CN110392448B

CN110392448B - Session reestablishment method, device and system

Info

Publication number: CN110392448B
Application number: CN201810351186.3A
Authority: CN
Inventors: 刘睿智; 熊春山; 吴义壮; 韦安妮
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-04-18
Filing date: 2018-04-18
Publication date: 2021-08-13
Anticipated expiration: 2038-04-18
Also published as: CN110392448A

Abstract

The application discloses a method, a device and a system for reestablishing a session, relates to the technical field of communication, and is beneficial to improving the transmission performance of a service. The method can comprise the following steps: when a network slice example related to a first PDU session of a terminal is unavailable and a network slice related to the first PDU session is available, the SMF network element sends first information to the terminal; the first information is used for indicating the terminal to initiate a PDU session reestablishment process. Wherein the PDU session reestablishment procedure is used to reestablish a PDU session based on the network slice.

Description

Session reestablishment method, device and system

Technical Field

The present application relates to the field of communications technologies, and in particular, to a method, an apparatus, and a system for session reestablishment.

Background

In the fifth generation (5rd generation, 5G) network architecture, the concepts of network slice (network slice) and Network Slice Instance (NSI) are introduced. A network slice is a logically isolated network used to support specific network functions and network characteristics, and may include the entire network from end to end (E2E), or a part of the network functions may be shared among multiple network slices. Network slicing is a technique for satisfying the requirements of 5G mobile communication technology with respect to network differentiation. Generally, the network characteristics of different network slices are different, and the network slices are required to be isolated from each other and not to be influenced by each other. Network slices such as enhanced (AR) or Virtual (VR) traffic require large bandwidth and low latency; the network slice of the internet of things (IOT) service requires to support mass terminal access, but has a small bandwidth and no requirement for delay. One or more network slice instances may be created based on one network slice. Typically, multiple network slice instances created based on the same network slice have the network characteristics of that network slice, and the network characteristics of different network slice instances are not identical.

In the specific implementation process, a network slice meeting the service requirement can be deployed in a certain area according to the service requirement of the area. For example, if a region has IOT traffic, then a network slice of IOT traffic may be deployed in the region. Additionally, on a per network slice basis, an operator may deploy one or more network slice instances in accordance with a customer order. The network may select a network slice and a network slice instance for the terminal according to the requirements of the terminal, so that the terminal may establish a Packet Data Unit (PDU) session based on the selected network slice instance.

The network slice instance related to a certain current PDU session of the terminal may be unavailable due to the movement of the terminal and the like. This can cause the PDU session established based on the network slice instance to be interrupted, thereby affecting the continuity of the traffic.

Disclosure of Invention

The embodiment of the application provides a method, a device and a system for reestablishing a session, which are beneficial to improving the transmission performance of a service.

In a first aspect, a session reestablishing method is provided, including: when a network slice example related to a first PDU session of a terminal is unavailable and a network slice related to the first PDU session is available, the SMF network element sends first information to the terminal; the first information is used for indicating the terminal to initiate a PDU session reestablishment process. Wherein the PDU session reestablishment procedure is used to reestablish a PDU session based on the network slice. Since the network slice selected by the network for a terminal is usually a network slice that is relatively consistent with the current service transmission of the terminal, reconstructing a PDU session through the network slice can guarantee the transmission performance of the service to some extent.

In one possible design, the information type of the first information is a request or a permission. If the information type of the first information is a request, the terminal typically initiates a PDU session reestablishment procedure immediately after receiving the first information. If the information type of the first information is allowed, the terminal may determine whether to initiate a PDU session reestablishment procedure according to its own condition after receiving the first information. Of course, the application does not limit the type of information of the first information.

In one possible design, the method may further include: the SMF network element receives second information sent by the first AMF network element; the second information is used for indicating: the first PDU session related network slice instance is not available and the first PDU session related network slice is available. In addition, the second information may also directly instruct the SMF network element to send the first information to the terminal.

Optionally, the receiving, by the SMF network element, the second information sent by the first AMF network element may include: and the SMF network element receives the second information sent by the first AMF network element through the second AMF network element. Wherein the first AMF network element does not support the network slice instance related to the first PDU. For example, in the registration procedure, the second AMF network element is an old AMF network element, and the first AMF network element is a new AMF network element. For example, in the handover procedure, the second AMF network element is a source AMF network element, and the first AMF network element is a target AMF network element. This alternative provides a transmission flow of the second information, and the application is not limited thereto, for example, reference may be made to the following detailed description.

In one possible design, the sending, by the SMF network element, the first information to the terminal may include: and the SMF network element sends the first information to the terminal through the third AMF network element and the fourth AMF network element. The fourth AMF network element does not support the first PDU session related network slice instance. For example, the third AMF network element is an old AMF network element and the fourth AMF network element is a new AMF network element. For example, in the handover procedure, the third AMF network element is a source AMF network element, and the fourth AMF network element is a target AMF network element. This possible design provides a first information sending flow, and the application is not limited to this, for example, reference may be made to the following detailed description.

In one possible design, the sending, by the SMF network element, the first information to the terminal via the third AMF network element and the fourth AMF network element may include: the SMF network element sends the first information to a fourth AMF network element through a third AMF network element; the first information is carried in a PDU session state message and is sent to the terminal by a fourth AMF network element; the PDU session status message includes: status information of at least one PDU session of the terminal; the state of any one PDU session includes present, released or reestablished; the at least one PDU session includes a first PDU session, the status information of the first PDU session indicating a re-establishment. This possible design provides a message carrying the first information. Of course, the specific implementation is not limited thereto.

In one possible design, the sending, by the SMF network element, the first information to the terminal may include: the SMF network element sends first information to the terminal according to the strategy information; the policy information is used to indicate: and when the network slice instance related to the first PDU session is unavailable and the network slice instance related to the first PDU session is available, initiating a strategy of a PDU session reestablishment process. Optionally, the policy information may be pre-stored locally in the SMF network element, or sent to the SMF network element by the policy control function PCF network element.

In a second aspect, a session reestablishing method is provided, including: when the network slice instance related to the first PDU session of the terminal is unavailable and the network slice related to the first PDU session is available, the first AMF network element sends second information to the SMF network element; and the second information is used for the SMF network element to send first information to the terminal according to the second information, and the first information is used for indicating the terminal to initiate a PDU session reestablishment process. For example, the second information is used to indicate that the first PDU session related network slice instance is not available and the first PDU session related network slice is available; or, the second information is directly used to instruct the SMF network element to send the first information to the terminal, in this case, the SMF network element may not need to know whether the current situation is "the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available".

In one possible design, the first AMF network element determining that the first PDU session related network slice instance of the terminal is not available and the first PDU session related network slice is available may be implemented by one of:

mode 1: and the first AMF network element receives third information sent by the second AMF network element or the NRF network element, and determines that the second AMF network element does not support the network slice example related to the first PDU session and supports the network slice related to the first PDU session according to the third information. Wherein the third information is used for indicating the network slice instance and the network slice supported by the second AMF network element. A first AMF network element. For example, in the registration procedure, the first AMF network element is an old AMF network element, and the second AMF network element is a new AMF network element. For example, in the handover procedure, the first AMF network element is a source AMF network element, and the second AMF network element is a target AMF network element.

Mode 2: and the first AMF network element receives fourth information sent by the second AMF network element or the NRF network element, and determines that the first AMF network element does not support the network slice example related to the first PDU session and supports the network slice related to the first PDU session according to the fourth information. Wherein the fourth information is used for indicating the network slice instance and the network slice related to the first PDU session. For example, in the registration procedure, the first AMF network element is a new AMF network element, and the second AMF network element is an old AMF network element. For example, in the handover procedure, the first AMF network element is a target AMF network element, and the second AMF network element is a source AMF network element.

Mode 3: and the first AMF network element determines that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available according to the position information of the terminal, the service area of the network slice instance related to the first PDU session and the service area of the network slice related to the first PDU session. Specifically, the first AMF network element may determine whether the network slice instance associated with the first PDU session is available according to the location information of the terminal and the service area of the network slice instance associated with the first PDU session. The first AMF network element may determine whether the network slice associated with the first PDU session is available according to the location information of the terminal and a service area of the network slice associated with the first PDU session. Optionally, as an alternative, the first AMF network element may determine whether the network slice associated with the first PDU session is available according to the location information of the terminal and the identification information/service area of the replaced network slice instance. Specific examples can be found in the detailed description section below.

Mode 4: the first AMF network element sends fifth information to the NSSF network element; the fifth information is used for indicating that the network slice instance related to the first PDU session is unavailable, and indicating that the NSSF network element sends the identification information of the available network slice instance to the first AMF network element. A first AMF network element receives identification information of an available network slice example sent by an NSSF network element; wherein the available network slice instance belongs to the same network slice as the network slice instance associated with the first PDU session.

In a third aspect, a session reestablishing method is provided, including: the terminal receives first information from the SMF network element; wherein a first PDU session related network slice instance of the terminal is unavailable and a first PDU session related network slice is available; the first information is used for indicating the terminal to initiate a PDU session reestablishment process. And after receiving the first information, the terminal initiates a PDU session reestablishment process. Optionally, the information type of the first information is request or permission.

In one possible design, the terminal, after receiving the first information, initiating a PDU session reestablishment procedure, which may include: and if the information type of the first information is allowed, the terminal initiates the PDU session reestablishment process when determining that the PDU session reestablishment process needs to be initiated.

In a fourth aspect, a session reestablishing method is provided, including: a terminal receives a PDU session state message sent by an AMF network element; wherein, the PDU conversation state information comprises: status information of at least one PDU session of the terminal; the state information indicates one of a presence, a release, and a reestablishment; the at least one PDU session includes a first PDU session, the status information of the first PDU session indicating a re-establishment; after receiving the first information sent by the SMF network element, the AMF network element sends a PDU session state message to the terminal; the first information is used for indicating the terminal to initiate a PDU session reestablishment process. Then, after receiving the first information, the terminal initiates a PDU session reestablishment process; and the SMF network element sends first information to the terminal when determining that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available. And after receiving the first information, the terminal initiates a PDU session reestablishment process.

In a fifth aspect, an SMF network element is provided. The SMF network element may be configured to perform any of the methods provided in the first aspect above. The SMF network element may specifically be the SMF network element described in the first aspect above.

In a possible design, the functional modules of the SMF network element may be divided according to the method provided in the first aspect, for example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module.

In another possible design, the SMF network element may include: a memory for storing a computer program which, when executed by the processor, causes any of the methods provided by the first aspect to be performed, and a processor.

In a sixth aspect, an embodiment of the present application provides a first AMF network element. The first AMF network element may be configured to perform any one of the methods provided by the second aspect above. The first AMF network element may specifically be the first AMF network element described in the second aspect above.

In a possible design, the first AMF network element may be divided into functional modules according to the method provided in the second aspect, for example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module.

In another possible design, the first AMF network element may include: a memory for storing a computer program which, when executed by the processor, causes any of the methods provided by the second aspect to be performed, and a processor.

In a seventh aspect, an embodiment of the present application provides a terminal device. The terminal device may be configured to perform any one of the methods provided in the third or fourth aspects. The terminal device may specifically be the terminal described in the above third or fourth aspect, or the terminal device may be a chip.

In a possible design, the terminal device may be divided into functional modules according to the method provided in the third aspect or the fourth aspect, for example, each functional module may be divided according to each function, or two or more functions may be integrated into one processing module.

In another possible design, the terminal device may include: a memory for storing a computer program which, when executed by the processor, causes any of the methods provided in the third or fourth aspect to be performed, and a processor.

The embodiment of the present application further provides a processing apparatus, configured to implement the function of the apparatus (for example, an SMF network element, a first AMF network element, or a terminal apparatus), where the processing apparatus includes a processor and an interface; the processing device may be a chip, and the processor may be implemented by hardware or software, and when implemented by hardware, the processor may be a logic circuit, an integrated circuit, or the like; when implemented in software, the processor may be a general-purpose processor implemented by reading software code stored in a memory, which may be integrated with the processor, located external to the processor, or stand-alone.

Embodiments of the present application also provide a computer-readable storage medium, on which computer instructions are stored, which, when executed on a computer, cause the computer to perform any one of the possible methods of the first to fourth aspects.

Embodiments of the present application also provide a computer program product, which when run on a computer causes any of the methods provided in the first to fourth aspects to be performed.

In an eighth aspect, a method for transmitting a PDU session status message is provided, including: the AMF network element sends a PDU session state message to the terminal; wherein, the PDU conversation state information comprises: status information of at least one PDU session of the terminal; the state information indicates one of a presence, a release, and a reestablishment. Optionally, the AMF network element may determine the status information of each PDU session in the at least one PDU session according to a technical scheme provided in the prior art, optionally, or in combination with the technical scheme provided in this application.

In a ninth aspect, a method for transmitting a PDU session status message is provided, which includes: the terminal receives a PDU session state message; wherein, the PDU conversation state information comprises: status information of at least one PDU session of the terminal; the state information indicates one of a presence, a release, and a reestablishment. For any PDU session, if the state information of the PDU session indicates release, the terminal initiates a PDU session release process. If the state information of the PDU conversation indicates reconstruction, the terminal initiates a PDU conversation reconstruction flow. The triggering condition for initiating the PDU session reestablishment procedure in this embodiment is not limited, for example, refer to the technical solution provided in this application, and also refer to the prior art. Reference may also be made to the prior art regarding triggering conditions for the PDU session release procedure. In addition, if the status information of one PDU session indicates existence, it indicates that there is no need to re-establish or release the PDU session.

In a tenth aspect, an embodiment of the present application provides an AMF network element. The AMF network element may be configured to perform any one of the methods provided in the above-mentioned eighth aspect. The AMF network element may specifically be the AMF network element described in the above eighth aspect.

In a possible design, the functional modules of the AMF network element may be divided according to the method provided in the above eighth aspect, for example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module.

In another possible design, the AMF network element may include: a memory for storing a computer program that, when executed by the processor, causes any of the methods provided by the eighth aspect to be performed.

In an eleventh aspect, embodiments of the present application provide a terminal device. The terminal device may be configured to perform any one of the methods provided by the ninth aspect above. The terminal device may specifically be the terminal described in the above ninth aspect, or the terminal device may be a chip.

In a possible design, the terminal device may be divided into functional modules according to the method provided in the ninth aspect, for example, each functional module may be divided according to each function, or two or more functions may be integrated into one processing module.

In another possible design, the terminal device may include: a memory for storing a computer program which, when executed by the processor, causes any of the methods provided by the ninth aspect to be performed, and a processor.

An embodiment of the present application further provides a processing apparatus, configured to implement a function of the apparatus (for example, the AMF network element provided in the tenth aspect or the terminal apparatus provided in the eleventh aspect), where the processing apparatus includes a processor and an interface; the processing device may be a chip, and the processor may be implemented by hardware or software, and when implemented by hardware, the processor may be a logic circuit, an integrated circuit, or the like; when implemented in software, the processor may be a general-purpose processor implemented by reading software code stored in a memory, which may be integrated with the processor, located external to the processor, or stand-alone.

Embodiments of the present application also provide a computer-readable storage medium, on which computer instructions are stored, which, when executed on a computer, cause the computer to perform any one of the possible methods of the eighth aspect to the ninth aspect.

Embodiments of the present application also provide a computer program product, which when run on a computer causes any of the methods provided by the eighth aspect to be performed.

The present application further provides a system on a chip comprising a processor for a communication device to perform the functions referred to in the above aspects, e.g. to generate, receive, transmit, or process data and/or information referred to in the above methods. In one possible design, the system-on-chip further includes a memory for storing program instructions and data necessary for the communication device. The chip system may be formed by a chip, or may include a chip and other discrete devices. The system-on-a-chip may also be a device.

It is understood that any one of the apparatus system, the computer storage medium, or the computer program product provided above is used for executing the corresponding method provided above, and therefore, the beneficial effects achieved by the apparatus system, the computer storage medium, or the computer program product may refer to the beneficial effects in the corresponding method, and are not described herein again.

Drawings

Fig. 1 is a schematic architecture diagram of a communication system to which the technical solution provided in the present application is applicable;

fig. 2 is a schematic diagram of a relationship between a network slice example, a PDU session, and a network functional network element according to an embodiment of the present application;

fig. 3 is a schematic diagram of a network slice example and a relationship between network slices provided in an embodiment of the present application;

fig. 4 is a first flowchart illustrating a method for PDU session reestablishment according to an embodiment of the present application;

fig. 5 is a second flowchart illustrating a PDU session reestablishment method according to an embodiment of the present application;

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

fig. 7 is a fourth flowchart illustrating a PDU session reestablishment method according to an embodiment of the present application;

fig. 8 is a fifth flowchart illustrating a method for PDU session reestablishment according to an embodiment of the present application;

fig. 9 is a sixth schematic flowchart of a method for PDU session reestablishment according to an embodiment of the present application;

fig. 10 is a seventh flowchart of a method for PDU session reestablishment according to an embodiment of the present application;

fig. 11 is an eighth flowchart of a PDU session reestablishment method according to an embodiment of the present application;

fig. 12 is a ninth flowchart of a method for PDU session reestablishment according to an embodiment of the present application;

fig. 13 is a schematic flowchart illustrating a tenth method for PDU session reestablishment according to an embodiment of the present application;

fig. 14 is an eleventh flowchart illustrating a method for PDU session reestablishment according to an embodiment of the present application;

fig. 15 is a twelfth flowchart illustrating a method for PDU session reestablishment according to an embodiment of the present application;

fig. 16 is a thirteenth schematic flowchart of a method for PDU session reestablishment according to an embodiment of the present application;

fig. 17 is a schematic structural diagram of an SMF network element according to an embodiment of the present application;

fig. 18 is a schematic structural diagram of a first AMF network element according to an embodiment of the present application;

fig. 19 is a schematic structural diagram of a terminal device according to an embodiment of the present application;

fig. 20 is a schematic structural diagram of a communication device according to an embodiment of the present application.

Detailed Description

The technical scheme provided by the embodiment of the application can be applied to a wireless communication system, and the wireless communication system can be a 5G system or other future communication systems. Of course, the system may also be a Long Term Evolution (LTE) system, an LTE-Advanced (LTE-a) system, or the like. Taking the wireless communication system as a 5G system as an example, as shown in fig. 1, it is a schematic structural diagram of a communication system to which the technical solution provided by the embodiment of the present application is applied.

In fig. 1, a communication system may include: a terminal 10, a Radio Access Network (RAN) or AN Access Network (AN) 20 (hereinafter referred to as (R) AN20), a core network 30, and a Data Network (DN) 40. The core network element (or referred to as a network function network element) in the core network 30 may include: an access and mobility management function (AMF) network element 301, a Session Management Function (SMF) network element 302, a Policy Control Function (PCF) network element 303, a Network Slice Selection Function (NSSF) network element 304, a network storage function (NRF) network element 305, a User Plane Function (UPF) network element 306, and so on. The connection between the network elements may be a wireless connection or a wired connection, and for convenience and intuition, the connection relationship between the network elements is shown by a solid line in fig. 1. The interfaces between the network elements are described in detail in the prior art, and are not described in detail in this application.

The terminal 10 may comprise various handheld devices having wireless communication capabilities, in-vehicle devices, wearable devices, computing devices, or other processing devices connected to a wireless modem; a subscriber unit (subscriber unit), a cellular phone (cellular phone), a smart phone (smart phone), a wireless data card, a Personal Digital Assistant (PDA) computer, a tablet computer, a wireless modem (modem), a handheld device (dhhand), a laptop computer (laptop computer), a cordless phone (cordless phone) or a Wireless Local Loop (WLL) station, a Machine Type Communication (MTC) terminal, a User Equipment (UE), a Mobile Station (MS), a terminal equipment (terminal device) or a relay user equipment, etc. may also be included. The relay user equipment may be, for example, a 5G home gateway (RG). For convenience of description, these devices are collectively referred to as a terminal (terminal) in this application.

The (R) AN20 may be used to provide a wireless connection between the terminal 10 and the core network 30. The network elements in the (R) AN20 may include, for example and without limitation, a base station, AN evolved node base (eNB), a next generation base station (gNB), a new radio base station (new radio eNB), a macro base station, a micro base station, a high frequency base station or a Transmission and Reception Point (TRP), a non-3GPP access network (e.g., WiFi), and/or a non-3GPP interworking function (N3 IWF). It should be noted that, hereinafter, the (R) AN20 may be understood as a network element in the (R) AN, and is described herein in a unified manner, and will not be described in detail below.

The AMF element 301 may be used for connection management, mobility management, registration management, access authentication and authorization, reachability management, security context management, selection of the SMF element 302, and the like. SMF network element 302 may be used for session management such as establishment, modification, and release of sessions, selection and control of UPF network element 306, selection of service and session continuity (session continuity) mode, roaming services, and the like. The PCF network element 303 may be configured to provide policy control services and obtain subscription information related to policy decisions. The NSSF network element 304 may be configured to select a network slice for the terminal 10, determine network slice selection assistance information, and determine one or more AMF network elements 301 serving the terminal 10, among other things. NRF network element 305 may be used for service discovery, maintaining available network function texts and services supported by these network functions. The UPF network element 306 may be configured to process events related to the user plane, such as transmitting or routing data packets, detecting data packets, reporting traffic, handling quality of service (QoS), lawful interception, storing downlink data packets, and the like.

DN40 may be, for example, an operator service, internet access or third party service, etc.

It is understood that, although not shown, the 5G network may further include other network elements, such as an authentication service function (AUSF) network element, an Application Function (AF) network element, and a network open function (NEF) network element, and the present application is not limited in this respect.

It should be noted that, in fig. 1, each network element, such as the terminal 10, (R) AN20, the AMF network element 301, the SMF network element 302, the PCF network element 303, the NSSF network element 304, the NRF network element 305, and the UPF network element 306, etc., is only a name, and the name does not limit the device itself. In the 5G network and other networks in the future, these network elements may also be given other names, which is not specifically limited in this embodiment of the present application. For example, the AMF network element 301 may also be replaced by the AMF301 or an AMF entity, etc., which are described herein in a unified manner and will not be described in detail below.

Optionally, each network element in fig. 1 may be implemented by one device, may also be implemented by multiple devices together, and may also be a functional module in one device, which is not specifically limited in this embodiment of the present application. It is understood that the above functions may be either network elements in a hardware device, software functions running on dedicated hardware, or virtualized functions instantiated on a platform (e.g., a cloud platform).

To facilitate understanding of the technical solutions of the embodiments of the present application, the following briefly introduces a network slice, a network slice instance, and a PDU session, and a relationship between the network slice, the network slice instance, the PDU session, and a core network element (or referred to as a network function network element).

The network slice is defined in a public mobile network (PLMN), and may include: core network control plane and user plane function network elements (NF). The concept of Network Slice Selection Assistance Information (NSSAI) is introduced into a network slice. As an example, standard SST types may include enhanced mobile broadband (eBB), high-reliability low-latency communications (ULC) and mass Internet of things (MIoT), etc.

One network slice instance may be associated with one or more S-NSSAIs, and one S-NSSAI may be associated with one or more network slice instances, based on the needs of the operator' S operation or deployment, etc. Multiple network slice instances associated with the same S-NSSAI may be deployed in the same or different Tracking Areas (TAs). When multiple network slice instances related to the same S-NSSAI are deployed in the same TA, the AMF network element serving the terminal may logically belong to more than one network slice instance related to the S-NSSAI. In a PLMN, when an S-NSSAI is associated with multiple network slice instances, one of the network slice instances serves a terminal that is allowed to use the S-NSSAI. For any S-NSSAI, the network may serve the terminal with only one network slice instance associated with that S-NSSAI at any time, unless the network slice instance is no longer valid in a given registration area or the terminal' S allowed NSSAI changes, etc.

One or more network slice instances associated with an S-NSSAI may be referred to as network slice instances that the S-NSSAI-tagged network slice includes (or contains). The one or more network slice instances belong to the network slice. The identification information of a network slice instance may be used to identify a network slice instance. The identification information of the network slice instance may be an identifier (NSI ID) of the network slice instance, and the like.

Each network slice instance may include (or correspond to) a set of network function network elements. Different network slice instances typically include different sets of network functional network elements. The network functional network element may include the AMF network element, the SMF network element, the UPF network element, and the like in fig. 1. Different groups of network function network elements may comprise the same network function network element. For example, different network slice instances may correspond to the same AMF/SMF network element. Each network slice may include a set of network functional network elements. A network slice comprising network functional network elements may be considered to be a collection of network functional network elements comprised by all network slice instances belonging to the network slice.

If a network slice instance/network slice includes a network functional network element, the network functional network element may be considered to support the network slice instance/network slice. For example, if a network slice instance/network slice includes an AMF network element, the AMF network element may be considered to support the network slice instance/network slice. Typically, when network deployment is performed, i.e., which network functional network element supports which network slice or slices and network slice instances are already deployed. Of course, it is also possible to update the network slice and the network slice instance supported by one or some network functional network elements during the network operation process, which is not limited in this application.

Each network function slice and each network slice have a certain service area, and the respective service area can be deployed when network deployment is performed. Although the application is not so limited. The service area of a network slice may be considered to be the sum of the service areas of all network slice instances belonging to that network slice.

A terminal may access multiple network slices and the terminal may access the same network slice based on one or more network slice instances. The terminal may establish one or more PDU sessions in one network slice instance. Each PDU session is established based on one network slice instance. In this application, the network slice instance on which a PDU session is established is referred to as the network slice instance related to the PDU session, and the network slice to which the network slice instance belongs is referred to as the network slice related to the PDU session. Where a PDU session is a connection between a terminal and a DN (i.e., DN40 in fig. 1) for providing a PDU connection service. The connection type may be an Internet Protocol (IP) connection, an ethernet connection, or an unstructured data connection. The PDU connection service supported by the 5G core network refers to a service providing PDU exchange between a terminal and a DN determined by a Data Network Name (DNN). The terminal may establish one or more PDU sessions to connect to the same DN or different DNs. Wherein the UE can establish PDU sessions served by different UPF network elements to connect to the same DN.

Fig. 2 is a schematic diagram illustrating a relationship between a network slice instance, a PDU session, and a network function network element according to an embodiment of the present application. In fig. 2, the terminal establishes PDU session 1, PDU session 2 and PDU session 3. Wherein PDU session 1 is established based on network slice instance 11, PDU session 2 is established based on network slice instance 21, and PDU session 3 is established based on network slice instance 31. Wherein PDU session 1 and PDU session 2 are both connected to DN1, and PDU session 3 is connected to DN 2. Each network slice instance (e.g., network slice instances 1, 2, and 3) includes a respective network function network element, wherein the SMF network element, the NRF network element, the PCF network element, and the UPF network element included in each network slice instance are illustrated in fig. 2, although the application is not limited thereto.

Fig. 3 is a schematic diagram illustrating a relationship between a network slice example and a network slice provided in an embodiment of the present application. Fig. 3 is a drawing based on fig. 2. Specifically, the network slice example 11 in fig. 2 belongs to the network slice 1, and in addition, the network slice 1 may further include network slice examples 12 and 13; network slice instance 21 belongs to network slice 2, and network slice 2 may further include network slice 22; network slice instance 31 belongs to network slice 3.

The concept that network slice instances/network slices are available and network slice instances/network slices are not available is also described in embodiments of the present application. Where a netslice instance/netslice is available, it can be understood that the netslice instance/netslice is valid (valid). Network slice instances/network slices are not available, it being understood that network slice instances/network slices are not valid. Hereinafter, a specific implementation of whether the network slice instance/network slice associated with the PDU session provided in the embodiment of the present application is available is explained.

In one implementation, if a network slice instance supported by an AMF network element includes a network slice instance related to a PDU session, the AMF network element supports the network slice instance related to the PDU session, in which case, the network slice instance is available for the PDU session; otherwise, the AMF network element does not support the network slice instance associated with the PDU session, in which case the network slice instance is not available for the PDU session. If the network slice supported by one AMF network element comprises a network slice related to the PDU session, the AMF network element supports the network slice related to the PDU session, and in this case, the network slice is available for the PDU session; otherwise, the AMF network element does not support the network slice associated with the PDU session, in which case the network slice is not available for the PDU session. It should be noted that, in the specific implementation process, it may be determined whether an AMF network element supports a network slice related to a PDU session, and if not, it may be determined that the AMF network element does not support all network slice instances included in the network slice, that is, does not support the network slice instance related to the PDU session. If so, it may be further determined whether the AMF network element supports the network slice instance associated with the PDU session.

In another implementation, if a terminal moves out of the service area of a network slice instance, the network determines that the network slice instance is not available to the terminal. If a terminal moves out of the service area of a network slice, the network determines that the network slice is not available to the terminal, and all network slice instances included in the network slice are not available. It should be noted that, if the terminal is in the service area of a network slice/network slice instance, the network slice/network slice instance is not necessarily available to the terminal, and whether the network slice/network slice instance is available is also related to registration information of the terminal, network requirements (for example, a requirement of load balancing of a network functional network element, a requirement of management of the network slice instance, and the like). For example, if the number of PDU sessions established based on a network slice instance supported by an AMF network element is large and the PDU sessions are established by different terminals, the network may set some terminals to be unavailable for the network slice instance based on the requirement of load balancing. In this case, the network determines that the network slice instance is not available to the terminal. Similarly, the terminal may be set to be unavailable with a certain network slice or slices. For another example, if the network is updating a certain network slice instance, or a network functional network element included in the network slice instance is down, the network may set some terminals to be unavailable for the network slice instance. In this case, the network determines that the network slice instance is not available to the terminal. Similarly, the terminal may be set to be unavailable with a certain network slice or slices. Although the application is not so limited.

Additionally, the network slice instance/network slice unavailability may also be embodied as: a network side network element (such as AN AMF network element, AN SMF network element, or AN (R) AN, etc.) cannot serve the network slice instance/network slice; or, the network determines that the terminal cannot access the network slice instance/network slice, thereby determining that the terminal cannot currently establish the PDU session through the network slice instance/network slice and/or that the PDU session established by the terminal through the network slice/network slice instance needs to be released; alternatively, the network determines that the terminal cannot accept the services of the network slice/network slice instance. Of course, not limited thereto. The reason that the network slice/network slice is not available may be that the terminal moves out of service range of the network slice/network slice instance, or subscription data of the terminal changes, or service area changes, etc. Taking an AMF network element as an example, a network slice/network slice instance may not be available under the same AMF network element (e.g., a network slice/network slice instance may not be available due to a change in terminal subscription data) or may not be available due to an AMF network element change (e.g., a network slice/network slice instance may not be available due to a change in registration area).

The following describes a scenario to which the technical solution provided in the embodiment of the present application is applied:

the technical scheme provided by the embodiment of the application can be applied to a scene of replacing the SMF network element and can also be applied to a scene of not replacing the SMF network element; the method can be applied to the scene of AMF network element replacement and can also be applied to the scene of AMF network element non-replacement.

The scenario in which the AMF network element is replaced and the scenario in which the AMF network element is not replaced may be a registration procedure or a handover procedure. In both the registration process and the handover process, a scenario in which the AMF network element is not replaced may be considered as a special case of a scenario in which the AMF network element is replaced, that is, in a scenario in which the AMF network element is not replaced, the AMF network element before replacement is the same as the AMF network element after replacement. The registration procedure is a procedure triggered by the terminal, and the handover procedure is a procedure triggered by the (R) AN. In the specific implementation process, the scenario that the AMF network element is not changed may also be a flow triggered by the AMF network element. For example, the AMF network element may determine, at least according to the location information of the terminal, that a network slice instance related to the PDU session established by the terminal is unavailable and a network slice related to the PDU session is available, so as to trigger execution of a process of the technical solution provided in the embodiment of the present application. Although the application is not so limited.

The scenario in which the SMF network element is changed and the scenario in which the SMF network element is not changed may be a registration procedure, a handover procedure, or the above-mentioned procedure triggered by the AMF network element. In the registration process, the handover process, and the process triggered by the AMF network element, the scenario in which the SMF network element is not replaced may be considered as a special case of the scenario in which the SMF network element is replaced, that is, the SMF network element before replacement and the SMF network element after replacement may be considered to be the same in the scenario in which the SMF network element is not replaced.

Hereinafter, a PDU session reestablishment method provided in the embodiments of the present application is described with reference to fig. 1 to 3. It should be noted that, in the following embodiments of the present application, a name of a message between network elements or a name of each parameter in the message is only an example, and other names may also be used in a specific implementation, which is described in a unified manner herein, and this is not limited in this embodiment of the present application.

As shown in fig. 4, a PDU session reestablishment method is provided in this embodiment of the present application. The method may be applied in a communication system as shown in fig. 1. The method may comprise the steps of:

s101: the first AMF network element determines that a first PDU session related network slice instance of the terminal is unavailable and a first PDU session related network slice is available.

The first PDU session may be any PDU session currently established by the terminal. The number of currently established PDU sessions of a terminal may be one or more.

The embodiment can be applied to a scene of replacing the SMF network element and can also be applied to a scene of not replacing the SMF network element; the method can be applied to the scene of AMF network element replacement and can also be applied to the scene of AMF network element non-replacement. Specifically, the method can be applied to a registration process, a handover process, or a process triggered by an AMF network element. For example, if the present embodiment is applied to the registration procedure, the first AMF network element may be a new AMF network element or an old AMF network element. For example, if the present embodiment is applied to a handover procedure, the first AMF network element may be a target AMF network element or a source AMF network element. For example, if the present embodiment is applied to a process triggered by an AMF network element, the first AMF network element is the AMF network element that triggers the process. With respect to how the first AMF network element determines that the first PDU session related network slice instance is not available and that the first PDU session related network slice is available in the scenarios, reference may be made to the following.

S102: and the first AMF network element sends the second information to the SMF network element. The SMF network element receives the second information. The second information is used to indicate that the first PDU session related network slice instance is not available and that the first PDU session related network slice is available.

In this embodiment, the second information is used to indicate that the network slice instance related to the first PDU session is not available, and the network slice related to the first PDU session is available, which may be considered as: the second information is used for a specific implementation mode that the SMF network element sends the first information to the terminal according to the second information; specifically, the second information instructs the SMF network element to send the first information to the terminal by indicating that the first PDU session-related network slice instance is not available and the first PDU session-related network slice is available.

For example, if the present embodiment is applied to a registration procedure, the SMF network element may be an old SMF network element. For example, if the present embodiment is applied to a handover procedure, the SMF network element may be a source SMF network element. For example, if the present embodiment is applied to a flow triggered by an AMF network element, the SMF network element may be referred to as an old SMF network element. With regard to how the first AMF network element sends the second information to the SMF network element in the above scenarios (or cases), reference may be made to the following specific examples.

The embodiment of the application does not limit what kind of message the second information is carried in and is sent to the SMF network element by the first AMF network element. The message may be a message in the prior art, or may be a new message.

In this embodiment, the SMF network element receives the second information, so as to know that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available, which may be considered as: the SMF network element determines that the first PDU session related network slice instance is not available and that the first PDU session related network slice is available.

S103: and after receiving the second information, the SMF network element sends the first information to the terminal. The terminal receives the first information. The first information is used for indicating the terminal to initiate a PDU session reestablishment process. Identification information of the first PDU session may be included in the first information to instruct the terminal to determine that a PDU session needs to be reestablished.

Optionally, the information type of the first information is not limited in this application. For example, the information type may be request or allowed (allowed), etc. If the information type of the first information is a request, the first information received by the terminal is a request information, and the terminal can generally initiate a PDU session reestablishment procedure immediately after receiving the request information. If the information type of the first information is allowed, the first information received by the terminal is allowed information, and usually, after receiving the allowed information, the terminal may determine whether to initiate a PDU session reestablishment procedure according to its own condition. For example, if the terminal determines that it is not necessary to continue to transmit the service carried by the first PDU session, it may not initiate the PDU session reestablishment procedure; if the terminal determines that the service carried by the first PDU session needs to be continuously transmitted subsequently, a PDU session reestablishment process can be initiated. It should be noted that, for convenience of description, the following description is given by taking the information type of the first information as an example, and the description is unified here and is not repeated below.

Generally, the SMF network element first sends the first information to the AMF network element, and then the AMF network element sends the first information to the terminal through the (R) AN. In any scenario listed in S101 and/or S102, a specific implementation manner and the like of how the SMF network element sends the first information to which AMF network element, and how the AMF network element sends the first information to the terminal may refer to a specific example below.

Optionally, in the embodiment of the present application, no limitation is imposed on what kind of message the first information sent by the SMF network element to the AMF network element is carried in and what kind of message the first information sent by the AMF network element to the terminal is carried in for transmission. For example, the message may be a message in the prior art or a new message.

For example, the SMF network element may carry the first information in a PDU session release message and send the PDU session release message to the AMF network element, and the AMF network element may forward the PDU session release message to the terminal. Specifically, a cause value may be carried in the PDU session release message, and the cause value may be used as the first information for indicating the re-establishment.

For example, no matter what kind of message the SMF network element carries the first information in, and sends the first information to the AMF network element, the AMF network element may carry the first information in the PDU session status message and send the PDU session status message to the terminal. In this application, the PDU session status message may include status information of at least one PDU session of the terminal, where the status information of any one PDU session indicates one of existence, release, and reestablishment. If the status information of a PDU session indicates presence, the terminal does not need to re-establish and does not need to release the PDU session. If the status information of a PDU session indicates release, the terminal needs to release the PDU session. If the status information of a PDU session indicates re-establishment, the terminal needs to re-establish the PDU session. It can be understood that the specific implementation manner of how the AMF network element determines that the terminal needs to exist or release a PDU session has been described in detail in the prior art, and is not described herein again. For a specific implementation manner of how the AMF network element determines that the terminal needs to reestablish a PDU session, reference may be made to relevant contents in this application.

Optionally, after receiving the second information, the SMF network element may send the first information to the terminal according to the policy information. The policy information is used to indicate a policy, and the policy content of the policy is as follows: and when the network slice instance related to the first PDU session is unavailable and the network slice instance related to the first PDU session is available, initiating a session reestablishment process.

In one aspect, the present application does not limit what granularity the policy is based on. For example, the policy may be a PDU session granularity-based policy, in which case the policy may be one having an association (or mapping or correspondence) with the first PDU session. For example, the policy may be a policy based on PDU session group granularity, in this case, the policy may be a policy having an association relationship with a PDU session group including a first PDU session, where the present application does not limit a specific implementation manner of how to determine a PDU session group, and in theory, any manner of determining a PDU session group may be applicable to the present application. For example, the policy may be a terminal granularity-based policy, in which case the policy may be one having an association with the terminal. Although the application is not so limited.

On the other hand, how the SMF network element obtains the policy information is not limited in the present application, for example, the policy information may be pre-stored locally in the SMF network element when network deployment is performed. For example, the policy information may be configured to the SMF network element by the PCF network element through signaling. The related procedure for the PCF network element to configure the policy (specifically, may be referred to as an SMF policy) to the SMF network element has been described in detail in the prior art, and is not described herein again. That is to say, it may be considered that a new SMF policy (that is, a policy indicated by the policy information) is proposed in the technical solution provided in the present application, and a related process for configuring the new SMF policy may refer to a process for configuring another SMF policy in the prior art, although the present application is not limited thereto.

S104: and after receiving the first information, the terminal initiates a PDU session reestablishment process.

Specifically, the terminal may determine that the first PDU session needs to be reestablished after receiving the first information. Then, the identification information of the network slice related to the first PDU session may be determined according to a locally stored correspondence between the currently established PDU session of the terminal and the identification information of the network slice related to the PDU session. And then, sending a PDU session reestablishment request message to the AMF network element. Wherein, in different scenes, the AMF network element is different. For example, if the present embodiment is applied to the registration procedure, the AMF network element may specifically be a new AMF network element. If the present embodiment is applied to the handover procedure, the AMF network element may specifically be a target AMF network element. The PDU session reestablishment request message carries identification information of the network slice related to the first PDU session. Subsequently, the AMF network element may select a new network slice instance for the terminal after receiving the PDU session reestablishment request message, and then select the SMF network element according to the new network slice instance. The subsequent process may refer to a PDU session reestablishment process provided in the prior art, which is not described herein again. In different scenes, the selected SMF network elements are different according to the new network slice example. For example, if the present embodiment is applied to the registration procedure, the selected SMF network element may specifically be a new SMF network element. For example, if the present embodiment is applied to a handover procedure, the selected SMF network element may specifically be a target SMF network element. For example, if the present embodiment is applied to a process triggered by an AMF network element, the selected SMF network element may specifically be a new SMF network element.

In the method for reestablishing a PDU session provided in this embodiment, the terminal may initiate a PDU session reestablishment procedure when the network slice instance related to the first PDU session of the terminal is unavailable and the network slice related to the first PDU session is available. Wherein the PDU session reestablishment procedure is used to reestablish a PDU session based on the network slice. Since the network slice selected by the network for a terminal is usually a network slice that is relatively consistent with the current service transmission of the terminal, reconstructing a PDU session through the network slice can guarantee the transmission performance of the service to some extent.

As shown in fig. 5, a PDU session reestablishment method is provided in this embodiment of the present application. The method may be applied in a communication system as shown in fig. 1. The method may comprise the steps of:

s201: reference may be made to S101 described above, although the present application is not limited thereto.

S202: and the first AMF network element sends the second information to the SMF network element. The SMF network element receives the second information. And the second information is used for directly indicating the SMF network element to send the first information to the terminal according to the second information.

In this embodiment, the second information is used to directly instruct the SMF network element to send the first information to the terminal according to the second information, and may be considered as: the second information is used for indicating a specific implementation mode of the SMF network element to send the first information to the terminal according to the second information. The present embodiment is different from the embodiment shown in fig. 4 in that the content indicated by the second information is different.

S203 to S204: reference may be made to S103 to S104 described above. Of course, the present application is not limited thereto.

It should be noted that, in this embodiment, since the second information directly instructs the SMF network element to send the first information to the terminal according to the second information, the SMF network element does not need to pay attention to whether the condition that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available currently is met. That is, in the implementation process, the SMF network element does not need to send the first information to the terminal according to the policy information described in the embodiment shown in fig. 4, but directly sends the first information to the terminal under the instruction of the second information.

For the explanation of the related content in this embodiment, reference may be made to the above description, which is not repeated herein.

The beneficial effects that the technical scheme provided by the embodiment can achieve can refer to the beneficial effects that the embodiment shown in fig. 4 can achieve. In addition, in this embodiment, the second information sent by the first AMF network element to the SMF network element directly indicates that the SMF network element sends, to the terminal, information for indicating to initiate the PDU session reestablishment procedure according to the second information. Therefore, the processing procedure of the SMF network element can be simplified.

As shown in fig. 6, a PDU session reestablishment method according to an embodiment of the present application is provided. The method may be applied in a communication system as shown in fig. 1. The method may comprise the steps of:

s301: and the first AMF network element sends the sixth information to the SMF network element. The SMF network element receives the sixth information. The sixth information is used to indicate network slices and network slice instances supported by the second AMF network element. For example, the sixth information may include identification information of a network slice supported by the second AMF network element and identification information of a network slice instance. Although the application is not so limited.

The embodiment can be applied to the scene of AMF network element replacement. In this scenario, the SMF network element may or may not be replaced. Such as a registration procedure or a handover procedure. The second AMF network element may be considered as a replaced AMF network element. The first AMF network element and the second AMF network element may be the same or different. Specifically, the method comprises the following steps:

when the embodiment is applied to the registration process, if the first AMF network element is different from the second AMF network element, the first AMF network element may be specifically an old AMF network element, and the second AMF network element is a new AMF network element. In this case, the old AMF network element may determine that the terminal cannot be served by itself when determining that the terminal cannot be served by itself (for example, when the new AMF network element establishes communication with the old AMF network element and the communication is about communication of the terminal, although the application is not limited thereto), and obtain (for example, receive, as described below, identification information of a network slice supported by the new AMF network element or NSSF network element) identification information of a network slice instance and send the sixth information to the SMF network element. And if the first AMF network element is the same as the second AMF network element, the first AMF network element and the second AMF network element are both new AMF network elements. In this case, the new AMF network element may send the sixth information to the SMF network element via the old AMF network element when determining that the old AMF network element cannot provide the service for the terminal (for example, when the new AMF network element establishes communication with the old AMF network element and the communication is about the terminal, it is determined that the old AMF network element cannot provide the service for the terminal, although the application is not limited thereto).

When the embodiment is applied to the handover procedure, if the first AMF network element is different from the second AMF network element, the first AMF network element may be specifically a source AMF network element, and the second AMF network element is a target AMF network element. In this case, the source AMF network element may send the sixth information to the SMF network element after determining that the source AMF network element cannot provide a service for the terminal itself and acquiring the identification information of the network slice supported by the target AMF network element and the identification information of the network slice instance. And if the first AMF network element is the same as the second AMF network element, the first AMF network element and the second AMF network element are both target AMF network elements. In this case, the target AMF network element may send the sixth information to the SMF network element through the source AMF network element when it is determined that the source AMF network element cannot provide the service for the terminal.

S302: and if the SMF network element determines that the second AMF network element does not support the network slice example related to the first PDU session of the terminal and supports the network slice related to the first PDU session, determining that the network slice example related to the first PDU session is unavailable and the network slice related to the first PDU session is available.

If this embodiment is applied to the registration procedure, the SMF network element may specifically be an old SMF network element. If this embodiment is applied to the handover procedure, the SMF network element may specifically be a source SMF network element. It can be understood that, in the old SMF network element (or the source SMF network element), the identification information of the network slice and the identification information of the network slice instance related to each PDU session currently established by the terminal may be maintained. Thus, after the old SMF network element (or source SMF network element) receives the information indicating the network slices and network slice instances supported by the second AMF network element, it may be determined whether the second AMF network element supports the first PDU session related network slice instance of the terminal and whether the first PDU session related network slice is supported.

In this embodiment, S302 may be regarded as a specific implementation manner of the SMF network element determining that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available. Regardless of the specific implementation of the following S303 to S305, the difference between this embodiment and the embodiments shown in fig. 4 and 5 is that the SMF network element determines that the network slice instance related to the first PDU session is not available, and the implementation manner of the network slice related to the first PDU session is different.

S303 to S304: reference may be made to S103 to S104 described above. Although the application is not so limited.

The technical scheme provided by the embodiment can achieve the beneficial effects by referring to the embodiment shown in fig. 4. In addition, in this embodiment, the SMF network element receives information indicating the network slices and network slice instances supported by the second AMF network element, so as to determine that the network slice instance related to the first PDU session is unavailable and the network slice instance related to the first PDU session is available, and therefore, the processing procedure of the AMF network element can be simplified.

Hereinafter, a specific implementation procedure of the embodiment shown in fig. 4 will be described by taking a scenario in which the embodiment shown in fig. 4 is applied to SMF network element replacement and a scenario in which the SMF network element is not replaced as an example. Specifically, based on the two scenarios, the explanation is performed based on a scenario in which the AMF network element is replaced and a scenario in which the AMF network element is not replaced. More specifically, in each scenario, the description is based on a registration procedure and a handover procedure as examples, and in a scenario where the AMF network element is not replaced, the description is further based on a procedure triggered by the AMF network element as an example.

Scene one, scene of SMF network element replacement

1) AMF network element replacement scene

Fig. 7 is an interaction diagram of a PDU session reestablishment method according to an embodiment of the present application. The present embodiment is an example of the embodiment shown in fig. 4 when applied to a registration flow. The method shown in fig. 7 may include the steps of:

s401: the terminal sends a registration request message to the (R) AN.

S402: and (R) after receiving the registration request message, the AN executes AN AMF network element selection process to determine AN AMF network element (hereinafter referred to as a new AMF network element) providing service for the terminal in the registration process.

It is understood that the AMF network element selection procedure is an optional step in the registration procedure. The application does not limit under which circumstances the AMF network element selection procedure is performed, and for example, reference may be made to the prior art. The following description is given by taking AN example in which the (R) AN performs the AMF network element selection procedure.

S403: (R) the AN sends a registration request message to the new AMF network element.

It can be understood that, the (R) AN may know whether the terminal accesses another AMF network element (i.e. AN old AMF network element) before performing the registration procedure. In this embodiment, the terminal is taken as an example to describe that the terminal has accessed the old AMF network element, in this case, the registration request message in S403 may carry identification information of the old AMF network element, such as an address of the old AMF network element, so that the new AMF may execute the following S404 according to the identification information of the old AMF network element.

S404: and the new AMF network element sends a context transfer request message to the old AMF network element. The context transfer request message carries third information, and the third information is used for indicating the network slices supported by the new AMF network element and the network slice instances included in each network slice.

For example, the third information may include identification information carrying network slices supported by the new AMF network element and identification information of network slice instances included in each of the network slices. It should be noted that, the third information is specifically what information is, so that the function of indicating the third information is realized, and the present application is not limited thereto. In principle, any information that enables this indicated function may be suitable for use in the present application.

It can be understood that, in the registration procedure, generally, when the new AMF network element performs S404, it is not known which PDU sessions are currently established by the terminal, and therefore, the context transfer request message may carry identification information of all network slices supported by the new AMF network element and identification information of a network slice instance corresponding to each of the network slices. Although the application is not so limited.

It can be understood that the context transfer request message may also carry identification information of the terminal, which is used to request the context information of the terminal. The identification information of the terminal may be the above-mentioned 5G temporary identification.

It should be noted that, in this embodiment, it is described by taking the example that the third information is carried in the context transfer request message, in a specific implementation process, the third information may also be carried in one or more messages, and any one of the one or more messages may be a new message or a message in the prior art. This is not limited in this application.

S405: and after the old AMF network element receives the context transfer request message, determining that one or more network slice instances related to the current PDU session of the terminal are unavailable and the one or more network slices related to the PDU session are available according to the current PDU session of the terminal and the third information.

As an example, if the identification information of the network slice instance supported by the new AMF network element does not include the identification information of a network slice instance related to a PDU session, it is determined that the network slice instance related to the PDU session is not available. And if the identification information of the network slice supported by the new AMF network element comprises the identification information of the network slice related to the PDU session, determining that the network slice related to the PDU session is available.

For example, assuming that there are 10 current PDU sessions of the terminal when S405 is executed, a PDU session satisfying the condition that "network slice instance related to the PDU session is not available and network slice instance related to the PDU session is available" may be a part or all of the 10 PDU sessions after S405 is executed. The application is not limited as to how other PDU sessions that do not satisfy this condition are handled. For example, reference may be made to the prior art.

For each of the one or more PDU sessions determined in S405, the following S406 to S413 may be respectively performed.

S406: and the old AMF network element sends the second information to the old SMF network element. Wherein the second information is used to indicate that the first PDU session related network slice instance is not available and the first PDU session related network slice is available. The first PDU session is any one of the one or more PDU sessions determined in S405.

The second information may include identification information of the terminal, such as a subscription permanent identifier (SUPI).

It can be understood that, before performing the registration procedure, the old AMF network element may select an SMF network element, that is, an old SMF network element, for the terminal, and maintain a corresponding relationship between the identification information of the terminal and the identification information of the old SMF network element, so that before performing S406, the identification information of the old SMF network element may be determined, and then S406 is performed.

S407: and after the old SMF network element receives the second information, determining that a PDU session reestablishment process needs to be initiated.

For example, after receiving the second information, the old SMF network element may determine that a PDU session reestablishment procedure needs to be initiated according to the policy information in the embodiment shown in fig. 4, which is not limited to this.

S408: the old SMF network element sends the first information to the old AMF network element. The first information is used for indicating the terminal to initiate a PDU session reestablishment process. For example, the first information may include identification information of the first PDU session, etc.

S409: and after receiving the first information, the old AMF network element sends the first information to the new AMF network element.

S410: and after receiving the first information, the new AMF network element sends the first information to the terminal.

In this embodiment, since the AMF network element that subsequently provides a service for the terminal is a new AMF network element, and the new AMF network element does not support the network slice instance in which the old SMF network element is located (i.e., the network slice instance related to the first PDU session), the new AMF network element needs to send the first information to the terminal. Since the old SMF network element cannot communicate directly with the new AMF network element, the old SMF network element may send the first information to the new AMF network element via the old AMF network element.

S411: and after receiving the first information, the terminal sends a PDU session reestablishment request message to the new AMF network element. And the PDU session reestablishment request message carries identification information of the network slice related to the first PDU session.

S412: and after receiving the PDU session reestablishment request message, the new AMF network element selects a new network slice example for the terminal. And selecting a new SMF network element according to the new network slice instance. The new SMF network element supports the new network slice instance.

The specific implementation manner of selecting a new network slice instance by the new AMF network element may refer to the prior art, and is not described herein again.

It should be noted that the old AMF network element may have a capability of determining a network slice instance, in this case, in S405, the old AMF network element may further determine identification information of a new network slice instance, and the identification information of the new network slice instance may be sent to the new AMF network element by the old AMF network element. In this case, the new AMF network element does not need to reselect a new network slice instance when performing S412.

S413: and executing subsequent steps in the PDU session reestablishment process according to the identification information of the new network slice example and the new SMF network element. The subsequent steps in the PDU session reestablishment procedure are described in the prior art, and are not described herein again.

For explanation and beneficial effects of relevant contents in this embodiment, reference may be made to the above corresponding embodiments, which are not described herein again.

Fig. 8 is an interaction diagram of a session reestablishment method according to an embodiment of the present application. The present embodiment is specifically another example when the embodiment shown in fig. 4 is applied to a registration flow. The method shown in fig. 8 comprises the following steps:

s501 to S503: reference may be made to the above S401 to S403, although the present application is not limited thereto.

S504: and the new AMF network element sends a context transfer request message to the old AMF network element.

S505: and after receiving the context transfer request message, the old AMF network element sends a context transfer response message to the new AMF network element. The context transfer response message carries fourth information, and the fourth information is used for indicating the network slice related to each PDU session in one or more current PDU sessions of the terminal and the network slice instance related to the PDU session.

For example, for any one of the one or more current PDU sessions of the terminal, the fourth information may include identification information of the PDU session, identification information of a network slice associated with the PDU session, and identification information of a network slice instance associated with the PDU session. Of course, the fourth information specifically includes what information to implement the indication function of the fourth information, and the present application is not limited thereto. In principle, any information that enables this indicated function may be suitable for use in the present application.

It should be noted that, in this embodiment, it is described by taking the fourth information carried in the context transfer response message as an example, in a specific implementation process, the fourth information may also be carried in one or more messages, and any one of the one or more messages may be a new message or a message in the prior art. This is not limited in this application.

For any one of the one or more PDU sessions, the following S506 may be performed.

S506: and after receiving the context transfer response message, the new AMF network element determines that the network slice instances related to part or all of the PDU sessions in the one or more PDU sessions are unavailable and the network slices related to the part or all of the PDU sessions are available according to the identification information of the network slices supported by the new AMF network element, the identification information of the network slice instances, and the fourth information. The specific implementation manner may refer to the related description in S405 above.

For each PDU session of the partial or entire PDU sessions determined in S506, the following S507 to S515 may be respectively performed.

S507: and the new AMF network element sends the second information to the old AMF network element. Wherein the second information is used to indicate that the first PDU session related network slice instance is not available and the first PDU session related network slice is available. Wherein the first PDU session is any one of the partial or all PDU sessions determined in S506.

S508: and after receiving the second information, the old AMF network element sends the second information to the old SMF network element.

S509 to S515: reference may be made to the above S407 to S413, although the present application is not limited thereto.

It should be noted that the new AMF network element may have the capability of determining a network slice instance, in this case, in/after S506, the new AMF network element may also determine the identification information of the new network slice instance. In this case, the new AMF network element does not need to reselect a new network slice instance when performing S514.

Fig. 9 is an interaction diagram of a session reestablishment method according to an embodiment of the present application. The present embodiment is specifically an example when the embodiment shown in fig. 4 is applied to a handover procedure. The method shown in fig. 9 comprises the following steps:

s601: (R) the AN sends a handover request message to the AMF network element currently serving the terminal, i.e. the source AMF network element. The handover request message may carry identification information of the terminal.

S602: and after the source AMF network element receives the switching request message, executing an AMF network element selection process to determine a target AMF network element. And in the flow, through information interaction with the NRF network element, it is determined that a network slice instance related to each PDU session in one or more current PDU sessions of the terminal is unavailable and a network slice related to the PDU session is available. Wherein the one or more PDU sessions may be part or all of all PDU sessions currently in use by the terminal.

It will be appreciated that NRF network elements are used for service discovery, maintaining available network function texts and services supported by these network functions. For example, in the present application, the NRF network element may be configured to maintain identification information of network slices supported by the AMF network element and identification information of network slice instances included in each of the network slices.

As an example, the source AMF network element may send names of target network function network elements, such as the AMF network element, the type of the target network function network element, and the like, to the NRF network element, and the NRF network element may select one AMF network element as the target AMF network element after receiving the information, and then send identification information of all network slices supported by the target AMF network element and identification information of network slice instances included in each of the network slices to the source AMF network element. After the source AMF network element receives the information, for any current PDU session of the terminal, whether the network slice instance of the PDU session is available can be determined by determining whether the target AMF network element supports the network slice instance related to the PDU session, and whether the network slice instance of the PDU session is available can be determined by determining whether the target AMF network element supports the network slice related to the PDU session.

It should be noted that, in S602, it is described that, in the process of performing the AMF network element selection procedure, the source AMF network element determines that a network slice instance related to each PDU session in one or more current PDU sessions of the terminal is unavailable, and a network slice related to the PDU session is available, which is not limited in this application. For example, after the target AMF network element is determined, the source AMF network element may acquire, through information interaction with the target AMF network element, identification information of the network slice supported by the target AMF network element and identification information of the network slice instance included in each network slice.

For each of the one or more PDU sessions determined in S602, the following S603 to S610 may be respectively performed.

S603: and the source AMF network element sends the second information to the source SMF network element. Wherein the second information indicates that the first PDU session related network slice instance is not available and the first PDU session related network slice is available. Wherein the first PDU session is any one of the one or more PDU sessions determined in S602.

S604: and after the source SMF network element receives the second information, determining that a PDU session reestablishment process needs to be initiated.

For example, after receiving the second information, the source SMF network element may determine that a PDU session reestablishment procedure needs to be initiated according to the policy information in the embodiment shown in fig. 4, which is not limited to this.

S605: and the source SMF network element sends the first information to the source AMF network element. The first information is used for indicating the terminal to initiate a PDU session reestablishment process, and the first information comprises identification information of the first PDU session.

S606: and after receiving the first information, the source AMF network element sends the first information to the target AMF network element.

S607: and after receiving the first information, the target AMF network element sends the first information to the terminal.

In this embodiment, since the AMF network element that subsequently provides a service for the terminal is the target AMF network element, and the target AMF network element does not support the network slice instance in which the source SMF network element is located (i.e., the network slice instance related to the first PDU session), the target AMF network element needs to send the first information to the terminal. Since the source SMF network element cannot directly communicate with the target AMF network element, the source SMF network element may send the first information to the target AMF network element via the source AMF network element.

S608: and after receiving the first information, the terminal sends a PDU session reestablishment request message to the target AMF network element. And the PDU session reestablishment request message carries identification information of the network slice related to the first PDU session.

S609: and after receiving the PDU session reestablishment request message, the target AMF network element selects a new network slice example (or called a target network slice example) for the terminal. And selecting a target SMF network element according to the new network slice example.

It should be noted that the source AMF network element may have a capability of determining a network slice instance, in this case, in S602, the source AMF network element may further determine identification information of a new network slice instance, and the identification information of the new network slice instance may be sent to the target AMF network element by the source AMF network element. In this case, the target AMF network element does not need to reselect a new network slice instance when performing S609. Furthermore, in another implementation, the NRF network element may have a capability of determining a network slice instance, in this case, in S602, the NRF network element may determine identification information of a new network slice instance, and the identification information of the new network slice instance may be sent by the NRF network element to the target AMF network element via the source AMF network element. In this case, the target AMF network element does not need to reselect a new network slice instance when performing S609. Although the application is not so limited.

S610: and executing subsequent steps in the PDU session reestablishment process according to the identification of the new network slice example and the target SMF network element.

Fig. 10 is an interaction diagram of a session reestablishment method according to an embodiment of the present application. The present embodiment is specifically another example when the embodiment shown in fig. 4 is applied to a handover procedure. The method shown in fig. 10 comprises the following steps:

s701: reference may be made to S601 described above, although the present application is not limited thereto.

S702: and after the source AMF network element receives the switching request message, executing an AMF network element selection process to determine a target AMF network element.

S703: and the source AMF network element sends the context message to the target AMF network element. The context message carries fourth information, and the fourth information is used for indicating a network slice related to each PDU session in one or more current PDU sessions of the terminal and a network slice instance related to the PDU session. In addition, the context information of the terminal can be carried in the context message.

S704: and after receiving the context message, the target AMF network element determines that part or all of the network slice instances related to the PDU session in the one or more PDU sessions are unavailable and the network slices related to the part or all of the PDU session are available according to the identification information of the network slice supported by the target AMF network element, the identification information of the network slice instances and the fourth information.

For each of the partial or all PDU sessions determined in S704, the following S705 to S713 may be respectively performed.

S705: and the target AMF network element sends the second information to the source AMF network element. Wherein the second information is used to indicate that the first PDU session related network slice instance is not available and the first PDU session related network slice is available. Wherein the first PDU session is any one of the partial or entire PDU sessions determined in S704.

S706: and after receiving the second information, the source AMF network element sends the second information to the source SMF network element.

S707 to S713: reference may be made to the above S604 to S610, although the present application is not limited thereto.

It should be noted that the target AMF network element may have the capability of determining a network slice instance, in this case, in/after S704, the target AMF network element may also determine identification information of a new network slice instance. In this case, the target AMF network element does not need to reselect a new network slice instance when performing S712.

2) Scene without replacing AMF network element

It should be noted that, a scenario in which the AMF network element is not replaced may include: registration process, handover process and process triggered by AMF network element. In this case, reference may be made to the examples shown in fig. 7 to 8 for the example that the embodiment shown in fig. 4 is applied to the registration process, and it can be understood that, since the AMF network element is not replaced, that is, the new AMF network element and the old AMF network element shown in any of fig. 7 and 8 are the same network element, no information interaction is required between the new AMF network element and the old AMF network element. As for the example of applying the embodiment shown in fig. 4 to the handover procedure, reference may be made to the examples shown in fig. 9 to fig. 10, and it can be understood that, since the AMF network element is not replaced, that is, the target AMF network element and the source AMF network element shown in any one of fig. 9 and fig. 10 are the same network element, information interaction between the target AMF network element and the source AMF network element is not required. Those skilled in the art should reasonably deduce that the AMF network element is not replaced without creative efforts, and the embodiment shown in fig. 4 is applied to specific examples in the registration procedure and the handover procedure, and will not be described herein again. In the following, a specific example is described when the embodiment shown in fig. 4 is applied to a flow triggered by an AMF network element.

Fig. 11 is an interaction diagram of a PDU session reestablishment method according to an embodiment of the present application. The present embodiment is an example of the case where the embodiment shown in fig. 4 is applied to a flow triggered by an AMF network element. The method shown in fig. 11 may include the steps of:

s801: and the AMF network element determines that the network slice example related to the first PDU session is unavailable and the network slice related to the first PDU session is available according to the position information of the terminal, the service area of the network slice example related to the first PDU session and the service area of the network slice related to the first PDU session.

As an example, if the current location of the terminal is within the service area of the first PDU session related network slice instance, then the first PDU session related network slice instance is available, otherwise, the first PDU session related network slice instance is not available. If the current position of the terminal is within the service area of the network slice related to the first PDU session, the network slice related to the first PDU session is available, otherwise, the network slice related to the first PDU session is unavailable.

In addition, in the specific implementation process, S801 may be replaced by the following steps: and the AMF network element determines that the network slice instance related to the first PDU session is available and the network slice related to the first PDU session is unavailable according to the position information of the terminal, the service area of the network slice instance related to the first PDU session and the identification information/service area of the replaced network slice instance. It should be noted that, in this case, the AMF network element has the capability of determining the replaced network slice instance. And if the AMF network element determines that the replaced network slice example and the network slice example related to the first PDU session belong to the same network slice, determining that the network slice related to the first PDU session is available, otherwise, determining that the network slice related to the first PDU session is unavailable. The AMF network element can determine that the replaced network slice instance and the network slice instance related to the first PDU session belong to the same network slice through the corresponding relation between the identification information of the network slice instance and the identification information of the network slice to which the network slice instance belongs, or through the corresponding relation between the service area of the network slice instance and the service area of the network slice to which the network slice instance belongs. Although the application is not so limited.

S802: and the AMF network element sends the second information to the old SMF network element. Wherein the second information is used to indicate that the first PDU session related network slice instance is not available and the first PDU session related network slice is available.

S803: and after the old SMF network element receives the second information, determining that a PDU session reestablishment process needs to be initiated.

S804: and the old SMF network element sends the first information to the AMF network element. The first information is used for indicating the terminal to initiate a PDU session reestablishment process.

S805: and the AMF network element sends the first information to the terminal.

S806: and after receiving the first information, the terminal sends a PDU session reestablishment request message to the AMF network element. And the PDU session reestablishment request message carries identification information of the network slice related to the first PDU session.

S807: and after receiving the PDU session reestablishment request message, the AMF network element selects a new network slice example for the terminal. And selecting a new SMF network element according to the new network slice instance. The new SMF network element supports the new network slice instance.

S808: and executing subsequent steps in the PDU session reestablishment process according to the identification information of the new network slice example and the new SMF network element. The subsequent steps in the PDU session reestablishment procedure are described in the prior art, and are not described herein again.

Fig. 12 is an interaction diagram of a PDU session reestablishment method according to an embodiment of the present application. The present embodiment is another example when the embodiment shown in fig. 4 is applied to a flow triggered by an AMF network element. The method shown in fig. 12 may include the steps of:

s901: and the AMF network element determines that the network slice example related to the first PDU session is unavailable according to the position information of the terminal and the service area of the network slice example related to the first PDU session.

S902: and the AMF network element sends the fifth information to the NSSF network element. Wherein the fifth information is used for indicating that the first PDU session related network slice instance is not available.

For example, the fifth information may include identification information of the first PDU session, and information indicating that the network slice instance is unavailable, and the like. Optionally, the fifth information may further include identification information of the network slice instance related to the first PDU session.

S903: and after receiving the fifth information, the NSSF network element sends the identification information of the available network slice instances to the AMF network element. The AMF network element receives identification information of available network slice examples sent by the NSSF network element; wherein the available network slice instance belongs to the same network slice as the network slice instance associated with the first PDU session.

The NSSF network element may be configured to select a network slice for the terminal, determine network slice selection assistance information, and the like. In this application, the NSSF network element may select a network slice instance for the terminal. In one implementation, the NSSF network element may select an available network slice instance for the terminal according to a manner of selecting a network slice instance by any functional network element provided in the prior art, then send identification information of the available network slice instance to the AMF network element, and determine, by the AMF network element, whether the available network slice instance and a network slice associated with the first PDU session belong to the same network slice. In another implementation, if the fifth information includes identification information of a network slice instance related to the first PDU session, the NSSF network element may directly select, as an available network slice instance, one network slice instance belonging to the same network slice as the network slice instance related to the first PDU session, and then send identification information of the available network slice implementation to the AMF network element.

S904 to S910: reference may be made to the above-mentioned S802 to S808, although the present application is not limited thereto.

Scene two, scene that SMF network element is not changed

1) AMF network element replacement scene

Fig. 13 is an interaction diagram of a session reestablishment method according to an embodiment of the present application. The present embodiment is specifically an example of the embodiment shown in fig. 4 when applied to a registration procedure. The method shown in fig. 13 comprises the following steps:

s1001 to S1005: reference may be made to the above S401 to S405, although the present application is not limited thereto.

For each of the one or more PDU sessions determined in S1005, the following S1006 to S1012 may be respectively performed.

S1006: and the old AMF network element sends the second information and the identification information of the new AMF network element to the SMF network element. Wherein the second information is used to indicate that the first PDU session related network slice instance is not available and the first PDU session related network slice is available. The first PDU session is any one of the one or more PDU sessions determined in S1005.

The old AMF network element sends the identification information of the new AMF network element to the SMF network element, so that the SMF network element can know the new AMF network element, and thus the following S1008 can be performed. The identification information of the new AMF network element may be an address of the new AMF network element, and the like. The second information and the identification information of the new AMF network element may be carried in the same message and sent to the SMF network element by the old AMF network element, or may be carried in different messages and sent to the SMF network element by the old AMF network element, which is not limited in the present application.

It can be understood that, before performing the registration procedure, the old AMF network element may select an SMF network element for the terminal, and maintain the corresponding relationship between the identification information of the terminal and the identification information of the SMF network element, so that before performing S1006, the identification information of the SMF network element may be determined, and then S1006 is performed.

S1007: and after receiving the second information, the SMF network element determines that a PDU session reestablishment process needs to be initiated.

S1008: the SMF network element sends the first information to the new AMF network element. The first information is used for indicating the terminal to initiate a PDU session reestablishment process.

It should be noted that, in S1006, the old AMF network element sends the identification information of the new AMF network element to the SMF network element, so that the SMF network element may find the new AMF network element according to the identification information of the new AMF network element, thereby executing the step of sending the first information to the new AMF network element in S1008, which may save a forwarding process of the first information. In addition, in the specific implementation process, if the SMF network element cannot find the new AMF network element according to the identification information of the new AMF network element, the SMF network element may first send the first information to the old AMF network element, and then the old AMF network element sends the first information to the new AMF network element. In addition, in another implementation manner, in S1006, the old AMF network element may not send the identification information of the new AMF network element to the SMF network element, in this case, in S1008, the SMF network element may send the first information to the old AMF network element first, and then the old AMF network element sends the first information to the new AMF network element. Although the application is not so limited.

S1009: and after receiving the first information, the new AMF network element sends the first information to the terminal.

S1010: and after receiving the first information, the terminal sends a PDU session reestablishment request message to the new AMF network element. The PDU session reestablishment request message carries identification information of a network slice related to the first PDU session and information used for indicating that the SMF network element is not changed. The specific implementation manner for indicating that the SMF network element is not changed is not limited in the present application.

S1011: and after receiving the PDU session reestablishment request message, the new AMF network element takes the SMF network element as a new SMF network element, and selects a new network slice example for the terminal in the network slice examples supported by the new SMF network element.

S1012: and executing subsequent steps in the PDU session reestablishment process according to the identification information of the new network slice example and the new SMF network element. The subsequent steps in the PDU session reestablishment procedure are described in the prior art, and are not described herein again.

Fig. 14 is an interaction diagram of a session reestablishment method according to an embodiment of the present application. The present embodiment is specifically another example when the embodiment shown in fig. 4 is applied to a registration flow. The method shown in fig. 14 comprises the following steps:

s1101 to S1103: reference may be made to the above S401 to S403, although the present application is not limited thereto.

S1104: and the new AMF network element sends a context transfer request message to the old AMF network element.

S1105: and after receiving the context transfer request message, the old AMF network element sends a context transfer response message to the new AMF network element. The context transfer response message carries fourth information and identification information of the SMF network element, where the fourth information is used to indicate a network slice related to each PDU session in one or more current PDU sessions of the terminal and a network slice instance related to the PDU session.

The old AMF network element sends the identification information of the SMF network element to the new AMF network element, so that the new AMF network element can know the SMF network element, and thus the following S1107 can be performed. The identification information of the SMF network element may be an address of the SMF network element, or the like. The fourth information and the identification information of the SMF network element may be carried in the same message and sent to the new AMF network element by the old AMF network element, or may be carried in different messages and sent to the new AMF network element by the old AMF network element, which is not limited in the present application.

For any one of the one or more PDU sessions, the following S1106 may be performed.

S1106: and after receiving the context transfer response message, the new AMF network element determines that the network slice instances related to part or all of the PDU sessions in the one or more PDU sessions are unavailable and the network slices related to the part or all of the PDU sessions are available according to the identification information of the network slices supported by the new AMF network element, the identification information of the network slice instances, and the fourth information.

For each of the partial or all PDU sessions determined in S1106, the following S1107 to S1113 may be performed, respectively.

S1107: and the new AMF network element sends the second information to the SMF network element. Wherein the second information is used to indicate that the first PDU session related network slice instance is not available and the first PDU session related network slice is available. Wherein the first PDU session is any one of the partial or all PDU sessions determined in S1106.

It should be noted that, because the old AMF network element sends the identification information of the SMF network element to the new AMF network element in S1105, the new AMF network element may find the SMF network element according to the identification information of the SMF network element, so as to execute the sending of the second information to the SMF network element in S1107, which may save a forwarding procedure of the second information. In addition, in the specific implementation process, if the new AMF network element cannot find the SMF network element according to the identification information of the SMF network element, the new AMF network element may first send the second information to the old AMF network element, and then the old AMF network element sends the second information to the AMF network element. In addition, in another implementation manner, in S1105, the old AMF network element may not send the identification information of the SMF network element to the new AMF network element, in this case, in S1107, the new AMF network element may send the second information to the old AMF network element first, and then the old AMF network element sends the second information to the AMF network element. Although the application is not so limited.

S1108: and after receiving the second information, the SMF network element determines that a PDU session reestablishment process needs to be initiated.

S1109: the SMF network element sends the first information to the new AMF network element. The first information is used for indicating the terminal to initiate a PDU session reestablishment process. For example, the first information may include identification information of the terminal.

Since the SMF network element and the new AMF network element have already had information interaction in S1107, the SMF network element can learn the identification information of the new AMF network element, thereby performing the sending of the first information to the new AMF network element in S1109.

S1110 to S1113: reference may be made to S1009 to S1012, although the present application is not limited thereto.

Fig. 15 is an interaction diagram of a session reestablishment method according to an embodiment of the present application. The present embodiment is specifically an example when the embodiment shown in fig. 4 is applied to a handover procedure. The method shown in fig. 15 comprises the following steps:

s1201 to S1202: reference may be made to the above S601 to S602, although the present application is not limited thereto.

For each of the one or more PDU sessions determined in S1202, the following S1203 to S1209 may be respectively performed.

S1203: and the source AMF network element sends the second information and the identification information of the target AMF network element to the SMF network element. Wherein the second information indicates that the first PDU session related network slice instance is not available and the first PDU session related network slice is available. The first PDU session is any one of the one or more PDU sessions determined in S1202.

S1204: and after receiving the second information, the SMF network element determines that a PDU session reestablishment process needs to be initiated.

S1205: the SMF network element sends the first information to the target AMF network element. The first information is used for indicating the terminal to initiate a PDU session reestablishment process.

S1206: and after receiving the first information, the target AMF network element sends the first information to the terminal.

S1207: and after receiving the first information, the terminal sends a PDU session reestablishment request message to the target AMF network element. The PDU session reestablishment request message carries identification information of a network slice related to the first PDU session and information used for indicating that the SMF network element is not changed. The specific implementation manner for indicating that the SMF network element is not changed is not limited in the present application.

S1208: and after receiving the PDU session reestablishment request message, the target AMF network element takes the SMF network element as a new SMF network element, and selects a new network slice example for the terminal in the network slice examples supported by the new SMF network element.

S1209: and executing subsequent steps in the PDU session reestablishment process according to the identification information of the new network slice example and the new SMF network element. The subsequent steps in the PDU session reestablishment procedure are described in the prior art, and are not described herein again.

Fig. 16 is an interaction diagram of a session reestablishment method according to an embodiment of the present application. The present embodiment is specifically another example when the embodiment shown in fig. 4 is applied to a handover procedure. The method shown in fig. 16 comprises the following steps:

S1301-S1302: reference may be made to the above S701 to S702, although the present application is not limited thereto.

S1303: and the source AMF network element sends the context message to the target AMF network element. The context message carries fourth information and identification information of the SMF network element, and the fourth information is used to indicate a network slice related to each PDU session in one or more current PDU sessions of the terminal and a network slice instance related to the PDU session. In addition, the context information of the terminal can be carried in the context message.

S1304: and after receiving the context message, the target AMF network element determines that part or all of the network slice instances related to the PDU session in the one or more PDU sessions are unavailable and the network slices related to the part or all of the PDU session are available according to the identification information of the network slice supported by the target AMF network element, the identification information of the network slice instances and the fourth information.

For each PDU session of the partial or entire PDU sessions determined in S1304, the following S1305 to S1311 may be respectively performed.

S1305: and the target AMF network element sends the second information to the SMF network element. Wherein the second information is used to indicate that the first PDU session related network slice instance is not available and the first PDU session related network slice is available. Wherein the first PDU session is any one of the partial or entire PDU sessions determined in S1304.

S1306 to S1311: reference may be made to the above S1204 to S1209, although the present application is not limited thereto.

2) Scene without replacing AMF network element

It should be noted that, a scenario in which the AMF network element is not replaced may include: registration process, handover process and process triggered by AMF network element. In this case: as for the example of applying the embodiment shown in fig. 4 to the registration process, reference may be made to the examples shown in fig. 13 to fig. 14, and it can be understood that, since the AMF network element is not replaced, that is, the new AMF network element and the old AMF network element shown in any of fig. 13 and fig. 14 are the same network element, no information interaction is required between the new AMF network element and the old AMF network element. As for the example of applying the embodiment shown in fig. 4 to the handover procedure, reference may be made to the examples shown in fig. 15 to fig. 16, and it can be understood that, since the AMF network element is not replaced, that is, the target AMF network element and the source AMF network element shown in any one of fig. 15 and fig. 16 are the same network element, information interaction between the target AMF network element and the source AMF network element is not required. As for the application of the embodiment shown in fig. 4 to the flow triggered by the AMF network element, reference may be made to the above examples shown in fig. 11 to fig. 12, and it can be understood that, since the AMF network element is not replaced, that is, the new SMF network element and the old SMF network element shown in any of fig. 11 and fig. 12 are the same network element, no information interaction is required between the new SMF network element and the old SMF network element. Those skilled in the art should be able to reasonably deduce that the AMF network element is not replaced without creative labor, and the embodiment shown in fig. 4 is applied to a specific example of a registration procedure, a handover procedure, and a procedure triggered by the AMF network element, and will not be described herein again.

The scheme provided by the embodiment of the application is mainly introduced from the perspective of a method. To implement the above functions, it includes hardware structures and/or software modules for performing the respective functions. Those of skill in the art would readily appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as hardware or combinations of hardware and computer software. Whether a function is performed as hardware or computer software drives hardware depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

In the embodiment of the present application, according to the above method example, a device (including a PCF network element, a first network element, and a UE) for configuring a policy of a UE, or a device (including a UDR network element or a first AMF network element) for determining a PCF network element may perform functional module division, for example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. It should be noted that, in the embodiment of the present application, the division of the module is schematic, and is only one logic function division, and there may be another division manner in actual implementation.

Fig. 17 is a schematic structural diagram of an SMF network element according to an embodiment of the present application. The SMF network element 17 shown in fig. 17 may be configured to perform the steps performed by the corresponding SMF network element in any of the session reestablishment methods provided above. The SMF network element 17 may include: a sending unit 1701, configured to send first information to the terminal when a network slice instance related to a first PDU session of the terminal is unavailable and a network slice related to the first PDU session is available; the first information is used for indicating the terminal to initiate a PDU session reestablishment process. For example, in conjunction with fig. 4 to 6, the SMF network element 17 may be the SMF network element in fig. 4 to 6. The transmission unit 1701 may be used to execute S103 in fig. 4, or to execute S203 in fig. 5, or to execute S303 in fig. 6. For example, the SMF network element 17 may be the old SMF network element in fig. 7, 8, 11, 12. For example, the SMF network element 17 may be the source SMF network element in fig. 9 and 10. The SMF network element 17 may be, for example, the SMF network element in fig. 13 to 16.

Optionally, the SMF network element 17 may further include: a receiving unit 1702, configured to receive second information sent by the first AMF network element; the second information is used for indicating: the first PDU session related network slice instance is not available and the first PDU session related network slice is available. For example, in conjunction with fig. 7, the first AMF network element may be an old AMF network element, and the receiving unit 1702 may be configured to perform the receiving step in S406. For example, in conjunction with fig. 8, the first AMF network element may be a new AMF network element, and the receiving unit 1702 may be configured to perform the receiving step in S508. For example, in conjunction with fig. 9, the first AMF network element may be a source AMF network element, and the receiving unit 1702 may be configured to perform the receiving step in S603. For example, in conjunction with fig. 10, the first AMF network element may be a target AMF network element, and the receiving unit 1702 may be configured to perform the receiving step in S706.

Optionally, the receiving unit 1702 may be specifically configured to receive, by the second AMF network element, the second information sent by the first AMF network element. In the registration procedure, the second AMF network element is an old AMF network element, and the first AMF network element is a new AMF network element, for example, see the example shown in fig. 8. Alternatively, in the handover procedure, the second AMF network element is a source AMF network element, and the first AMF network element is a target AMF network element, for example, refer to the example shown in fig. 10. The first AMF network element does not support the first PDU related network slice instance.

Optionally, the sending unit 1701 is specifically configured to send the first information to the terminal through the third AMF network element and the fourth AMF network element; in the registration process, the third AMF network element is an old AMF network element, and the fourth AMF network element is a new AMF network element, for example, refer to the example shown in fig. 7 or fig. 8; alternatively, in the handover procedure, the third AMF network element is a source AMF network element, and the fourth AMF network element is a target AMF network element, for example, refer to the example shown in fig. 9 or fig. 10. The fourth AMF network element does not support the first PDU session related network slice instance.

Optionally, the sending unit 1701 is specifically configured to send the first information to the fourth AMF network element through the third AMF network element; the first information is carried in a PDU session state message and is sent to the terminal by a fourth AMF network element; the PDU session status message includes: status information of at least one PDU session of the terminal; the state information indicates one of a presence, a release, and a reestablishment; the at least one PDU session includes a first PDU session, the status information of the first PDU session indicating a re-establishment.

Optionally, the sending unit 1701 may be specifically configured to send the first information to the terminal according to the policy information; the policy information is used to indicate: and when the network slice instance related to the first PDU session is unavailable and the network slice instance related to the first PDU session is available, initiating a strategy of a PDU session reestablishment process. Optionally, the policy information is pre-stored locally in the SMF network element 17, or is sent to the SMF network element 17 by the policy control function PCF network element.

Fig. 18 is a schematic structural diagram of a first AMF network element according to an embodiment of the present application. The first AMF network element 18 shown in fig. 18 may be configured to perform the steps performed by the corresponding AMF network element in any of the session re-establishment methods provided above. The first AMF network element 18 may include: a sending unit 1801, configured to send, when a network slice instance related to a first PDU session of the terminal is unavailable and a network slice related to the first PDU session is available, second information to an SMF network element; the second information is used for the SMF network element to send first information to the terminal, and the first information is used for indicating the terminal to initiate a PDU session reestablishment process. For example, in conjunction with fig. 4 or fig. 5, the first AMF network element 18 may be the first AMF network element in fig. 4 or fig. 5. In conjunction with fig. 4, the sending unit 1801 may be configured to execute the sending step in S102 in fig. 4. In conjunction with fig. 5, the sending unit 1801 may be configured to execute the sending step in S202 in fig. 5. For example, referring to fig. 7, the first AMF network element 18 may be an old AMF network element, and the sending unit 1801 may be configured to perform the sending step in S406. For example, in connection with fig. 8, the first AMF network element 18 may be a new AMF network element. Referring to fig. 9, the first AMF network element may be a source AMF network element. Referring to fig. 10, the first AMF network element may be a target AMF network element.

Optionally, the first AMF network element 18 may further include: a receiving unit 1802 and a processing unit 1803.

Optionally, the receiving unit 1802 may be configured to receive third information sent by a second AMF network element or an NRF network element; the third information is used for indicating a network slice example and a network slice supported by the second AMF network element; in the registration procedure, the first AMF network element 18 is an old AMF network element, and the second AMF network element is a new AMF network element, for example, refer to the example shown in fig. 7. Alternatively, in the handover procedure, the first AMF network element 18 is a source AMF network element, and the second AMF network element is a target AMF network element, for example, refer to the example shown in fig. 9. The processing unit 1803 may be configured to determine, according to the third information, that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available if it is determined that the second AMF network element does not support the network slice instance related to the first PDU session and supports the network slice related to the first PDU session. For example, in conjunction with fig. 7, the receiving unit 1802 may be configured to perform the receiving step in S404, and the processing unit 1803 may be configured to perform S405.

Optionally, the receiving unit 1802 may be configured to receive fourth information sent by the second AMF network element or the NRF network element; wherein the fourth information is used for indicating a network slice instance and a network slice related to the first PDU session; in the registration procedure, the first AMF network element 18 is a new AMF network element, and the second AMF network element is an old AMF network element, for example, refer to the example shown in fig. 8. Alternatively, in the handover procedure, the first AMF network element 18 is a target AMF network element, and the second AMF network element is a source AMF network element, for example, refer to the example shown in fig. 10. The processing unit 1803 may be configured to, according to the fourth information, determine that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available if it is determined that the first AMF network element 18 does not support the network slice instance related to the first PDU session and supports the network slice related to the first PDU session. For example, in connection with the example shown in fig. 8, the receiving unit 1802 may be configured to perform the receiving step in S505, and the processing unit 1803 may be configured to perform S506.

Optionally, the processing unit 1803 may be configured to determine that the network slice instance related to the first PDU session is unavailable and the network slice associated with the first PDU session is available according to the location information of the terminal, the service area of the network slice instance related to the first PDU session, and the service area of the network slice related to the first PDU session.

Optionally, the sending unit 1801 is further configured to send fifth information to the NSSF network element; wherein the fifth information is used to indicate that the network slice instance related to the first PDU session is not available, and to indicate that the NSSF network element sends the identification information of the available network slice instance to the first AMF network element 18. A receiving unit 1802, configured to receive identification information of an available network slice instance sent by an NSSF network element; wherein the available network slice instance belongs to the same network slice as the network slice instance associated with the first PDU session. For example, in connection with the example shown in fig. 12, the first AMF network element 18 may be the AMF network element in fig. 2 in this case. The transmitting unit 1801 may be configured to perform the transmitting step in S902. The receiving unit 1802 may be configured to perform the receiving step in S903.

Fig. 19 is a schematic structural diagram of a terminal device according to an embodiment of the present application. The terminal device 19 shown in fig. 19 may be configured to perform the steps performed by the corresponding terminal in any of the session reestablishment methods provided above. The terminal device 19 may include: a receiving unit 1901 and a processing unit 1902.

In a possible example, the receiving unit 1901 may be configured to receive a first information from an SMF network element; wherein the first PDU session related network slice instance of terminal device 19 is unavailable and the first PDU session related network slice is available; the first information is used to instruct the terminal device 19 to initiate a PDU session re-establishment procedure. The processing unit 1902 may be configured to initiate a PDU session reestablishment procedure after the receiving unit 1901 receives the first information. For example, in conjunction with fig. 4-6, the terminal device 19 may be the terminal of fig. 4-6. The receiving unit 1901 may be used to perform the receiving step in S103 in fig. 4, or to perform the receiving step in S193 in fig. 5, or to perform the receiving step in S303 in fig. 6. Correspondingly, the processing unit 1902 may be configured to execute S104 in fig. 4, or execute S194 in fig. 5, or execute S304 in fig. 6.

Optionally, the processing unit 1902 may be specifically configured to, if the information type of the first information is allowed, initiate a PDU session reestablishment procedure when the terminal 19 determines that the PDU session reestablishment procedure needs to be initiated.

In a possible example, the receiving unit 1901 may be configured to receive a PDU session status message sent by an AMF network element; wherein, the PDU conversation state information comprises: status information of at least one PDU session of terminal device 19; the state information indicates one of a presence, a release, and a reestablishment; the at least one PDU session includes a first PDU session, the status information of the first PDU session indicating a re-establishment; after receiving the first information sent by the SMF network element, the AMF network element sends a PDU session status message to the terminal device 19; the first information is used to instruct the terminal device 19 to initiate a PDU session reestablishment procedure; the SMF network element sends the first information to terminal device 19 upon determining that the first PDU session-related network slice instance is not available and that the first PDU session-related network slice is available. The processing unit 1902 may be configured to initiate a PDU session reestablishment procedure after the receiving unit 1901 receives the first information.

The embodiment of the present application further provides a schematic structural diagram of the communication device 2000. The communication device 2000 may include: at least one processor 2001, communication lines 2002, memory 2003, and at least one communication interface 2004. The communication device 2000 may specifically be any one of the SMF network elements (e.g. SMF17), the first AMF network element (e.g. first AMF network element 18) or the terminal (e.g. terminal device 19) provided above. For example, in conjunction with any of fig. 17 to 19, the transmitting unit and the receiving unit may be the communication interface 2004 in fig. 20, and the processing unit may correspond to the processor 2001 or the processor 2007 in fig. 20.

The processor 2001 may be a general-purpose Central Processing Unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more ics for controlling the execution of programs in accordance with the teachings of the present disclosure.

The communication link 2002 may include a path to communicate information between the aforementioned components.

Communication interface 2004, using any transceiver or the like, for communicating with other devices or communication networks, such as ethernet, RAN, Wireless Local Area Networks (WLAN), etc.

The memory 2003 may be, but is not limited to, a read-only memory (ROM) or other type of static storage device that may store static information and instructions, a Random Access Memory (RAM) or other type of dynamic storage device that may store information and instructions, an electrically erasable programmable read-only memory (EEPROM), a compact disk read-only memory (CD-ROM) or other optical disk storage, optical disk storage (including compact disk, laser disk, optical disk, digital versatile disk, blu-ray disk, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. The memory may be separate and coupled to the processor via communication line 2002. The memory may also be integral to the processor.

The memory 2003 is used for storing computer-executable instructions for implementing the embodiments of the present application, and is controlled by the processor 2001. The processor 2001 is used to execute computer-executable instructions stored in the memory 2003 to implement the methods provided by the embodiments described below in the present application.

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

In particular implementations, processor 2001 may include one or more CPUs such as CPU0 and CPU1 in fig. 2, as one embodiment.

In particular implementations, communication device 2000 may include multiple processors, such as processor 2001 and processor 2007 in fig. 2, for one embodiment. Each of these processors may be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. A processor herein may refer to one or more devices, circuits, and/or processing cores for processing data (e.g., computer program instructions).

In particular implementations, communication device 2000 may also include an output device 2005 and an input device 2006, as one embodiment. The output device 2005 is in communication with the processor 2001 and can display information in a variety of ways. For example, the output device 2005 may be a Liquid Crystal Display (LCD), a Light Emitting Diode (LED) display device, a Cathode Ray Tube (CRT) display device, a projector (projector), or the like. The input device 2006 is in communication with the processor 2001 and may receive user input in a variety of ways. For example, the input device 2006 may be a mouse, keyboard, touch screen device, or sensing device, among others.

The communication device 2000 may be a general-purpose device or a special-purpose device. In a specific implementation, the communication device 2000 may be a desktop computer, a laptop computer, a network server, a Personal Digital Assistant (PDA), a mobile phone, a tablet computer, a wireless terminal device, an embedded device, or a device with a similar structure as in fig. 2. The embodiment of the present application does not limit the type of the communication device 2000.

The embodiment of the application also provides a session reestablishing system. The system may include: SMF network element and terminal. Wherein: the SMF network element is used for sending first information to the terminal when a network slice example related to a first PDU session of the terminal is unavailable and a network slice related to the first PDU session is available; the first information is used for indicating the terminal to initiate a PDU session reestablishment process. The terminal is used for receiving the first information and initiating a PDU session reestablishment process.

Optionally, the system may further include a first AMF network element. The first AMF network element is used for determining that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available; and sending the second information to the SMF network element; and the second information is used for the SMF network element to send the first information to the terminal according to the second information. The SMF network element is also used for receiving the second information sent by the first AMF network element.

Optionally, the system may further include a second AMF network element. The SMF network element, configured to receive the second information sent by the first AMF network element, may include: the SMF network element is used for receiving second information sent by the first AMF network element through the second AMF network element; in the registration process, the second AMF network element is an old AMF network element, and the first AMF network element is a new AMF network element; or, in the handover procedure, the second AMF network element is a source AMF network element, and the first AMF network element is a target AMF network element; the first AMF network element does not support the first PDU related network slice instance.

Optionally, the system may further include: a third AMF network element and a fourth AMF network element. The SMF network element is further configured to send first information to the terminal, where the first information may include: the SMF network element is also used for sending first information to the terminal through the third AMF network element and the fourth AMF network element; in the registration process, the third AMF network element is an old AMF network element, and the fourth AMF network element is a new AMF network element; or, in the handover procedure, the third AMF network element is a source AMF network element, and the fourth AMF network element is a target AMF network element; the fourth AMF network element does not support the first PDU session related network slice instance.

Optionally, the SMF network element is further configured to send the first information to the terminal through the third AMF network element and the fourth AMF network element, and the sending may include: the SMF network element is also used for sending the first information to a fourth AMF network element through a third AMF network element; the first information is carried in a PDU session state message and is sent to the terminal by a fourth AMF network element; the PDU session status message includes: status information of at least one PDU session of the terminal; the state information comprises one of a present state, a released state and a rebuilt state; the at least one PDU session includes a first PDU session, the status information of the first PDU session indicating a re-establishment. The terminal is configured to receive the first information from the SMF network element, and may include: and the terminal is used for receiving the PDU session state message sent by the fourth AMF network element.

Optionally, the SMF network element is further configured to send the first information to the terminal, and may include: the SMF network element is also used for sending first information to the terminal according to the strategy information; the policy information is used to indicate: and when the network slice instance related to the first PDU session is unavailable and the network slice instance related to the first PDU session is available, initiating a strategy of a PDU session reestablishment process.

Optionally, the policy information is pre-stored locally in the SMF network element, or is sent to the SMF network element by the PCF network element.

Optionally, the system may further include: a second AMF network element or an NRF network element. The second AMF network element or the NRF network element is used for sending third information to the first AMF network element; the third information is used for indicating a network slice example and a network slice supported by the second AMF network element; in the registration process, the first AMF network element is an old AMF network element, and the second AMF network element is a new AMF network element; or, in the handover procedure, the first AMF network element is a source AMF network element, and the second AMF network element is a target AMF network element. The first AMF network element is configured to determine that the network slice instance associated with the first PDU session is not available and the network slice associated with the first PDU session is available, and may include: the first AMF network element is used for receiving the third information and determining that the second AMF network element does not support the network slice example related to the first PDU session and supports the network slice related to the first PDU session according to the third information.

Optionally, the system may further include: a second AMF network element or an NRF network element. The second AMF network element or the NRF network element is used for sending fourth information to the first AMF network element; wherein the fourth information is used for indicating a network slice instance and a network slice related to the first PDU session; in the registration process, the first AMF network element is a new AMF network element, and the second AMF network element is an old AMF network element; or, in the handover procedure, the first AMF network element is a target AMF network element, and the second AMF network element is a source AMF network element. The first AMF network element is configured to determine that the network slice instance associated with the first PDU session is not available and the network slice associated with the first PDU session is available, and may include: the first AMF network element is used for receiving the fourth information and determining that the first AMF network element does not support the network slice example related to the first PDU session and supports the network slice related to the first PDU session according to the fourth information.

Optionally, the determining, by the first AMF network element, that the network slice instance related to the first PDU session is not available and the network slice related to the first PDU session is available may include: the first AMF network element is used for determining that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available according to the position information of the terminal, the service area of the network slice instance related to the first PDU session and the service area of the network slice related to the first PDU session.

Optionally, the system may further include: an NSSF network element; the first AMF network element is configured to determine that the network slice instance associated with the first PDU session is not available and the network slice associated with the first PDU session is available, and may include: the first AMF network element is used for sending fifth information to the NSSF network element; the fifth information is used for indicating that the network slice instance related to the first PDU session is unavailable and indicating that the NSSF network element sends the identification information of the available network slice instance to the first AMF network element; receiving identification information of available network slice examples sent by the NSSF network element; wherein the available network slice instance belongs to the same network slice as the network slice instance associated with the first PDU session. And the NSSF network element is used for receiving the fifth information and sending the identification information of the available network slice instances to the first AMF network element.

Optionally, the information type of the first information is request or permission. Further optionally, the terminal is configured to initiate a PDU session reestablishment procedure after receiving the first information, and the initiating procedure may include: the terminal is used for initiating the PDU conversation reestablishment process when the first information is received and the PDU conversation reestablishment process needs to be initiated if the information type of the first information is allowed.

For the explanation of the related content in any device (such as the SMF network element, the AMF network element, and the terminal device) and the session reestablishment system provided in the embodiment of the present application and the technical effects that can be obtained, reference may be made to the above method embodiment, and details are not described here again.

In the description of the present application, "/" indicates an OR meaning, for example, A/B may indicate A or B; "and/or" herein is merely an association describing an associated object, and means that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. Also, in the description of the present application, "a plurality" means two or more than two unless otherwise specified. In addition, in order to facilitate clear description of technical solutions of the embodiments of the present application, in the embodiments of the present application, terms such as "first" and "second" are used to distinguish the same items or similar items having substantially the same functions and actions. Those skilled in the art will appreciate that the terms "first," "second," etc. do not denote any order or quantity, nor do the terms "first," "second," etc. denote any order or importance.

The network architecture and the application 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 constitute a limitation to the technical solution provided in the embodiment of the present application, and it is known by those skilled in the art that the technical solution provided in the embodiment of the present application is also applicable to similar technical problems along with the evolution of the network architecture and the appearance of new application scenarios.

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

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

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

Claims

1. A method for session reestablishment, comprising:

a Session Management Function (SMF) network element receives second information sent by a first access and mobility management function (AMF) network element; the second information is used for indicating that: a first packet data unit, PDU, session related network slice instance is unavailable and the first PDU session related network slice is available;

and when the network slice instance related to the first PDU session of the terminal is unavailable and the network slice related to the first PDU session is available, the SMF network element sends first information to the terminal according to second information, wherein the first information is used for indicating the terminal to initiate a PDU session reestablishment process.

2. The method of claim 1, wherein the receiving, by the SMF network element, the second information sent by the first AMF network element comprises:

the SMF network element receives the second information sent by the first AMF network element through a second AMF network element; in the registration process, the second AMF network element is an old AMF network element, and the first AMF network element is a new AMF network element; or, in the handover procedure, the second AMF network element is a source AMF network element, and the first AMF network element is a target AMF network element; the first AMF network element does not support the network slice instance related to the first PDU.

3. The method according to claim 1 or 2, wherein the SMF network element sends the first information to the terminal, including:

the SMF network element sends the first information to the terminal through a third AMF network element and a fourth AMF network element; in the registration process, the third AMF network element is an old AMF network element, and the fourth AMF network element is a new AMF network element; or, in the handover procedure, the third AMF network element is a source AMF network element, and the fourth AMF network element is a target AMF network element; the fourth AMF network element does not support the network slice instance related to the first PDU session.

4. The method of claim 3, wherein the sending, by the SMF network element to the terminal via a third AMF network element and a fourth AMF network element, the first information comprises:

the SMF network element sends the first information to a fourth AMF network element through a third AMF network element; the first information is carried in a PDU session state message and is sent to the terminal by the fourth AMF network element; the PDU session status message includes status information of at least one PDU session of the terminal; the state information indicates one of a presence, a release, and a reestablishment; the at least one PDU session includes the first PDU session, and the status information of the first PDU session indicates a re-establishment.

5. The method according to claim 1 or 2, wherein the SMF network element sends the first information to the terminal, including:

the SMF network element sends the first information to the terminal according to the strategy information; the policy information is used to indicate: and when the network slice instance related to the first PDU session is unavailable and the network slice instance related to the first PDU session is available, initiating a strategy of a PDU session reestablishment process.

6. The method of claim 5, wherein the policy information is pre-stored locally in the SMF network element or is sent to the SMF network element by a Policy Control Function (PCF) network element.

7. A method for session reestablishment, comprising:

when a network slice example related to a first Packet Data Unit (PDU) session of a terminal is unavailable and a network slice related to the first PDU session is available, a first access and mobility management function (AMF) network element sends second information to a Session Management Function (SMF) network element; the second information is used for indicating that: the network slice instance related to the first PDU session is unavailable, the network slice related to the first PDU session is available, the second information is used for the SMF network element to send first information to the terminal according to the second information, and the first information is used for indicating the terminal to initiate a PDU session reestablishment procedure.

8. The method of claim 7, further comprising:

the first AMF network element receives third information sent by a second AMF network element or a network storage function (NRF) network element; wherein the third information is used for indicating a network slice instance and a network slice supported by the second AMF network element; in a registration process, the first AMF network element is an old AMF network element, and the second AMF network element is a new AMF network element; or, in the handover procedure, the first AMF network element is a source AMF network element, and the second AMF network element is a target AMF network element;

and according to the third information, if the first AMF network element determines that the second AMF network element does not support the network slice example related to the first PDU session and supports the network slice related to the first PDU session, determining that the network slice example related to the first PDU session is unavailable and the network slice related to the first PDU session is available.

9. The method of claim 7, further comprising:

the first AMF network element receives fourth information sent by a second AMF network element or an NRF network element; wherein the fourth information is used for indicating a network slice instance and a network slice related to the first PDU session; in a registration process, the first AMF network element is a new AMF network element, and the second AMF network element is an old AMF network element; or, in the handover procedure, the first AMF network element is a target AMF network element, and the second AMF network element is a source AMF network element;

and if the first AMF network element determines that the first AMF network element does not support the network slice example related to the first PDU session and supports the network slice related to the first PDU session according to the fourth information, determining that the network slice example related to the first PDU session is unavailable and the network slice related to the first PDU session is available.

10. The method of claim 7, further comprising:

and the first AMF network element determines that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available according to the position information of the terminal, the service area of the network slice instance related to the first PDU session and the service area of the network slice related to the first PDU session.

11. The method of claim 7, further comprising:

the first AMF network element sends fifth information to a network slice selection function NSSF network element; wherein, the fifth information is used to indicate that the network slice instance related to the first PDU session is unavailable, and indicate that the NSSF network element sends identification information of an available network slice instance to the first AMF network element;

the first AMF network element receives the identification information of the available network slice example sent by the NSSF network element; wherein the available network slice instance belongs to the same network slice as the network slice instance associated with the first PDU session.

12. A method for session reestablishment, comprising:

the terminal receives first information sent to the terminal by a SMF network element according to the second information from a session management function; wherein a first packet data unit, PDU, session related network slice instance of the terminal is unavailable and the first PDU session related network slice is available; the second information is used for indicating that: a network slice instance related to a first Packet Data Unit (PDU) session is unavailable, and a network slice related to the first PDU session is available, wherein the first information is used for indicating the terminal to initiate a PDU session reestablishment process;

and the terminal initiates a PDU session reestablishment process after receiving the first information.

13. The method according to claim 12, wherein the terminal initiates a PDU session re-establishment procedure after receiving the first information, comprising:

and if the information type of the first information is allowed, the terminal initiates a PDU session reestablishment process when determining that the PDU session reestablishment process needs to be initiated.

14. A method for session reestablishment, comprising:

a terminal receives a Packet Data Unit (PDU) session state message sent by an access and mobility management function (AMF) network element; the PDU session status message includes status information of at least one Packet Data Unit (PDU) session of the terminal; the state information indicates one of a presence, a release, and a reestablishment; the at least one PDU session comprises a first PDU session, the status information of the first PDU session indicating re-establishment; the PDU session state message is the PDU session state message sent to the terminal by the AMF network element after receiving the first information sent by the SMF network element according to the second information; the first information is used for indicating the terminal to initiate a PDU session reestablishment process; the second information is used for indicating that: the first PDU session related network slice instance is unavailable and the first PDU session related network slice is available.

15. A session management function, SMF, network element, comprising:

the receiving unit is used for receiving second information sent by the first access and mobility management function (AMF) network element; the second information is used for indicating that: a first packet data unit, PDU, session related network slice instance is unavailable and the first PDU session related network slice is available;

a sending unit, configured to send first information to a terminal according to second information when it is determined that a network slice instance related to the first PDU session of the terminal is unavailable and a network slice related to the first PDU session is available; the first information is used for indicating the terminal to initiate a PDU session reestablishment process.

16. The SMF network element of claim 15,

the receiving unit is specifically configured to receive, by a second AMF network element, the second information sent by the first AMF network element; in the registration process, the second AMF network element is an old AMF network element, and the first AMF network element is a new AMF network element; or, in the handover procedure, the second AMF network element is a source AMF network element, and the first AMF network element is a target AMF network element; the first AMF network element does not support the network slice instance related to the first PDU.

17. The SMF network element according to claim 15 or 16,

the sending unit is specifically configured to send the first information to the terminal through a third AMF network element and a fourth AMF network element; in the registration process, the third AMF network element is an old AMF network element, and the fourth AMF network element is a new AMF network element; or, in the handover procedure, the third AMF network element is a source AMF network element, and the fourth AMF network element is a target AMF network element; the fourth AMF network element does not support the network slice instance related to the first PDU session.

18. The SMF network element of claim 17,

the sending unit is specifically configured to send the first information to a fourth AMF network element through a third AMF network element; the first information is carried in a PDU session state message and is sent to the terminal by the fourth AMF network element; the PDU session status message includes status information of at least one PDU session of the terminal; the state information indicates one of a presence, a release, and a reestablishment; the at least one PDU session includes the first PDU session, and the status information of the first PDU session indicates a re-establishment.

19. The SMF network element according to claim 15 or 16,

the sending unit is specifically configured to send the first information to the terminal according to policy information; the policy information is used to indicate: and when the network slice instance related to the first PDU session is unavailable and the network slice instance related to the first PDU session is available, initiating a strategy of a PDU session reestablishment process.

20. A first access and mobility management function, AMF, network element, comprising:

a sending unit, configured to send second information to a session management function SMF network element when a network slice instance related to a first packet data unit PDU session of a terminal is unavailable and a network slice related to the first PDU session is available; the second information is used for indicating that: the network slice instance related to the first PDU session is unavailable, the network slice related to the first PDU session is available, the second information is used for the SMF network element to send first information to the terminal according to the second information, and the first information is used for indicating the terminal to initiate a PDU session reestablishment procedure.

21. The first AMF network element of claim 20, wherein the first AMF network element further comprises:

the receiving unit is used for receiving third information sent by a second AMF network element or a network storage function (NRF) network element; wherein the third information is used for indicating a network slice instance and a network slice supported by the second AMF network element; in a registration process, the first AMF network element is an old AMF network element, and the second AMF network element is a new AMF network element; or, in the handover procedure, the first AMF network element is a source AMF network element, and the second AMF network element is a target AMF network element;

and a processing unit, configured to determine, according to the third information, that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available if it is determined that the second AMF network element does not support the network slice instance related to the first PDU session and supports the network slice related to the first PDU session.

22. The first AMF network element of claim 20, wherein the first AMF network element further comprises:

a receiving unit, configured to receive fourth information sent by the second AMF network element or the NRF network element; wherein the fourth information is used for indicating a network slice instance and a network slice related to the first PDU session; in a registration process, the first AMF network element is a new AMF network element, and the second AMF network element is an old AMF network element; or, in the handover procedure, the first AMF network element is a target AMF network element, and the second AMF network element is a source AMF network element;

and a processing unit, configured to determine, according to the fourth information, that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available if it is determined that the first AMF network element does not support the network slice instance related to the first PDU session and supports the network slice related to the first PDU session.

23. The first AMF network element of claim 20, wherein the first AMF network element further comprises:

and the processing unit is used for determining that the network slice example related to the first PDU session is unavailable and the network slice related to the first PDU session is available according to the position information of the terminal, the service area of the network slice example related to the first PDU session and the service area of the network slice related to the first PDU session.

24. The first AMF network element of claim 20,

the sending unit is further configured to send fifth information to a network slice selection function NSSF network element; wherein, the fifth information is used to indicate that the network slice instance related to the first PDU session is unavailable, and indicate that the NSSF network element sends identification information of an available network slice instance to the first AMF network element; the first AMF network element further comprises:

a receiving unit, configured to receive identifier information of the available network slice instance sent by the NSSF network element; the available network slice instance belongs to the same network slice as a network slice instance associated with the first PDU session.

25. A terminal device, comprising:

a receiving unit, configured to receive first information sent to the terminal by a SMF network element according to the second information; wherein a first packet data unit, PDU, session related network slice instance of the terminal is unavailable and the first PDU session related network slice is available; the second information is used for indicating that: a network slice instance related to a first Packet Data Unit (PDU) session is unavailable, and a network slice related to the first PDU session is available, wherein the first information is used for indicating the terminal to initiate a PDU session reestablishment process;

and the processing unit is used for initiating a PDU session reestablishment process after the receiving unit receives the first information.

26. The terminal apparatus according to claim 25,

the processing unit is specifically configured to, if the information type of the first information is allowed, initiate a PDU session reestablishment procedure when the terminal device determines that the PDU session reestablishment procedure needs to be initiated.

27. A terminal device, comprising:

the receiving unit is used for receiving a Packet Data Unit (PDU) session state message sent by an access and mobility management function (AMF) network element; wherein the PDU session status message includes: status information of at least one PDU session of the terminal; the state information indicates one of a presence, a release, and a reestablishment; the at least one PDU session comprises a first PDU session, the status information of the first PDU session indicating re-establishment; the PDU session state message is the PDU session state message sent to the terminal by the AMF network element after receiving the first information sent by the SMF network element; the first information is used for indicating the terminal to initiate a PDU session reestablishment process; the first information is information sent to the terminal by the SMF network element according to second information when the SMF network element determines that the network slice instance related to the first PDU session is unavailable and the network slice related to the first PDU session is available; the second information is used for indicating that: the first PDU session related network slice instance is unavailable and the first PDU session related network slice is available;

28. A session reestablishment system, comprising: a session management function, SMF, network element according to any of claims 15 to 19, and a terminal device according to any of claims 25 to 27.

29. The session re-establishment system according to claim 28, further comprising a first access and mobility management function, AMF, network element according to any of claims 20 to 24.

30. A computer readable storage medium comprising computer instructions which, when run on a computer, cause the method of any of claims 1 to 14 to be performed.