CN110149665B

CN110149665B - Network element selection method and device

Info

Publication number: CN110149665B
Application number: CN201810151839.3A
Authority: CN
Inventors: 聂胜贤; 周润泽; 陈中平
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-02-14
Filing date: 2018-02-14
Publication date: 2021-02-23
Anticipated expiration: 2038-02-14
Also published as: CN110149665A; WO2019158109A1

Abstract

The application provides a network element selection method and a network element selection device, which are used for solving the problem of data service interruption. The method comprises the following steps: the method comprises the steps that a first session management network element receives a first message from a mobility management network element, wherein the first message is used for indicating a terminal to be switched from a source area to a target area; the first session management network element determines whether a user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element; and when determining that no user plane network element capable of establishing connection with the base station of the target area exists, the first session management network element sends a second message to the mobility management network element, wherein the second message is used for triggering the mobility management network element to execute an operation of selecting the second session management network element.

Description

Network element selection method and device

Technical Field

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

Background

In a fifth generation mobile communication technology (5G) system, a Session Management Function (SMF) currently selected by an access and mobility management entity (AMF) can serve the entire Public Land Mobile Network (PLMN). A User Plane Function (UPF) managed by the SMF can simultaneously connect a base station and a Data Network (DN) to ensure data connection between a User Equipment (UE) and the DN.

When the network system is deployed, specific UPFs are deployed, and the specific UPFs are only controlled by specific SMFs, so that the specific SMFs cannot serve the whole PLMN. Therefore, when the UE is handed over from the source base station to the new base station, there may be a case where neither the current UPF nor other UPFs within the control range of the current SMF can establish a connection with the new base station, resulting in interruption of data service.

Disclosure of Invention

The application provides a network element selection method and a network element selection device, which are used for solving the problem of data service interruption.

In a first aspect, an embodiment of the present application provides a method for selecting a network element, where the method includes: the method comprises the steps that a first session management network element receives a first message from a mobility management network element, wherein the first message is used for indicating a terminal to be switched from a source area to a target area; the first session management network element determines whether a user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element; and when determining that no user plane network element capable of establishing connection with the base station of the target area exists, the first session management network element sends a second message to the mobility management network element, wherein the second message is used for triggering the mobility management network element to execute an operation of selecting the second session management network element. The base station corresponding to the source area is a source base station, and the base station corresponding to the target area is a target base station.

When the UE moves from the source base station to the service area of the target base station, the user plane selected by the first session managing element serving the source base station may only be able to establish a connection with the DN, and may not be able to establish a connection with the target base station, by the above-described scheme, the first session management element serving the source base station determines whether there is a user plane element capable of establishing a connection with the target base station among the plurality of user plane elements under its control, if not, notifying the mobility management network element, so that the mobility management network element can reselect other session management network elements to ensure that the user plane network elements in the control range of the reselected other session management network elements have the user plane network elements establishing connection with the target base station, therefore, the UE can establish connection with the DN through the target base station to carry out data transmission, and the interruption of data transmission caused by the fact that the first session management network element of the source base station cannot serve the target base station is avoided.

In a possible design, the first message includes target area information of the terminal, and the first session management network element determines that no user plane network element capable of establishing a connection with the base station in the target area exists in the user plane network elements managed by the first session management network element, which may be implemented as follows:

the first session management network element determines, according to the target area information of the terminal and the service area information of one or more user plane network elements managed by the first session management network element, that the terminal is not in the service area of any user plane network element managed by the first session management network element, and then determines that no user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element; alternatively, the first and second electrodes may be,

and the first session management network element determines that the terminal is not in the service area of any user plane network element managed by the first session management network element according to the target area information of the terminal and the service area information of the first session management network element, and determines that no user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element.

Through the design, a simple and effective mode for determining that no user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element is provided.

In a possible design, the first message includes target area information of the terminal and session management information of the terminal, and the first session management network element determines that no user plane network element capable of establishing a connection with the base station of the target area exists in the user plane network elements managed by the first session management network element, which may specifically be implemented in the following manner:

the first session management network element determines that the terminal is located in a service area of at least one user plane network element managed by the first session management network element according to the target area information of the terminal and the service area information of the one or more user plane network elements managed by the first session management network element; the first session management network element determines that the at least one user plane network element cannot establish connection with the base station of the target area according to the session management information of the terminal; alternatively, the first and second electrodes may be,

the first session management network element determines that the terminal is located in a service area of at least one user plane network element managed by the first session management network element according to the target area information of the terminal and the service area information of the first session management network element; and the first session management network element determines that the at least one user plane network element cannot establish connection with the base station of the target area according to the session management information of the terminal.

In one possible design, the determining, by the first session management network element, that there is no user plane network element capable of establishing a connection with the base station of the target area in the user plane network elements managed by the first session management network element includes:

and the first session management network element determines that a first user plane network element connected with the base station of the source area cannot establish connection with the base station of the target area, and determines that the user plane network elements managed by the first session management network element except the first user plane network element cannot establish connection with the base station of the target area.

Optionally, it may be determined, by the first session management network element, whether the first user plane network element connected to the base station of the source area can establish a connection with the base station of the target area, and it may also be determined, by the mobility management network element, whether the first user plane network element connected to the base station of the source area can establish a connection with the base station of the target area.

Specifically, the first message further includes first indication information, where the first indication information is used to indicate that the first user plane network element cannot establish a connection with the base station in the target area; the first session management network element determines that the first user plane network element cannot establish a connection with the base station of the target area, and specifically, the method is implemented as follows:

and the first session management network element determines that the first user plane network element cannot establish connection with the base station of the target area based on the first indication information.

According to the design, the mobility management network element firstly makes a first judgment on whether the first user plane network element of the base station connected with the source area can establish connection with the base station of the target area, and if the first user plane network element can establish connection with the base station of the target area, the first session management network element does not need to be triggered to make a judgment, so that signaling resources are saved.

In a possible design, the second message is used to notify the mobility management element that no user plane network element capable of establishing a connection with the base station of the target area exists in the user plane network elements managed by the first session management element; or, the second message includes second indication information, where the second indication information is used to indicate that no user plane network element capable of establishing a connection with the base station of the target area exists in the user plane network elements managed by the first session management network element.

The above design provides two operations for triggering the mobility management element to perform the selection of the second session management element.

In a possible design, the second message includes third indication information, where the third indication information is used to instruct the mobility management element to perform an operation of adding the second session management element on the basis of maintaining the first session management element as the terminal; or, the third indication information is used to indicate the mobility management network element to perform an operation of reselecting the second session management network element.

In the above design, the first session management network element determines that the mobility management network element performs an operation of newly adding or reselecting the second session management network element.

In one possible design, the second message includes an identification of the first user plane network element. Based on this, after the mobility management network element selects the second session management network element according to the second message, the mobility management network element may send the identifier of the first user plane network element to the second session management network element, so that the second user plane network element selected by the second session management network element can establish connection with the base station of the target area and the first user plane network element, respectively.

In a second aspect, an embodiment of the present application provides a method for selecting a network element, where the method includes:

a mobility management network element sends a first message to a first session management network element, wherein the first message is used for indicating a terminal to be switched from a source area to a target area; a mobility management network element receives a second message sent by the first session management network element, where the second message is used to indicate that no user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element; and the mobility management network element selects a second session management network element according to the second message, so that the second session management network element selects a user plane network element which establishes connection with the base station of the target area.

In the above scheme, when the UE moves from the source base station to the service area of the target base station, the user plane selected by the first session management element serving the source base station may only be able to establish a connection with the DN, and may not be able to establish a connection with the target base station, by the above-mentioned scheme, when the first session management network element serving the source base station determines that there is no user plane network element capable of establishing a connection with the target base station among the plurality of user plane network elements under control of the first session management network element, informing the mobile management network element, after receiving the notification, the mobile management network element can reselect other session management network elements to ensure that the user plane network elements in the control range of the reselected other session management network elements have the user plane network elements establishing connection with the target base station, therefore, the UE can establish connection with the DN through the target base station to carry out data transmission, and the interruption of data transmission caused by the fact that the first session management network element of the source base station cannot serve the target base station is avoided.

In one possible design, before the mobility management element sends the first message to the first session management element, the method further includes: the mobility management network element determines that the first user plane network element cannot establish connection with the base station of the target area according to the information of the first user plane network element of the base station connected with the source area; the service area information of the first user plane network element is sent to the mobility management network element by the first session management network element in a process that the terminal accesses the base station of the source area, and the information of the first user plane network element includes the service area information of the first user plane network element and/or the identifier of the first user plane network element; the first message sent by the mobility management network element to the first session management network element further includes first indication information, where the first indication information is used to indicate that the first user plane network element cannot establish a connection with the base station in the target area.

In the design, the mobility management network element obtains information of the first user plane network element of the base station connected with the source area in advance, so that whether the first user plane network element can establish connection with the base station of the target area can be predetermined in the process that the terminal is switched from the source area to the target area, and if yes, the session management network element does not need to be triggered to execute judgment operation.

In a possible design, the second message is used to notify the first session management network element that no user plane network element capable of establishing a connection with the base station of the target area exists in the user plane network elements managed by the first session management network element; or, the second message includes second indication information, where the second indication information is used to indicate that no user plane network element capable of establishing a connection with the base station of the target area exists in the user plane network elements managed by the first session management network element.

In a possible design, the second message includes third indication information, where the third indication information is used to instruct the mobility management element to perform an operation of adding a session management element serving the terminal on the basis of keeping the first session management element serving the terminal; or, the third indication information is used to indicate the mobility management network element to perform an operation of reselecting a session management network element serving the terminal.

In one possible design, the first message includes an identification of a first user plane network element of a base station connected to the source region; after the mobility management network element selects the second session management network element according to the second message, the method further includes: and the mobility management network element sends the identifier of the first user plane network element to the second session management network element, so that the second user plane network element selected by the second session management network element can establish connection with the base station of the target area and the first user plane network element respectively.

Through the design, the first session management network element sends the identifier of the first user plane network element of the base station connected with the source area to the mobility management network element in the first message, so that the mobility management network element sends the identifier to the selected second session management network element, and the second session management network element selects the user plane network element connected with the target base station according to the first user plane network element.

In a third aspect, an embodiment of the present application provides a method for selecting a network element, where the method includes:

in the process that a terminal accesses a first communication network, a first mobility management network element acquires service area information of a first session management network element, wherein the first session management network element is used for providing services for the terminal in the process of connecting with the first communication network; in the process that the terminal is switched from the first communication network to the second communication network, the first mobility management network element sends a first message to the second mobility management network element; the first message includes service area information of the first session management network element, so that the second mobility management network element determines whether to select a second session management network element according to the service area information of the first session management network element, where the second session management network element is used to provide a service for the terminal in a process of connecting with the second communication network.

The above-mentioned scheme provides a way how to decide to select the second session management network element in the handover process between base stations in different communication networks. Such as: the terminal is switched from 4G to 5G, and the MME acquires the service area information of a first session management network element serving in the process of connecting the terminal with the 4G when the terminal is switched from 4G to 5G, so that the MME informs the AMF of the service area information of the first session management network element when the terminal is switched from 4G to 5G, and the AMF can determine whether the service area information of the first session management network element can serve in the process of connecting the terminal with the 5G and further determine whether the operation of selecting other session management network elements needs to be executed.

In a fourth aspect, an embodiment of the present application provides a method for selecting a network element, where the method includes: in the process that the terminal is switched from the first communication network to the second communication network, the second mobility management network element receives a first message from the first mobility management network element, wherein the first message comprises service area information of the first session management network element, and the first session management network element is used for providing services for the terminal in the process of connecting with the first communication network; and the second mobility management network element determines whether to select a second session management network element according to the service area information of the first session management network element, wherein the second session management network element is used for providing services for the terminal in the process of connecting with the second communication network.

The above-mentioned scheme provides a way how to decide to select the second session management network element in the handover process between base stations in different communication networks. For example, when the terminal is switched from 4G to 5G, the MME acquires the service area information of the first session management network element serving in the process of terminal connection to 4G, so that when the terminal is switched from 4G to 5G, the MME notifies the AMF of the service area information of the first session management network element, so that the AMF can determine whether the service area information of the first session management network element can also serve in the process of terminal connection to 5G, and further determine whether an operation of selecting another session management network element needs to be performed.

In one possible design, the first message further includes location information of the terminal; the second mobility management network element determining whether to select a second session management network element according to the service area information of the first session management network element, including: when the terminal is determined not to be in the service area of the first session management network element according to the position information of the terminal and the service area information of the first session management network element, the second mobility management network element determines to select the second session management network element; or, when the terminal is determined to be in the service area of the first session management network element according to the location information of the terminal and the service area information of the first session management network element, the second mobility management network element determines not to select the second session management network element.

The above design provides a simple and effective way for the second mobility management element to determine whether to select the second session management element.

In a fifth aspect, an embodiment of the present application provides an apparatus, where the apparatus may be a session management network element, and may also be a chip that can be applied to the session management network element. The apparatus has the function of implementing the embodiments of the first aspect described above. The function 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 sixth aspect, an embodiment of the present application provides an apparatus, including: a processor and a memory; the memory is configured to store instructions, and when the apparatus is running, the processor executes the instructions stored in the memory to cause the apparatus to perform the method for selecting a network element in the method according to the first aspect or any implementation method of the first aspect. It should be noted that the memory may be integrated into the processor or may be independent from the processor.

In a seventh aspect, an embodiment of the present application provides an apparatus, where the apparatus includes a processor, where the processor is configured to couple with a memory, read an instruction in the memory, and execute a method for selecting a multimedia system entry network element in any of the foregoing implementation methods of the first aspect or the first aspect according to the instruction.

In an eighth aspect, an embodiment of the present application provides an apparatus, where the apparatus may be a mobility management network element, and may also be a chip applied in the mobility management network element. The apparatus has a function of implementing the embodiments of the second aspect described above or the apparatus has a function of implementing the third aspect described above or the apparatus has a function of implementing the fourth aspect described above. The function 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 ninth aspect, an embodiment of the present application provides an apparatus, including: a processor and a memory; the memory is configured to store instructions, and when the apparatus runs, the processor executes the instructions stored by the memory to cause the apparatus to perform a method for selecting a network element in any one of the implementation methods of the second aspect or the second aspect, or perform a method for selecting a network element in the third aspect, or perform a method for selecting a network element in any one of the implementation methods of the fourth aspect or the fourth aspect. It should be noted that the memory may be integrated into the processor or may be independent from the processor.

In a tenth aspect, an embodiment of the present application provides an apparatus, which includes a processor, configured to couple with a memory, and read an instruction in the memory and execute, according to the instruction, a method for selecting a network element in any implementation method of the second aspect or the second aspect, or execute a method for selecting a network element in the third aspect, or execute a method for selecting a network element in any implementation method of the fourth aspect or the fourth aspect.

In an eleventh aspect, the present embodiments also provide a readable storage medium, which stores a program or instructions, and when the readable storage medium is run on a computer, the method for selecting any network element in the above aspects is executed.

In a twelfth aspect, embodiments of the present application further provide a computer program product containing instructions, which when run on a computer, cause the computer to perform the method for selecting any network element in the above aspects.

In a thirteenth aspect, an embodiment of the present application further provides a system, where the system includes a session management network element and a mobility management network element, and the session management network element is configured to perform the steps performed by the first session management network element in any of the methods of the first aspect and the first aspect.

In a possible design, the system may further include other devices, such as a user plane network element or a terminal, that interact with the session management network element and/or the mobility management network element in the solution provided in the embodiment of the present invention.

In a fourteenth aspect, an embodiment of the present application further provides a system, where the system includes a first mobility management network element of a first communication network and a second mobility management network element of a second communication network, where the first mobility management network element is configured to perform the steps performed by the first mobility management network element in the third aspect, and the second mobility management network element is configured to perform the steps performed by the second mobility management network element in any one of the methods in the fourth aspect or the fourth aspect. In a possible design, the system may further include other devices, such as a terminal, a session management network element, and the like, interacting with the two mobility management network elements in the solution provided in the embodiment of the present invention.

In addition, for technical effects brought by any design manner of the fifth aspect to the fourteenth aspect, reference may be made to technical effects brought by different implementation manners of the first aspect to the fourth aspect, and details are not described here again. These and other aspects of the embodiments of the present application will be more readily apparent from the following description of the embodiments.

Drawings

Fig. 1A to fig. 1C are schematic diagrams of system architectures according to embodiments of the present disclosure;

fig. 2A to fig. 2B are schematic structural diagrams of a system in an application scenario provided in the embodiment of the present application;

fig. 3 is a flowchart of a network element selection method according to an embodiment of the present application;

fig. 4 is a schematic diagram illustrating a network element selection method according to an embodiment of the present application;

fig. 5 is a schematic diagram illustrating a network element selection method according to a second embodiment of the present application;

fig. 6 is a flowchart of another network element selection method according to an embodiment of the present application;

fig. 7 is a schematic diagram of a UE attach method according to a third embodiment of the present application;

fig. 8 is a schematic diagram illustrating a network element selection method according to a third embodiment of the present application;

FIG. 9 is a schematic structural diagram of an apparatus according to an embodiment of the present disclosure;

fig. 10 is a schematic structural diagram of a session management network element according to an embodiment of the present application;

FIG. 11 is a schematic structural diagram of another apparatus provided in the embodiments of the present application;

fig. 12 is a schematic diagram of a mobility management network element structure according to an embodiment of the present application.

Detailed Description

The embodiments of the present application may be applicable to a 4G (fourth generation mobile communication system) evolution system, such as a Long Term Evolution (LTE) system, or may also be applicable to a 5G (fifth generation mobile communication system) system, such as an access network using a New radio access technology (New RAT); a Cloud Radio Access Network (CRAN) and other communication systems.

Fig. 1A illustrates a system architecture diagram applicable to the embodiment of the present application. It should be understood that the embodiments of the present application are not limited to the system shown in fig. 1A, and the apparatus in fig. 1A may be hardware, software divided from functions, or a combination of the two. As shown in fig. 1A, a system architecture provided in the embodiment of the present application includes a terminal, a base station, a mobility management network element, a session management network element, a user plane network element, and a Data Network (DN). And the terminal communicates with the DN through the base station and the user plane network element. The base station is connected with the mobility management network element through an N2 interface. The user plane network element is connected with the base station through an N3 interface, the user plane network element is connected with the DN through an N6 interface, and the UPFs are connected through an N9 interface. The interface name is only an example, and the embodiment of the present application is not particularly limited thereto.

The network element shown in fig. 1A may be a network element in a 4G architecture or a network element in a 5G architecture.

A Data Network (DN) for providing data transmission Service to users, which may be a PDN network, such as internet (internet), IP Multimedia Service (IMS), etc.

Referring to the schematic diagram of the system architecture of 5G shown in fig. 1B and the fused system architecture diagram of 4G and 5G shown in fig. 1C: the mobility management element may include an access and mobility management entity (AMF) in 5G, a control plane function (SGW-C) and a Mobility Management Entity (MME) of a Serving GateWay (SGW) in 4G, or all or part of a control function formed after the convergence of the above network elements. And the mobility management network element is responsible for the access and mobility management of the UE in the mobile network. The AMF is responsible for UE access and mobility management, NAS message routing, SMF selection and the like. The AMF may act as an intermediate network element for transmitting session management messages between the UE and the SMF. In the embodiment of the present application, the first mobility management network element is an MME, and the second mobility management network element is an AMF. In future communications (e.g. 6G or other networks), the mobility management network element may still be an AMF network element, or have another name, and this application is not limited thereto.

And the session management network element is responsible for forwarding path management, and if a message forwarding strategy is issued to the user plane network element, the user plane network element is instructed to process and forward the message according to the message forwarding strategy. The session management network element may be a Session Management Function (SMF) in 5G, and is responsible for session management, such as session creation/modification/deletion, UPF selection, and allocation and management of user plane tunnel information. The session management network element may also be a control plane function (SGW-C) of a Serving GateWay (SGW) in 4G or a control plane function (PGW-C) of a Packet Data Network (PDN) GateWay (GateWay way, GW), and the session management network element may also be all or part of a control function formed after the SMF and PGW-C network elements are fused. In future communications (e.g. 6G or other networks), the session management network element may still be an SMF network element or have another name, which is not limited in this application.

The user plane network element may be a User Plane Function (UPF) in a 5G architecture, as shown in fig. 1B or fig. 1C. The UPF is responsible for message processing and forwarding. The user plane network element may also be a forwarding plane function (PGW-U) of the PGW, a forwarding plane function (SGW-U) of the SGW, a router, a switch, or other physical or virtual forwarding devices. In future communications (e.g. 6G or other networks), the user plane network element may still be a UPF network element or have another name, which is not limited in this application.

The system architecture provided in the embodiment of the present application may further include a Policy Control Function (PCF) or a policy and charging control function (PCRF). Wherein, the PCF or PCRF is responsible for policy control decision and flow charging based control.

The system architecture may further include a subscriber data management entity (SDM), or a Home Subscriber Server (HSS). The User Data Management entity may also correspond to User Data Management or unified Data Management, or UDM for short. SDM, UDM or HSS are used to help operators achieve a uniform management of all user-related data.

The network function library function (NF) is stored with information of many network elements, such as SMF information, UPF information, and AMF information. Network elements such as an AMF, an SMF, and a UPF in the network may be connected to an NRF, so that on one hand, the network element information of the network element itself may be registered in the NRF, and on the other hand, other network elements may obtain the information of the registered network element from the NRF. Other network elements (such as AMF) may obtain optional network elements by requesting NRF according to network element type, data network identification, unknown area information, etc. If a Domain Name System (DNS) server is integrated in the NRF, the corresponding selection function network element (such as AMF) may request from the NRF to obtain other network elements (such as SMF) to be selected.

As a specific implementation form of AN Access Network (AN), a base station may also be referred to as AN access node, and if the access node is in a radio access form, the access node is referred to as a Radio Access Network (RAN), as shown in fig. 1B or 1C, and provides a radio access service for a terminal. The access node may specifically be a base station in a global system for mobile communication (GSM) system or a Code Division Multiple Access (CDMA) system, may also be a base station (NodeB) in a Wideband Code Division Multiple Access (WCDMA) system, may also be an evolved node B (eNB) or eNodeB in an LTE system, or may be a base station device, a small base station device, a wireless access node (WiFi AP), a wireless interworking microwave access base station (WiMAX BS) in a 5G network, and the like, which is not limited in this application.

A terminal, which may also be referred to as an access terminal, User Equipment (UE), subscriber unit, subscriber station, mobile station, remote terminal, mobile device, user terminal, wireless communication device, user agent, or user device, etc. Fig. 1B and 1C illustrate a UE as an example. The terminal may be a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device with wireless communication capability, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device, a wearable device, an internet of things terminal device, such as a fire detection sensor, a smart water/electricity meter, a factory monitoring device, and so forth.

In addition, the system architecture may further include an Application Function (AF). And the AF is mainly used for carrying out dynamic policy/charging control on the forwarding plane behavior. These services require dynamic policy and charging control. The AF transmits dynamic session information needed by the PCF, receives specific information of the IP connectivity access network (IP-CAN) and acknowledgements of IP-CAN bearer layer events.

The above functions may be network elements in a hardware device, software functions running on dedicated hardware, or virtualization functions instantiated on a platform (e.g., a cloud platform).

In the present application, the plurality of the present invention means two or more. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.

Meanwhile, it should be understood that although the terms first, second, third, etc. may be used to describe various messages, requests, network elements in the embodiments of the present application, these messages, requests, devices, and core network devices should not be limited to these terms. These terms are only used to distinguish messages, requests, network elements from one another.

In the prior art, the SMF serves the whole PLMN, so the AMF selects the SMF by means of one or more items of information such as a Data Network Name (DNN), a slice information, a subscription information, an access technology, and the like, for example, only selects one SMF according to the Data Network Name (DNN), and the SMF can always select a proper UPF according to the user location information to ensure data connection with the base station. When a network system is deployed, specific UPFs are deployed, and the specific UPFs are only controlled by specific SMFs, and the service areas of the specific SMFs are limited to a specific range and cannot serve the whole PLMN. Therefore, when the UE moves from the source area to the target area and is switched from the source base station to the target base station, the AMF selects the SMF according to the information such as DNN, and the UPF selected by the SMF can only ensure to establish a connection with the DN, and may not establish a connection with the target base station, so that the UE cannot establish a connection with the DN through the target base station after the base station is switched during the moving process, thereby causing data transmission interruption.

Based on this, embodiments of the present application provide a network element selection method and apparatus, so as to solve the problem that data transmission is interrupted when the existing UE is handed over to the target base station. Specifically, how the AMF determines that the current SMF cannot meet the data transmission requirement, the SMF needs to be selected. In addition, how the AMF selects a proper SMF enables the UPF managed by the SMF to establish a connection with the target base station, thereby ensuring that the UE can perform data transmission between the selected UPF and the DN. The method and the device are based on the same inventive concept, and because the principles of solving the problems of the method and the device are similar, the implementation of the device and the method can be mutually referred, and repeated parts are not repeated.

The selection of the appropriate SMF may be to add an SMF based on a source SMF determined by the AMF based on information such as DNN, or to reselect an SMF by the AMF.

Specifically, when the UE initially accesses the base station 1, the AMF first selects an SMF according to information such as DNN, and referring to the prior art, the SMF selects one or more UPFs to ensure that the user plane connection is established with the base station 1 and the data network, for example, one UPF may be connected with both the base station 1 and the DN, or one UPF may be connected with the base station 1 and the other UPF may be connected with the DN. But the UE is being handed off from base station 1 to base station 2, the SMF may not be able to select one or more UPFs to ensure that a user plane connection is established with base station 2.

On one hand, the current SMF may select at least one UPF to connect with the DN, and may select one SMF from the AMF, and the SMF selected by the AMF may select one UPF or multiple UPFs to connect with the base station 2.

On the other hand, the AMF may also reselect an SMF, and the one or more UPFs selected by the SMF can establish a connection with both the DN and the base station 2.

For example, referring to FIG. 2A, SMF1 manages UPF1 and SMF2 manages UPF 2. When the UE is connected with AN1, the SMF selected by the AMF according to the DNN is SMF2, and the UPF2 selected by the SMF2 can be connected with both DN and AN 1. But since the SMF2 is not serving the entire PLMN, the UPF2 managed by the SMF2 cannot establish a connection with the AN2 when handed over from the AN1 to the AN2 after the UE moves. On the basis, the AMF can select one SMF1, so that the UPF1 selected by the SMF1 can establish connection with the UPF2 and the AN2, and the data transmission between the UE and the DN is not interrupted.

In addition, it should be noted that, a connection is established between the UE and the DN, a plurality of SMFs are required in the network for deployment and the like, and a plurality of UPFs are selected under the control of the SMFs to establish a user plane connection. Thus, in the architecture shown in fig. 2A, there may be additional SMFs between SMF1 and SMF2 and additional UPFs between UPF1 and UPF 2.

For example, referring to FIG. 2B, SMF1 manages UPF1 and SMF2 manages UPF 2. When the UE is connected with AN1, the SMF selected by the AMF according to the DNN is SMF2, and the UPF2 selected by the SMF2 can be connected with both DN and AN 1. But since the SMF2 is not serving the entire PLMN, the UPF2 managed by the SMF2 cannot establish a connection with the AN2 when the UE moves from the service area of the AN1 to the service area of the AN 2. On the basis, the AMF can reselect one SMF1, so that the UPF1 selected by the SMF1 can establish connection with the DN and the AN2, and data transmission between the UE and the DN is not interrupted.

The following is a detailed description of the selection scheme of the session management network element.

Referring to fig. 3, a schematic flow chart of a network element selection method provided in the embodiment of the present application is shown. The UE moves from one area (source area) to another area (target area). The corresponding base stations in the two areas are different, and for convenience of description, the base station in the source area is referred to as a source base station, and the base station in the target area is referred to as a target base station.

S301, the mobility management network element sends a first message to the first session management network element, wherein the first message is used for indicating that the terminal is switched from the source area to the target area. The first session management network element is a session management network element determined by the mobility management network element according to one or more items of information such as DNN, slicing information, subscription information, access technology and the like.

The first message may be a handover request (handover request) message, or a message for instructing the terminal to switch from the source area to the target area is applicable to the embodiments of the present application.

S302, the first session management network element receives a first message from a mobility management network element.

S303, the first session managing network element determines whether a user plane network element capable of establishing a connection with the base station in the target area exists in the user plane network elements managed by the first session managing network element.

S304, when it is determined that there is no user plane network element capable of establishing a connection with the base station in the target area, the first session management network element sends a second message to the mobility management network element, where the second message is used to trigger the mobility management network element to perform an operation of selecting a second session management network element. And the second session management network element selects the user plane network element which establishes the connection with the base station of the target area.

S305, the mobility management network element selects a second session management network element according to the second message, so that the second session management network element selects a user plane network element connected to the base station in the target area.

When the UE moves from the source base station to the service area of the target base station, the user plane selected by the first session management element serving the source base station may only be able to establish a connection with the DN, and may not be able to establish a connection with the target base station. Through the scheme, the first session management network element serving the source base station determines whether the user plane network element capable of establishing connection with the target base station exists in the plurality of user plane network elements under the control of the first session management network element, if the user plane network element does not exist, the first session management network element notifies the mobility management network element, so that the mobility management network element can reselect other session management network elements to ensure that the user plane network elements in the control range of the reselected other session management network elements have the user plane network elements capable of establishing connection with the target base station, and therefore the UE can establish connection with the DN through the target base station to perform data transmission, and data transmission interruption caused by the fact that the first session management network element of the source base station cannot serve the target base station is.

Optionally, the first message may further include target area information of the terminal (e.g., location information of the terminal). The target area information of the terminal may be location information/identifier of a base station located in a target area or location information/identifier of a target cell corresponding to the target area, and the like), and the first session management network element determines whether a user plane network element capable of establishing a connection with the base station of the target area exists in the user plane network elements managed by the first session management network element, which may be implemented in any one of the following manners:

a first possible implementation: and the first session management network element determines, according to the target area information of the terminal and the service area information of the one or more user plane network elements managed by the first session management network element (or the service area information of the first session management network element), that the terminal is not in the service area of any user plane network element managed by the first session management network element, that is, it is determined that no user plane network element capable of establishing a connection with the base station of the target area exists in the user plane network element managed by the first session management network element.

If a first session management network element obtains its own service area information, which may reflect the service area information of one or more user plane network elements managed by the first session management network element, the first session management network element determines, according to the target area information of the terminal and the service area information of the first session management network element, that the terminal is not in the service area of any user plane network element managed by the first session management network element, that is, it is determined that no user plane network element capable of establishing a connection with a base station of the target area exists in the user plane network element managed by the first session management network element.

A second possible implementation: the first session management network element determines, according to the target area information of the terminal and the service area information of one or more user plane network elements managed by the first session management network element (or the service area information of the first session management network element), that the terminal is located in a service area of at least one user plane network element (such as a user plane network element a) managed by the first session management network element; and the first session management network element determines that the at least one user plane network element (such as a user plane network element A) can not establish connection with the base station of the target area according to the session management information of the terminal.

If a first session management network element obtains its own service area information, which may reflect the service area information of one or more user plane network elements managed by the first session management network element, the first session management network element determines that the terminal is in the service area of any user plane network element managed by the first session management network element according to the target area information of the terminal and the service area information of the first session management network element; and the first session management network element determines that the at least one user plane network element cannot establish connection with the base station of the target area according to the session management information of the terminal.

Said first session managing network element attempting to select at least one UPF in said at least one user plane network element to match session managing information of the terminal. And if at least one UPF can not be matched with the session management information of the terminal, the at least one user plane network element can not establish connection with the base station of the target area.

The session management information of the terminal comprises the following information: one or more of DNN, Session and Service Continuity mode (SSC mode), slice information, Session type, capabilities of user plane network elements (caching, local breakout, etc.), Service area of user plane network elements, etc. The session management information of the terminal may be obtained from the subscription server by the mobility management network element and then sent to the first session management network element.

For example: the user plane network element managed by the first session management network element comprises a user plane network element A and a user plane network element B, the first session management network element determines that a target area where a terminal is located in a service area of the user plane network element A managed by the first session management network element, then the first session management network element determines whether the user plane network element A meets the session management information, if not, the user plane network element A is determined not to be capable of establishing connection with a base station of the target area, and for example, the user plane network element A does not meet the requirement of SSC mode in the session management information of the terminal, the user plane network element A is determined not to be capable of establishing connection with the base station of the target area.

The session management information of the terminal may be acquired by the first session management network element in the session creation process. Such as SSC mode, is sent by the terminal to the first session managing network element during session creation. For another example, the capability of the user plane network element (cache, local breakout, etc.), the service area of the user plane network element, etc. may be obtained from the subscription data of the first session management network element user.

A third possible implementation: the first session managing network element attempts to select a user plane network element that satisfies a condition, and if selected, is present, and if not, is absent. Specific conditions may include: one or more items of information such as UE location, DNN, SSC mode, slice information, PDU session type, capability (cache, local offload, etc.) of user plane network element, service area of user plane network element, etc. See the way existing SMF selects UPF specifically.

In addition, in this embodiment of the present application, the determining, by the first session management network element, whether a user plane network element capable of establishing a connection with the base station of the target area exists in the user plane network elements managed by the first session management network element may specifically be implemented by:

in the method 1, the first session management network element may first determine whether the first user plane network element connected to the source base station can establish a connection with the target base station, and if not, then determine whether the user plane network elements managed by the first session management network element, except for the first user plane network element, can establish a connection with the target base station.

In the mode 2, the user plane network element connected to the source base station and the other user plane network elements are not distinguished in the user plane network element managed by the first session management network element. Further, the first session management network element may directly determine whether a user plane network element capable of establishing a connection with the target base station exists in one or more user plane network elements managed by the first session management network element.

In the mode 3, the mobility management network element determines whether the first user plane network element connected to the source base station can establish connection with the target base station.

And in the process of accessing the terminal to the source base station, after the first session management network element selects the first user plane network element, sending the information of the first user plane network element to a mobility management network element. The information of the first user plane network element includes service area information of the first user plane network element and/or an identifier of the first user plane network element, and the service area information of the first user plane network element is taken as an example for description later. Therefore, after the mobility management network element receives the handover request, whether the terminal is located in the service area of the first user plane network element can be determined according to the target area information of the terminal and the information of the first user plane network element, and if not, the first user plane network element cannot establish connection with the target base station.

The following takes the handover between ANs in the 5G communication network as AN example, that is, in the embodiment corresponding to fig. 2A, the mobility management element is AN AMF, the session management element is AN SMF, and the user plane element is a UPF.

Mode 1 and mode 2 are described in detail in the following examples.

The first embodiment is as follows:

referring to fig. 4, a schematic flowchart of network element selection provided in the embodiment of the present application is shown. For convenience of description, the SMF corresponding to the DN will be referred to as ASMF (i.e., corresponding to SMF2 in fig. 2A, SMF before handover), the SMF corresponding to the target AN (target AN, T-AN) will be referred to as ISMF (i.e., corresponding to SMF1 in fig. 2A, newly selected SMF), and similarly, the UPF connected to the DN will be referred to as AUPF (i.e., UPF corresponding to S-AN, corresponding to UPF2 in fig. 2A), and the selected UPF connected to T-AN will be referred to as IUPF.

S401, when it is determined that the UE needs to be switched from S-AN to T-AN (target AN), S-AN (source AN) sends a switching indication (handover required) to S-AMF. The handover request includes AN identifier of a Protocol Data Unit (PDU) session and target area information (UE location) of the UE, where the target area information of the UE is also location information of the target AN or a cell ID corresponding to the target area. The identification of the PDU session may be a PDU session ID.

S402, after the S-AMF receives the switching indication, the S-AMF sends a forward redirection request (forward redirection request) to the T-AMF. The forward redirection request includes an ID of the PDU session and target area information of the UE.

Wherein S-AMF serves S-AN, and T-AMF serves T-AN.

In addition, it should be noted that, if the S-AN and the T-AN are both located in the service area of the same AMF, the S-AMF and the T-AMF are the same AMF, and S402 is not executed in the process of network element selection in the embodiment of the present application.

S403, the T-AMF sends a PDU handover request (handover request)1 to the ASMF, wherein the handover request1 includes the target area information of the UE.

S404, after receiving the handover request1, the ASMF determines that no UPF capable of establishing a connection with the T-AN exists in the UPFs managed by the ASMF.

If the ASMF determines whether the UPF1 (i.e., AUPF) establishing connection with the S-AN can establish connection with the T-AN according to the target area information of the UE, if so, the ASMF triggers a flow of establishing user plane connection between the T-AN and the UPF1, that is, the ASMF sends AN N4session update request (N4session update) to the UPF1, and at this time, the corresponding scenario is that the UPF1 can connect with the AN and can connect with the S-AN and the T-AN, respectively.

If the ASMF determines that the UPF1 cannot establish a connection with the T-AN according to the target area information of the UE, the ASMF determines whether other UPFs managed by the ASMF, except the UPF1, can establish a connection with the T-AN.

If the ASMF determines that the UPF2 managed by the ASMF, except the UPF1, can establish a connection with the T-AN, the ASMF triggers a flow of establishing a user plane connection between the T-AN and the UPF2, and specifically, the ASMF sends AN N4session update request (N4session update) to the UPF 2.

If the ASMF determines that no UPF managed by the ASMF except the UPF1 can establish connection with the T-AN, no UPF capable of establishing connection with the T-AN exists in the UPF managed by the ASMF.

S405, the ASMF sends a message 1 to the T-AMF, where the message 1 is used to trigger the T-AMF to perform an operation of selecting an SMF. The message 1 may be a PDU handover response (PDU handover response)1, and certainly, other messages for triggering the T-AMF to perform the operation of selecting the SMF are all applicable to the embodiment of the present application, and the message 1 is taken as the PDU handover response 1 in fig. 4 as an example.

The result of the determination that the ASMF determines that there is no UPF that can establish a connection with the T-AN among the UPFs managed by the ASMF may be sent to the T-AMF through message 1. The T-AMF thus performs an operation of selecting an SMF according to the decision structure.

Wherein, the message 1 has the function of informing the judgment result, that is, if the T-AMF does not need to be triggered to execute the operation of selecting the SMF, the ASMF does not need to send the message 1 to the T-AMF, and once the message 1 is sent to the sending T-AMF, the T-AMF is triggered to execute the operation of selecting the SMF. Or in a form that carries an indication value (indicator) in message 1, such as: 1 indicates that the T-AMF needs to perform the operation of selecting the SMF, and 0 indicates that the T-AMF does not need to perform the operation of selecting the SMF and does not need the SMF reselection); or the judgment result is notified in a form that the message 1 carries a reason value, for example, the reason value is used to indicate that the reason for sending the message 1 is: and no UPF capable of establishing connection with the T-AN exists in the UPFs managed by the ASMF.

Optionally, the PDU switch response 1 may also carry indication information for indicating the action performed by the T-AMF. The actions include: reselecting the SMF or adding the SMF.

The ASMF, when determining the action that the T-AMF needs to perform, can:

the ASMF determines the actions that the T-AMF needs to perform according to network policies, wherein the network policies may be pre-configured in the ASMF.

The network policy may include: and executing a newly-added satisfied condition and executing a reselected satisfied condition.

For example, the new addition may be performed on a specific session according to the service-related information, where, for example, if a certain session includes a locally-distributed service, the new addition is correspondingly performed on the session. The Data Network Access Identifier (DNAI), the service identifier, or the data characteristic indicates a service type corresponding to data transmitted by the UE. The DNAI may be obtained by the SMF from the policy control network element during session creation or update, or the DNAI may be pre-configured on the SMF.

The specific network policy may include: executing a Data Network Access Identifier (DNAI) corresponding to the action of the newly added isff, or executing a service identifier range corresponding to the action of the newly added isff, or executing a data feature corresponding to the action of the newly added isff.

For another example, the addition or reselection is determined to be performed according to the SSC mode information. If the SSC mode information indicates that the session continuity is required to be maintained, the UPF (AUPF) as the anchor point cannot be changed, and an ISMF needs to be added; if session continuity is not required to be maintained, then the SMF and UPF may be reselected.

Optionally, the network policy may also be preconfigured in the T-AMF, and the PDU switching response 1 may not carry the above indication information for indicating the action performed by the T-AMF. The actions that need to be performed are determined by the T-AMF according to the network policy.

And S406, after receiving the PDU switching response 1 sent by the ASMF, the T-AMF executes the operation of adding or reselecting the SMF. In fig. 4, an operation of adding an SMF is taken as an example. And after the T-AMF determines to reselect the SMF, a session creation or session update flow is executed. Specifically, refer to the existing PDU session establishment or update or modification process, which is not described herein again.

When determining that the SMF needs to be reselected, the T-AMF can be specifically implemented by the following means:

on one hand, the T-AMF queries an optional list 1 of SMFs from the NRF (or DNS server) according to the target area information of the UE (such as the cell identity, the location information of the base station, etc.), and obtains an optional list 2 of SMFs according to the DNN query. Then, the T-AMF selects an SMF from the optional list 2 as a session anchor or an IP anchor, which may be selected according to information such as load and capability of each SMF, for example, the selected SMF is SMF 1. Then comparing the SMF with the optional list 1, preferentially selecting the SMF with the same identification as the SMF1 in the optional list 1, if the same SMF is not identified, comparing the identification of the SMF included in the optional list 1 with the identification of the SMF1, and selecting the SMF with the topology nearest to the SMF 1. Currently, the identities of the SMFs are determined according to service areas, and the closer the service areas of the two SMFs are, the closer the identities of the two SMFs are. Thus, the two SMF topologies are the closest, i.e., the two SMF identities are the closest.

In practice, the final goal of selecting AN SMF is to select to a UPF, which can be connected to a T-AN and DN, respectively. The SMF service area is considered in the process of selecting the SMF by the AMF, the SMF service area is associated with the service area range of the corresponding UPF, for example, when the SMF can control a plurality of UPFs, the SMF service area is split into a plurality of small service areas corresponding to the UPFs, and the SMF knows the SMF service area and thus knows the UPF service area when selecting the UPF. It is guaranteed that after selecting AN SMF, one UPF must be found that can connect to the T-AN. For another example, when the SMF can manage a plurality of UPFs, the service area of the SMF is a union or union of the service areas of the plurality of UPFs, and the SMF knows that the service area of the SMF is within the range when selecting the UPF, that is, knows that the service area of at least one UPF is within the range. It is guaranteed that after selecting AN SMF, one UPF must be found that can connect to the T-AN.

On the other hand, the T-AMF may also send the UE location and DNN information to the DNS server (or NRF) at the same time, and the DNS server (or NRF) queries to obtain two optional lists and selects the SMF, and returns the selection result to the T-AMF. If the DNS server (or NRF) determines that one SMF can simultaneously satisfy two query conditions of UE location and DNN, returning the identifier of the SMF; if the DNS server (or NRF) selects two SMFs, one of which satisfies the UE location and the other one of which satisfies the DNN, then two SMFs are returned and the AMFs are instructed about the role of each SMF, i.e. which corresponding T-AN is indicated as the ISMF and which corresponding DN is indicated as the ASMF (for connecting DNS).

When determining that the SMF needs to be newly added, the T-AMF keeps the current ASMF as a session anchor point or an IP anchor point, which may specifically be implemented as follows:

since the ASMF is selected based on DNN, DNN is always kept unchanged during the holding of PDU session, the ASMF can always keep the connection with DN. Only one more SMF is needed to ensure that a UPF can be selected for connection with the T-AN.

In one aspect, the T-AMF queries a DNS server (or NRF) to obtain an optional list 1 of SMFs according to target area information (such as cell identifiers, base station locations, etc.) of the UE, compares the ASMF with the optional list 1, preferentially selects an SMF in the optional list 1 that is the same as the identifier of the ASMF, and if the same SMF is not identified, compares the identifier of the SMF included in the optional list 1 with the identifier of SMF1, and selects an SMF that is topologically closest to SMF1 as the ISMF.

On the other hand, it is also possible for the T-AMF to send the UE location and the identifier of the ASMF to the DNS server (or NRF) at the same time, query the optional list 1 and select the SMF by the DNS server (or NRF), and return the selection result to the T-AMF.

Optionally, the PDU handover response sent by the T-AMF received by the ASMF may further include AN identifier of AN AUPF connected to the S-AN, and if the T-AMF determines that a new ISMF needs to be added, the T-AMF may send the identifier of the AUPF connected to the S-AN to the new ISMF after selecting the new ISMF, so that the new ISMF may select AN IUPF closest to the topology of the AUPF according to the identifier of the AUPF when selecting the UPF.

Referring to fig. 4, the T-AMF performs the operation of adding SMF. And after determining the new I-SMF, the T-AMF performs a subsequent session updating process, namely updating the user plane connection between the UE and the DN. The method specifically comprises the following steps:

s407, the T-AMF sends a PDU handover request (PDU handover request)2 to the ISMF. The PDU switch request 2 may include tunnel information of T-AN (T-AN tunnel info), AN ID of PDU session, and AN ASMF ID. After the I-SMF obtains the information of the ASMF, such as the AMF ID or the AMF address, a signaling message may be sent to the AMF.

S408, after receiving PDU switch request 2 sent by T-AMF, the ISMF selects IUPF, and then sends N4session management request1 to IUPF, where N4session management request may be N4session establishment/modification/update request (N4session establishment/modification/update request). The N4session management request may include the ID of the PDU session and the T-AN tunnel info. The N4session management request is used to instruct the IUPF to establish a user plane connection with the T-AN.

S409, after the IUPF establishes the user plane connection with the T-AN, it sends N4session management response 1 to the ISMF.

Wherein the N4session management response may be an N4session setup/modify/update response (N4session initialization/modification/update response). N4session management response 1 is used to indicate whether the IUPF successfully established the user plane connection with the T-AN.

In the N4session management flow, the I-SMF may obtain tunnel information of the IUPF, which may include N3tunnel information (N3tunnel info) corresponding to a user plane connection between the IUPF and the T-AN, and may also include N9 tunnel information (N9 tunnel info) between the IUPF and the AUPF. N3 is the interface between a UPF and AN, N9 is the interface between two UPFs, such as IUPF and AUPF. If the tunnel information is allocated by the SMF, N3tunnel information and N9 tunnel information are transmitted by the I-SMF to the IUPF in the N4session management request of S408; if the tunnel information is allocated by the UPF, N3tunnel information and N9 tunnel information are transmitted to the I-SMF by the IUPF in an N4session management response of S409.

S410, the ISMF sends a PDU switch request 3 to the ASMF, where the PDU switch request 3 includes the tunnel information (N3tunnel info) and N9 tunnel information of N3, and the ID of the PDU session. The PDU handover request 3 is used to instruct the ASMF to establish a user plane connection between the IUPF and the AUPF.

S411, after receiving the PDU switch request 3 sent by the ISMF, the ASMF sends an N4session management request 2 to the AUPF. The N4session management request 2 includes the ID of the PDU session and N9 tunnel info. N4session management request 2 is used to instruct the AUPF to establish a user plane connection with the IUPF.

S412, after receiving the N4session management request 2 sent by the ASMF, the AUPF sends an N4session management response2 to the ASMF. N4session management response2 is used to indicate whether the AUPF successfully established the user plane connection with the IUPF. N4session management response2 may include N9 tunnel info of AUPF.

S413, the ASMF sends a PDU switch response 3 to the ISMF, the PDU switch response 3 includes N9 tunnel info of AUPF.

And S414, after receiving the PDU switching response 3 sent by the ASMF, the ISMF sends a PDU switching response2 to the T-AMF, wherein the PDU switching response2 comprises N3tunnel info of IUPF.

S415, after receiving PDU switching response2 sent by I-SMF, T-AMF sends switching request to T-AN, carrying N3tunnel info of IUPF, so T-AN can send uplink data to IUPF.

S416, after receiving the switching request sent by the T-AMF, the T-AN confirms the PDU session information which can be switched and sends a switching response to the T-AMF.

S417, after receiving the switching response sent by the T-AN, the T-AMF sends a modify PDU request (modify PDU request) to the I-SMF, wherein the modify PDU request may include N9 tunnel info of AUPF.

And S418, after receiving the PDU modification request sent by the T-AMF, the I-SMF sends an N4session management request 3 to IUPF. N9 tunnel info of AUPF may be included in the N4session modification request so that IUPF may send upstream data on AUPF.

S419, the IUPF receives the N4session management request 3 sent by the I-SMF, completes PDU session modification, and sends an N4session management response 4 to the I-SMF, wherein the N4session management response 4 may be an N4session modification response (N4session modification response).

And S420, after receiving the N4session modification response 4 sent by the IUPF, the I-SMF sends a modification PDU response (modify PDU response) to the T-AMF.

And S421, after receiving the PDU modification response sent by the I-SMF, the T-AMF sends a forward redirection response (forward redirection response) to the S-AMF, wherein the forward redirection response is used for indicating that the switching from the S-AN to the T-AN is successfully completed.

In the foregoing embodiment, when the AMF cannot sense the service area range of the UPF, and when the current SMF cannot select an appropriate UPF to establish a connection with the target base station due to UE mobility, the current SMF may determine whether there is an UPF that establishes a connection with the target base station in the control range, and notify the determination result to the AMF, so that the AMF may reselect or newly add an SMF, and the newly added SMF selects an appropriate UPF(s), so that a user plane connection can be established between the target base station and the DN. Specifically, the SMF judges whether the current SMF can select the UPF connected with the target base station or not according to the target area information of the UE, if not, the AMF is informed, and the AMF reselects or adds the SMF according to the judgment result, so that the reselected or added SMF selects the UPF connected with the target base station.

The following second embodiment will be described in detail with respect to the above-described mode 3.

Example two:

referring to fig. 5, a schematic flowchart of network element selection provided in the embodiment of the present application is shown. For convenience of description, the SMF corresponding to the DN will be referred to as ASMF, the SMF corresponding to the target AN (T-AN) will be referred to as ISMF, and similarly, the UPF connected to the DN will be referred to as AUPF (i.e., UPF corresponding to S-AN), and the selected UPF connected to the T-AN will be referred to as IUPF.

The second embodiment is premised on that the AMF knows location information of the AUPF connected to the S-AN, such as service area information or identification information (related to location) of the AUPF, but the AMF does not know service range information of all UPFs managed by the current ASMF.

In a session creation procedure in which the UE connects to the S-AN, after the ASMF selects the AUPF, location information of the AUPF, for example, service area information (UPF service area) of the AUPF, may be sent to the S-AMF.

S501, when the S-AN determines that the UE needs to be switched from the S-AN to the T-AN (target AN), the S-AN sends a switching instruction (handover required) to the S-AMF. The handover request includes AN identifier of the PDU session and target area information (UE location) of the UE, where the target area information of the UE may be location information of the target AN. The identification of the PDU session may be a PDU session ID.

S502, after the S-AMF receives the switching indication, the S-AMF sends a forward redirection request (forward redirection request) to the T-AMF. The forward redirection request includes an ID of the PDU session and target area information of the UE.

Wherein S-AMF serves S-AN, and T-AMF serves T-AN.

In addition, it should be noted that, if the S-AN and the T-AN are both located in the service area of the same AMF, the S-AMF and the T-AMF are the same AMF, and S502 is not executed in the process of network element selection in this embodiment.

The S-AMF stores the service area information of the AUPF, and in step S502, the forward redirection request sent by the S-AMF to the T-AMF further includes the service area information of the AUPF.

And after receiving the forward redirection request, the T-AMF determines that the UE is located in the service area of the AUPF according to the target area information of the UE and the service area information of the AUPF, and does not need to execute the operation of updating the SMF and the UPF.

S503, the T-AMF determines that the UE is located outside the service area of the AUPF according to the target area information of the UE and the service area information of the AUPF.

S504, the T-AMF sends a PDU handover request 1(handover request) to the ASMF, and the handover request1 comprises the target area information of the UE. The handover request1 further includes indication information, where the indication information is used to indicate that the UE is located outside the service area of the AUPF, that is, the AUPF cannot establish a user plane connection with the T-AN.

The handover request1 may further include one or more of DNN, session and service continuity mode (SSC mode), slice information, PDU session type, capability of UPF (cache, local breakout, etc.), service area of UPF, service area of SMF, etc.

And S505, after receiving the switching request1, the ASMF determines that no UPF capable of establishing connection with the T-AN exists in other UPFs managed by the ASMF except the AUPF. For a specific determination manner, refer to the first embodiment, which is not described herein again.

S506 to S522, specifically refer to S405 to S421 in fig. 4, which are not described herein again.

In the above embodiment, the AMF determines whether the current UPF can be connected to the target base station according to the UE location and the stored service area information of the UPF, and sends the initial determination result to the current SMF, and the current SMF performs the subsequent action according to the initial determination result. If the initial judgment result is that the current UPF can establish connection with the target base station, only simple session updating is needed; if the initial judgment result is that the current UPF can not establish connection with the target base station, the SMF further judges whether other UPFs which can be connected with the target base station exist in the management range of the SMF. If the SMF further judgment result is that the UPF connected with the target base station can be found, reselecting or newly adding the UPF and finishing session updating; if the UPF is not found, the judgment result is returned to the AMF, the AMF adds or reselects the SMF, and the added or reselected SMF selects the proper UPF to ensure the connection with the target base station.

The difference between the second embodiment and the first embodiment is that: in the second embodiment, after two determinations by the AMF and the SMF, if the SMF finally determines that there is no UPF establishing connection with the target base station within the current SMF management range, the SMF will notify the AMF, the SMF is newly added or reselected by the AMF, and accordingly, the SMF selects the UPF, and finally completes the user plane connection between the base station and the DN.

Referring to fig. 6, a schematic flow chart of a method for selecting a network element according to an embodiment of the present application is shown. The method is applied to handover between base stations in different communication networks.

S601, in the process of accessing the terminal to the first communication network, the first mobility management network element obtains service area information of the first session management network element.

And in the process of connecting the terminal with the first communication network, the first session management network element provides service for the terminal so as to meet the requirement that the terminal establishes user plane connection with the first communication network.

S602, in a process that the terminal is switched from the first communication network to the second communication network, the first mobility management network element sends a first message to the second mobility management network element. Wherein the first message includes service area information of the first session management network element, so that the second mobility management network element determines whether to select the second session management network element according to the service area information of the first session management network element.

And determining whether to select a second session management network element, that is, determining whether to provide a service for the terminal by the second session management network element after the terminal is switched from the first communication network to the second communication network, so as to satisfy the requirement that the terminal establishes a user plane connection with the second communication network.

The first mobility management network element is a mobility management network element corresponding to the first communication network, and the second mobility management network element is a mobility management network element corresponding to the second communication network.

S603, the second mobility management network element receives the first message from the first mobility management network element.

S604, the second mobility management element determines whether to select the second session management element according to the service area information of the first session management element.

The above-mentioned scheme provides a way how to decide to select the second session management network element in the handover process between base stations in different communication networks. Such as: the terminal is switched from 4G to 5G, and when the terminal accesses 4G, the MME acquires service area information of a first session management network element (such as an SMF (short message service) deployed in the same device as a PGW-C (packet gateway network-core) in the process of connecting the terminal to 4G, so that when the terminal is switched from the 4G network to the 5G network, the MME notifies the AMF of the service area information of the first session management network element, and therefore the AMF can determine whether the service area information of the first session management network element can also serve in the process of connecting the terminal to 5G, and further determine whether an operation of selecting other session management network elements needs to be performed.

Optionally, the first message may further include location information of the terminal. The location information of the terminal is also the target area information where the terminal is located.

The second mobility management network element determines whether to select the second session management network element according to the service area information of the first session management network element, which may specifically be implemented as follows:

when the terminal is determined not to be in the service area of the first session management network element according to the position information of the terminal and the service area information of the first session management network element, the second mobility management network element determines to select the second session management network element; alternatively, the first and second electrodes may be,

and when the terminal is determined to be in the service area of the first session management network element according to the position information of the terminal and the service area information of the first session management network element, the second mobility management network element determines not to select the second session management network element.

In the third embodiment, a base station (eNB) of a 4G communication network located in a source area is handed over to a base station (AN) of a 5G communication network located in a target area. The first mobility management network element is an MME, and the second mobility management network element is an AMF. The session management network element is a network element (namely PGW-C + SMF) which is deployed by the fusion of PGW-C and SMF. The user plane network element is a network element (PGW-U + UPF) which is deployed by the fusion of the PGW-U and the UPF.

As a premise of the third embodiment, in a process of creating a session in 4G, for example, in an attach procedure (attach procedure), an MME may obtain service area information of a PGW-c (smf). The service area information of PGW-c (smf) may be an identifier of PGW-c (smf), or a service area range of PGW-c (smf), etc. Service areas of the PGW-C and the SMF which are deployed in a unified mode may be the same or different, and if the service areas are the same, the service area information is the service area of both the PGW-C and the SMF; and if the difference is positive, the service area information is the service area of the SMF.

Referring to fig. 7, a flowchart for acquiring the service area information of (PGW-C + SMF) is shown.

S701, the UE sends an attach request (attach request) to the eNB.

S702, after receiving the attach request sent by the UE, the eNB forwards the attach request to the MME. The attach request includes target area information (UE location) of the UE.

S703, after the MME receives the attach request, the SGW-C and PGW-C (i.e. SMF) are selected.

Specifically, the MME queries a DNS server according to the UE location to obtain an SGW-C list, queries the DNS server according to an Access Point Name (APN) to obtain a PGW-C list, determines a PGW-C in the PGW-C list (which may depend on information such as a load and a capability of a network element), compares the selected PGW-C with the SGW-C list, preferentially selects an SGW-C having the same IP address as the selected SGW-C from the SGW-C list, and if the IP addresses are the same, compares the IP address of the selected PGW-C with the IP address of the SGW-C in the SGW-C list to select an SGW-C having a topology close to that of the PGW-C.

In practice, the final goal of selecting the SGW-C and PGW-C is to select the corresponding SGW-U and PGW-U, where the SGW-U can be connected to the base station and the PGW-U can be connected to the data network DN. In the process of selecting the SGW-C and the PGW-C, the MME considers service areas of the SGW-C and the PGW-C, where the service areas of the SGW-C and the PGW-C are related to service area ranges of corresponding user planes, for example, in the case that the SGW-C can control a plurality of SGW-us, the service area of the SGW-C is split into a plurality of small service areas corresponding to the SGW-us, and if the MME knows the service area of the SGW-C when selecting the SGW-C, the MME knows the service area of the SGW-U. It is guaranteed that after one SGW-C is selected, one SGW-U can be found to be connected to the base station.

S704, the MME sends a create session request1 (create session request1) to the selected SGW-C.

S705, after receiving the create session request1 sent by the MME, the SGW-C sends the create session request 2 to the selected PGW-C (i.e., SMF), where the create session request 2 is used to instruct the SGW-C to establish a user plane connection.

S706, after receiving the session creation request 2, the PGW-C selects a PGW-U (UPF), and sends a session establishment request (session establishment request) to the selected PGW-U.

S707, after receiving the session establishment request, the PGW-U establishes a user plane connection, and sends a session establishment response (session establishment request) to the PGW-C.

S708, after receiving the session initiation request, the PGW-C sends a create session response2 (create session response2) to the SGW-C. The PGW-C may carry the service area information of itself (SMF) in the create session response2 and send the result to the SGW-C.

S709, the SGW-C forwards the create session response2 to the MME. And the MME stores the service area information of the SMF after receiving the service area information.

S710, the MME sends an initialization context setup request (initial context setup request) to the eNB.

S711, RRC connection reconfiguration is completed between the eNB and the UE.

S712, the eNB sends an attach complete message (attach complete) to the MME.

In the above procedure, the MME acquires the service area information of the PGW-c (smf) through the create session response message.

Optionally, when the MME selects the PGW-C, that is, when step S703 is executed, the MME may obtain the service area information of the PGW-C (smf) from the DNS server.

After the MME acquires the service area information of the PGW-C (SMF), and in the process that the UE is switched to a base station (AN) of a 5G communication network from a base station (eNB) of the 4G communication network, the MME sends the service area information of the PGW-C (SMF) to the AMF, so that the AMF can determine whether the SMF needs to be selected again according to the service area information of the PGW-C (SMF) to ensure the user plane connection between the UE and the data network.

Referring to fig. 8, a flowchart illustrating a handover of a UE from a base station (eNB) of a 4G communication network to a base station (AN) of a 5G communication network is shown. For convenience of description, the SMF (PGW-C) corresponding to the 4G communication network is referred to as ASMF, the SMF corresponding to the AN is referred to as ISMF, and similarly, the UPF (PGW-U) connected to the DN is referred to as AUPF ((i.e., UPF corresponding to eNB)), and the selected UPF connected to the AN is referred to as IUPF.

S801, when determining that the UE needs to be switched from the eNB to the AN, the eNB sends a handover required instruction (handover) to the MME. The handover request includes AN identifier of AN, AN identifier of AMF, and target area information (UE location) of the UE. The target area information of the UE may be location information of the target AN, or location information of the UE, or AN identifier of a target cell corresponding to the location of the UE.

S802, after receiving the handover required, the MME sends a forward redirection request (forward redirection request) to the AMF. The forward location request includes the UE location and the service area information of the ASMF. The forward location request may also include AN identity of the AN, a session context, and a bearer context (including AN address of the ASMF).

And S803, after receiving the forward location request, the AMF determines whether to select the second session management network element according to the service area information of the ASMF.

Specifically, if it is determined that the UE is not in the service area of the ASMF, the AMF determines that the ISMF needs to be selected, i.e., performs the selection operation. If the UE is determined to be in the service area of the ASMF, the AMF does not execute the operation of selecting the ISMF.

The AMF can be configured with a network strategy, and when determining that the ISMF needs to be selected, the AMF can determine to execute a newly added ISMF or reselect the ISMF to replace the original ASMF according to the network strategy. For a specific determination manner, reference may be made to the description in the first embodiment, and details are not described herein again.

When it is determined to execute the newly added ISMF, S804 is executed. After determining to reselect the ISMF, the AMF executes a process of establishing a PDU session between the UE and the DN, which may specifically refer to an existing PDU session establishment procedure, and is not described herein again.

S804, the AMF sends a PDU session management request1 to the selected ISMF.

The ISMF can obtain the address of the ASMF according to the PDU session update request1, so that signaling interaction can be performed with the ASMF. The PDU session management request may be a PDU session establishment/update/modification request (PDU session establishment/update/modification request). For example, the PDU session update request may be an Nsmf _ PDU sesseion _ update SMC Context request. The PDU session update request1 includes bearer context (bearer context) information. The address information (address) of PGW-C (i.e., ASMF) is included in the bearer context.

S805, after receiving the PDU session management request1 sent by the AMF, the ISMF sends a PDU session management request 2 to the ASMF (PGW-C).

S806, after receiving the PDU session management request 2, the ASMF performs session modification corresponding to the N4 interface according to the pointer context and the PGW-U (i.e. AUPF).

S807, the ASMF sends a PDU session update response2 to the ISMF, where the PDU session update response2 is used to send some session information obtained in advance by the ASMF to the ISMF. The PDU session management response may be a PDU session setup/update/modification response (PDU session acknowledgement/update/modification response). For example, the PDU session management response may be Nsmf _ PDU sesseion _ update SMC Context response. The PDU session management response includes tunnel information (a-CN tunnel info) of the AUPF. The PDU session management response further includes session management information (such as N2 SM information) that is not perceived by the mobility management network element, and an identifier of the PDU session. The session management information not perceived by the mobility management element may also include quality of service (QoS) configuration (profile).

And S808, after receiving the PDU session update response2, the ISMF controls the IUPF to establish a tunnel between the IUPF and the AUPF and a tunnel between the IUPF and the AN according to the tunnel information of the AUPF and the N2 SM information.

And S809, the ISMF sends the PDU session management response 1 to the AMF. The PDU session management response 1 includes information of a tunnel between the IUPF and the AUPF (N9 tunnel info) and information of a tunnel between the IUPF and the AN (N3tunnel info). N9 tunnel info and N3tunnel info are collectively referred to as I-CN tunnel info.

S810, after receiving the PDU session management response 1 sent by the ISMF, the AMF sends a handover request (handover request) to the AN. The handover request includes I-CN tunnel info.

S811, after receiving the handover request, the AN sends a handover request acknowledgement (handover request ACK) to the AMF. AN tunnel information (AN tunnel info) is included in the handover request ACK.

S812, after receiving the handover request ACK, the AMF sends a PDU session management request 3 to the ISMF. The PDU session management request instructs the ISMF to create an indirect forwarding tunnel for the session that needs to be switched. For example, the PDU session update request 3 may be an Nsmf _ PDU sesseion _ update SMC Context request. The PDU session update request 3 includes the AN tunnel info of the intermediate forwarding tunnel.

S813, after receiving PDU session management request 3 sent by AMF, the ISMF executes N4session management procedure between the ISMF and IUPF, and sends the AN tunnel info to IUPF in N4session management procedure, so that the IUPF obtains tunnel information of AN and controls the IUPF to establish a tunnel between the IUPF and the AN. Further, in the N4session management flow between the ISMF and the IUPF, the ISMF and the IUPF obtain N3tunnel information and N9 tunnel information of the intermediate forwarding tunnel of the IUPF.

S814, the ISMF sends the PDU session management request 4 to the ASMF, where the PDU session management request includes N9 tunnel info of the intermediate forwarding tunnel of IUPF.

S815, after receiving the PDU session management request, the ASMF sends an N4session management request, such as an N4session modification request, to the AUPF. The N4session modification request includes the N9 tunnel info of the intermediate forwarding tunnel of the IUPF.

S816, after receiving the N4session modification request, the AUPF sends an N4session management response, such as an N4session modification response, to the ASMF. The N4session modification request includes the A-CN tunnel info.

S817, the ASMF sends a PDU session management response 4 to the ISMF. For example, the PDU session management response 4 is an acknowledgement message corresponding to the PDU session management request 3, and may be, for example, Nsmf _ PDU sesseion _ update SMC Context response. The PDU session management response 4 includes the a-CN tunnel info.

S818, the ISMF sends the PDU session management response 4 to the AMF. The PDU session management response 4 includes the a-CN tunnel info.

S819, AMF sends forward redirect response to MME after receiving PDU session update response 4 sent by ISMF. The A-CN tunnel info is included in the Forward redirect response.

S820, the MME sends a request for creating an indirect data forwarding tunnel to the SGW, so as to notify the SGW of the need of indirect data forwarding and notify the SGW of the uplink destination tunnel information indirectly forwarded. For example, the request for creating the indirect data forwarding tunnel is a createindiniret data forwarding tunnel request, the request for creating the indirect data forwarding tunnel includes a-CN tunnel info, and data needing indirect forwarding is sent to the AUPF indicated by the a-CN tunnel info after being sent to the SGW upstream.

S821, the SGW-C sends a create indirect data forwarding tunnel response, such as createindiniret data forwarding tunnel response (including SGW tunnel info), to the MME.

It should be noted that the message names mentioned in the embodiments of the present application are only used as an example, and the message names are not specifically limited.

The above embodiments provide a way for determining how to select the second session management network element in the handover process between base stations in different communication networks, and describe a specific handover procedure in detail. Such as: the terminal is switched from 4G to 5G, MME acquires the service area information of the first session management network element serving the terminal in the process of connecting 4G when the terminal accesses 4G, so that, when the terminal is handed over from 4G to 5G, the MME notifies the AMF of the service area information of the first session management network element, the AMF is thus able to determine whether the service area information of the first session managing network element can also serve in the course of the terminal connection 5G, and thus whether an operation of selecting another session managing network element needs to be performed, if the selection is determined, the user plane network element which establishes connection with the target base station exists in the user plane network element in the control range of the other reselected session management network elements, therefore, the UE can establish connection with the DN through the target base station to carry out data transmission, and the interruption of data transmission caused by the fact that the first session management network element of the source base station cannot serve the target base station is avoided.

Based on the same inventive concept as the method embodiment, the embodiment of the present application further provides a device, and the device 900 is applied to a session management network element. The apparatus 900 may specifically be a processor, or a chip system, or a functional module in a session management network element. The apparatus may comprise a receiving unit 901, a processing unit 902, a transmitting unit 903. The processing unit 902 is used for controlling and managing the operation of the apparatus 900. The receiving unit 901 is configured to perform S302, the processing unit 902 is configured to perform S303, and the sending unit 903 is configured to perform S304, which is repeated here and is not described here again. The processing unit 902 may further be configured to indicate a processing procedure involving a session management network element (SMF or PGW-C) in any of the embodiments described above and/or other procedures of the technical solutions described in this application.

An embodiment of the present application further provides another structure of a session management network element, as shown in fig. 10, a session management network element 1000 may include a communication interface 1010 and a processor 1020. Optionally, the session management network element 100 may further include a memory 1030. The memory 1030 may be disposed inside the session management network element, or may be disposed outside the session management network element. The processing unit 902 shown in fig. 9 described above may be implemented by the processor 1020. The receiving unit 901 and the transmitting unit 903 may be implemented by a communication interface 1010. The processor 1020 receives the information or message through the communication interface 1010 and is configured to implement the method performed by the session management network element (SMF or PGW-C) described in fig. 3 to 8. In implementation, the steps of the processing flow may implement the method performed by the session management network element described in fig. 3 to 8 through an integrated logic circuit of hardware in the processor 1020 or instructions in the form of software.

The communication interface 1010 in the embodiments of the present application may be a circuit, a bus, a transceiver, or any other device that can be used for information interaction. The other device may be, for example, a device connected to the session management apparatus 1000, for example, the other device may be an AMF or a UPF.

The processor 1020 in the embodiments of the present application may be a general purpose processor, a digital signal processor, an application specific integrated circuit, a field programmable gate array or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, and may implement or perform the methods, steps, and logic blocks disclosed in the embodiments of the present application. A general purpose processor may be a microprocessor or any conventional processor or the like. The steps of a method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware processor, or may be implemented by a combination of hardware and software elements in a processor. Program code executed by processor 1020 to implement the above-described methods may be stored in memory 1030. A memory 1030 is coupled to the processor 1020.

The coupling in the embodiments of the present application is an indirect coupling or a communication connection between devices, units or modules, and may be an electrical, mechanical or other form for information interaction between the devices, units or modules.

Processor 1020 may operate in conjunction with memory 1030. The memory 1030 may be a nonvolatile memory such as a Hard Disk Drive (HDD) or a solid-state drive (SSD), and may also be a volatile memory such as a random-access memory (RAM). The memory 1030 is any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited to such.

The specific connection medium among the communication interface 1010, the processor 1020 and the memory 1030 is not limited in the embodiments of the present application. In the embodiment of the present application, the memory 1030, the processor 1020, and the communication interface 1010 are connected by a bus in fig. 10, the bus is represented by a thick line in fig. 10, and the connection manner between other components is merely illustrative and not limited thereto. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 10, but this is not intended to represent only one bus or type of bus.

Based on the same inventive concept as the method embodiment, the embodiment of the application also provides a device. Referring to fig. 11, the apparatus 1100 is applied to a mobility management network element. The apparatus may specifically be a processor, or a chip system, or a functional module in a mobility management network element.

Referring to fig. 11, the apparatus may include a communication 1101, a processing unit 1102. The communication unit 1101 includes a transmitting unit and a receiving unit. The apparatus may apply the mobility management network element in the embodiments shown in fig. 3 to fig. 5, such as the AMF, the communication unit 1101 is configured to execute S301, the processing unit 1102 is configured to execute S305, and the processing unit 1102 may also be configured to execute the processing procedure related to the mobility management network element in the embodiments shown in fig. 3 to fig. 5 and/or other procedures of the technical solutions described in this application. The apparatus may apply the first mobility management network element, such as an MME, in the embodiments shown in fig. 6 to 8, then the communication unit 1101 is configured to execute S602, and the processing unit 1102 is configured to execute S601, or perform a processing procedure involving the first mobility management network element (MME) in the embodiments shown in fig. 6 to 8 and/or other procedures of the technical solutions described in this application. The apparatus may also apply the second mobility management element, such as the AMF, in the embodiments shown in fig. 6 to 8, then the communication unit 1101 is configured to execute S603, and the processing unit 1102 is configured to execute S604, or perform the processing procedure involving the second mobility management element (AMF) in the embodiments shown in fig. 6 to 8 and/or other procedures of the technical solutions described in this application.

An embodiment of the present application further provides another structure of a mobility management network element, as shown in fig. 12, a mobility management network element 1200 may include a communication interface 1210 and a processor 1220. A memory 1230 may also be included in the mobility management element 1200. The memory 1230 may be located within the mobility management element or external to the mobility management element. The processing unit 1102 shown in fig. 11 described above may be implemented by the processor 1220. The communication unit 1101 may be implemented by a communication interface 1210. The processor 1220 receives traffic data via the communication interface 1210 and is configured to implement the method performed by any of the mobility management network elements (e.g., MME or AMF) described in fig. 3-8. In implementation, the steps of the processing flow may implement the method performed by any mobility management network element described in fig. 3 to 8 through instructions in the form of hardware integrated logic circuits or software in the processor 1220.

The communication interface 1210 in the embodiments of the present application may be a circuit, a bus, a transceiver, or any other device that can be used for information interaction. The other apparatus may be, for example, a device connected to the mobility management network element 1200, for example, the other apparatus may be AN or a UE, etc.

The processor 1220 in the embodiments of the present application may be a general purpose processor, a digital signal processor, an application specific integrated circuit, a field programmable gate array or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, and may implement or perform the methods, steps, and logic blocks disclosed in the embodiments of the present application. A general purpose processor may be a microprocessor or any conventional processor or the like. The steps of a method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware processor, or may be implemented by a combination of hardware and software elements in a processor. Program code executed by processor 1220 to implement the above-described methods may be stored in memory 1230. Memory 1230 is coupled to processor 1220. The processor 1220 may cooperate with the memory 1230. The memory 1230 may be a nonvolatile memory such as a Hard Disk Drive (HDD) or a solid-state drive (SSD), and may also be a volatile memory such as a random-access memory (RAM). The memory 1230 is any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited to such.

The specific connection medium among the communication interface 1210, the processor 1220 and the memory 1230 is not limited in the embodiments of the present application. In the embodiment of the present application, the memory 1230, the processor 1220 and the communication interface 1210 are connected by a bus in fig. 12, the bus is represented by a thick line in fig. 12, and the connection manner between other components is merely illustrative and not limited thereto. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 12, but this is not intended to represent only one bus or type of bus.

Based on the above embodiments, the present application further provides a computer storage medium, in which a software program is stored, and the software program can implement the method provided by any one or more of the above embodiments when being read and executed by one or more processors. The computer storage medium may include: u disk, removable hard disk, read only memory, random access memory, magnetic or optical disk, etc. for storing program codes.

Based on the above embodiments, the present application further provides a chip, where the chip includes a processor, and is configured to implement the functions related to any one or more of the above embodiments, such as obtaining or processing information or messages related to the above methods. Optionally, the chip further comprises a memory for the processor to execute the necessary program instructions and data. The chip may be constituted by a chip, or may include a chip and other discrete devices.

In the embodiment provided by the application, when the UE moves from the source base station to the service area of the target base station, the user plane selected by the first session managing network element serving the source base station may only be able to establish a connection with the DN, and may not be able to establish a connection with the target base station, by the above-described scheme, the first session management element serving the source base station determines whether there is a user plane element capable of establishing a connection with the target base station among the plurality of user plane elements under its control, if not, notifying the mobility management network element, so that the mobility management network element can reselect other session management network elements to ensure that the user plane network elements in the control range of the reselected other session management network elements have the user plane network elements establishing connection with the target base station, therefore, the UE can establish connection with the DN through the target base station to carry out data transmission, and the interruption of data transmission caused by the fact that the first session management network element of the source base station cannot serve the target base station is avoided.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

1. A method for selecting a network element, comprising:

the method comprises the steps that a first session management network element receives a first message from a mobility management network element, wherein the first message is used for indicating a terminal to be switched from a source area to a target area;

the first session management network element determines whether a user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element;

and when determining that no user plane network element capable of establishing connection with the base station of the target area exists, the first session management network element sends a second message to the mobility management network element, wherein the second message is used for triggering the mobility management network element to execute an operation of selecting the second session management network element.

2. The method of claim 1, wherein the first message includes target area information of the terminal, and wherein the first session management network element determines that no user plane network element capable of establishing a connection with a base station of the target area exists in the user plane network elements managed by the first session management network element, comprising:

3. The method of claim 1, wherein the first message includes target area information of the terminal and session management information of the terminal, and wherein the first session management network element determines that no user plane network element capable of establishing a connection with a base station of the target area exists in the user plane network elements managed by the first session management network element, comprising:

4. The method of claim 1, wherein the determining, by the first session management network element, that there is no user plane network element capable of establishing a connection with the base station of the target area among the user plane network elements managed by the first session management network element comprises:

5. The method of claim 4, wherein the first message further comprises first indication information indicating that the first user plane network element cannot establish a connection with the base station of the target area;

the determining, by the first session management network element, that the first user plane network element cannot establish a connection with the base station of the target area includes:

6. The method according to any of claims 1 to 5, wherein the second message is used to notify the mobility management element that there is no user plane network element capable of establishing connection with the base station of the target area among the user plane network elements managed by the first session management element; alternatively, the first and second electrodes may be,

the second message includes second indication information, where the second indication information is used to indicate that no user plane network element capable of establishing a connection with the base station of the target area exists in the user plane network elements managed by the first session management network element.

7. The method according to any of claims 1 to 5, wherein the second message comprises third indication information, the third indication information being used for instructing the mobility management network element to perform an operation of adding the second session management network element on the basis of keeping the first session management network element serving the terminal; alternatively, the first and second electrodes may be,

the third indication information is used to instruct the mobility management network element to perform an operation of reselecting the second session management network element.

8. The method of claim 4 or 5, wherein the second message includes an identification of the first user plane network element.

9. A method for selecting a network element, comprising:

a mobility management network element sends a first message to a first session management network element, wherein the first message is used for indicating a terminal to be switched from a source area to a target area;

a mobility management network element receives a second message sent by the first session management network element, where the second message is used to indicate that no user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element;

and the mobility management network element selects a second session management network element according to the second message, so that the second session management network element selects a user plane network element which establishes connection with the base station of the target area.

10. The method of claim 9, wherein prior to the mobility management element sending the first message to the first session management element, the method further comprises:

the mobility management network element determines that the first user plane network element cannot establish connection with the base station of the target area according to the information of the first user plane network element of the base station connected with the source area; the information of the first user plane network element is sent to the mobility management network element by the first session management network element in a process that the terminal accesses the base station of the source area, and the information of the first user plane network element includes service area information of the first user plane network element and/or an identifier of the first user plane network element;

the first message sent by the mobility management network element to the first session management network element further includes first indication information, where the first indication information is used to indicate that the first user plane network element cannot establish a connection with the base station in the target area.

11. The method of claim 9, wherein the second message is used to notify the first session management network element that there is no user plane network element capable of establishing a connection with the base station of the target area among the user plane network elements managed by the first session management network element; alternatively, the first and second electrodes may be,

12. The method according to any of claims 9 to 11, wherein the second message comprises third indication information for instructing the mobility management element to perform an operation of adding a session management element serving the terminal on the basis of keeping the first session management element serving the terminal; or, the third indication information is used to indicate the mobility management network element to perform an operation of reselecting a session management network element serving the terminal.

13. A method according to any of claims 9 to 11, wherein the first message includes an identification of a first user plane network element of a base station connecting the source area;

after the mobility management network element selects the second session management network element according to the second message, the method further includes:

and the mobility management network element sends the identifier of the first user plane network element to the second session management network element, so that the second user plane network element selected by the second session management network element can establish connection with the base station of the target area and the first user plane network element respectively.

14. An apparatus, for use in a first session management network element, comprising:

a receiving unit, configured to receive a first message from a mobility management network element, where the first message is used to instruct a terminal to switch from a source area to a target area;

a processing unit, configured to determine whether a user plane network element capable of establishing a connection with the base station in the target area exists in the user plane network elements managed by the first session management network element;

a sending unit, configured to send a second message to the mobility management network element when the processing unit determines that there is no user plane network element that can establish a connection with the base station in the target area, where the second message is used to trigger the mobility management network element to perform an operation of selecting a second session management network element.

15. The apparatus of claim 14, wherein the first message includes target area information of the terminal, and wherein the processing unit is specifically configured to:

determining that the terminal is not in the service area of any user plane network element managed by the first session management network element according to the target area information of the terminal and the service area information of one or more user plane network elements managed by the first session management network element, and determining that no user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element; alternatively, the first and second electrodes may be,

and determining that the terminal is not in the service area of any user plane network element managed by the first session management network element according to the target area information of the terminal and the service area information of the first session management network element, and determining that no user plane network element capable of establishing connection with the base station of the target area exists in the user plane network elements managed by the first session management network element.

16. The apparatus according to claim 14, wherein the first message includes target area information of the terminal and session management information of the terminal, and the processing unit is specifically configured to:

determining that the terminal is located in a service area of at least one user plane network element managed by the first session management network element according to the target area information of the terminal and the service area information of the one or more user plane network elements managed by the first session management network element; the first session management network element determines that the at least one user plane network element cannot establish connection with the base station of the target area according to the session management information of the terminal; alternatively, the first and second electrodes may be,

17. The apparatus as claimed in claim 14, wherein said processing unit is specifically configured to:

and determining that a first user plane network element connected with the base station of the source area cannot establish connection with the base station of the target area, and determining that no user plane network element managed by the first session management network element except the first user plane network element can establish connection with the base station of the target area.

18. The apparatus of claim 17, wherein the first message further comprises first indication information indicating that the first user plane network element cannot establish a connection with the base station of the target area;

the processing unit is specifically configured to determine, based on first indication information, that the first user plane network element cannot establish a connection with the base station in the target area when it is determined that the first user plane network element cannot establish a connection with the base station in the target area.

19. The apparatus according to any of claims 14 to 18, wherein the second message is used to inform the mobility management element that no user plane network element capable of establishing connection with the base station of the target area exists among the user plane network elements managed by the first session management element; alternatively, the first and second electrodes may be,

20. The apparatus according to any of claims 14 to 18, wherein the second message comprises third indication information, the third indication information being used to instruct the mobility management network element to perform an operation of adding the second session management network element on the basis of keeping the first session management network element serving the terminal; alternatively, the first and second electrodes may be,

21. The apparatus of claim 17 or 18, wherein the second message includes an identification of the first user plane network element.

22. An apparatus, wherein the apparatus is applied to a mobility management network element, and comprises:

a sending unit, configured to send a first message to a first session management network element, where the first message is used to instruct a terminal to switch from a source area to a target area;

a receiving unit, configured to receive a second message sent by the first session management network element, where the second message is used to indicate that no user plane network element capable of establishing a connection with the base station in the target area exists in the user plane network elements managed by the first session management network element;

and the processing unit is configured to select a second session management network element according to the second message, so that the second session management network element selects a user plane network element that establishes a connection with the base station in the target area.

23. The apparatus of claim 22, wherein the processing unit is further configured to determine, before the sending unit sends the first message to the first session management network element, that the first user plane network element cannot establish a connection with the base station of the target area according to information of the first user plane network element connected to the base station of the source area; the service area information of the first user plane network element is sent to a mobility management network element by the first session management network element in a process that the terminal accesses the base station of the source area, and the information of the first user plane network element includes the service area information of the first user plane network element and/or the identifier of the first user plane network element;

the first message sent by the sending unit to the first session management network element further includes first indication information, where the first indication information is used to indicate that the first user plane network element cannot establish a connection with the base station in the target area.

24. The apparatus of claim 22, wherein the second message is used to notify the first session management network element that there is no user plane network element capable of establishing a connection with the base station of the target area among the user plane network elements managed by the first session management network element; alternatively, the first and second electrodes may be,

25. The apparatus according to any of claims 22 to 24, wherein the second message comprises third indication information for instructing a mobility management network element to perform an operation of adding a session management network element serving the terminal on the basis of keeping the first session management network element serving the terminal; or, the third indication information is used to instruct the mobility management network element to perform an operation of reselecting the session management network element serving the terminal.

26. The apparatus according to any of claims 22 to 24, wherein the first message comprises an identification of a first user plane network element of a base station connecting the source area;

the sending unit is further configured to send, after the processing unit selects the second session management network element according to the second message, the identifier of the first user plane network element to the second session management network element, so that the second user plane network element selected by the second session management network element can establish a connection with the base station in the target area and the first user plane network element, respectively.

27. A computer-readable storage medium, in which a program or instructions are stored which, when run on a computer, cause the computer to perform the method of any one of claims 1 to 13.