CN113950111A

CN113950111A - Session switching method and device

Info

Publication number: CN113950111A
Application number: CN202010693848.2A
Authority: CN
Inventors: 朱方园; 李岩
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-07-17
Filing date: 2020-07-17
Publication date: 2022-01-18

Abstract

The application provides a session switching method and a session switching device, wherein the method comprises the following steps: receiving, by a target access network device, a handover request message from a source access network device, where the handover request message is used to request that a session of a terminal device be handed over to the target access network device, and the handover request message includes an identifier of a first network slice and an identifier of a first network slice instance, where the first network slice is associated with the session; when the target access network equipment does not support the first network slice, the target access network equipment determines a second network slice supported by the target access network equipment according to the identifier of the first network slice instance, and switches the session to the target access network equipment; the second network slice, the first network slice, and the second network slice each correspond to the first network slice instance.

Description

Session switching method and device

Technical Field

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

Background

In future 5G communication systems, air interface resources in a network will be abstracted into multiple "network slices (network slices), which may be referred to as slices for short. One network slice meets the requirement of a certain type or one use case of connection communication service, and the whole 5G network is composed of a large number of network slices meeting different connection capacities. In a 5G network, a corresponding Network Slice Instance (NSI) may be created according to a communication requirement related to a network slice, and the network slice instance may be referred to as a slice instance for short. One network slice instance can provide complete end-to-end network services, and one network slice instance corresponds to an identity (NSI ID) of one network slice instance. In practical applications, different network slice instances may be deployed for different users, for example, an operator may access different levels of users to different network slice instances, or the operator may access different users to different network slice instances according to load conditions of different network slice instances.

At present, when a User Equipment (UE) moves into a coverage area of a slice, a Protocol Data Unit (PDU) session (session) corresponding to the slice may be established through a source Radio Access Network (RAN) device in the coverage area of the slice, and an anchor point of the PDU session is located on a Network slice instance corresponding to the slice. If the UE moves out of the coverage of the slice, a handover procedure is triggered, and if an Xn interface exists between a source RAN device accessed by the UE and a target RAN device to be handed over, the UE is handed over to the target RAN device through the handover procedure of the Xn interface. However, if the target RAN device does not support the slice corresponding to the PDU session currently established by the UE, the target RAN device will reject the PDU session to be switched to the target RAN device side, which results in that the PDU session cannot maintain session continuity on the target RAN device side, and service experience of the UE is affected.

Disclosure of Invention

The application provides a session switching method and device, which are used for solving the problem of how to maintain session continuity.

In a first aspect, the present application provides a session handover method, including: receiving, by a target access network device, a handover request message from a source access network device, where the handover request message is used to request that a session of a terminal device be handed over to the target access network device, and the handover request message includes an identifier of a first network slice and an identifier of a first network slice instance, where the first network slice is associated with the session; when the target access network equipment does not support the first network slice, the target access network equipment determines a second network slice supported by the target access network equipment according to the identifier of the first network slice instance, and switches the session to the target access network equipment; the second network slice, the first network slice, and the second network slice each correspond to the first network slice instance.

By the method, when the target access network equipment does not support the first network slice, the second network slice is associated with the session again, and the second network slice also corresponds to the first network slice example, so that the current session of the terminal equipment can be smoothly switched to the target access network equipment in the switching process, and the continuity of the session service is ensured.

In a possible implementation manner, before the target access network device receives the handover request message from the source access network device, the method further includes: the target access network equipment receives first information from core network equipment; the first information includes an identification of at least one network slice and an identification of a network slice instance corresponding to each of the at least one network slice, wherein the target access network device supports the at least one network slice.

In the method, the target access network device may determine, by obtaining the first information, an identifier of a network slice instance corresponding to each network slice supported by the target access network device.

In a possible implementation manner, the determining, by the target access network device, a second network slice supported by the target access network device according to the identifier of the first network slice instance includes: and the target access network equipment determines the network slice corresponding to the first network slice instance in the at least one network slice as the second network slice according to the first information and the identifier of the first network slice instance.

In one possible implementation manner, the switching the session to the target access network device by the target access network device includes: the target access network equipment sends a path switching request message to core network equipment; the path switch request message includes an identification of the second network slice.

In the method, the target access network device directly sends the identifier of the second network slice to the core network device, so that the core network device can determine that the first network slice associated with the session is changed into the second network slice, and the session can be served through the second network slice after being switched to the target access network device.

In a possible implementation manner, the path switching request message further includes an identifier of the first network slice instance.

In a possible implementation manner, after the target access network device switches the session to the target access network device, the method further includes: the target access network device receives, from the core network device, an identifier of at least one network slice allowing the terminal device to access in a registration area of the target access network device, and an identifier of a network slice instance corresponding to each network slice in the identifier of the at least one network slice allowing the terminal device to access in the registration area of the target access network device.

In a possible implementation manner, the core network device is an access and mobility management function AMF network element.

In a second aspect, the present application further provides a communication device having any one of the methods provided for implementing the first aspect. The communication device may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software includes one or more units or units corresponding to the above functions.

In one possible implementation, the communication device includes: a processor configured to enable the communication device to perform the respective functions of the target access network apparatus in the above illustrated method. The communication device may also include a memory, which may be coupled to the processor, that retains program instructions and data necessary for the communication device. Optionally, the communication device further includes a communication interface, and the communication interface is configured to support communication between the communication device and a source access network device or the like.

In one possible implementation, the communication device comprises corresponding functional units, each for implementing the steps in the above method. The functions may be implemented by hardware, or by hardware executing corresponding software. The hardware or software includes one or more units corresponding to the above functions.

In a possible implementation manner, the structure of the communication device includes a processing unit and a communication unit, and these units may perform corresponding functions in the above method example, specifically refer to the description in the method provided in the first aspect, and are not described herein again.

In a third aspect, the present application provides a method comprising: the source access network equipment determines that the terminal equipment triggers session switching and determines target access network equipment; the source access network device sends a switching request message to a target access network device, wherein the switching request message is used for requesting to switch a session of the terminal device to the target access network device, the switching request message comprises an identifier of a first network slice and an identifier of a first network slice instance corresponding to the first network slice, and the first network slice is associated with the session.

In a possible implementation, the method further includes: the source access network equipment sends a session establishment request message to core network equipment; the session establishment request message is used for establishing the session; the source access network device receives a session establishment response message from the core network device, where the session establishment response message includes an identification of the first network slice and an identification of the first network slice instance.

In a possible implementation, the method further includes: the source access network equipment receives third information from core network equipment; the third information comprises an identifier of at least one network slice and an identifier of a network slice instance corresponding to each network slice in the at least one network slice; wherein the source access network device supports the at least one network slice; and the source access network equipment acquires the identifier of the first network slice, and determines the identifier of the first network slice instance corresponding to the first network slice from the third information according to the identifier of the first network slice.

In a possible implementation, the method further includes: in a registration process, the source access network device receives second information from the core network device, where the second information is an identifier of at least one network slice allowing the terminal device to access and an identifier of a network slice instance corresponding to each network slice in the at least one network slice allowing the terminal device to access; and the source access network equipment acquires the identifier of the first network slice, and determines the identifier of the first network slice instance corresponding to the first network slice from the second information according to the identifier of the first network slice.

In the method, the source access network device may determine, through the second information, the identifier of the network slice instance corresponding to the identifier of the at least one network slice to which the terminal device is allowed to access, so that the identifier of the first network slice instance may be accurately determined.

In a possible implementation manner, the source access network device obtains an identifier of a first network slice, and the method further includes: the source access network equipment sends a session establishment request message to core network equipment; the session establishment request message is used for establishing the session; the source access network device receives a session establishment response message from the core network device, where the session establishment response message includes an identification of the first network slice.

In a fourth aspect, the present application further provides a communication device having a function of implementing any one of the methods provided in the third aspect. The communication device may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software includes one or more units or units corresponding to the above functions.

In one possible implementation, the communication device includes: a processor configured to enable the communication device to perform the respective functions of the source access network apparatus in the above-illustrated method. The communication device may also include a memory, which may be coupled to the processor, that retains program instructions and data necessary for the communication device. Optionally, the communication device further includes a communication interface, and the communication interface is configured to support communication between the communication device and a target access network device or the like.

In a possible implementation manner, the structure of the communication device includes a processing unit and a communication unit, and these units may perform corresponding functions in the above method example, specifically refer to the description in the method provided in the third aspect, and are not described herein again.

In a fifth aspect, a method is provided, comprising: receiving, by a target access network device, a handover request message from a source access network device, where the handover request message is used to request that a session of a terminal device be handed over to the target access network device, and the handover request message includes an identifier of a first network slice and an identifier of a first network slice instance, where the first network slice is associated with the session; when the target access network device does not support the first network slice, the target access network device sends the location information of the target access network device and the identifier of the first network slice instance to a network slice selection function NSSF network element; the target access network equipment receives the identifier of the second network slice from the NSSF network element and switches the session to the target access network equipment; the second network slice and the first network slice both correspond to the first network slice instance; and the second network slice is associated with the position information of the target access network equipment.

In a possible implementation manner, the target access network device switches the session to the target access network device, and the method further includes: the target access network equipment sends a path switching request message to core network equipment; the path switch request message includes an identification of the second network slice.

In a possible implementation manner, the core network device is an AMF network element.

In a sixth aspect, the present application further provides a communication device having any one of the methods provided in the fifth aspect. The communication device may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software includes one or more units or units corresponding to the above functions.

In one possible implementation, the communication device includes: a processor configured to enable the communication device to perform the respective functions of the target access network apparatus in the above illustrated method. The communication device may also include a memory, which may be coupled to the processor, that retains program instructions and data necessary for the communication device. Optionally, the communication device further includes a communication interface, and the communication interface is configured to support communication between the communication device and an NSSF network element or the like.

In a possible implementation manner, the structure of the communication device includes a processing unit and a communication unit, and these units may perform corresponding functions in the above method example, specifically refer to the description in the method provided in the fifth aspect, and are not described herein again.

A seventh aspect provides a method comprising: the NSSF network element receives a first network slice instance identification from target access network equipment and position information of the target access network equipment; the NSSF network element determines a second network slice according to the position information of the target access network equipment and sends the identification of the second network slice to the target access network equipment; wherein the target access network device supports the second network slice, and the second network slice corresponds to the first network slice instance.

In an eighth aspect, the present application further provides a communication device having any one of the methods provided in the fifth aspect. The communication device may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software includes one or more units or units corresponding to the above functions.

In one possible implementation, the communication device includes: a processor configured to enable the communication device to perform the respective functions of the NSSF network element in the above-illustrated method. The communication device may also include a memory, which may be coupled to the processor, that retains program instructions and data necessary for the communication device. Optionally, the communication device further includes a communication interface, and the communication interface is configured to support communication between the communication device and a target access network device or the like.

In a ninth aspect, there is provided a computer readable storage medium for storing a computer program comprising instructions for performing the method of the first aspect or any one of the possible implementations of the first aspect.

In a tenth aspect, a computer-readable storage medium is provided for storing a computer program comprising instructions for performing the method of the third aspect or any of the possible implementations of the third aspect.

In an eleventh aspect, there is provided a computer-readable storage medium for storing a computer program comprising instructions for performing the method of any one of the possible implementations of the fifth aspect or the fifth aspect.

In a twelfth aspect, there is provided a computer program product comprising: computer program code for causing a computer to perform the method of the first aspect or any of the possible implementations of the first aspect when the computer program code runs on a computer.

In a thirteenth aspect, there is provided a computer program product comprising: computer program code for causing a computer to perform the method of any of the possible implementations of the third aspect and the third aspect as described above, when the computer program code runs on a computer.

In a fourteenth aspect, there is provided a computer program product comprising: computer program code for causing a computer to perform the method of any of the possible implementations of the fifth aspect and the fifth aspect described above, when the computer program code runs on a computer.

In a fifteenth aspect, the present application provides a chip comprising a processor, coupled with a memory, for executing a computer program or instructions stored in the memory, which when executed by the processor, causes the method of any one of the first to eighth aspects to be implemented.

In a sixteenth aspect, the present application provides a communication device comprising a processor, wherein the method according to any of the first to eighth aspects is performed when the processor executes a computer program or instructions in a memory.

In a seventeenth aspect, the present application provides a communication device comprising a processor and a memory for storing computer programs or instructions; the processor is configured to execute the computer program or instructions stored by the memory to cause the communication device to perform the method according to any of the first to eighth aspects.

In an eighteenth aspect, the present application provides a communication device comprising a processor, a memory, and a transceiver for receiving signals or transmitting signals; the memory for storing computer programs or instructions; the processor is configured to invoke the computer program or instructions from the memory to perform the method according to any of the first to eighth aspects.

Drawings

Figure 1 shows a schematic diagram of a communication system suitable for use in the method of an embodiment of the present application;

fig. 2 is a schematic diagram of an example network slice provided in an embodiment of the present application;

fig. 3 is a schematic diagram of a mapping relationship of a network slice according to an embodiment of the present application;

fig. 4 is a flowchart illustrating a session switching method according to an embodiment of the present application;

fig. 5 is a schematic flowchart of a session switching method according to an embodiment of the present application;

fig. 6 is a schematic flowchart of a session switching method according to an embodiment of the present application;

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

fig. 8 is a schematic flowchart of a session switching method according to an embodiment of the present application;

fig. 9 is a schematic structural diagram of a communication device according to an embodiment of the present application;

fig. 10 is a schematic structural diagram of a communication device according to an embodiment of the present application.

Detailed Description

The embodiments of the present application will be described in detail below with reference to the drawings attached hereto.

The embodiment of the application can be applied to various mobile communication systems, such as: a New Radio (NR) system, a Long Term Evolution (LTE) system, an advanced long term evolution (LTE-a) system, an evolved Long Term Evolution (LTE) system, a future communication system, and other communication systems, and in particular, is not limited herein.

For the convenience of understanding the embodiments of the present application, a communication system applicable to the embodiments of the present application will be first described in detail by taking the communication system shown in fig. 1 as an example. Fig. 1 shows a schematic diagram of a communication system suitable for use with the method of an embodiment of the present application. As shown in fig. 1, fig. 1 exemplarily illustrates a system architecture diagram suitable for the embodiment of the present application, and as shown in fig. 1, in a future 5G system architecture, a terminal device may communicate with a core network via an access network device, and the terminal device may refer to a User Equipment (UE), an access terminal, a subscriber unit, a subscriber station, a mobile station, a remote terminal, a mobile device, a User terminal, a wireless communication device, a User agent, or a User Equipment. An access 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, a terminal device in a future 5G network, etc. For convenience of description, fig. 1 only illustrates 1 terminal device, and in an actual network, multiple terminal devices may coexist, which is not described herein again.

Access Network (AN) devices, which may also be referred to as Radio Access Network (RAN) devices, are hereinafter collectively referred to as Access Network devices, and are mainly responsible for providing wireless connection for a terminal device, ensuring reliable transmission of uplink and downlink data of the terminal device, and the like. The Access network device may be a gbb (generation Node B) in a 5G System, a Base Transceiver Station (BTS) in a Global System for Mobile communications (GSM) System or a Code Division Multiple Access (CDMA) System, a Base Station (NodeB, NB) in a Wideband Code Division Multiple Access (WCDMA) System, an evolved Node B (eNB, eNodeB) in a Long Term Evolution (Long Term Evolution, LTE) System, or the like.

An Access and Mobility Management (AMF) network element is responsible for Mobility Management of users, including Mobility state Management, allocating user temporary identity, authenticating and authorizing users.

A User Plane Function (UPF) network element, which is a functional network element of a User Plane of a terminal device, and supports all or part of the following functions: interconnecting the PDU session with a data network; packet routing and forwarding; and detecting the data packet.

A Session Management Function (SMF) network element, a Session Management Function, which is responsible for Internet Protocol (IP) address allocation, for bearer establishment, modification, and release, for Quality of Service (QoS) control, and the like.

A Policy Control Function (PCF) network element, which is mainly responsible for the functions of establishing, releasing, and changing a user plane transmission path.

An Authentication Server Function (AUSF) network element, whose main functions include user Authentication and the like.

A User Data Management (UDM) network element, which is mainly responsible for managing subscription Data of users, and the like.

A Data Network (DN) may refer to a Network providing services for a terminal device, for example, providing an internet function for the terminal device.

The above are merely examples, and the Network shown in fig. 1 may further include other Network elements, for example, a Network Slice Selection Function (NSSF) Network element: the selection of the network slice is responsible; network storage Function (NRF) Network element: is responsible for the registration and discovery functions of the network element and maintains information of the network element, such as an instance identification, type, PLMN, slice-related identification, IP address or FQDN of the network element, capabilities of the network element, supported services, etc.

Fig. 1 also shows possible implementations of interfaces in various entities, such as an N2 interface between the access network device and the AMF network element, an N9 interface between the access network device and the UPF network element 4, and so on, which are not described in detail herein.

Before describing the embodiments of the present application, some technical terms referred to in the embodiments of the present application will be introduced.

Single Network Slice Selection Assistance Information (S-NSSAI): one network Slice is identified by S-NSSAI, which includes Slice type/Service type (SST), Slice differentiation identifier (SD), and the like.

Wherein: SST: for characterizing the slice in terms of characteristics and traffic. SD: optional information to distinguish between different network slices having the same SST characteristics.

Network Slice Selection Assistance Information (NSSAI): NSSAI is a set of S-NSSAIs, multiple network slices may be identified by NSSAI, and NSSAI in a 5G network may refer to Configured (Configured) NSSAI, or Requested (Requested) NSSAI or Allowed (Allowed) NSSAI.

Allowed (Allowed) NSSAI refers to NSSAI provided by the network side to the terminal device during the registration process of the terminal device, and includes at least one S-NSSAI that the terminal device can use in the current registration area.

Example network slicing: the network slice instance is created according to a communication requirement related to the network slice, one network slice instance corresponds to an identifier (NSI ID) of one network slice instance, and the network slice instance can provide a complete end-to-end network service.

For example, as shown in FIG. 2: in a multi-slice instance deployment scenario, an AMF network element supports two network slices: S-NSSAI-1 and S-NSSAI-2, while the core network deploys two network slice instances for S-NSSAI-1 and S-NSSAI-2, respectively. Specifically, the identifiers of two network slice instances associated with S-NSSAI-1 are NSI-ID-1 and NSI-ID-2 respectively; the identities of the two network slice instances associated with S-NSSAI-2 are NSI-ID-3 and NSI-ID-4, respectively. Network elements supported by different network slice instances associated with one S-NSSAI can provide the service of the S-NSSAI, and according to the deployment situation of an operator, network elements with the same function or network elements with different functions can be provided between different network slice instances. For example, the operator may implement some functional optimization, or charging differentiation, for different network slice instances. For example, a user accessing NSI-ID-1 may use the service of S-NSSAI-1 for free, but a user accessing NSI-ID-2 must pay for the service of S-NSSAI-1. It should be noted that, when the terminal device accesses the network, how to specifically select a network slice example for the terminal device is not limited in the embodiment of the present application.

In the embodiment of the present application, the existence of a mapping relationship between two network slices means that the two network slices correspond to at least one identical network slice instance. At present, the coverage area of a network slice is a limited geographical area, and a terminal device can only access the network slice when the terminal device is located within the coverage area of the network slice. For example, as shown in fig. 3, two network slices, network slice a and network slice X, are included in the network.

The fact that the network slice A and the network slice X have a mapping relation means that: network slice a and network slice X may correspond to one and the same network slice instance, which may also be referred to as a network slice instance shared by network slice a and network slice X. For example, the presence of a network slice instance in the network may serve both network slice a and network slice X. When an anchor network element (e.g., an SMF network element, a UPF network element) belongs to a network slice instance shared by network slice a and network slice X, then the anchor network element can serve both network slice a and network slice X.

When the terminal device moves into the coverage of network slice X and establishes a PDU session corresponding to network slice X through the source access network device, the anchor point of the PDU session is located on the network slice instance corresponding to network slice X, if the terminal device moves out of the coverage of network slice X, for example, the terminal device switches to the target access network device, if network slice a and network slice X can share the network slice instance, then there is a mapping relationship between network slice a and network slice X, in this application embodiment, the access network device can connect to the anchor point of the PDU session through access network slice a, thereby ensuring the service continuity of the PDU session.

In addition, in the embodiments of the present application, the word "exemplary" is used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, the term using examples is intended to present concepts in a concrete fashion.

The network architecture and the service scenario described in the embodiment of the present application are for more clearly illustrating the technical solution of the embodiment of the present application, and do not form a limitation on the technical solution provided in the embodiment of the present application, and as a person of ordinary skill in the art knows that along with the evolution of the network architecture and the appearance of a new service scenario, the technical solution provided in the embodiment of the present application is also applicable to similar technical problems.

Some scenarios in the embodiment of the present application are described by taking a scenario of an NR network in a wireless communication network as an example, it should be noted that the scheme in the embodiment of the present application may also be applied to other wireless communication networks, and corresponding names may also be replaced by names of corresponding functions in other wireless communication networks.

The first embodiment is as follows:

in the first embodiment, it is mainly described that the target access network device obtains the mapping relationship between the network slice and the network slice instance through the AMF network element, and when the PDU session request of the terminal device is switched to the target access network device, the target access network device may determine whether to allow switching of the PDU session according to the obtained mapping relationship between the network slice and the network slice instance, which will be described in detail below.

In the embodiment of the present application, a case where a terminal device is switched from a source access network device to a target access network device is taken as an example for description. The source access network device refers to an access network device to which the terminal device is currently connected, and the target access network device refers to an access network device to which the terminal device is connected after being switched.

Referring to fig. 4, a schematic flow chart of a session switching method provided in the embodiment of the present application is shown. The method comprises the following steps:

step 401: and the target access network equipment sends an N2 message to the AMF network element, wherein the N2 message is used for requesting the identification of the network slice instance corresponding to each network slice in at least one network slice supported by the target access network equipment.

The interface between the target access network device and the AMF network element is an N2 interface, and the N2 interface may also be referred to as an NG interface, so that the N2 message may also be referred to as an NG message. The N2 message may be an N2 connection request (connection request) message or an NG setup request (NG setup request) message, and the N2 message may carry information such as an identifier of the target access network device, a Tracking Area identifier (Tracking Area Identity) of a Tracking Area where the target access network device is located, and a network slice set NSSAI supported by the target access network device. The network slice set includes at least one network slice, and the network slice set may also be referred to as a network slice list. The network slice set NSSAI supported by the target access network device may be a network slice set NSSAI supported by a tracking area where the target access network device is located.

It should be noted that, if the target access network device has an N2 interface with multiple AMF network elements, the target access network device needs to send the above-mentioned N2 message to multiple AMF network element nodes, respectively.

In a possible scenario, the AMF network element does not configure the mapping relationship between the network slice and the network slice instance, and at this time, the AMF network element may request the NSSF network element for the mapping relationship between the network slice and the network slice instance, specifically refer to steps 402 and 403.

Step 402: and the AMF network element sends a request message to the NSSF network element, wherein the request message comprises at least one S-NSSAI.

The specific name of the request message is not limited, and may be, for example, a network slice instance request (slice instance request) message.

In one possible scenario, the at least one S-NSSAI may be used to identify at least one network slice supported by the AMF network element. The at least one network slice supported by the AMF network element includes the at least one network slice supported by the target access network device, that is, the at least one network slice supported by the target access network device may be a subset of the at least one network slice supported by the AMF network element.

In another possible scenario, the at least one S-NSSAI may be used to identify at least one network slice supported by the target access network device.

Step 403: and the NSSF network element returns a response message to the AMF network element, wherein the response message carries the identifier of the network slice instance corresponding to each network slice in at least one network slice supported by the AMF network element.

For example, as shown in table 1, the network slices supported by the AMF network element include S-NSSAI-X, S-NSSAI-a and S-NSSAI-Y. The identifier of the network slice example corresponding to the S-NSSAI-X is NSI-ID-1; the identifiers of the network slice examples corresponding to the S-NSSAI-A are NSI-ID-1 and NSI-ID-2; the network slice instances corresponding to S-NSSAI-Y are identified as NSI-ID-3 and NSI-ID-4.

Table 1: correspondence between S-NSSAI and NSI

S-NSSAI supported by AMF network elements	Identification of network slice instances
		S-NSSAI-X	NSI-ID-1
S-NSSAI-A	NSI-ID-1；NSI-ID-2
		S-NSSAI-Y	NSI-ID-3；NSI-ID-4

As can be seen from table 1, network slice X corresponding to S-NSSAI-X and network slice a corresponding to S-NSSAI-a may correspond to the same network slice instance, and then network slice X and network slice a may be mapped to each other. Specifically, when an anchor point network element (e.g., an SMF network element or a UPF network element) belongs to a network slice instance that network slice X and network slice a correspond to together, the anchor point network element may serve both network slice X and network slice a.

In another possible scenario, the AMF network element configures a mapping relationship between a network slice and a network slice instance, and at this time, step 404 may be directly performed.

If the network slice set supported by the AMF network element is NSSAI, the AMF network element may configure an identifier of a network slice instance corresponding to each S-NSSAI in the NSSAI. It is to be understood that the AMF network element configures an NSI ID corresponding to each S-NSSAI supported by the AMF network element.

It should be noted that the correspondence between each S-NSSAI and NSI may be one-to-one (i.e., one S-NSSAI corresponds to one NSI), or one-to-many (i.e., one S-NSSAI corresponds to multiple NSIs), and the embodiment of the present application is not limited thereto.

Step 404: and the AMF network element sends the first information to the target access network equipment.

The first information includes an identification of at least one network slice supported by the target access network device and an identification of a network slice instance corresponding to each of the at least one network slice.

The AMF network element may carry the first information through an N2 message, and the N2 message may be an N2 connection response (connection response) message or an NG setup response (setup response) message, etc.

The target access network device may store the first information.

It should be noted that, if the target access network device has an N2 interface with multiple AMF network elements, the target access network device may obtain first information sent by multiple AMF network element nodes, respectively.

It should be noted that, steps 401 to 404 are described by taking the target access network device as an example, other access network devices may also obtain, by using the same method, the identifier of the network slice instance corresponding to each network slice supported by the AMF network element from the AMF network element, and details of the specific process are not described again.

Step 405: the source access network equipment acquires the identifier of at least one network slice supported by the source access network equipment and the identifier of a network slice instance corresponding to each network slice in the at least one network slice from the AMF network element.

The specific process of the source access network device obtaining the identifier of the at least one network slice supported by the source access network device and the identifier of the network slice instance corresponding to each network slice in the at least one network slice may refer to the descriptions in step 401 to step 404, and is not described herein again.

It should be noted that, the source access network device obtains the identifier of the at least one network slice supported by the source access network device, the identifier of the network slice instance corresponding to each network slice in the at least one network slice, and the sequence in which the target access network device obtains the first information.

Step 406: the terminal device initiates a registration procedure (registration procedure) through the source access network device.

In this embodiment, the access network device to which the terminal device is currently connected is referred to as a source access network device.

Through the registration process, the terminal device may register to the AMF network element, and the specific process of the registration process is not limited in this embodiment.

After the terminal device is successfully registered, the network slice set supported by the source access network device, that is, the NSSAI supported by the source access network device, may be determined.

Step 407: the terminal equipment initiates a PDU session establishment Procedure (PDU).

The process may include the steps of: the terminal device may send the PDU session identifier, the first S-NSSAI, and a Data Network Name (DNN) to which the terminal device is connected to the AMF Network element. Wherein the first S-NSSAI is an identification of a network slice supported by the source access network device, the network slice being associated with the PDU session. For convenience of description, in the embodiment of the present application, the network slice associated with the PDU session is referred to as a first network slice.

It should be noted that, since the terminal device is registered to the AMF network element in step 406, the AMF network element determines an Allowed NSSAI for the terminal device, where the Allowed NSSAI includes the first S-NSSAI, and the source access network device supports the first S-NSSAI. Furthermore, the AMF network element stores the Allowed NSSAI in the context of the terminal device.

The AMF network element determines from the first S-NSSAI an instance of the first network slice. For convenience of description, in the embodiment of the present application, a network slice instance determined according to an identifier of a first network slice in a PDU session establishment procedure is referred to as a first network slice instance.

The first network slice instance is one of at least one network slice instance corresponding to the first S-NSSAI, and the first network slice instance is used for providing a service for a terminal device. The first network slice instance corresponds to the first network slice, and it should be noted that the first network slice instance may correspond to not only a plurality of S-NSSAIs, that is, the first network slice instance may correspond to not only the first S-NSSAI (i.e., the first network slice), but also the S-NSSAI having a mapping relationship with the first S-NSSAI.

Further, the AMF network element may select the SMF network element according to the first S-NSSAI, the first network slice example, and the DNN, and a specific selection process is not limited, and is not described herein again. The AMF network element sends the parameters of the AMF network element, the terminal equipment, the position information of the terminal equipment, the PDU session identification, the identification of the first network slice example, the first S-NSSAI (namely the identification of the first network slice), the DNN and the like to the SMF network element. The position information of the terminal equipment comprises the TAI of the terminal equipment.

Further, the AMF network element stores the PDU session identification, the identification of the SMF network element associated with the PDU session, the first S-NSSAI and the identification of the first network slice instance in the context of the terminal device.

To this end, the context information of the terminal device stored on the AMF network element may be represented by table 2, for example.

Table 2: context of terminal device

The SMF may select an anchor UPF network element for the PDU session according to the first S-NSSAI, the first network slice instance, and the DNN, and how to select the anchor UPF network element specifically is not limited in this embodiment of the present application, and details are not described here again.

Further, in the PDU session establishment procedure, the AMF network element may also send an identifier of the first network slice instance to the source access network device.

For example, the AMF network element may send an N2 PDU session request message, where the N2 PDU session request message includes N2 session management information, and the N2 session management information carries an identifier of a PDU session, an identifier of a first network slice associated with the PDU session (i.e., a first S-NSSAI), and an identifier of a first network slice instance. And the source access network equipment stores the received information.

After the PDU session is established, when the terminal device moves, the handover procedure of the Xn interface may be triggered.

Specifically, when the terminal device is in a connected state, the terminal device moves out of the coverage of the first network slice, and the terminal device may perform related measurement according to a measurement configuration message issued by the source access network device and send a measurement report to the source access network device, where the measurement report includes a candidate Target identifier list (a list of candidate Target IDs) to be switched to the Target side and a result of a measurement index between each candidate Target and the terminal device. Each candidate target identifier is an identifier of an access network device, and the measurement index includes at least one of Received Signal Strength Indication (RSSI) of a Reference Signal obtained by the terminal device, Reference Signal Receiving Power (RSRP), Reference Signal Receiving Quality (RSRQ) of the Reference Signal, and the like. And the source access network equipment selects one from the candidate access network equipment as target access network equipment according to the result of the measurement index reported by the terminal equipment. Further, the source access network device determines that an Xn interface exists between the source access network device and the target access network device, and then triggers an Xn-based handover procedure. For example, the following steps may be included:

step 408: the target access network device receives the handover request message from the source access network device.

The switching request message is used for requesting to switch the PDU session of the terminal equipment to the target access network equipment, and the switching request message comprises a PDU session identifier, an identifier of the first network slice and an identifier of the first network slice instance. As mentioned above, the PDU session identifier is used to identify a PDU session to be switched to a target side, the first network slice is associated with the PDU session, and the first network slice instance is determined according to the first network slice in a PDU session establishment procedure.

The handover request message may include PDU session information corresponding to all PDU sessions established by the terminal device. The PDU session information corresponding to each PDU session may include the S-NSSAI associated with the PDU session, the identifier of the network slice instance corresponding to the S-NSSAI, and the QoS file (profile (S)) information corresponding to the PDU session. The handover request message may also carry information such as a target cell identifier, which is not described herein again.

Step 409: the target access network device judges whether to support a first network slice associated with the PDU session, and when the target access network device does not support the first network slice, the target access network device may determine, according to an identifier of the first network slice instance, that the target access network device supports a second network slice, and switch the PDU session to the target access network device.

When the target access network equipment determines that the second network slice is supported, in the process of switching the PDU session to the target access network equipment or after switching, the association relationship between the PDU session and the second network slice is established, and the PDU session can be served through the second network slice.

And the second network slice and the first network slice have a mapping relation, namely the second network slice and the first network slice correspond to the first network slice instance.

For example, if the target access network device determines that a Tracking Area (TA) in which the target access network device is located does not support the first network slice, for example, the TA in which the target access network device is located does not deploy the first network slice, the target access network device does not support the first network slice.

Further, the target access network device may determine, according to the first information and the identifier of the first network slice instance, a network slice corresponding to the first network slice instance in at least one network slice indicated by the first information as a second network slice.

Further, if the target access network device may determine, according to the first information and the identifier of the first network slice instance, that there are multiple network slices corresponding to the first network slice instance in at least one network slice indicated by the first information, the network slice supported by the AMF network element may be preferentially determined as the second network slice.

For example, the first network slice associated with the PDU session currently established by the terminal device is S-NSSAI-X, the identifier of the network slice instance corresponding to S-NSSAI-X is NSI ID-1, the TA in which the target access network device is located does not support S-NSSAI-X, but the TA in which the target access network device is located supports S-NSSAI-Y, and the identifier of the network slice instance corresponding to S-NSSAI-Y is NSI ID-1, that is, the S-NSSAI-X and S-NSSAI-Y have a mapping relationship, and the target access network device takes the network slice corresponding to S-NSSAI-Y as the second network slice and allows the PDU session to be switched to the target access network device.

For another example, the first network slice of the PDU session association currently established by the terminal device is S-NSSAI-X, the identifier of the network slice instance corresponding to S-NSSAI-X is NSI ID-1, the TA in which the target access network device is located does not support S-NSSAI-X, but the TA in which the target access network device is located supports S-NSSAI-Y1 and S-NSSAI-Y2, and both S-NSSAI-Y1 and S-NSSAI-Y2 correspond to the network slice instance identified as NSI ID-1. Since the AMF network element connected to the target access network device only supports S-NSSAI-Y1 and does not support S-NSSAI-Y2, the target access network device takes S-NSSAI-Y1 as the second network slice and allows the PDU session to be handed over to the target access network device.

The PDU session of the terminal equipment is allowed to be switched to the target access network equipment, so that the continuity of the PDU session can be maintained, and the service experience of the terminal equipment is improved.

Step 410: and the target access network equipment sends a path switching request message to the AMF network element.

The path switch request message includes a PDU session identification, an identification of the second network slice, and an identification of the first network slice instance. The PDU session identification, the identification of the second network slice, and the identification of the first network slice instance may be located in the N2 session management information in the path switch request message.

The path switching request message may further include location information of the terminal device;

optionally, the N2 session management information may further include information such as an identifier of the first network slice.

Step 411: and the AMF network element sends a PDU session update context request message to the SMF network element.

The AMF network element determines the identifier of the SMF network element associated with the PDU session according to the path switch request message including the PDU session identifier and the stored context information of the terminal device (as shown in table 2).

The PDU session update context request message may carry N2 session management information including information such as a PDU session identifier, an identifier of the second network slice, and an identifier of the first network slice instance.

As one implementation, the PDU session update context request message may be a service operation of the SMF: nsmf _ pdusesion _ UpdateSMContext Request.

Step 412: and the SMF network element and the UPF network element execute the PDU session modification process, and the specific process is not described again.

Step 413: and after the PDU session modification process is completed, the SMF network element sends a PDU session update context response message to the AMF network element.

The response message includes N2 session management information, PDU session identification, and identification of the second network slice. The AMF network element stores the PDU session identifier and the identifier of the second network slice, and it can be understood that the AMF network element stores the correspondence between the PDU session identifier and the identifier of the first network slice before the handover, and the target access network device switches the PDU session to the second network slice, and the AMF network element stores the correspondence between the PDU session identifier and the identifier of the second network slice after the handover.

As an implementation manner, the PDU session update context response message may be a service operation of the SMF network element: nsmf _ pdusesion _ UpdateSMContext Response.

Step 414: the AMF network element sends a path switch request acknowledgement (path switch request acknowledgement) message to the target access network equipment.

Through the above process, the PDU session is successfully switched to the target access network device.

In addition, after step 413, the terminal device initiates a mobility registration update procedure, and the terminal device sends a registration request message to the AMF network element. As the network slice identifier associated with the PDU session changes, in the mobility registration update procedure, the AMF network element determines a new (new) Allowed NSSAI for the terminal device, and sends the new Allowed NSSAI to the terminal device through the registration accept message. The new Allowed NSSAI includes at least one S-NSSAI, and the at least one S-NSSAI included in the new Allowed NSSAI is an identifier of a network slice that the terminal device is Allowed to access in a registration area of the target access network device.

Wherein the new Allowed NSSAI contains an identification of the second network slice. The new Allowed NSSAI may be an update to the Allowed NSSAI in step 407, and it is understood that the Allowed NSSAI determined by the AMF network element for the terminal device before the handover includes the identifier of the first network slice, and the new Allowed NSSAI determined by the AMF network element for the terminal device after the handover includes the identifier of the second network slice but not the identifier of the first network slice.

After the mobility registration updating process is finished, the SMF initiates a PDU session modification process, in which the SMF sends N1 session management information to the terminal device, where the message includes a PDU session identifier and an identifier of the second network slice, and is used to update the network slice associated with the PDU session stored on the terminal device.

By the method shown in the first embodiment, for example, based on the context information of the terminal device shown in table 2, the context information of the terminal device stored in the AMF may be updated to table 3.

Table 3: context of terminal equipment (after switching)

Further, the AMF network element may send, to the target access network device, the new Allowed NSSAI and an identifier of a network slice instance corresponding to each S-NSSAI in the new Allowed NSSAI, where the identifier of the second network slice is an identifier of the first network slice instance corresponding to the second S-NSSAI. The identifier of the network slice instance corresponding to each S-NSSAI in the new Allowed NSSAI is configured by the AMF network element, and the specific configuration process is not described again.

And the target access network equipment locally stores the received new Allowed NSSAI and the network slice instance identifier corresponding to each S-NSSAI in the new Allowed NSSAI.

Example two:

in the second embodiment, the main difference from the first embodiment is that the source access network device obtains the identifier of the first network slice instance in the registration procedure of the terminal device, not in the PDU session establishment procedure, which will be described in detail below.

Referring to fig. 5, a schematic flow chart of a session switching method provided in the embodiment of the present application is shown. The method comprises the following steps:

step 501: and the target access network equipment sends an N2 message to the AMF network element, wherein the N2 message is used for requesting the identification of the network slice instance corresponding to each network slice in at least one network slice supported by the target access network equipment.

In a possible scenario, the AMF network element does not configure the mapping relationship between the network slice and the network slice instance, and at this time, the AMF network element may request the NSSF network element for the mapping relationship between the network slice and the network slice instance, specifically referring to step 502 and step 503.

Step 502: and the AMF network element sends a request message to the NSSF network element, wherein the request message carries the network slice set supported by the AMF network element.

Step 503: and the NSSF network element returns a response message to the AMF network element, wherein the response message carries the corresponding relation between each network slice supported by the AMF network element and the network slice instance.

In another possible scenario, the AMF network element configures a mapping relationship between a network slice and a network slice instance, and at this time, step 504 may be directly performed.

Step 504: and the AMF network element sends the first information to the target access network equipment.

In steps 501 to 504, reference may be made to the descriptions in steps 401 to 404, which are not described herein again.

Step 505: the terminal device sends a registration request message to the source access network device, and the registration request message is used for initiating a registration process (registration procedure) through the source access network device.

Through the registration process, the terminal device can be registered on the AMF network element.

In the registration process, the terminal device may send a registration request message, where the registration request message carries the requested NSSAI. And after receiving the registration request message, the AMF network element determines the Allowed NSSAI according to the subscription data of the terminal equipment and the requested NSSAI. The Allowed NSSAI includes at least one S-NSSAI, and the at least one S-NSSAI included in the Allowed NSSAI is an identifier of a network slice Allowed to be accessed by the terminal device, and specifically may be an identifier of a network slice Allowed to be accessed by the terminal device in a current registration area.

Further, the AMF network element may configure an identifier of a network slice instance corresponding to each S-NSSAI in the Allowed NSSAI.

For example, the AMF network element may determine, according to the local configuration information, an identifier of a network slice instance corresponding to each S-NSSAI in the Allowed NSSAI; or, the AMF network element may obtain, from the NSSF network element, a network slice instance identifier corresponding to each S-NSSAI in the Allowed NSSAI, which is not limited in this embodiment of the present application.

Step 506: in the registration process, the AMF network element sends second information to the source access network equipment; the second information includes an identification of the Allowed NSSAI and a network slice instance corresponding to each S-NSSAI in the Allowed NSSAI. The source access network equipment locally stores the received Allowed NSSAI and the network slice instance identifier corresponding to each S-NSSAI in the Allowed NSSAI.

In addition, the AMF network element stores the Allowed NSSAI and an identification of the network slice instance corresponding to each S-NSSAI in the Allowed NSSAI in the context of the terminal device.

Step 507: the terminal equipment initiates a PDU session establishment flow.

In this step, the terminal device may send parameters such as a PDU session identifier, a first S-NSSAI (identifier of a first network slice associated with the PDU session), and DNN accessed by the terminal device to the AMF network element.

It should be noted that the first S-NSSAI is one of Allowed NSSAIs.

And the AMF network element determines a first network slice example for providing service for the terminal equipment according to the first S-NSSAI.

To this end, the context information of the terminal device stored on the AMF network element may be represented by table 4, for example.

Table 4: context of terminal device

Further, in the PDU session establishment procedure, the AMF network element may also send information such as a PDU session identifier, an identifier of a first network slice associated with the PDU session (i.e., a first S-NSSAI), and the like to the source access network device.

Step 508: the source access network device determines an identification of a first network slice instance of a first network slice associated with the PDU session.

Since the first S-NSSAI is one of the Allowed NSSAIs, the source access network device has already acquired the identifier of the network slice instance corresponding to each of the Allowed NSSAIs, and thus the source access network device may determine the identifier of the first network slice instance corresponding to the first S-NSSAI.

Specifically, when the terminal device is in a connected state, the terminal device moves out of the coverage of the first network slice, and then the Xn-based handover procedure may be triggered. For example, the following steps may be included:

step 509: the target access network device receives the handover request message from the source access network device.

Step 510: the target access network device judges whether to support a first network slice associated with the PDU session, and when the target access network device does not support the first network slice, the target access network device may determine, according to an identifier of the first network slice instance, that the target access network device supports a second network slice, and switch the PDU session to the target access network device.

Step 511: and the target access network equipment sends a path switching request message to the AMF network element.

Step 512: and the AMF network element sends a PDU session update context request message to the SMF network element.

Step 513: and the SMF network element and the UPF network element execute the PDU session modification process, and the specific process is not described again.

Step 514: and after the PDU session modification process is completed, the SMF network element sends a PDU session update context response message to the AMF network element.

Step 515: the AMF network element sends a path switch request acknowledgement (path switch request acknowledgement) message to the target access network equipment.

For details of step 511 to step 515, reference may be made to the description of the relevant steps from step 410 to step 414 in the first embodiment, and details are not described herein again.

In addition, after step 515, the terminal device initiates a mobility registration update procedure, and the terminal device sends a registration request message to the AMF network element, and because the network slice identifier associated with the PDU session changes, in the mobility registration update procedure, the AMF network element determines new Allowed NSSAI for the terminal device, and sends the new Allowed NSSAI to the terminal device through a registration accept message. The new Allowed NSSAI includes at least one S-NSSAI, and the at least one S-NSSAI included in the new Allowed NSSAI is an identifier of a network slice that the terminal device is Allowed to access in a registration area of the target access network device.

Wherein the new Allowed NSSAI contains an identification of the second network slice. The new Allowed NSSAI may be an update to the Allowed NSSAI in step 507, where it is understood that the Allowed NSSAI determined by the AMF network element for the terminal device before the handover includes the identifier of the first network slice, and the new Allowed NSSAI determined by the AMF network element for the terminal device after the handover includes the identifier of the second network slice but not the identifier of the first network slice.

After the mobility registration updating process is finished, the SMF network element initiates a PDU session modification process, and in the PDU session modification process, the SMF network element sends N1 session management information to the terminal device, where the session management information includes a PDU session identifier and an identifier of a second network slice, and is used to update a network slice associated with a PDU session stored on the terminal device.

By the method shown in the second embodiment, for example, based on the context information of the terminal device shown in table 4, the context information of the terminal device stored by the AMF network element may be updated to table 5.

Table 5: context of terminal equipment (after switching)

Example three:

in the third embodiment, when the PDU session request of the terminal device is switched to the target access network device, it may be determined, by the NSSF network element, whether to allow switching of the PDU session, which will be described in detail below.

Referring to fig. 6, a schematic flow chart of a session switching method provided in the embodiment of the present application is shown. The method comprises the following steps:

step 601: the terminal device initiates a registration procedure (registration procedure) through the source access network device.

Through the registration process, the terminal device may register on the AMF network element, and a specific process of the registration process is not limited in the embodiment of the present application, and specifically, reference may be made to the prior art, which is not described herein again.

In the registration process, the AMF network element determines an Allowed NSSAI for the terminal equipment, wherein the Allowed NSSAI comprises a first S-NSSAI, and the source access network equipment supports the first S-NSSAI. Furthermore, the AMF network element stores the Allowed NSSAI in the context of the terminal device.

Step 602: the terminal equipment initiates a PDU session establishment procedure (PDU session initialization procedure).

The process may include the steps of: the terminal device may send the PDU session identifier, the first S-NSSAI, and a Data Network Name (DNN) to which the terminal device is connected to the AMF Network element. Wherein the first S-NSSAI is an identifier of a network slice supported by the terminal equipment, and the network slice is associated with the PDU session.

The AMF network element determines from the first S-NSSAI an instance of the first network slice.

To this end, for example, the context information of the terminal device stored on the AMF network element may be represented by table 3 in the first embodiment.

After the PDU session is established, when the terminal device moves, the switching procedure of the Xn interface may be triggered, and specifically, how to trigger the switching procedure of the Xn interface may refer to the foregoing description, which is not described herein again.

Step 603: the target access network device receives the handover request message from the source access network device.

The handover request message may further include other information, which is not described herein again.

Step 604: and when the target access network equipment does not support the first network slice, the target access network equipment sends the position information of the target access network equipment and the identifier of the first network slice instance to the NSSF network element.

The location information of the target access network device is used to identify the location information of the terminal device, and the location information of the target access network device may be represented by a TAI of the target access network device.

For example, the target access network device may send a network slice remapping request (slice remapping request) message to the NSSF network element, where the network slice remapping request message may include information such as location information of the target access network device and an identifier of the first network slice instance. The location information of the target access network device may be information such as TAI of the target access network device.

Optionally, the target access network device may further send the identifier of the first network slice to the NSSF network element.

It should be noted that the message sent by the target access network device to the NSSF network element is forwarded by the AMF network element, that is, the target access network device first sends the network slice remapping request message to the AMF network element, and the AMF network element forwards the network slice remapping request message to the NSSF network element.

Step 605: and the NSSF network element determines a second network slice according to the position information of the target access network equipment and sends the identifier of the second network slice to the target access network equipment.

The NSSF network element may determine, according to the location information of the target access network device, at least one network slice deployed in the location information, and if a network slice corresponding to the identifier of the first network slice instance exists in the at least one network slice deployed in the location information, may determine the network slice as the second network slice. And the NSSF network element determines that the second network slice is the network slice supported by the target access network equipment.

Step 606: and the target access network equipment receives the identification of the second network slice from the NSSF network element and switches the PDU session to the target access network equipment.

After the target access network device obtains the identifier of the second network slice, the association relationship between the PDU session and the second network slice may be established, and the PDU session may be served through the second network slice.

Step 607: and the target access network equipment sends a path switching request message to the AMF network element.

Step 608: and the AMF network element sends a PDU session update context request message to the SMF network element.

Step 609: and the SMF network element and the UPF network element execute the PDU session modification process, and the specific process is not described again.

Step 610: and after the PDU session modification process is completed, the SMF network element sends a PDU session update context response message to the AMF network element.

The response message includes N2 session management information, PDU session identification, and identification of the second network slice.

Step 611: the AMF network element sends a path switch request acknowledgement (path switch request acknowledgement) message to the target access network equipment.

For details of steps 607 to 611, reference may be made to the description of the relevant steps from step 410 to step 414 in the first embodiment, and details are not described herein again.

In addition, after step 611, the terminal device initiates a mobility registration update procedure, and the terminal device sends a registration request message to the AMF network element, and because the network slice identifier associated with the PDU session changes, in the mobility registration update procedure, the AMF network element determines a new Allowed NSSAI for the terminal device, and sends the new Allowed NSSAI to the terminal device through a registration accept message. The new Allowed NSSAI includes at least one S-NSSAI, and the at least one S-NSSAI included in the new Allowed NSSAI is an identifier of a network slice that the terminal device is Allowed to access in a registration area of the target access network device.

Wherein the new Allowed NSSAI contains an identification of the second network slice. The new Allowed NSSAI may be an update to the Allowed NSSAI in step 601 above, where the new Allowed NSSAI contains an identification of the second network slice. It is to be understood that the Allowed NSSAI determined by the AMF network element for the terminal device before handover includes the identifier of the first network slice, and the new Allowed NSSAI determined by the AMF network element for the terminal device after handover includes the identifier of the second network slice, but not the identifier of the first network slice.

By the method shown in the third embodiment, for example, based on the context information of the terminal device shown in table 3 (refer to the first embodiment), the context information of the terminal device stored by the AMF network element may be updated to table 4 (refer to the first embodiment).

Fig. 7 is a flowchart illustrating a session handover method according to an embodiment of the present application. The method shown in fig. 7 may embody the method shown in fig. 4 or fig. 5. For example, the target access network device in fig. 7 may perform the steps performed by the target access network device in fig. 4 or fig. 5, and the source access network device in fig. 7 may perform the steps performed by the source access network device in fig. 4 or fig. 5. In fig. 7, the source access network device refers to an access network device to which the terminal device is currently connected, and the target access network device refers to an access network device to which the terminal device is connected after being switched. The method shown in fig. 7 comprises the following steps:

step 701: the source access network equipment determines that the terminal equipment triggers session switching, and determines target access network equipment.

The session may refer to a PDU session.

Before step 701, the source access network device may obtain an identifier of the first network slice and an identifier of the first network slice instance, which may specifically refer to the description of step 405 in fig. 4, or refer to the description of step 506 in fig. 5.

It should be noted that, before step 701, the terminal device needs to register to the core network device and establish a session, which may specifically refer to the descriptions of step 406 and step 407 in fig. 4, or refer to corresponding steps in fig. 5. The core network device may refer to an AMF network element.

Step 702: and the source access network equipment sends a switching request message to the target access network equipment.

The handover request message is used for requesting to handover a session of the terminal device to the target access network device, and includes an identifier of a first network slice and an identifier of a first network slice instance corresponding to the first network slice, where the first network slice is associated with the session.

The details of this step may refer to the description of step 408 in fig. 4, or to the corresponding steps in fig. 5.

Step 703: the target access network device receives the handover request message from the source access network device.

The handover request message is used for requesting to handover a session of a terminal device to the target access network device, and the handover request message includes an identifier of a first network slice and an identifier of a first network slice instance, where the first network slice is associated with the session.

Before step 703, the target access network device may obtain an identifier of the first network slice and an identifier of the first network slice instance, which may specifically refer to the contents of steps 401 to 404 in fig. 4.

Step 704: when the target access network equipment does not support the first network slice, determining a second network slice supported by the target access network equipment according to the identifier of the first network slice example, and switching the session to the target access network equipment.

Wherein the second network slice, the first network slice, and the second network slice each correspond to the first network slice instance.

After the target access network device determines that the second network slice is supported, an association relationship between the session and the second network slice may be established, and the session may be served through the second network slice.

The details of this step may refer to the description of step 409 in fig. 4, or to the corresponding step in fig. 5.

Further, how the target access network switches the session specifically may refer to the description of steps 410 to 414 in fig. 4, or refer to corresponding steps in fig. 5.

Fig. 8 is a flowchart illustrating another session handover method according to an embodiment of the present application. The method shown in fig. 8 may embody the method shown in fig. 4 or fig. 5. For example, the target access network device in fig. 8 may perform the steps performed by the target access network device in fig. 4 or fig. 5, and the NSSF network element in fig. 8 may perform the steps performed by the NSSF network element in fig. 4 or fig. 5. In fig. 8, the source access network device refers to an access network device to which the terminal device is currently connected, and the target access network device refers to an access network device to which the terminal device is connected after being switched. The method shown in fig. 8 comprises the following steps:

step 801: the target access network device receives the handover request message from the source access network device.

The handover request message is used for requesting to handover a session of a terminal device to the target access network device, and includes an identifier of a first network slice and an identifier of a first network slice instance, where the first network slice is associated with the session. The session may be referred to as a PDU session.

It should be noted that, before step 801, the terminal device needs to register with the core network device and establish a session, which may specifically refer to the description of step 601 and step 602 in fig. 6. The core network device may refer to an AMF network element.

Step 802: and when the target access network equipment does not support the first network slice, sending the position information of the target access network equipment and the identifier of the first network slice instance to the NSSF network element.

The details of step 802 can be found in the description of step 604.

Step 803: the NSSF network element receives the first network slice instance identification from the target access network equipment and the position information of the target access network equipment.

Step 804: and the NSSF network element determines a second network slice according to the position information of the target access network equipment and sends the identifier of the second network slice to the target access network equipment.

Wherein the target access network device supports the second network slice, and the second network slice corresponds to the first network slice instance.

The details of step 804 can be referred to the description of step 605.

Step 805: and the target access network equipment receives the identification of the second network slice from the NSSF network element and switches the session to the target access network equipment.

After the target access network device obtains the identifier of the second network slice, the association relationship between the session and the second network slice may be established, and the session may be served through the second network slice.

Further, how the target access network switches the session specifically may refer to the descriptions of step 607 to step 611 in fig. 6.

The various embodiments described herein may be implemented as stand-alone solutions or combined in accordance with inherent logic and are intended to fall within the scope of the present application.

In the embodiments provided in the present application, the method provided in the embodiments of the present application is introduced from the perspective of interaction between the devices. In order to implement the functions in the method provided by the embodiment of the present application, the first user equipment or the second user equipment may include a hardware structure and/or a software module, and the functions are implemented in the form of a hardware structure, a software module, or a hardware structure plus a software module. Whether any of the above-described functions is implemented as a hardware structure, a software module, or a hardware structure plus a software module depends upon the particular application and design constraints imposed on the technical solution.

The division of the modules in the embodiment of the present application is schematic, and is only a logic function division, and there may be another division manner in actual implementation. In addition, functional modules in the embodiments of the present application may be integrated into one processor, may exist alone physically, or two or more modules are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode.

Similar to the above concept, as shown in fig. 9, an apparatus 900 is further provided for implementing the function of the first user equipment or the second user equipment in the above method. The device may be a software module or a system-on-a-chip, for example. In the embodiment of the present application, the chip system may be composed of a chip, and may also include a chip and other discrete devices. The apparatus 900 may include: a processing unit 901 and a communication unit 902.

In this embodiment of the present application, the communication unit may also be referred to as a transceiver unit, and may include a transmitting unit and/or a receiving unit, which are respectively configured to perform the steps of transmitting and receiving by the first user equipment or the second user equipment in the foregoing method embodiment.

Hereinafter, the communication device according to the embodiment of the present application will be described in detail with reference to fig. 9 to 10. It should be understood that the description of the apparatus embodiments corresponds to the description of the method embodiments, and therefore, for brevity, details are not repeated here, since the details that are not described in detail may be referred to the above method embodiments.

The communication unit may also be referred to as a transceiver, a transceiving means, etc. A processing unit may also be referred to as a processor, a processing board, a processing module, a processing device, or the like. Alternatively, a device in the communication unit 902 for implementing a receiving function may be regarded as a receiving unit, and a device in the communication unit 902 for implementing a sending function may be regarded as a sending unit, that is, the communication unit 902 includes a receiving unit and a sending unit. A communication unit may also sometimes be referred to as a transceiver, transceiving circuitry, or the like. A receiving unit may also be referred to as a receiver, a receiving circuit, or the like. A transmitting unit may also sometimes be referred to as a transmitter, or a transmitting circuit, etc.

It should be understood that the communication unit 902 is configured to perform the transmitting operation and the receiving operation in the method embodiment shown in fig. 7 or fig. 8, and the processing unit 901 is configured to perform other operations besides the transceiving operation in the method embodiment shown in fig. 7 or fig. 8.

When communications apparatus 900 performs the functions of the target access network device in fig. 7:

a communication unit, configured to receive a handover request message from a source access network device, where the handover request message is used to request that a session of a terminal device is handed over to a target access network device, and the handover request message includes an identifier of a first network slice and an identifier of a first network slice instance, where the first network slice is associated with the session;

a processing unit, configured to determine, when the first network slice is not supported, a second network slice supported by a target access network device according to an identifier of the first network slice instance, and switch the session to the target access network device; the second network slice, the first network slice, and the second network slice each correspond to the first network slice instance.

In a possible implementation manner, before receiving the handover request message from the source access network device, the communication unit is further configured to:

receiving first information from core network equipment; the first information includes an identification of at least one network slice and an identification of a network slice instance corresponding to each of the at least one network slice, wherein the target access network device supports the at least one network slice.

In a possible implementation manner, the processing unit is specifically configured to:

and determining a network slice corresponding to the first network slice instance in the at least one network slice as the second network slice according to the first information and the identifier of the first network slice instance.

In a possible implementation manner, the communication unit is specifically configured to:

sending a path switching request message to core network equipment; the path switch request message includes an identification of the second network slice.

In a possible implementation manner, after the handing over the session to the target access network device, the communication unit is further configured to:

and receiving at least one identifier of a network slice, which allows the terminal device to access in the registration area of the target access network device, from the core network device, and an identifier of a network slice instance corresponding to each network slice in the at least one identifier of a network slice which allows the terminal device to access in the registration area of the target access network device.

When communications apparatus 900 performs the functions of the source access network device in fig. 7:

the processing unit is used for determining that the terminal equipment triggers session switching and determining target access network equipment;

a communication unit, configured to send a handover request message to a target access network device, where the handover request message is used to request that a session of the terminal device is handed over to the target access network device, and the handover request message includes an identifier of a first network slice and an identifier of a first network slice instance corresponding to the first network slice, and the first network slice is associated with the session.

In a possible implementation manner, the communication unit is further configured to:

sending a session establishment request message to core network equipment; the session establishment request message is used for establishing the session;

receiving a session setup response message from the core network device, the session setup response message including an identification of the first network slice and an identification of the first network slice instance.

receiving third information from the core network equipment; the third information comprises an identifier of at least one network slice and an identifier of a network slice instance corresponding to each network slice in the at least one network slice; wherein the source access network device supports the at least one network slice;

and acquiring the identifier of the first network slice, and determining the identifier of the first network slice instance corresponding to the first network slice from the third information according to the identifier of the first network slice.

receiving second information from the core network device, where the second information is an identifier of at least one network slice allowing the terminal device to access and an identifier of a network slice instance corresponding to each network slice in the at least one network slice allowing the terminal device to access;

and acquiring an identifier of a first network slice, and determining an identifier of the first network slice instance corresponding to the first network slice from the second information according to the identifier of the first network slice.

receiving a session establishment response message from the core network device, the session establishment response message including an identification of the first network slice.

When communications apparatus 900 performs the functions of the target access network device in fig. 8:

a communication unit, configured to receive a handover request message from a source access network device, where the handover request message is used to request that a session of a terminal device is handed over to a target access network device, and the handover request message includes an identifier of a first network slice and an identifier of a first network slice instance, where the first network slice is associated with the session; when the first network slice is not supported, sending the position information of the target access network equipment and the identifier of the first network slice instance to a network slice selection function NSSF network element; receiving an identification of a second network slice from the NSSF network element;

a processing unit, configured to switch the session to the target access network device; the second network slice and the first network slice both correspond to the first network slice instance; and the second network slice is associated with the position information of the target access network equipment.

When the communication device 900 performs the functions of the NSSF network element in fig. 7:

a communication unit, configured to receive a first network slice instance identifier from a target access network device and location information of the target access network device;

the processing unit is used for determining a second network slice according to the position information of the target access network equipment and sending the identifier of the second network slice to the target access network equipment; wherein the target access network device supports the second network slice, and the second network slice corresponds to the first network slice instance.

As shown in fig. 10, which is a device 1000 provided in the embodiment of the present application, the device shown in fig. 10 may be implemented as a hardware circuit of the device shown in fig. 9. For convenience of explanation, fig. 10 shows only the main components of the communication apparatus.

The apparatus 1000 may also include at least one memory 1030 for storing program instructions and/or data. 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. Processor 1020 may execute program instructions stored in memory 1030. At least one of the at least one memory may be included in the processor.

The apparatus 1000 shown in fig. 10 includes at least one processor 1020 and a communication interface 1010, the processor 1020 for executing instructions or programs stored in a memory 1030. When the instructions or programs stored in the memory 1030 are executed, the processor 1020 is configured to perform the operations performed by the processing unit 901 in the above embodiments, and the communication interface 1010 is configured to perform the operations performed by the communication unit 902 in the above embodiments.

In embodiments of the present application, the communication interface may be a transceiver, circuit, bus, module, or other type of communication interface. In the embodiment of the present application, when the communication interface is a transceiver, the transceiver may include an independent receiver and an independent transmitter; a transceiver that integrates transceiving functions, or a communication interface may also be used.

The apparatus 1000 may also include a communication line 1040. Wherein the communication interface 1010, the processor 1020, and the memory 1030 may be connected to each other by a communication line 1040; the communication line 1040 may be a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, or the like. The communication lines 1040 may be divided into address buses, data buses, control buses, and the like. 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.

Embodiments of the present application further provide a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, may implement the process related to the target access network device in the embodiments shown in fig. 7 or fig. 8 and provided by the foregoing method embodiments.

Embodiments of the present application further provide a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, may implement the process related to the source access network device in the embodiment shown in fig. 7 and provided by the foregoing method embodiments.

An embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, can implement the process related to the NSSF network element in the embodiment shown in fig. 8 and provided in the foregoing method embodiment.

Embodiments of the present application also provide a computer program product containing instructions, which when executed perform the method performed with the target access network device in the embodiments shown in fig. 7 or fig. 8.

Embodiments of the present application further provide a computer program product containing instructions, which when executed perform the method performed with the source access network device in the embodiment shown in fig. 7.

Embodiments of the present application further provide a computer program product containing instructions, where the instructions, when executed, perform the method performed by the NSSF network element in the method embodiment shown in fig. 8.

An embodiment of the present application further provides a chip, which includes a processor, where the processor is coupled to a memory, and is configured to execute a computer program or an instruction stored in the memory, and when the processor executes the computer program or the instruction, the method for accessing a target access network device in the embodiment shown in fig. 7 or fig. 8 is performed.

An embodiment of the present application further provides a chip, which includes a processor, where the processor is coupled to a memory, and is configured to execute a computer program or an instruction stored in the memory, and when the processor executes the computer program or the instruction, the method of the source access network device in the method embodiment shown in fig. 7 is performed.

An embodiment of the present application further provides a chip, which includes a processor, where the processor is coupled to a memory, and is configured to execute a computer program or an instruction stored in the memory, and when the processor executes the computer program or the instruction, the method performed by the NSSF network element in the method embodiment shown in fig. 8 is performed.

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, 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.

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 session handoff, comprising:

receiving, by a target access network device, a handover request message from a source access network device, where the handover request message is used to request that a session of a terminal device be handed over to the target access network device, and the handover request message includes an identifier of a first network slice and an identifier of a first network slice instance, where the first network slice is associated with the session;

when the target access network equipment does not support the first network slice, the target access network equipment determines a second network slice supported by the target access network equipment according to the identifier of the first network slice instance, and switches the session to the target access network equipment; the second network slice, the first network slice, and the second network slice each correspond to the first network slice instance.

2. The method of claim 1, wherein before the target access network device receives the handover request message from the source access network device, the method further comprises:

the target access network equipment receives first information from core network equipment; the first information includes an identification of at least one network slice and an identification of a network slice instance corresponding to each of the at least one network slice, wherein the target access network device supports the at least one network slice.

3. The method of claim 2, wherein the determining, by the target access network device, the second network slice supported by the target access network device according to the identity of the first network slice instance comprises:

and the target access network equipment determines the network slice corresponding to the first network slice instance in the at least one network slice as the second network slice according to the first information and the identifier of the first network slice instance.

4. The method of any of claims 1 to 3, wherein the target access network device handing over the session to the target access network device comprises:

the target access network equipment sends a path switching request message to core network equipment; the path switch request message includes an identification of the second network slice.

5. The method of claim 4, wherein the path switch request message further comprises an identification of the first network slice instance.

6. The method of any of claims 2 to 5, wherein after the target access network device hands over the session to the target access network device, the method further comprises:

the target access network device receives, from the core network device, an identifier of at least one network slice allowing the terminal device to access in a registration area of the target access network device, and an identifier of a network slice instance corresponding to each network slice in the identifier of the at least one network slice allowing the terminal device to access in the registration area of the target access network device.

7. The method according to any of claims 2 to 6, wherein the core network device is an Access and mobility management function, AMF, network element.

8. A method for session handoff, comprising:

the source access network equipment determines that the terminal equipment triggers session switching and determines target access network equipment;

the source access network device sends a switching request message to a target access network device, wherein the switching request message is used for requesting to switch a session of the terminal device to the target access network device, the switching request message comprises an identifier of a first network slice and an identifier of a first network slice instance corresponding to the first network slice, and the first network slice is associated with the session.

9. The method of claim 8, further comprising:

the source access network equipment sends a session establishment request message to core network equipment; the session establishment request message is used for establishing the session;

the source access network device receives a session establishment response message from the core network device, where the session establishment response message includes an identification of the first network slice and an identification of the first network slice instance.

10. The method of claim 8, further comprising:

the source access network equipment receives third information from core network equipment; the third information comprises an identifier of at least one network slice and an identifier of a network slice instance corresponding to each network slice in the at least one network slice; wherein the source access network device supports the at least one network slice;

and the source access network equipment acquires the identifier of the first network slice, and determines the identifier of the first network slice instance corresponding to the first network slice from the third information according to the identifier of the first network slice.

11. The method of claim 8, further comprising:

in a registration process, the source access network device receives second information from the core network device, where the second information is an identifier of at least one network slice allowing the terminal device to access and an identifier of a network slice instance corresponding to each network slice in the at least one network slice allowing the terminal device to access;

and the source access network equipment acquires the identifier of the first network slice, and determines the identifier of the first network slice instance corresponding to the first network slice from the second information according to the identifier of the first network slice.

12. The method of claim 10 or 11, wherein the source access network device obtains an identification of the first network slice, the method further comprising:

the source access network device receives a session establishment response message from the core network device, where the session establishment response message includes an identification of the first network slice.

13. A method for session handoff, comprising:

when the target access network device does not support the first network slice, the target access network device sends the location information of the target access network device and the identifier of the first network slice instance to a network slice selection function NSSF network element;

the target access network equipment receives the identifier of the second network slice from the NSSF network element and switches the session to the target access network equipment; the second network slice and the first network slice both correspond to the first network slice instance; and the second network slice is associated with the position information of the target access network equipment.

14. The method of claim 13, wherein the target access network device hands over the session to the target access network device, the method further comprising:

15. A method for session handoff, comprising:

a network slice selection function NSSF network element receives a first network slice instance identification from target access network equipment and position information of the target access network equipment;

the NSSF network element determines a second network slice according to the position information of the target access network equipment and sends the identification of the second network slice to the target access network equipment; wherein the target access network device supports the second network slice, and the second network slice corresponds to the first network slice instance.

16. A communication apparatus, comprising

17. The apparatus of claim 16, wherein prior to receiving the handover request message from the source access network device, the communication unit is further configured to:

18. The apparatus according to claim 17, wherein the processing unit is specifically configured to:

19. The apparatus according to any of claims 16 to 18, wherein the communication unit is specifically configured to:

20. The apparatus according to any of claims 17 to 19, wherein after the handover of the session to the target access network device, the communication unit is further configured to:

21. A session switching apparatus, comprising:

22. The apparatus of claim 21, wherein the communication unit is further configured to:

23. The apparatus of claim 21, wherein the communication unit is further configured to:

24. The apparatus of claim 21, wherein the communication unit is further configured to:

25. The apparatus according to claim 23 or 24, wherein the communication unit is further configured to:

26. A session switching apparatus, comprising:

27. A session switching apparatus, comprising:

28. A communications apparatus, comprising a processor and a memory:

the processor for executing a computer program or instructions stored in the memory, the method according to any of claims 1 to 15 being performed when the computer program or instructions are executed.

29. A readable storage medium, comprising a computer program or instructions which, when executed, perform the method of any one of claims 1 to 15.

30. A computer program product comprising computer readable instructions which, when read and executed by a communication device, cause the communication device to perform the method of any one of claims 1 to 15.