPS through the EPS fall-back procedure.

After receiving the Forward Relocation Request message, the MME finds that the session context carried by the message includes qci=1, and then the MME can determine that the qci=1 corresponds to the voice-specific bearer, where the MME considers that the terminal is performing voice service, or that the corresponding terminal is about to perform voice service. For example, the terminal may have just initiated a call, and the voice has not been switched on. As a possible implementation, the MME marks the terminal with second indication information to indicate that the terminal is performing voice service or is about to perform voice service. Subsequently, the MME may determine, according to the second indication information, that deletion of the current voice PDN connection of the terminal is not allowed, so as to avoid affecting the voice service of the terminal.

The second indication information may be flexibly set based on the MME's own policy. For example, the identification bit and the character string can be preconfigured. The embodiment of the application does not limit the specific implementation of the second indication information.

It should be noted that, this step S810a is an optional step. That is, the MME may not make the second indication information for the terminal. In this implementation manner, subsequently, the MME determines, according to the first identifier, not to delete the current voice PDN connection of the terminal.

S809a, 5GS to EPS handover (handover) procedure.

The specific implementation of S809a can be seen in the prior art. Through the handover procedure, the terminal drops back from 5GS to EPS for voice traffic in the 4G network.

In other embodiments, in the handover procedure, the SMF receives a bearer modification request to learn that the terminal has fallen back to the EPS, and the SMF may send a bearer modification response to the MME. The bearer modification response may carry the first identification described above.

S810a, SMF sends a bearer creation request to MME (create bearer request).

It is easy to understand that when the terminal has switched to the 4G network, the SMF sends a bearer creation request for requesting the MME to create a voice-specific bearer and/or a video-specific bearer. So as to transmit traffic data for voice and/or video calls over the created voice and/or video specific bearer.

Optionally, the bearer creation request includes one or more of the following information: the identity, QCI, of the voice and/or video specific bearer requested to be created. Illustratively, the bearer creation request includes a QCI of 1 (corresponding to a voice-specific bearer) and an EBI of 8 to request the MME to create a voice-specific bearer with qci=1 and ebi=8.

Optionally, the SMF sends a bearer creation request to the MME, which may be implemented as: the SMF sends a bearer creation request to the SGW, and the SGW sends the bearer creation request to the MME.

S811a, TAU flow.

After the terminal is switched from 5GS to EPS, in order for the EPC device to know the location of the terminal, the TAU procedure of the terminal needs to be performed. This TAU procedure can be seen in the prior art.

And S812a, the MME reserves PDN connection corresponding to the terminal according to the first identification (or the second indication information).

In the embodiment of the present application, under the condition that S808a is not executed, according to the first identifier, that is, the information of the voice private bearer and/or the information of the video private bearer, the MME considers that the terminal is in a call through the information of the voice private bearer and/or the information of the video private bearer, and in order not to interrupt the audio and video service of the terminal, the MME reserves the PDN connection corresponding to the terminal.

In the case of executing S808a, the MME can learn, according to the second indication information, that the EPS fallback of the terminal is triggered, and then the MME will reserve the PDN connection corresponding to the terminal.

As a possible implementation manner, the network side can establish a second dedicated bearer (dedicated bearer) on the PDN connection corresponding to the terminal. Specifically, the SMF establishes a QoS Flow on the PDU session, which can be mapped to a second proprietary bearer in the EPS. The SMF sends the information of the second dedicated bearer to the MME. And the MME sends the information of the second proprietary bearer to the terminal so as to connect the second proprietary bearer from the end to the end. In an exemplary application scenario where a user dials a call, after the second proprietary bearer is connected, the mobile phone rings, and the called party presses the on-hook key to answer the call.

The second proprietary bearer is a voice proprietary bearer and/or a video proprietary bearer. The second proprietary bearer is used for bearing voice service data and/or video service data of the terminal. The voice dedicated bearer is used for carrying voice service data, for example, carrying voice packets in voice call. The video dedicated bearer is used to carry video traffic data, for example, voLTE high definition video data. The information of the second proprietary bearer includes, but is not limited to, EBI, QCI of the second proprietary bearer. The information of the second proprietary bearer can be referred to as the information of the first proprietary bearer.

For example, if the terminal initiates the VoLTE high definition video call, the second proprietary bearer that needs to be established by the network side includes a voice proprietary bearer with QCI of 1 and a video proprietary bearer with QCI of 2.

Specific implementation of the network side to establish voice and/or video specific bearers can be seen in the prior art.

In the prior art, when the MME obtains the target access network device identifier from the AMF, it can know to which target access network device the terminal is switched. If the target access network device is in a preset area in the MME service area, the MME defaults to delete the PDN connection corresponding to the terminal, for example, the MME may delete the PDN connection corresponding to the terminal in the TAU procedure. And reestablishing the PDN connection for the terminal so as to reallocate the user plane IP address for the terminal. As such, as above, it is likely to cause a service interruption of the terminal.

Unlike the prior art, in the embodiment of the present application, when the terminal enters the first TA of the MME, the MME reserves PDN connection according to the first identifier, so that continuity of the terminal service can be ensured, and the probability of failure or interruption of the terminal service is reduced.

S814a, SMF sends a second message to MME.

Accordingly, the MME receives the second message from the SMF.

The second message is for requesting deletion of the first dedicated bearer.

As one possible implementation, the second message may be a delete bearer request (Delete Bearer Request) message.

It should be noted that, in the above procedure, the SMF may interact with the MME, for example, send information of the first dedicated bearer, such as QCI, to the MME, so as to trigger the MME to create the first dedicated bearer.

In this embodiment, considering that the MME has established a second dedicated bearer for carrying voice and/or video traffic data, the first dedicated bearer may not be used for carrying voice traffic data and not carrying video traffic data. Therefore, the SMF may send a second message to the MME in case it is determined that the second dedicated bearer for carrying the service data has been established successfully, so that the MME deletes the first dedicated bearer and releases the resource corresponding to the first dedicated bearer.

Optionally, the second message carries EBI. Also as exemplified above, assuming ebi=7 for the first proprietary bearer, the second message sent by the SMF includes ebi=7 in order to request the MME to delete the first proprietary bearer with EBI of 7.

S815a, the MME sends a third message to the access network device.

Accordingly, the access network device receives the third message from the MME.

The access network device may be, for example but not limited to, an E-UTRAN device.

It should be understood that after receiving the second message, the MME knows that the first dedicated bearer needs to be deleted, and then sends a third message to the E-UTRAN device to request the E-UTRAN device to release the resource corresponding to the first dedicated bearer.

As a possible implementation, the third message may be an E-UTRAN radio access bearer release order (E-RAB Release Command).

S816a, the E-UTRAN equipment feeds back the response of the third message to the MME.

It will be appreciated that after the E-UTRAN device has completed releasing the resources of the first dedicated bearer, it replies with a response to the third message to the MME.

As one possible implementation, the response of the third message may be an E-UTRAN radio access bearer release response (E-RAB Release Response).

S817a, MME sends a response of the second message to SMF.

Accordingly, the SMF receives a response of the second message from the MME.

The response of the second message is used to indicate that the first proprietary bearer has been deleted.

As one possible implementation, the response of the second message may be a delete bearer response (Delete Bearer Response).

The (optional) S818a, SMF sends a first notification to the PCF.

Accordingly, the PCF receives the first notification from the SMF.

It should be appreciated that if in the above procedure the SMF does not inform the PCF that the second dedicated bearer has been established successfully, the SMF needs to send a first notification in order to inform the PCF that the second dedicated bearer, i.e. the voice and/or video dedicated bearer, has been established successfully.

As one possible implementation, the SMF invokes a session management policy control Update Request (npcf_smpolicy control_update Request) service of the PCF to send the first notification to the PCF.

In some embodiments, the terminal drops back to the EPS from 5GS through a handover. The SMF sends a first identifier to the MME through the AMF to implicitly indicate that the terminal is falling back to the EPS through an EPS fallback procedure. The network element establishes a first proprietary bearer to transmit traffic data. In this case, referring to fig. 8 (b), the communication method in the embodiment of the present application specifically includes:

s801b, the terminal initiates a service request to the IMS, and the IMS triggers a special bearing establishment flow.

The specific implementation of this S801b can be seen in S701 described above.

S802b, the SMF determines that EPS fallback of the terminal is triggered.

The specific implementation of S802b can be seen in S702 above.

S803b, the SMF obtains the information of the first proprietary bearer.

Alternatively, S803b may be implemented as the following steps S803b1 and S803b2:

s803b1, SMF sends a first message to AMF.

Accordingly, the AMF receives the first message from the SMF.

The specific implementation of S803b1 can be seen in S803a1 described above.

S803b2, AMF sends a response of the first message to SMF.

Accordingly, the SMF receives a response of the first message from the AMF.

The specific implementation of S803b2 can be seen in S803a2 described above.

S804b, the NG-RAN device sends a handover request to the AMF (Handover Required).

Accordingly, the AMF receives a handover request from the NG-RAN device.

The specific implementation of S804b may be referred to above in S804a.

S805b, the AMF sends a session context request to the SMF.

Accordingly, the SMF receives a session context request from the AMF.

The specific implementation of S805b may be seen in S805a above.

S806b, the SMF sends a session context response to the AMF.

Accordingly, the AMF receives the session context response from the SMF.

The specific implementation of S806b can be seen in S806a above.

S807b, the AMF sends the first identity to the MME.

Accordingly, the MME receives the first identity from the AMF.

The specific implementation of this S807b can be seen in S807a described above.

(optional) S808b, the MME assigning the terminal with the second indication information based on the first identity.

The specific implementation of S808b can be seen from S808a described above.

S809b, 5GS to EPS handover (handover) procedure.

The specific implementation of S809b can be seen in the prior art.

S810b, SMF sends a bearer creation request to MME (create bearer request).

The specific implementation of S810b can be seen in S810a above.

S811b, TAU flow.

This TAU procedure can be seen in the prior art.

And S812b, the MME reserves the PDN connection corresponding to the terminal according to the first identification (or the second indication information).

The specific implementation of S812b can be seen in S812a above.

S813b, the MME sends information of the first dedicated bearer to the terminal.

As a possible implementation, the MME does not have to newly establish the second dedicated bearer, but may utilize the established first dedicated bearer to carry traffic data.

It should be understood that the first dedicated bearer is created in the above procedure, but after the terminal switches to EPS, the first dedicated bearer is not available because the information of the first dedicated bearer exists only on the network side, and the terminal does not know the information of the first dedicated bearer. The information of the first proprietary bearer exists in the SMF, and the SMF may send the information of the first proprietary bearer to the MME through the AMF, and the MME may also send the information of the first proprietary bearer to the access network device.

Therefore, consider that the MME sends information of the first dedicated bearer to the terminal to communicate the terminal to the first dedicated bearer of the network side. In this way, the terminal may transmit traffic data over the first dedicated bearer.

As one possible implementation, the MME sends an activate dedicated EPS bearer context request (Activate dedicated EPS bearer context request) message to the terminal, the message carrying information of the first dedicated bearer.

Optionally, the terminal feeds back an activate dedicated EPS bearer context accept (Activate dedicated EPS bearer context accept) message to the MME.

(optional) S814b, SMF sends a second notification to the PCF.

Accordingly, the PCF receives the second notification from the SMF.

Optionally, after determining that the first dedicated bearer is connected, the SMF sends a second notification to notify the PCF that the first dedicated bearer has been established successfully.

As one possible implementation, the SMF invokes the nccf_smpolicy control_update Request service of the PCF to send the second notification to the PCF.

Unlike the embodiment corresponding to fig. 8 (a) in which the network side transmits the service data of the terminal by establishing the second dedicated bearer, in the embodiment corresponding to fig. 8 (b), the MME can send the first dedicated bearer information of the network side to the terminal on the basis that the network side has established the first dedicated bearer, so as to open the first dedicated bearer, and the terminal can transmit the service data through the first dedicated bearer.

In other embodiments, the terminal drops back to the EPS from 5GS by handover. The AMF determines that EPS fallback of the terminal is triggered, and the AMF sends a first identification to the MME so as to implicitly indicate the terminal to fall back to the EPS through an EPS fallback flow. The MME establishes a second dedicated bearer for carrying traffic data. In this case, referring to fig. 8 (c), the communication method in the embodiment of the present application specifically includes:

s801c, the terminal initiates a service request to the IMS, and the IMS triggers a special bearing establishment flow.

The specific implementation of this S801c can be seen in S701 described above.

S802c, AMF determines that EPS fallback of the terminal is triggered.

The specific implementation of S802c can be seen in S702 above.

S803c, the AMF obtains the information of the first proprietary bearer.

As one possible implementation, the AMF may generate the information of the first proprietary bearer based on the local information. The information of the first proprietary bearer includes a first identification.

S804c, the NG-RAN device sends a handover request to the AMF.

Accordingly, the AMF receives a handover request from the NG-RAN device.

The specific implementation of S804c may be referred to above in S804a.

S805c, the AMF sends a session context request to the SMF.

Accordingly, the SMF receives a session context request from the AMF.

The specific implementation of this S805c may be seen in S805a above.

S806c, the SMF sends a session context response to the AMF.

Accordingly, the AMF receives the session context response from the SMF.

Note that, if the AMF has obtained the first identifier in S803, the session context response may not include the first identifier.

S807c, the AMF sends the first identity to the MME.

Accordingly, the MME receives the first identity from the AMF.

The specific implementation of this S807c can be seen in S807a described above.

(optional) S808c, the MME assigning the second indication information to the terminal based on the first identity.

The second indication information is used for indicating the terminal to fall back to the EPS through the EPS fall-back process.

The specific implementation of S808c can be seen in S808a described above.

S809c, 5GS to EPS handover (handover) procedure.

The specific implementation of this S809c can be seen in the prior art.

S810c, SMF sends a bearer creation request to MME.

The specific implementation of this S810c can be seen in S810a above.

S811c, TAU flow.

This TAU procedure can be seen in the prior art.

And S812c, the MME reserves the PDN connection corresponding to the terminal according to the first identification (or the second indication information).

The specific implementation of S812c can be seen in S812a above.

In this way, the network side can establish a second proprietary bearer on the PDN connection corresponding to the terminal, so as to carry voice and/or video service data of the terminal.

S814c, the SMF sends a second message to the MME.

Accordingly, the MME receives the second message from the SMF.

The second message is for requesting deletion of the first dedicated bearer.

The specific implementation of S814c may be referred to above in S814a.

S815c, the MME sends a third message to the E-UTRAN device.

The specific implementation of S815c may be referred to above in S815a.

S816c, the E-UTRAN equipment feeds back the response of the third message to the MME.

The specific implementation of S816c may be referred to above in S816a.

S817c, the MME sends a response of the second message to the SMF.

Accordingly, the SMF receives a response of the second message from the MME.

The specific implementation of S817c can be seen in S817a above.

(optional) S818c, SMF sends a first notification to the PCF.

Accordingly, the PCF receives the first notification from the SMF.

The implementation of S818c can be seen from S818a above.

Unlike the embodiment corresponding to fig. 8 (a) in which EPS fallback by the SMF detection terminal is triggered, the embodiment corresponding to fig. 8 (c) in which EPS fallback by the AMF detection terminal can be triggered.

In some embodiments, the terminal drops back to the EPS from 5GS through a handover. And determining by the AMF that EPS fallback of the terminal is triggered, and sending a first identification to the MME so as to implicitly indicate that the terminal is falling back to the EPS through an EPS fallback procedure. The network element transmits traffic data over the first proprietary bearer. In this case, referring to fig. 8 (d), the communication method in the embodiment of the present application specifically includes:

S801d, the terminal initiates a service request to the IMS, and the IMS triggers a special bearing establishment flow.

The specific implementation of this S801d can be seen in S701 described above.

S802d, AMF determines that EPS fallback of the terminal is triggered.

The specific implementation of S802d can be seen in S702 above.

S803d, the AMF obtains the information of the first proprietary bearer.

Optionally, the AMF generates the information of the first proprietary bearer according to the local information. The information of the first proprietary bearer includes a first identification.

S804d, the NG-RAN device sends a handover request to the AMF.

Accordingly, the AMF receives a handover request from the NG-RAN device.

The specific implementation of S804d may be referred to above in S804a.

S805d, the AMF sends a session context request to the SMF.

Accordingly, the SMF receives a session context request from the AMF.

The specific implementation of S805d may be referred to above in S805a.

S806d, the SMF sends a session context response to the AMF.

Accordingly, the AMF receives the session context response from the SMF.

The specific implementation of S806d can be seen in S806c above.

S807d, AMF sends the first identity to MME.

Accordingly, the MME receives the first identity from the AMF.

The specific implementation of S807d can be seen in S807a described above.

(optional) S808d, the MME assigning the second indication information to the terminal based on the first identity.

The specific implementation of S808d can be seen in S808a described above.

S809d, 5GS to EPS handover (handover) procedure.

The specific implementation of this S809d can be seen in the prior art.

S810d, SMF sends a bearer creation request to MME (create bearer request).

The specific implementation of S810d can be seen in S810a above.

S811d, TAU flow.

This TAU procedure can be seen in the prior art.

And S812d, the MME reserves the PDN connection corresponding to the terminal according to the first identification (or the second indication information).

The specific implementation of S812d can be seen in S812a above.

S813d, the MME sends information of the first dedicated bearer to the terminal.

The specific implementation of S813d can be seen in S813b described above.

(optional) S814d, SMF sends a second notification to the PCF.

Accordingly, the PCF receives the second notification from the SMF.

The specific implementation of S814d may be referred to above in S814b.

In other embodiments, the terminal drops back from 5GS to EPS by redirection. The SMF sends a first identifier to the MME through the AMF to implicitly indicate that the terminal is falling back to the EPS through an EPS fallback procedure. In this case, referring to fig. 9 (a), the communication method in the embodiment of the present application specifically includes:

S901a, a terminal initiates a service request to an IMS, and the IMS triggers a special bearing establishment flow.

Specific implementation of S901a can be seen in S701 described above.

S902a, SMF determines that EPS fallback of the terminal is triggered.

Specific implementation of S902a can be seen from S702 above.

S903a, SMF obtain the information of the first proprietary bearer.

Alternatively, the step S903a may be implemented as the following steps S903a1 and S903a2:

s903a1, SMF sends a first message to AMF.

Accordingly, the AMF receives the first message from the SMF.

Specific implementation of S903a1 can be seen in S803a1 described above.

S903a2, AMF sends a response of the first message to SMF.

Accordingly, the SMF receives a response of the first message from the AMF.

Specific implementation of S903a2 can be seen in S803a2 described above.

S906a, the terminal initiates a redirection flow.

Specifically, the redirection may be accomplished through AN access network side release (access network release, AN release) procedure and a reattachment procedure. Specific implementations of redirection can be seen in the prior art.

It is easy to understand that through the redirection procedure, the terminal drops back from 5GS to EPS for voice traffic in the 4G network.

S907a, the terminal initiates a TAU flow.

Specific implementation of the TAU procedure can be seen in the prior art.

Through the TAU procedure, the terminal can report information such as its own position to the 5GS.

S908a, AMF sends a session context request to SMF.

Accordingly, the SMF receives a session context request from the AMF.

Specific implementation of S908a can be seen in S805a above.

S909a, SMF sends a session context response to AMF.

Accordingly, the AMF receives the session context response from the SMF.

Specific implementations of S909a can be found in S806a described above.

S910a, the AMF sends the first identity to the MME.

Accordingly, the MME receives the first identity from the AMF.

Specific implementation of S910a can be seen from S807a described above.

The (optional) S911a, MME assigns the terminal with the second indication information based on the first identity.

The second indication information is used for indicating that the EPS fallback of the terminal is triggered, and the second indication information may be different from the first indication information.

Specific implementations of S911a can be found in S808a described above.

S912a, the TAU procedure is continued.

Specific implementations of S912a can be seen in the prior art.

S913a, SMF sends a bearer creation request to MME.

Specific implementation of S913a can be found in S810a above.

S914a, continuing the TAU flow.

This TAU procedure can be seen in the prior art.

S915a, MME reserves PDN connection corresponding to the terminal according to the second indication information or the first identification.

The specific implementation of S915a may be found in S812a described above.

In this way, the network side can establish a second proprietary bearer on the PDN connection corresponding to the terminal.

S917a, SMF sends a second message to MME.

Accordingly, the MME receives the second message from the SMF.

Specific implementation of S917a can be found in S814a described above.

S918a, the MME sends a third message to the E-UTRAN device.

Specific implementations of S918a can be found in S815a described above.

The E-UTRAN device feeds back a response of the third message to the MME S919 a.

Specific implementation of S919a can be found in S816a above.

S920a, the MME sends a response of the second message to the SMF.

Accordingly, the SMF receives a response of the second message from the MME.

Specific implementation of S920a may be found in S817a above.

The (optional) S921a, SMF sends a first notification to the PCF.

Accordingly, the PCF receives the first notification from the SMF.

Specific implementation of S921a can be found in S818a described above.

In other embodiments, the terminal drops back from 5GS to EPS by redirection. And determining that the EPS fallback of the terminal is triggered by the SMF, and sending a first identification to the MME so as to implicitly indicate that the terminal is falling back to the EPS through the EPS fallback flow. And transmitting the service data of the terminal through the first proprietary bearer. In this case, referring to fig. 9 (b), the communication method in the embodiment of the present application specifically includes:

S901a-S915a、S916b、S917b。

the specific implementation of S901a-S915a and S921a may be referred to the corresponding embodiment (a) in fig. 9.

S916b, the MME sends information of the first dedicated bearer to the terminal.

Specific implementation of S916b may be found in S813b described above.

S917b, SMF sends a second notification to PCF.

Specific implementation of S917b can be found in S814b above.

In other embodiments, the terminal drops back from 5GS to EPS by redirection. And determining by the AMF that EPS fallback of the terminal is triggered, and sending a first identification to the MME so as to implicitly indicate that the terminal is falling back to the EPS through an EPS fallback procedure. And transmitting the service data of the terminal through the second proprietary bearer. In this case, referring to fig. 9 (c), the communication method in the embodiment of the present application specifically includes:

s901a, wherein, the specific implementation of S901a may be referred to the embodiment corresponding to (a) in fig. 9.

S902c, the AMF determines that the EPS fallback of the terminal is triggered.

Specific implementation of S902c can be seen in S802c described above.

S903c, AMF obtain the information of the first proprietary bearer.

Specific implementation of S903c can be found in S803c described above.

Specific implementations of S906a-S921a can be found in the embodiments described above.

In other embodiments, the terminal drops back from 5GS to EPS by redirection. And determining by the AMF that EPS fallback of the terminal is triggered, and sending a first identification to the MME so as to implicitly indicate that the terminal is falling back to the EPS through an EPS fallback procedure. And transmitting the service data of the terminal through the first proprietary bearer. In this case, referring to fig. 9 (d), the communication method in the embodiment of the present application specifically includes:

S902d, the AMF determines that the EPS fallback of the terminal is triggered.

Specific implementation of S902d can be found in S802c described above.

S903d, AMF obtain the information of the first proprietary bearer.

Specific implementation of S903d can be found in S803c described above.

Specific implementations of S906a-S917b can be found in the embodiments described above.

In other embodiments, the terminal drops back to the EPS from 5GS by handover. The SMF sends first indication information to the MME through the AMF so as to explicitly indicate that the terminal is falling back to the EPS through the EPS falling-back flow. In this case, referring to fig. 10, the communication method in the embodiment of the present application specifically includes:

s1001, the terminal initiates a service request to the IMS, and the IMS triggers a special bearing establishment flow.

The specific implementation of S1001 may be referred to above in S701.

S1002, the NG-RAN device sends a handover request to the AMF.

Accordingly, the AMF receives a handover request from the NG-RAN device.

The specific implementation of S1002 can be seen in S806 above.

S1003, the AMF sends a session context request to the SMF.

Accordingly, the SMF receives a session context request from the AMF.

The specific implementation of this S1003 can be seen in S807 described above.

S1004, the SMF sends a session context response to the AMF.

Accordingly, the AMF receives the session context response from the SMF.

The session context response includes the session context of the terminal.

Optionally, if the SMF determines that EPS fallback of the terminal is triggered, the session context optionally includes first indication information. The first indication information is used for indicating that the terminal falls back to the EPS through an EPS fall-back procedure.

The first indication information is denoted EPS Fallback Indicator. The EPS Fallback Indicator may be a flag bit, a cause value, or other forms, which are not limited in the embodiments of the present application.

S1005, the AMF sends first indication information to the MME.

Accordingly, the MME receives the first indication information from the AMF.

As one possible implementation, the AMF sends Forward Relocation Request a message to the MME, the message containing the session context of the terminal. The session context includes first indication information.

Optionally, the AMF determines that the EPS Fallback of the terminal is triggered, and the AMF may identify that the terminal is falling back to the EPS through the EPS Fallback procedure according to the cause value IMS Voice EPS Fallback or RAT Fallback Triggered obtained from the NG-RAN device, encapsulate the first indication information in the user context, and send the first indication information to the MME.

S1006, continuing the switching flow.

A specific implementation of this S1006 can be seen in the prior art.

(optional) S1007, SMF sends a bearer modification response to MME (Modify Bearer Response).

Accordingly, the MME receives a bearer modification response from the SMF.

In the above procedure, the SMF receives the bearer modification request, so that the SMF knows that the terminal has been switched to the 4G network.

Alternatively, if the SMF does not carry the first indication information in the session context response of S1004, the SMF needs to carry the first indication information in a bearer modification response sent to the MME.

S1008, the SMF sends a bearer creation request to the MME (create bearer request).

The specific implementation of S1008 can be seen from S812 above.

S1009, the TAU procedure is continued.

This TAU procedure can be seen in the prior art.

S1010, the MME reserves PDN connection corresponding to the terminal according to the first indication information.

In this way, a second dedicated bearer may be subsequently established on the PDN connection to which the terminal corresponds.

In other embodiments, the terminal drops back from 5GS to EPS by redirection. The SMF sends first indication information to the MME through the AMF so as to explicitly indicate that the terminal is falling back to the EPS through the EPS falling-back flow. In this case, referring to fig. 11, the communication method in the embodiment of the present application specifically includes:

S1101, the terminal initiates a service request to IMS, which triggers a special bearing establishment flow.

The specific implementation of S1101 can be seen in S701 described above.

S1102, the terminal initiates a redirection flow.

Specific implementation of this redirection procedure can be seen in the prior art.

S1103, the terminal initiates a TAU flow.

Specific implementation of the TAU procedure can be seen in the prior art.

S1104, the AMF sends a session context request to the SMF.

Accordingly, the SMF receives a session context request from the AMF.

The specific implementation of S1104 may be found in S807 described above.

S1105, the SMF sends a session context response to the AMF.

Accordingly, the AMF receives the session context response from the SMF.

The session context response includes the session context of the terminal. Optionally, the session context includes first indication information. The first indication information is used for indicating that the terminal falls back to the EPS through an EPS fall-back procedure.

The specific implementation of S1105 can be seen from S1004 described above.

S1106, the AMF sends first indication information to the MME.

Accordingly, the MME receives the first indication information from the AMF.

The specific implementation of S1106 can be seen from S1005 above.

S1107, continuing to execute the TAU flow.

Specific implementation of the TAU procedure can be seen in the prior art.

The (optional) S1108, SMF sends a bearer modification response to the SGW.

Accordingly, the SGW receives a bearer modification response from the SMF (Modify Bearer Response).

It should be appreciated that in the above procedure, the SMF receives (bearer modification request) Modify Bearer Request knowing that the terminal has redirected to the 4G network. If the SMF does not carry the first indication information in the session context response in S1105, the SMF needs to carry the first indication information in the bearer modification response.

(optional) S1109, SGW sends session creation response to MME (Create session Response).

Accordingly, the MME receives a session creation response from the SGW.

The session creation response includes the first indication information.

S1110, the SMF sends a bearer creation request to the MME.

The specific implementation of S1110 may be referred to above in S812.

S1111, continuing the TAU flow.

This TAU procedure can be seen in the prior art.

S1112, the MME reserves PDN connection corresponding to the terminal according to the first indication information.

It should be understood that various aspects of the embodiments of the present application may be used in reasonable combination, and that the explanation or illustration of the various terms presented in the embodiments may be referred to or explained in the various embodiments without limitation.

It should also be understood that, in various embodiments of the present application, the size of the sequence number of each process does not mean that the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

It will be appreciated that, in order to implement the functions of any of the above embodiments, the first core network device, the second core network device, or other network devices (e.g., PCF network elements) include corresponding hardware structures and/or software modules that perform the respective functions. Those of skill in the art will readily appreciate that the elements and algorithm steps of the examples described in connection with the embodiments disclosed herein may be implemented as hardware or combinations of hardware and computer software. Whether a function is implemented as hardware or computer software driven 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.

The embodiment of the application can divide the functional modules of the first core network device, the second core network device or other network devices (such as PCF network elements) and the like, for example, each functional module can be divided corresponding to each function, or two or more functions can be integrated in one processing module. The integrated modules may be implemented in hardware or in software functional modules. It should be noted that, in the embodiment of the present application, the division of the modules is schematic, which is merely a logic function division, and other division manners may be implemented in actual implementation.

For example, in the case where the functional modules are divided in an integrated manner, as shown in fig. 12, a block diagram of a communication device according to an embodiment of the present application is provided. The communication apparatus 1600 may be a first core network device or an apparatus supporting the functionality of the first core network device (such as but not limited to a system-on-a-chip), or a second core network device (such as an MME) or an apparatus supporting the functionality of the second core network device. The communication device may include a transceiver unit 1610 and a processing unit 1620.

Wherein, when the communication apparatus is a first core network device, the transceiver unit 1610 is configured to support the first core network device to perform the step S703 and/or other processes for the techniques described herein. The processing unit 1620 is configured to assist the first core network device in performing step S702 described above, and/or other processes for the techniques described herein.

Specifically, when the first core network device is an SMF, the transceiver 1610 is configured to support the SMF to perform the steps S703, S803a1, S803a2, S805a, S806a, S810a, S814a, S817a, S818a, S803b1, S803b2, S805b, S810b, S814b, S805c, S806c, S810c, S814c, S817c, S818c, S805d, S806d, S903a1, S903a2, S1003, S1004, S1104, S1105, and/or other procedures for the techniques described herein. The processing unit 1620 is configured to assist the SMF in performing the steps S702, S802a, S803a, S802b, S803b, S902a, S903a described above, and/or other processes for the techniques described herein.

Specifically, when the first core network device is an AMF, the transceiver unit 1610 is configured to support the AMF to perform the steps S703, S803a1, S803a2, S805a, S806a, S807a, S803b1, S803b2, S805b, S806b, S807b, S805c, S806c, S807c, S805d, S806d, S807d, S903a1, S903a2, S1003, S1004, S1005, S1104, S1105, S1106, and/or other procedures for the techniques described herein. The processing unit 1620 is configured to assist the AMF in performing the steps S702, S802c, S803c, S802d, S803d, S902c, S903c, S902d, S903d described above, and/or other processes for the techniques described herein.

When the communication device is an MME, the transceiving unit 1610 is configured to support the MME to perform the steps S703, S807a, S814a, S817a, S815a, S816a, S807b, S810b, S813b, S807c, S810c, S815c, S814c, S816c, S817c, S807d, S910a, S916b, S1005, S1104, S1105 described above, and/or other procedures for the techniques described herein. The processing unit 1620 is configured to assist the MME to perform the steps S701, S704, S808a, S810a, S812a, S808b, S812c, S812d, S915a, S1010, S1112 described above, and/or other processes for the techniques described herein.

Optionally, the communication device further comprises a storage unit (not shown in fig. 12). And a storage unit for storing the program code and data of the communication device, the data may include, but is not limited to, raw data or intermediate data, etc.

In one possible implementation, the processing unit 1620 may be a controller or the processor 401 or 408 shown in FIG. 6, such as a central processing unit (Central Processing Unit, CPU), a general purpose processor, a digital signal processing (Digital Signal Processing, DSP), an application specific integrated circuit (Application Specific Integrated Circuit, ASIC), a Field programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic device, a transistor logic device, a hardware component, or any combination thereof. Which may implement or perform the various exemplary logic blocks, modules, and circuits described in connection with this disclosure. A processor may also be a combination that performs computing functions, e.g., including one or more microprocessors, a combination of a DSP and a microprocessor, and so forth. The transceiver 1610 may be the communication interface 404 shown in fig. 6, a transceiver circuit, etc. The memory unit may be the memory 403 shown in fig. 6.

Currently, in a scenario that a terminal is switched or redirected from a 5G network to a 4G network, or is switched or redirected from the 4G network to the 5G network, a core network device may delete a PDN connection corresponding to the terminal by mistake.

In order to reduce the probability of the core network device deleting the PDN connection by mistake, the embodiment of the application further provides a communication method, which can be applied to the terminal moving from the first TA of the third network to the second TA of the fourth network, where the RAT of the third network is different from the RAT of the fourth network. It should be noted that "the terminal moves from the first TA of the third network to the second TA of the fourth network" may be caused by a change in the location of the terminal, or may be caused by a service of the terminal, for example, a voice service of the terminal causes the terminal to move from the 5G network to the 4G network, or may be caused by a network signal coverage situation where the terminal is located.

In some embodiments, the third network is, for example, a 5GS network, and the fourth network is, for example, an EPS network. The radio access technology (radio access technology, RAT) of the third network is, for example but not limited to, NR and the RAT of the fourth network is, for example but not limited to, LTE. In other embodiments, the third network is e.g. EPS and the fourth network is e.g. 5GS. That is, the method can be applied to a flow of 5GS to EPS, or a flow of EPS to 5GS. Or other similar process. Referring to fig. 13, the method includes:

S1301, the third core network device obtains information of the first TA and information of the second TA.

The third core network device may be an SMF as shown in fig. 3 or fig. 4. And the SMF may be a converged SMF, for example, the converged SMF may have the functions of an existing SMF and PGW-C functions. The PGW-C functions include control plane functions such as session management, bearer control, etc. Alternatively, the third core network device may be an MME shown in fig. 3 or fig. 4, or may be an AMF shown in fig. 3 or fig. 4.

Alternatively, the first TA may be referred to as a source TA (source TA); the information of the first TA may be, for example but not limited to, a TAI of the first TA, and may also be referred to as a source TAI (source TAI). The second TA may be referred to as a target TA (target TA); the information of the second TA may be, for example but not limited to, a TAI of the second TA, and may also be referred to as a target TAI (target TAI).

Currently, the TAI format of 5G is typically different from that of 4G. Specifically, a TAI of 5G is three bytes long and a TAI of 4G is two bytes long. Since the formats of the 4G TAI and the 5G TAI are different, the 4G network element (e.g., MME, etc.) cannot identify the TAI of the 5G, and therefore the 4G network element cannot perceive the 5G area, i.e., does not know from which TA of the 5G the terminal falls back to the TA of the 4G. Similarly, AMF can only recognize 5G TAI, but not 4G TAI.

Taking the example that the terminal moves between the 5G TA and the 4G TA, in order to enable the third core network device to identify the 4G TAI and the 5G TAI at the same time, the third core network device may pre-configure information of the third preset area. Wherein the third preset area may include at least one TA of the third network and at least one TA of the fourth network. The information of the third preset area includes information of at least one TA of the third network and information of at least one TA of the fourth network. Illustratively, the information of the third predetermined area includes at least one TAI of the third network and at least one TAI of the fourth network.

The terminal enters a third preset area, the terminal re-registers to the core network equipment, or the PDU session of the terminal is deleted by the core network equipment, and the core network equipment instructs the terminal to re-establish the PDU session.

As one possible design, the third preset area may be a regulatory domain as defined above, where communication is restricted, e.g. terminals entering the regulatory domain will be reassigned IP addresses which may be restricted to only part of the type of traffic. The third predetermined area may also be referred to as a third control area. The third core network device is illustratively configured with information of a third preset area as shown in (a) of fig. 14, which includes TA1 of 5G, TA2 of 4G. The information of the third preset area comprises identification of TA1 and identification of TA2.

As such, since the third core network device is configured with the 4G TAI and the 5G TAI, it can recognize both the TAI in the 4G format and the TAI in the 5G format.

It is identified from which 5G TA the terminal falls back to the 4G TA, or it is identified from which 4G TA the terminal moves to the 5G TA.

The third core network device obtains the information of the second TA, and the specific implementation can be seen below. For example, when the third core network device is an SMF, the SMF may acquire information of the second TA according to step S1503 described below. For another example, when the third core network device is an MME, the MME may acquire the information of the second TA according to step S2202 described below. For another example, when the third core network device is an AMF, the AMF may acquire information of the second TA according to step S2703 described below.

As a possible implementation manner, if the third core network device is an MME, the third core network device obtains information of the first TA, which may be specifically implemented as: information of the first TA is received from a fourth core network device of the third network. The fourth core network device is, for example but not limited to, an AMF. For example, in a scenario where a terminal moves from a 5G network to a 4G network, an MME of the 4G network may receive a 5G TAI from an AMF of the 5G network.

As a possible implementation manner, if the third core network device is an AMF, the third core network device obtains the information of the first TA, which may be specifically implemented as: information of the first TA is received from a fourth core network device of the third network. The fourth core network device is, for example but not limited to, an MME. For example, in a scenario where a terminal moves from a 4G network to a 5G network, the AMF of the 5G network may receive a 4G TAI from the MME of the 4G network.

As a possible implementation manner, if the third core network device is a converged SMF, the third core network device obtains the information of the first TA, and for a specific implementation, see, for example, S1503.

And S1302, the third core network equipment reserves or deletes the PDN connection of the packet data network corresponding to the terminal according to the information of the second TA and the information of the first TA.

As an optional implementation manner, the third core network device first determines whether to delete the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA. If the PDN connection corresponding to the terminal is determined to be deleted, deleting the PDN connection corresponding to the terminal by the third core network equipment; or if the PDN connection corresponding to the terminal is not deleted, reserving the PDN connection corresponding to the terminal.

The PDN connection corresponding to the terminal may refer to a PDN connection of a 4G network that has been established by the terminal. In a scenario supporting the interoperability of a 4G network with a 5G network, the PDN connection of the 4G network may also be mapped as a PDU session of the 5G network.

As a possible implementation manner, the third core network device determines the PDN connection corresponding to the reserved terminal according to the following rule:

optionally, if the first TA and the second TA both belong to a third preset area, the third core network device reserves PDN connection corresponding to the terminal. Indicating that the terminal moves in the third preset area, and does not cross-region (moves out of a certain control area or moves into a certain control area), the converged SMF can reserve the PDN connection corresponding to the terminal. Accordingly, the converged SMF may not reassign the IP address for the terminal. This scenario can be seen, for example, in fig. 14 (a). See also (a) of fig. 18 or others, for example.

Or optionally, if the second TA belongs to the third preset area, the first TA does not belong to the third preset area, and EPS fallback of the terminal is triggered, the third core network device reserves PDN connection corresponding to the terminal. For example, referring to fig. 14 (c), the third core network device senses that the terminal falls back from TA1 of 5GS to TA6 of EPS, where TA1 and TA6 are not in the same preset area range, the terminal crosses a region, that is, moves into the preset area, and in this case, if the third core network device detects that the EPS fall back of the terminal is triggered, in order to reduce the probability of service failure or interruption of the terminal, the fusion SMF reserves the PDN connection corresponding to the terminal.

Or if the second TA does not belong to the third preset area, the first TA belongs to the third preset area, and the EPS fallback of the terminal is triggered, the third core network device reserves the PDN connection corresponding to the terminal. Referring to fig. 14 (b), the terminal goes through the cross-zone and falls back from TA1 to TA6, and if the third core network device detects that the EPS of the terminal falls back, the third core network device may reserve the PDN connection corresponding to the terminal, so as to improve the continuity of the voice service.

As a possible implementation manner, the third core network device determines to delete the PDN connection corresponding to the terminal according to the following rule:

Optionally, if the second TA belongs to the third preset area, the first TA does not belong to the third preset area, and the terminal performs the non-voice service, the third core network device deletes the PDN connection corresponding to the terminal. Referring still to fig. 14 (c), the terminal crosses a zone and drops from TA1 to TA6, and in some embodiments, if the third core network device does not detect EPS drop of the terminal, the third core network device may delete the PDN connection corresponding to the terminal. In other embodiments, if the third core network device detects that the terminal performs the non-voice service, the third core network device may delete the PDN connection corresponding to the terminal because the non-voice service has a low requirement for service continuity.

If the third core network device is a converged SMF or AMF, how the converged SMF or AMF specifically detects whether the EPS fallback of the terminal is triggered may be referred to the foregoing embodiment, for example, refer to S702.

If the third core network device is an MME, the MME may receive corresponding indication information from the AMF to learn whether EPS fallback of the terminal is triggered. For example, the first indication information EPS Fallback Indicator is received. The MME may also learn by other means whether EPS fallback is triggered, which is not limited by the embodiment of the present application.

Or, optionally, the second TA does not belong to the third preset area, the first TA belongs to the third preset area, and the terminal performs the non-voice service, and then the third core network device deletes the PDN connection corresponding to the terminal. Referring still to fig. 14 (b), the terminal crosses a zone and drops from TA1 to TA6, and in some implementations, if the third core network device detects EPS drop of the terminal, the third core network device may delete the PDN connection corresponding to the terminal. In other embodiments, if the third core network device detects that the terminal performs the non-voice service, the third core network device may delete the PDN connection corresponding to the terminal because the non-voice service has a low requirement for service continuity.

Or, optionally, the second TA does not belong to the third preset area, the first TA belongs to the third preset area, and if EPS fallback of the terminal is not triggered, the third core network device deletes the PDN connection corresponding to the terminal.

Or, optionally, the second TA belongs to a third preset area, the first TA does not belong to the third preset area, and if EPS fallback of the terminal is not triggered, the third core network device deletes the PDN connection corresponding to the terminal.

Or, optionally, if the second TA belongs to the third preset area, the first TA does not belong to the third preset area. In this case, the first TA may belong to other regulatory regions, or the first TA belongs to an unregulated region. That means, the terminal moves from the other control area or the non-control area to the third control area, and the terminal spans the area, and then the third core network device may delete the PDN connection corresponding to the terminal. This scenario can be seen in fig. 14 (c). See also (b) of fig. 18, for example.

Or, optionally, if the first TA belongs to the third preset area, the second TA does not belong to the third preset area. In this case, the second TA may belong to other regulatory domain or non-regulatory domain. Meaning that the terminal moves out of the third control area, and the terminal spans a region, the third core network device may delete the PDN connection corresponding to the terminal. This scenario can be seen in fig. 14 (b). See also (c) of fig. 18, for example.

It is easy to understand that when it is determined that the PDN connection corresponding to the terminal is deleted, the third core network device needs to execute a procedure of deleting the PDN connection. Wherein, since the PDN connection has multiple bearers, the multiple bearers include a unique default bearer, once the default bearer is deleted, the entire PDN connection is equivalent to being deleted. Therefore, the third core network device may delete the PDN connection corresponding to the terminal by deleting the default bearer of the terminal. Specifically, as a possible implementation manner, the third core network device deleting the PDN connection corresponding to the terminal may refer to the third core network device sending a message for deleting the default bearer of the terminal, that is, a message equivalent to sending a message for deleting the PDN connection corresponding to the terminal. The third core network device sends a message for deleting the PDN connection corresponding to the terminal, which can be seen in the prior art. For example, if the third core network device is an SMF, the message for deleting the PDN connection corresponding to the terminal may be a delete bearer request (delete bearer request).

In the embodiment of the present application, the PDN connection corresponding to the reserved terminal may be replaced with a PDN connection corresponding to the terminal that is not deleted. As a possible implementation manner, the third core network device reserves a specific implementation of the PDN connection corresponding to the terminal, which may mean that the third core network device does not send a message for deleting the PDN connection. For example, when the third core network device is an SMF, the SMF does not send a delete bearer request (delete bearer request) for deleting the PDN connection.

In the scenario of fig. 14 (a), the terminal moves from TA1 to TA2 in the third preset area, and the MME considers that the terminal moves from outside the third preset area to TA2 because it cannot perceive that the terminal is from TA1 to TA2, and then deletes the PDN connection corresponding to the terminal. Similarly, in the scenarios of fig. 14 (b), fig. 14 (c), etc., the MME may also erroneously delete the PDN connection corresponding to the calling terminal. In the embodiment of the present application, in the scenario of fig. 14 (a) or the like, the third core network device may keep or delete the PDN connection corresponding to the terminal according to the information of the first TA and the information of the second TA, that is, the third core network device may not delete the PDN connection corresponding to the terminal. Thus, the probability of terminal service interruption caused by deleting PDN connection by mistake can be reduced.

The corresponding scheme of fig. 13 is explained below in connection with the specific scenarios of fig. 15-19. In the embodiments corresponding to fig. 15 to fig. 19, the converged SMF replaces the mobility management network element (MME or AMF) to determine whether to delete the PDN connection corresponding to the terminal. Specifically, the embodiment corresponding to fig. 15 is applied to the terminal switching from 5GS to EPS (i.e. 4G), the embodiment corresponding to fig. 16 is applied to the terminal redirecting from 5GS to EPS, the embodiment corresponding to fig. 17 is applied to the terminal switching from EPS to 5GS, and the embodiment corresponding to fig. 19 is applied to the terminal redirecting from EPS to 5GS.

Taking the terminal falling back to the EPS from 5GS through the handover manner, and the third core network device being an SMF as an example, referring to fig. 15, the communication method provided in the embodiment of the present application specifically includes:

s1501, the SMF configuration information of a third preset area is fused.

Wherein the third preset area comprises at least one TA of the third network and at least one TA of the fourth network. Still taking fig. 14 (b) as an example, the third preset area of the converged SMF configuration includes 5g TA1, 4g TA2.

The number of the third preset areas configured is not limited in the embodiment of the application. The number of TAs included in the third preset area is not limited.

S1502, the fusion SMF acquires the information of the first TA.

As a possible implementation manner, as shown in fig. 15, in the IMS-triggered private bearer establishment procedure of the EPS fallback scenario, step S1502 may be implemented as follows: the AMF sends an update session context request (nsmf_pduse_ UpdateSMContext Request) to the converged SMF, the update session context request carrying information of the first TA. The specific implementation of the IMS-triggered bearer establishment procedure can be seen from step S701 above.

In other embodiments, step S1502 may also be implemented as: in a service request (service request) procedure, an access network device (e.g., NG-RAN device) reports information of a first TA, such as a 5G TAI before terminal handover, to a converged SMF.

Alternatively, the converged SMF may obtain the information of the first TA through other possible flows, which is not limited in the embodiment of the present application.

S1503, SMF obtains the information of the second TA.

As a possible implementation manner, step S1503 may be implemented as: in the switching procedure from 5GS to EPS, the MME sends a bearer modification request (Modify Bearer Request) to the SGW, and then the SGW sends a bearer modification request to the converged SMF, where the bearer modification request carries information of the second TA, such as the 4G TAI to which the terminal is switched.

Optionally, after the converged SMF receives the bearer modification request, a bearer modification response is fed back to the MME (Modify Bearer Response). Specifically, the converged SMF sends a bearer modification response to the MME via the SGW.

S1504, the fusion SMF reserves or deletes PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

Because the fusion SMF also has the PGW-C function, the fusion SMF can judge whether the PDN connection corresponding to the terminal needs to be deleted according to the 4G TAI after the switching, the 5G TAI before the switching and the configured third preset area. Specific judging methods can be seen in the above embodiments.

S1504 may be executed after the completion of the handover, or may be executed immediately after S1503.

S1505, TAU procedure.

And if the third core network equipment is SMF, the SMF is responsible for reserving or deleting the PDN connection corresponding to the terminal according to the information of the first TA and the information of the second TA, and the MME is not responsible for reserving or deleting the PDN connection corresponding to the terminal. Specifically, when the MME determines that the terminal is switched or redirected from the third network to the fourth network, the MME does not determine whether to delete the PDN connection corresponding to the terminal.

As one possible implementation, the MME receives Forward Relocation Request a message from the AMF, the message carrying N26 interface indication information. The MME judges that the flow is a switching flow according to the N26 interface indication information, namely, the MME determines that the terminal falls back from the third network to the fourth network in a switching mode.

As one possible implementation, the MME receives a TAU Request (TAU Request) message from the terminal, the message comprising a terminal identity (UE Status) cell (information element, IE). As a possible implementation, the identity cell comprises a first identification bit. The MME determines the flow Cheng Weichong targeting procedure based on the first identity of the terminal identity information element, i.e. the terminal is redirected from the third network to the fourth network.

Alternatively, the MME receives a Context Response (Context Response) message from the AMF, the message including RAT type=nr. The MME determines that the terminal is redirected from the third network to the fourth network according to the RAT Type.

S1506, a procedure for establishing a voice-specific bearer and/or a video-specific bearer.

This step is an optional step. When the terminal triggers the EPS to fall back, the call service is needed, and the process comprises the step. A common handoff procedure may not include this step.

Some of the steps of the corresponding embodiment of fig. 15 are not described in detail, and the specific implementation of this part of the steps may be referred to other embodiments or to the prior art.

Taking an example that a terminal redirects from 5GS to EPS and the third core network device is a converged SMF, referring to fig. 16, the communication method provided in the embodiment of the present application specifically includes:

S1601, information of a third preset area is fused with SMF configuration.

S1602, the fusion SMF acquires the information of the first TA.

As a possible implementation manner, in the IMS triggered private bearer establishment procedure, the AMF carries the information of the first TA (5G TAI) to nsmf_pduse_ UpdateSMContext Request sent by the converged SMF.

S1603, the MME sends information of the second TA to the SGW.

Accordingly, the SGW receives information of the second TA from the MME.

As one possible implementation, the MME sends a session creation request (Create Session Request) to the SGW, the session creation request including information of the second TA, such as a 4G TAI to which the terminal is handed over.

S1604, the SGW sends information of the second TA to the converged SMF.

The SGW sends information of the second TA to the converged SMF.

Accordingly, the converged SMF receives information of the second TA from the SGW.

As a possible implementation manner, after receiving the session creation request from the MME, the SGW sends a bearer modification request to the converged SMF, where the bearer modification request carries information of the second TA.

S1605, the fusion SMF reserves or deletes PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

Specifically, the converged SMF determines whether to delete the PDN connection corresponding to the terminal according to the 4G TAI after switching, the 5G TAI before switching, and the configured third preset area. Specific judging methods can be seen in the above embodiments.

(optional) S1606, setup procedure of voice-specific bearer and/or video-specific bearer.

Some of the steps of the corresponding embodiment of fig. 16 are not described in detail, and the specific implementation of this part of the steps may be referred to other embodiments or to the prior art.

Taking an example that the terminal is switched from EPS to 5GS and the third core network device is SMF, referring to fig. 17, the communication method provided in the embodiment of the present application specifically includes:

s1701, the information of the third preset area is fused and configured by the SMF.

S1702, the terminal sends a service request (service request) to the E-UTRAN device.

For example, an idle state terminal initiates a service request procedure to establish a connection with the E-UTRAN device.

S1703, the E-UTRAN device sends information of the first TA to the SMF.

In the service request flow, the E-UTRAN device reports the location information of the terminal, i.e. the information of the first TA, such as the 4G TAI, to the converged SMF.

S1704, the AMF sends information of the second TA to the converged SMF.

Accordingly, the converged SMF receives information of the second TA from the MME.

As one possible implementation, after the AMF receives the Forward Relocation Request from the MME, the AMF sends a create session management context request, i.e., smf_pdustion_ CreateSMContext Request, to the converged SMF, where smf_pdustion_ CreateSMContext Request includes information of the second TA (5G TAI).

S1705, the fusion SMF reserves or deletes PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

The converged SMF judges whether to delete the PDN connection corresponding to the terminal according to the following rule:

optionally, the first TA and the second TA belong to a third preset area, and the fusion SMF reserves PDN connection corresponding to the terminal. For example, as shown in fig. 18 (a), if the converged SMF senses that the terminal is from TA2 to TA1 in the third preset area, the converged SMF reserves the PDN connection corresponding to the terminal.

Or, optionally, the second TA belongs to a preset area, the first TA does not belong to the preset area, and EPS fallback of the terminal is not triggered, and/or, if the terminal performs a non-voice service, the fusion SMF deletes the PDN connection corresponding to the terminal. For example, as shown in fig. 18 (b), if the converged SMF senses that the terminal moves from the non-controlled area TA2 to TA1 in the third preset area and does not sense that the EPS fallback of the terminal is triggered, the converged SMF deletes the PDN connection corresponding to the terminal.

Or, optionally, the second TA belongs to a preset area, the first TA does not belong to the preset area, and EPS fallback of the terminal is not triggered, and/or, if the terminal performs a non-voice service, the fusion SMF deletes the PDN connection corresponding to the terminal. For example, as shown in fig. 18 (b), when the converged SMF senses that the terminal moves from the non-controlled area TA2 to TA1 in the third preset area and senses that the EPS fallback of the terminal is triggered, the converged SMF deletes the PDN connection corresponding to the terminal.

Or, optionally, the second TA does not belong to the third preset area, the first TA belongs to the third preset area, and if EPS fallback of the terminal is not triggered, the fusion SMF deletes the PDN connection corresponding to the terminal. For example, as shown in fig. 18 (c), if the converged SMF senses that the terminal is from TA1 of the third preset area to TA2 of the unregulated area, and senses that EPS fallback of the terminal is not triggered, the converged SMF deletes the PDN connection corresponding to the terminal.

Or, optionally, the second TA does not belong to the third preset area, the first TA belongs to the third preset area, and if EPS fallback of the terminal is triggered, the fusion SMF reserves the PDN connection corresponding to the terminal. For example, as shown in fig. 18 (c), if the converged SMF senses that the terminal is from TA1 of the third preset area to TA2 of the unregulated area and senses that EPS fallback of the terminal is triggered, the converged SMF deletes the PDN connection corresponding to the terminal.

Some of the steps of the corresponding embodiment of fig. 17 are not described in detail, and the specific implementation of this part of the steps may be referred to other embodiments or to the prior art.

Taking the terminal from EPS to 5GS in a redirection manner, and the third core network device is an SMF as an example, referring to fig. 19, the communication method provided in the embodiment of the present application specifically includes:

S1901, the SMF configuration information of the third preset area is fused.

S1902, the fusion SMF acquires the information of the first TA.

Specific implementations of this step can be seen in the prior art.

S1903, the AMF sends information of the second TA to the converged SMF.

Accordingly, the converged SMF receives information of the second TA from the AMF.

As one possible implementation, after the AMF sends nudm_uecm_registration/nudm_sdm_get/subscore to the UDM, the AMF sends an AMF to the converged SMF an smf_pduse_ CreateSMContext Request message, which smf_pduse_ CreateSMContext Request message includes information of the second TA.

And S1904, the fusion SMF reserves or deletes the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

Specific methods for determining the fusion SMF can be found in the above embodiments.

The embodiment of the present application further provides a communication method, where the third core network device is a mobility management network element (MME or AMF), and a third preset area needs to be configured in advance in the mobility management network element.

Embodiments of the present application are described below in conjunction with the specific scenarios of fig. 20-27.

The embodiment corresponding to fig. 20 is applied to switching the terminal from 5GS to EPS (i.e. 4G), where the MME obtains information of the first TA from the AMF, and determines whether to delete the PDN connection corresponding to the terminal. The embodiment corresponding to fig. 21 is applied to switching the terminal from 5GS to EPS, and the MME acquires the information of the first TA from the converged SMF and determines whether to delete the PDN connection corresponding to the terminal.

The embodiment corresponding to fig. 22 is applied to redirection from 5GS to EPS by the terminal, and MME obtains information of the first TA from AMF and determines whether to delete PDN connection corresponding to the terminal. The embodiment corresponding to fig. 23 is applied to redirection from 5GS to EPS at the terminal, and MME obtains information of the first TA from the converged SMF and determines whether to delete the PDN connection corresponding to the terminal.

The embodiment corresponding to fig. 24 is applied to the terminal being switched from EPS to 5gs, and the amf obtains the information of the first TA from MME, and determines whether to delete the PDN connection corresponding to the terminal. The embodiment corresponding to fig. 25 is applied to the terminal switching from EPS to 5gs, and the amf obtains the information of the first TA from the converged SMF, and determines whether to delete the PDN connection corresponding to the terminal.

The embodiment corresponding to fig. 26 is applied to the redirection from EPS to 5gs, where the amf obtains the information of the first TA from MME, and determines whether to delete the PDN connection corresponding to the terminal. The embodiment corresponding to fig. 27 is applied to the redirection from EPS to 5gs, where the amf obtains the information of the first TA from the converged SMF, and determines whether to delete the PDN connection corresponding to the terminal.

Taking an example that a terminal is switched from 5GS to EPS (i.e. 4G), an MME acquires information of a first TA from an AMF and determines whether to delete a PDN connection corresponding to the terminal, referring to fig. 20, a communication method provided in an embodiment of the present application includes:

S2201, the MME configures information of the third preset area.

Wherein the third preset area comprises at least one TA of the third network and at least one TA of the fourth network. Still taking fig. 18 (a) as an example, the third preset area configured by the MME includes 4g TA2, 5g TA1.

Optionally, the terminal initiates a service request to the IMS, and the IMS triggers a dedicated bearer establishment procedure.

S2202, the AMF sends information of the first TA and information of the second TA to the MME.

Accordingly, the MME receives information of the first TA and information of the second TA from the AMF.

As a possible implementation, after the AMF receives the smf_pduse_context Response from the converged SMF in the handover procedure, the AMF sends Forward Relocation Request a message to the MME, where the message carries a user Context, and the user Context includes information of the first TA (5G TAI) and information of the second TA (4G TAI).

S2203, TAU flow.

S2204, the MME reserves or deletes the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

The rules and methods for judging whether to delete the PDN connection corresponding to the terminal by the MME can refer to the fusion SMF to judge whether to delete the relevant content of the PDN connection.

Optionally, a procedure of establishing a voice-specific bearer and/or a video-specific bearer is performed.

Some of the steps of the corresponding embodiment of fig. 20 are not described in detail, and the specific implementation of this part of the steps may be referred to other embodiments or to the prior art.

Taking a terminal switching manner from 5GS to EPS, an MME acquires information of a first TA from an AMF, and determines whether to delete a PDN connection corresponding to the terminal as an example, referring to fig. 21, a communication method provided in an embodiment of the present application specifically includes:

s2301, the MME configures information of a third preset area.

Optionally, in the EPS fallback scenario, the method further includes: the terminal initiates a service request to the IMS, and the IMS triggers a special bearing establishment flow.

S2302, the AMF sends information of the second TA to the MME.

Accordingly, the MME receives information of the second TA from the AMF.

The specific implementation of this step S2302 can be seen in step S2202 described above.

S2303, the converged SMF sends the information of the first TA to the MME.

Accordingly, the MME receives the information of the first TA from the converged SMF.

As a possible implementation, in the handover procedure, after the converged SMF receives Modify Bearer Request from the SGW, the converged SMF sends a bearer modification response (Modify Bearer Response) to the MME via the SGW, the bearer modification response including the information of the first TA.

S2304, TAU flow.

S2305, the MME reserves or deletes the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

Optionally, the method further comprises a procedure for establishing a voice-specific bearer and/or a video-specific bearer.

Redirecting the terminal from 5GS to EPS, acquiring information of the first TA from the AMF by the MME, and judging whether to delete the PDN connection corresponding to the terminal, referring to FIG. 22, the communication method provided by the embodiment of the application specifically comprises the following steps:

s2401, the MME configures information of the third preset area.

S2402, the E-UTRAN device sends the information of the second TA to the MME.

As a possible implementation, in the TAU procedure, the E-UTRAN device receives the TAU Request from the terminal and sends a TAU Request message to the MME, which carries the information of the second TA (4G TAI).

S2403, the AMF sends information of the first TA to the MME.

As one possible implementation, after the AMF receives the smf_pduse_context Response from the converged SMF, the AMF sends a Context Response message to the MME, where the message carries the user Context, and the user Context includes the information of the first TA (5G TAI).

S2404, the MME reserves or deletes the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

As a possible implementation, after the TAU procedure, the MME performs this step S2404.

Optionally, in the EPS fallback scenario, the method further includes: and establishing a voice special bearer and/or a video special bearer.

Taking redirection of the terminal from 5GS to EPS, the MME acquires information of the first TA from the converged SMF, and determines whether to delete the PDN connection corresponding to the terminal, as an example, referring to fig. 23, the communication method provided in the embodiment of the present application specifically includes:

s2501, the MME configures information of the third preset area.

S2502, the E-UTRAN device sends the information of the second TA to the MME.

Accordingly, the MME receives information of the second TA from the E-UTRAN device.

As a possible implementation manner, after receiving the TAU Request message from the terminal, the E-UTRAN device sends the TAU Request message to the MME, where the TAU Request message includes information of the second TA.

S2503, the fusion SMF sends the information of the first TA to the SGW.

As one possible implementation, after the converged SMF receives the Modify Bearer Request message from the SGW, the converged SMF feeds Modify Bearer Response a message back to the SGW, where Modify Bearer Response the message includes information of the first TA.

S2504, the SGW sends information of the first TA to the MME.

As one possible implementation, after the SGW receives the Modify Bearer Response message from the converged SMF, the SGW sends a session creation response (Create Session Reponse) message to the MME, the Create Session Reponse message including information of the first TA.

S2505, the MME reserves or deletes the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

Taking an example that a terminal is switched from EPS to 5gs, and an amf obtains information of a first TA from MME and determines whether to delete PDN connection corresponding to the terminal, referring to fig. 24, a communication method provided in this embodiment of the present application includes:

s2601, AMF configures information of the third preset region.

Still taking fig. 14 (a) as an example, one of the third preset areas of the AMF configuration includes 5g TA1, 4g TA2.

S2602, the E-UTRAN equipment sends information of the first TA and information of the second TA to the MME.

Due to mobility of the terminal, the E-UTRAN equipment initiates a 4G to 5G handover procedure according to a measurement report of the terminal, etc., and sends Handover Required a message to the MME, which carries information of the first TA (4G TAI) and information of the second TA (5G TAI).

S2603, the MME sends information of the first TA and information of the second TA to the AMF.

Accordingly, the AMF receives the information of the first TA and the information of the second TA from the MME.

As a possible implementation, the MME queries the DNS and selects one AMF according to the Target TAI received from the E-UTRAN device. The MME sends Forward Relocation Request a message to the selected AMF carrying a user context including information of the first TA (4G TAI) and information of the second TA (5G TAI).

S2604, the AMF reserves or deletes the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

The rules and methods for the AMF to determine whether to delete the PDN connection corresponding to the terminal can refer to the fusion SMF to determine whether to delete the PDN connection or the MME to determine whether to delete the relevant content of the PDN connection.

Some of the steps of the corresponding embodiment of fig. 24 are not described in detail, and the specific implementation of this part of the steps may be referred to other embodiments or to the prior art.

Taking an example that a terminal is switched from EPS to 5gs, and an amf obtains information of a first TA from a converged SMF, and determines whether to delete a PDN connection corresponding to the terminal, referring to fig. 25, a communication method provided in an embodiment of the present application specifically includes:

S2701, AMF configures information of the third preset area.

S2702, the E-UTRAN device sends information of the second TA to the MME.

As a possible implementation, the E-UTRAN device sends Handover Required a message to the MME, which carries the information of the second TA (5G TAI).

S2703, the MME sends information of the second TA to the AMF.

The MME queries the DNS and selects an AMF according to the 5G TAI received from the E-UTRAN device. The MME sends Forward Relocation Request a message to the selected AMF, which carries the information of the second TA (5G TAI).

S2704, the converged SMF sends information of the first TA to the AMF.

Accordingly, the AMF receives the information of the first TA from the converged SMF.

As a possible implementation, in the handover procedure, the converged SMF sends an smf_pduse_ CreateSMContext Response message to the AMF, where the message carries a session context, and the session context includes information of the first TA (4G TAI).

S2705, the AMF reserves or deletes the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

The terminal is redirected to 5gs by the EPS, and the amf obtains information of the first TA from the MME, and determines whether to delete the PDN connection corresponding to the terminal, referring to fig. 26, a communication method provided in the embodiment of the present application specifically includes:

S2801, AMF configures information of the third preset area.

S2802, the terminal transmits a registration request to the NG-RAN device (Registration Request).

The terminal moves to the coverage area of the 5G network, initiates a mobility registration process and sends a registration request to the NG-RAN equipment.

S2803, the NG-RAN device sends information of the second TA to the AMF.

As a possible implementation, after receiving Registration Request from the terminal, the NG-RAN sends Registration Request a message to the AMF, which carries the information of the second TA, i.e. Current TAI,5G TAI.

S2804, the AMF sends a Context Request (Context Request) to the MME.

S2805, the MME feeds back a Context Response (Context Response) to the AMF.

The context response includes a user context including information of the first TA (4G TAI).

And S2806, the AMF reserves or deletes the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

Optionally, the execution time of the step is after the redirection procedure is finished.

Taking an example that a terminal is redirected to 5gs by EPS, and the amf obtains information of a first TA from a converged SMF, and determines whether to delete a PDN connection corresponding to the terminal, referring to fig. 27, the communication method provided in the embodiment of the present application specifically includes:

S2901, AMF configures information of the third preset area.

S2902, the terminal transmits a registration request to the NG-RAN device (Registration Request).

S2903, the NG-RAN device sends information of the second TA to the AMF.

S2904, the converged SMF sends information of the first TA to the AMF.

In the redirection procedure, the converged SMF sends an smf_pduse_ CreateSMContext Response message to the AMF, the message carrying a session context, the session context carrying the information of the first TA (4G TAI).

S2905, the AMF reserves or deletes the PDN connection corresponding to the terminal according to the information of the second TA and the information of the first TA.

It will be appreciated that the third core network device, the fourth network device or other network devices (e.g., PCF network elements) comprise corresponding hardware structures and/or software modules for performing the functions of any of the above embodiments. Those of skill in the art will readily appreciate that the elements and algorithm steps of the examples described in connection with the embodiments disclosed herein may be implemented as hardware or combinations of hardware and computer software. Whether a function is implemented as hardware or computer software driven 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.

The embodiment of the application can divide the functional modules of the third core network device, the fourth core network device or other network devices (such as PCF network elements) and the like, for example, each functional module can be divided corresponding to each function, or two or more functions can be integrated in one processing module. The integrated modules may be implemented in hardware or in software functional modules. It should be noted that, in the embodiment of the present application, the division of the modules is schematic, which is merely a logic function division, and other division manners may be implemented in actual implementation.

For example, in the case where the respective functional modules are divided in an integrated manner, fig. 28 is a block diagram of a communication device according to an embodiment of the present application. The communication apparatus 2800 is a third core network device or an apparatus supporting a function of the third core network device (such as, but not limited to, a system-on-a-chip), or is a fourth core network device or an apparatus supporting a function of the fourth core network device. The communication device may include a transceiver unit 2810 and a processing unit 2820.

Wherein, when the communication apparatus is a third core network device, the transceiver unit 2810 is configured to support the third core network device to perform the above step S1301 and/or other processes for the technology described herein. The processing unit 2820 is used to assist the third core network device in performing step S1302 described above, and/or other processes for the techniques described herein.

In connection with a specific scenario, when the communication device is a converged SMF, the transceiver unit 2810 is configured to support the converged SMF to perform the steps S1502, S1503, S1602, S1604, S1703, S1704, S1902, S1903 described above, and/or other processes for the techniques described herein. The processing unit 2820 is configured to support the fusion SMF to perform steps S1504, S1605, S1705, S1904 described above, and/or other processes for the techniques described herein.

When the communication device is an MME, the transceiver unit 2810 is configured to support the MME to perform the steps S2202, S2302, S2303, S2402, S2403, S2502, S2504 described above, and/or other procedures for the techniques described herein. The processing unit 2820 is configured to support the MME to perform steps S2204, S2305, S2404, S2505 described above, and/or other processes for the techniques described herein.

When the communication device is an AMF, the transceiver unit 2810 is configured to support the AMF to perform the steps S2603, S2703, S2704, S2803, S2805, S2903, S2904 described above, and/or other processes for the techniques described herein. The processing unit 2820 is configured to support the AMF to perform steps S2604, S2705, S2806, S2905 described above, and/or other processes for the techniques described herein.

In one possible implementation, the processing unit 2820 may be a controller or the processor 401 or 408 shown in fig. 6, such as a central processing unit (Central Processing Unit, CPU), general purpose processor, digital signal processing (Digital Signal Processing, DSP), application specific integrated circuit (Application Specific Integrated Circuit, ASIC), field programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic device, transistor logic device, hardware components, or any combination thereof. Which may implement or perform the various exemplary logic blocks, modules, and circuits described in connection with this disclosure. A processor may also be a combination that performs computing functions, e.g., including one or more microprocessors, a combination of a DSP and a microprocessor, and so forth. The transceiver unit 2810 may be the communication interface 404 shown in fig. 6, a transceiver circuit, or the like. The memory unit may be the memory 403 shown in fig. 6.

Those of ordinary skill in the art will appreciate that: in the above embodiments, it may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions in accordance with embodiments of the present application are produced in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer instructions may be stored in or transmitted from one computer-readable storage medium to another, for example, by wired (e.g., coaxial cable, fiber optic, digital subscriber line (Digital Subscriber Line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means from one website, computer, server, or data center. Computer readable storage media can be any available media that can be accessed by a computer or data storage devices, including servers, data centers, etc. that can be integrated with one or more available media. Usable media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., digital video discs (Digital Video Disc, DVDs)), or semiconductor media (e.g., solid State Discs (SSDs)), or the like.

In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods may be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of elements is merely a logical functional division, and there may be additional divisions of actual implementation, e.g., multiple elements or components may be combined or integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, or may be in electrical or other forms.

The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network devices (for example, terminal devices). Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, each functional unit may exist independently, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in hardware plus software functional units.

From the above description of the embodiments, it will be clear to those skilled in the art that the present application may be implemented by means of software plus necessary general purpose hardware, or of course by means of hardware, but in many cases the former is a preferred embodiment. Based on such understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art in the form of a software product stored in a readable storage medium, such as a floppy disk, a hard disk, or an optical disk of a computer, etc., including several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to perform the method of the embodiments of the present application.

The foregoing is merely a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and all changes or substitutions within the technical scope of the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A communication method, characterized in that the method is applied to a terminal moving from a first preset area of a first network to a second preset area of a second network, the second preset area being a regulatory domain, a radio access technology, RAT, of the first network being different from a RAT of the second network, the method comprising:

The first core network equipment of the first network determines that an Evolved Packet System (EPS) fallback of the terminal is triggered;

the first core network device sends first information to second core network device of the second network, wherein the first information is used for the second core network device to reserve packet data network PDN connection corresponding to the terminal, and the first information comprises a first identifier or first indication information;

the first identifier is used for identifying a first proprietary bearer corresponding to the terminal, and the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer; the first indication information is used for indicating the terminal to fall back to the second network through an EPS fall-back process.

2. The method according to claim 1, characterized in that the first core network device is an access and mobility management function AMF or a session management function SMF and the second core network device is a mobility management entity MME.

3. The method according to claim 1 or 2, characterized in that the method further comprises:

the first core network device obtains information of the first proprietary bearer, where the information of the first proprietary bearer includes: the EPS bearer identifier EBI of the first proprietary bearer and the first identifier.

4. A method according to claim 3, wherein the first core network device is an SMF, and wherein the first core network device obtains the information of the first proprietary bearer, comprising:

the first core network device sends a first message to an AMF, where the first message is used to request the AMF to allocate the EBI for the first proprietary bearer;

the first core network device receives the EBI from the AMF.

5. The method according to any of claims 1-4, wherein the first core network device is an SMF, the method further comprising:

the first core network device sends a second message to the second core network device, where the second message is used to request deletion of the first proprietary bearer;

6. The method according to any of claims 1-5, wherein the first core network device is an SMF, the first core network device sending first information to a second core network device of a second network, comprising:

the first core network device sends a session context to the AMF, wherein the session context comprises the first identifier or the first indication information.

7. The method according to any of claims 1-6, wherein the first core network device is an AMF, the first core network device sending first information to a second core network device of the second network, comprising:

the first core network device sends a user context of the terminal to the second core network device, wherein the user context comprises the first identifier or the first indication information; or alternatively, the first and second heat exchangers may be,

the first core network device sends a session context of the terminal to the second core network device, wherein the session context comprises the first identifier or the first indication information.

8. A communication method, characterized in that the method is applied to a terminal moving from a first preset area of a first network to a second preset area of a second network, the second preset area being a regulatory domain, a radio access technology, RAT, of the first network being different from a RAT of the second network, the method comprising:

a second core network device of the second network receives first information from a first core network device of the first network; the first information comprises a first identifier or first indication information, the first identifier is used for identifying a first proprietary bearer corresponding to the terminal, the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer, and the first indication information is used for indicating the terminal to fall back to an EPS through an EPS fall-back process;

And the second core network equipment reserves the PDN connection of the packet data network corresponding to the terminal according to the first information.

9. The method according to claim 8, wherein the first core network device comprises a session management function, SMF, network element or an access and mobility management function, AMF, network element, and the second core network device is a mobility management entity, MME.

10. The method according to claim 8 or 9, characterized in that the method further comprises:

the second core network device sends the information of the first proprietary bearer to the terminal; the information of the first proprietary bearer includes: the EPS bearer identifier EBI of the first proprietary bearer and the first identifier.

11. The method according to any of claims 8-10, wherein the first core network device is an AMF and the second core network device receives the first identification from the first core network device of the first network, comprising:

the second core network device receives a user context of the terminal from the first core network device, wherein the user context comprises information of the first proprietary bearer, and the information of the first proprietary bearer comprises the first identifier; or alternatively, the first and second heat exchangers may be,

The second core network device receives a session context of the terminal from the first core network device, wherein the session context comprises information of the first proprietary bearer, and the information of the first proprietary bearer comprises the first identifier.

12. The method according to any of claims 8-10, wherein the first core network device is an AMF and the second core network device receives first indication information from the first core network device of the first network, comprising:

the second core network device receives a user context of the terminal from the first core network device, wherein the user context comprises the first indication information; or alternatively, the first and second heat exchangers may be,

the second core network device receives a session context of the terminal from the first core network device, wherein the session context comprises the first indication information.

13. The method according to any of claims 8-12, wherein the first core network device is an SMF, the method further comprising:

the second core network device receives a second message from the first core network device, where the second message is used to request deletion of the first dedicated bearer;

the second core network device sends a response of the second message to the first core network device, where the response of the second message is used to indicate that the first proprietary bearer has been deleted.

14. The method of claim 13, wherein the method further comprises:

the second core network device receives a response to a third message from the access network device, the response to the third message indicating that the first dedicated bearer has been deleted.

15. A communication device, the communication device being located in a first network, the communication device comprising:

the method comprises the steps that a processor determines that an Evolved Packet System (EPS) fallback of a terminal is triggered, the terminal moves from a first preset area of a first network to a second preset area of a second network, the second preset area is a management and control area, and a Radio Access Technology (RAT) of the first network is different from a RAT of the second network;

a communication interface, configured to send first information to a second core network device of the second network, where the first information is used for the second core network device to reserve a PDN connection of a packet data network corresponding to the terminal, and the first information includes a first identifier or first indication information;

The first identifier is used for identifying a first proprietary bearer corresponding to the terminal, the first proprietary bearer comprises a voice proprietary bearer and/or a video proprietary bearer, and the first indication information is used for indicating the terminal to fall back to the second network through an EPS fall-back process.

16. The apparatus of claim 15, wherein the apparatus is an access and mobility management function, AMF, or a session management function, SMF, and the second core network device is a mobility management entity, MME.

17. The apparatus according to claim 15 or 16, wherein,

the processor is further configured to obtain information of the first proprietary bearer, where the information of the first proprietary bearer includes: the EPS bearer identifier EBI of the first proprietary bearer and the first identifier.

18. The apparatus of claim 17, wherein the apparatus is an SMF, and wherein the processor is configured to obtain the information of the first dedicated bearer, comprises:

the method comprises the steps that the communication interface is controlled to send a first message to an AMF, wherein the first message is used for requesting the AMF to allocate the EBI for the first proprietary bearer; the communication interface is controlled to receive the EBI from the AMF.

19. The apparatus according to any of claims 15-18, wherein the apparatus is an SMF, the communication interface further configured to send a second message to the second core network device, the second message being configured to request deletion of the first dedicated bearer; a response to the second message is received from the second core network device, the response of the second message indicating that the first proprietary bearer has been deleted.

20. The apparatus according to any of claims 15-19, wherein the apparatus is an SMF, the communication interface being configured to send first information to a second core network device of the second network, comprising:

for sending a session context to the AMF, the session context comprising the first identification or the first indication information.

21. The apparatus according to any of claims 15-20, wherein the apparatus is an AMF, the communication interface being configured to send first information to a second core network device of the second network, comprising:

the user context is used for sending the user context of the terminal to the second core network equipment, and the user context comprises the first identification or the first indication information; or alternatively, the first and second heat exchangers may be,

And sending the session context of the terminal to the second core network equipment, wherein the session context comprises the first identification or the first indication information.

22. A communication device, wherein the communication device is located in a second network, the communication device comprising:

a communication interface for receiving first information from a first core network device of a first network; the first information comprises a first identifier or first indication information, the first identifier is used for identifying a first special bearer corresponding to the terminal, the first special bearer comprises a voice special bearer and/or a video special bearer, and the first indication information is used for indicating the terminal to fall back to the EPS through an EPS fall-back process; the terminal moves from a first preset area of the first network to a second preset area of the second network, wherein the second preset area is a control area, and a Radio Access Technology (RAT) of the first network is different from a RAT of the second network;

23. The apparatus of claim 22, wherein the apparatus is a mobility management entity, MME, and wherein the first core network device comprises a session management function, SMF, network element or an access and mobility management function, AMF, network element.

24. The apparatus according to claim 22 or 23, wherein the communication interface is further configured to send the information of the first proprietary bearer to the terminal; the information of the first proprietary bearer includes: the EPS bearer identifier EBI of the first proprietary bearer and the first identifier.

25. The apparatus according to any of claims 22-24, wherein the first core network device is an AMF, the communication interface for receiving a first identification from a first core network device of a first network, comprising:

receiving a user context of the terminal from the first core network device, the user context including information of the first proprietary bearer, the information of the first proprietary bearer including the first identification; or alternatively, the first and second heat exchangers may be,

and receiving a session context of the terminal from the first core network device, wherein the session context comprises information of the first proprietary bearer, and the information of the first proprietary bearer comprises the first identifier.

26. The apparatus according to any of claims 22-24, wherein the first core network device is an AMF, and wherein the communication interface is configured to receive the first indication information from the first core network device of the first network, and comprises:

Receiving a user context of the terminal from the first core network device, the user context comprising the first indication information; or alternatively, the first and second heat exchangers may be,

a session context of the terminal is received from the first core network device, the session context comprising the first indication information.

27. The apparatus according to any of claims 22-26, wherein the first core network device is an SMF, the communication interface further configured to receive a second message from the first core network device, the second message being configured to request deletion of the first dedicated bearer; and sending a response of the second message to the first core network device, wherein the response of the second message is used for indicating that the first proprietary bearer is deleted.

28. The apparatus of claim 27, wherein the communication interface is further configured to send a third message to an access network device of the second network, the third message being configured to request deletion of the first proprietary bearer; a response to a third message is received from the access network device, the response to the third message indicating that the first proprietary bearer has been deleted.

29. A computer readable storage medium, characterized in that the computer readable storage medium has stored thereon a computer program code which, when executed by a processing circuit, implements the method according to any of claims 1-14.

30. A chip system, comprising a processing circuit, a storage medium having computer program code stored therein; the computer program code implementing the method of any of claims 1-14 when executed by the processing circuit.

31. A communication system, comprising: the communication device according to any of claims 15-21 and the communication device according to any of claims 22-28.