CN113163390B

CN113163390B - Roaming user session establishment method, roaming site AMF and roaming site NSSF

Info

Publication number: CN113163390B
Application number: CN202110512690.9A
Authority: CN
Inventors: 张伦泳
Original assignee: China United Network Communications Group Co Ltd
Current assignee: China United Network Communications Group Co Ltd
Priority date: 2021-05-11
Filing date: 2021-05-11
Publication date: 2022-04-26
Anticipated expiration: 2041-05-11
Also published as: CN113163390A

Abstract

The present disclosure provides a roaming user session establishment method based on an AMF, an AMF of a roaming place, an NSSF of a roaming place, a computer device and a storage medium, the method comprising: receiving a PDU session request initiated by UE in a roaming area network; determining whether the request satisfies a condition that the first S-NSSAI cannot be used in the roaming place; if yes, initiating a request of mapping S-NSSAI to a home network to the NSSF of the roaming place so that the NSSF of the roaming place NSSF request the home network allocates a second S-NSSAI which corresponds to the first S-NSSAI and is applied to the UE home place; receiving a second S-NSSAI sent by the roaming place NSSF; a message is sent to the UE attempting to re-initiate the PDU session using the second S-NSSAI to cause the UE to subscribe to the second S-NSSAI and re-initiate the request. The technical scheme of the disclosure can solve the problem that the user cannot obtain the corresponding network fragment in the roaming place.

Description

Roaming user session establishment method, roaming site AMF and roaming site NSSF

Technical Field

The present disclosure belongs to the field of communications technologies, and in particular, to a roaming user session establishment method based on an AMF, an AMF at a roaming site, an NSSF at a roaming site, a computer device, and a computer-readable storage medium.

Background

According to the existing 5G Network specification of 3GPP, after a roaming user registers in a roaming area Network, the roaming user obtains an allowed NSSAI from the roaming area Network according to the NSSAI (Network Slice Selection Assistance Information) subscribed in the home Network and the NSSAI mapping relationship between the home Network and the current roaming area Network.

But the allowed NSSAI obtained from the roaming site Network does not necessarily contain all the S-NSSAIs (Single Network Slice Selection Assistance Information) that need to be used in the roaming site. For example, a user downloads an application in the roaming area network that is available only at the location (area) of the roaming area. This application is not or cannot be used at the home network location (zone) of the user. This results in the home network not having the network slice selection assistance information for the application. Therefore, the user has no subscription to the S-NSSAI matched with the application program in the home network of the user in advance. Therefore, when the user uses the application program in the roaming area network, the corresponding network segment cannot be obtained, and the user experience is reduced.

Disclosure of Invention

The present disclosure provides an Access and Mobility Management Function (AMF) -based roaming user session establishment method, an AMF of a roaming location, a NSSF of a roaming location, a computer device, and a computer-readable storage medium, which can create a session corresponding to a new S-NSSAI requirement for a user when the user enters the new S-NSSAI requirement generated after entering a roaming location Network, and solve a problem that the user cannot obtain a corresponding Network fragment because the home location Network does not have Network fragment Selection auxiliary information for a specific application program at the roaming location.

In a first aspect, an embodiment of the present disclosure provides a roaming user session establishment method based on an access and mobility management function entity, AMF, which is applied to an AMF in a roaming area, and the method includes:

receiving a PDU (Protocol Data Unit) session request initiated by user UE after roaming network registration;

judging whether the PDU session request meets a first preset condition, wherein the first preset condition is that the UE cannot use a first S-NSSAI which needs to be used in a roaming place;

if yes, initiating a request of home network mapping S-NSSAI to the roaming place NSSF, wherein the request of home network mapping S-NSSAI comprises a first S-NSSAI value, so that the roaming place NSSF initiates a request of allocating a second S-NSSAI corresponding to the first S-NSSAI and applied to the UE home network to the NSSF of the home network according to the first S-NSSAI value, so that the NSSF of the home network allocates a second S-NSSAI and returns the second S-NSSAI to the roaming place AMF through the roaming place NSSF, and the service configuration of the second S-NSSAI is completed in a home core network;

receiving the second S-NSSAI;

and sending a message for attempting to reinitiate the PDU session by using the second S-NSSAI to the UE, so that the UE subscribes the second S-NSSAI to a UDM (Unified Data Management entity) of a home network, and reinitiating a PDU session request to the roaming AMF by using the second S-NSSAI after successful subscription, wherein the reinitiated PDU session request comprises the first S-NSSAI corresponding to the second S-NSSAI.

Further, the first preset condition includes: the PDU session request does not carry S-NSSAI;

alternatively, the first and second electrodes may be,

the first preset condition includes: the S-NSSAI carried in the PDU session request is a default S-NSSAI, and the opposite end of the PDU session request meets a second preset condition, wherein the second preset condition is that: and adopting a first S-NSSAI which is different from the default S-NSSAI carried in the PDU session request by the UE which has a session with the opposite terminal and exceeds the preset proportion, wherein the value of the first S-NSSAI is a non-standard S-NSSAI value.

Further, the message for re-initiating the PDU session request includes: the "second S-NSSAI is an indication of the S-NSSAI in the UE' S home network".

Further, the method further comprises:

receiving a message sent by a UDM of a home network that S-NSSAI subscription information of the UE is updated, wherein the message that S-NSSAI subscription information of the UE is updated is sent by the UDM of the home network, and after receiving a request for subscribing the second S-NSSAI initiated by the UE, the UDM of the home network notifies a PCF (Policy Control function) of the home network to update a URSP (UE Route Selection Policy) of the UE, so that the PCF of the home network sends the updated URSP to the UE and then sends the updated URSP to a roaming AMF;

initiating a configuration updating process to the UE, wherein the updated allowed network segment selection auxiliary information configured by the UE includes the first S-NSSAI and a mapping relationship between the first S-NSSAI and the second S-NSSAI, so that the UE re-initiates a PDU session request to the roaming AMF using the second S-NSSAI after completing the configuration updating, and the re-initiated PDU session request includes the first S-NSSAI corresponding to the second S-NSSAI;

receiving a PDU Session request reinitiated by UE, and selecting a network fragment instance and an SMF (Session Management Function) responsible for Session Management for the UE according to a first S-NSSAI in the reinitiated PDU Session request.

In a second aspect, an embodiment of the present disclosure provides an AMF-based roaming user session establishment method, which is applied to a roaming site NSSF, and the method includes:

receiving a home network mapping S-NSSAI request initiated by a roaming AMF, wherein the home network mapping S-NSSAI request is sent by the roaming AMF after receiving a PDU session request initiated by user UE after the roaming AMF registers in a roaming network, and judging that the PDU session request meets a first preset condition; the home network mapping S-NSSAI request includes a value of the first S-NSSAI; the first preset condition is that the UE cannot use the first S-NSSAI which needs to be used in a roaming place;

initiating a request for allocating a second S-NSSAI corresponding to the first S-NSSAI and applied to the UE home network to the NSSF of the home network according to the value of the first S-NSSAI, so that the NSSF of the home network allocates the second S-NSSAI and returns the second S-NSSAI to the NSSF of the roaming place, and completing the service configuration of the second S-NSSAI in the core network of the home place;

and sending the second S-NSSAI to a roaming AMF, so that the roaming AMF receives the second S-NSSAI, sending a message for attempting to reinitiate the PDU session by using the second S-NSSAI to the UE, and enabling the UE to subscribe the second S-NSSAI to the UDM of the home network, and reinitiating the PDU session request to the roaming AMF by using the second S-NSSAI after the subscription is successful, wherein the reinitiated PDU session request comprises the first S-NSSAI corresponding to the second S-NSSAI.

Further, the first preset condition includes:

the PDU session request does not carry S-NSSAI;

alternatively, the first and second electrodes may be,

Further, the initiating, according to the value of the first S-NSSAI, a request for allocating a second S-NSSAI corresponding to the first S-NSSAI and applied to the UE home network to the NSSF of the home network includes:

according to the value of the first S-NSSAI, finding out a network fragmentation parameter corresponding to the value of the first S-NSSAI and a corresponding flow descriptor;

and sending the value of the first S-NSSAI, the corresponding flow descriptor and the corresponding network fragmentation parameter to NSSF of a home network to request the NSSF of the home network to allocate a second S-NSSAI which corresponds to the value of the first S-NSSAI and is applied to the UE home network.

Further, the corresponding network fragmentation parameter includes one or more of the following:

a resource type, the resource type comprising: GBR (Guaranteed Bit Rate), delay-sensitive GBR, non-GBR; a resource scheduling priority; a packet delay tolerance; error rate; an averaging window; a maximum burst tolerance; time delay jitter; packet loss rate; whether to use a reflection Quality of Service (QoS); assigning and retaining priorities.

In a third aspect, an embodiment of the present disclosure provides a roaming location AMF, including:

the first receiving module is arranged to receive a Protocol Data Unit (PDU) session request initiated by User Equipment (UE) after roaming area network registration;

a determining module, configured to determine whether the PDU session request meets a first preset condition, where the first preset condition is that the UE cannot use a first single network segment that the UE needs to use in a roaming area to select an auxiliary information S-NSSAI;

a first sending module, configured to initiate a home network mapping S-NSSAI request to a roaming-location network fragment selection function entity NSSF if the PDU session request meets the first preset condition, where the home network mapping S-NSSAI request includes a first S-NSSAI value, so that the roaming-location NSSF initiates a request for allocating a second S-NSSAI, which corresponds to the first S-NSSAI and is applied to the UE home network, to the NSSF of the home network according to the first S-NSSAI value, so that the NSSF of the home network allocates a second S-NSSAI and returns the second S-NSSAI to the AMF of the roaming location via the roaming-location NSSF, and completes service configuration of the second S-NSSAI in the home core network;

the first receiving module is further configured to receive the second S-NSSAI;

the first sending module is further configured to send a message attempting to re-initiate the PDU session using the second S-NSSAI to the UE, so that the UE subscribes to the second S-NSSAI to a unified data management function entity, UDM, of a home network, and re-initiates a PDU session request to the roaming AMF using the second S-NSSAI after successful subscription, where the re-initiated PDU session request includes a first S-NSSAI corresponding to the second S-NSSAI.

In a fourth aspect, an embodiment of the present disclosure provides a roaming site NSSF, including:

a second receiving module, configured to receive a request for home network mapping single network segment selection auxiliary information S-NSSAI initiated by a roaming AMF, where the request for home network mapping S-NSSAI is sent by the roaming AMF after receiving a protocol data unit PDU session request initiated by a user UE after roaming network registration, and determining that the PDU session request satisfies a first preset condition; the home network mapping S-NSSAI request includes a value of the first S-NSSAI; the first preset condition is that the UE cannot use the first S-NSSAI which needs to be used in a roaming place;

a second sending module, configured to initiate, according to the value of the first S-NSSAI, a request for allocating a second S-NSSAI, which corresponds to the first S-NSSAI and is applied to the UE in the home network, to the NSSF of the home network, so that the NSSF of the home network allocates a second S-NSSAI and returns the second S-NSSAI to the roaming NSSF, and complete service configuration of the second S-NSSAI in the home core network;

the second sending module is further configured to send the second S-NSSAI to the roaming AMF, so that the roaming AMF receives the second S-NSSAI, and send a message to the UE, where the message attempts to re-initiate the PDU session using the second S-NSSAI, so that the UE subscribes to the second S-NSSAI to a unified data management function entity (UDM) of a home network, and re-initiates a PDU session request to the roaming AMF using the second S-NSSAI after the subscription is successful, where the re-initiated PDU session request includes the first S-NSSAI corresponding to the second S-NSSAI.

In a fifth aspect, the disclosed embodiments further provide a computer device, including a memory and a processor, where the memory stores a computer program, and when the processor runs the computer program stored in the memory, the processor executes the AMF-based roaming user session establishment method according to any one of the first and second aspects.

In a sixth aspect, this disclosed embodiment also provides a computer-readable storage medium, including: a computer program which, when run on a computer, causes the computer to perform the AMF-based roaming user session establishment method according to any one of the first and second aspects.

Has the advantages that:

the AMF-based roaming user session establishment method, the AMF of the roaming place, the NSSF of the roaming place, the computer equipment and the computer readable storage medium provided by the disclosure, the AMF of the roaming place receives a PDU session request initiated by user UE after network registration of the roaming place; judging whether the PDU session request meets a first preset condition, wherein the first preset condition is that the UE cannot use a first S-NSSAI which needs to be used in a roaming place; if yes, initiating a request of home network mapping S-NSSAI to the roaming place NSSF, wherein the request of home network mapping S-NSSAI comprises a first S-NSSAI value, so that the roaming place NSSF initiates a request of allocating a second S-NSSAI corresponding to the first S-NSSAI and applied to the UE home network to the NSSF of the home network according to the first S-NSSAI value, so that the NSSF of the home network allocates a second S-NSSAI and returns the second S-NSSAI to the roaming place AMF through the roaming place NSSF, and the service configuration of the second S-NSSAI is completed in a home core network; receiving the second S-NSSAI by the roaming AMF; and sending a message for attempting to reinitiate the PDU session by using the second S-NSSAI to the UE so that the UE subscribes to the second S-NSSAI from the UDM of the home network, and reinitiating a PDU session request to the AMF of the roaming place by using the second S-NSSAI after successful subscription, wherein the reinitiated PDU session request comprises the first S-NSSAI. According to the technical scheme, when the user enters the network of the roaming place and needs a new S-NSSAI, a session corresponding to the new S-NSSAI needs is created for the user, the problem that the user cannot obtain the corresponding network fragment due to the fact that the home network of the user does not select auxiliary information aiming at the network fragment of a specific application program in the roaming place is solved, and user experience is improved.

Drawings

Fig. 1 is a schematic flowchart illustrating a roaming user session establishment method based on AMF according to an embodiment of the present disclosure;

fig. 2 is a schematic flowchart of a roaming user session establishment method based on AMF according to a second embodiment of the present disclosure;

fig. 3 is a schematic flowchart of a roaming user session establishment method based on AMF according to a third embodiment of the present disclosure;

fig. 4 is an architecture diagram of an AMF of a roaming site according to a fourth embodiment of the disclosure;

fig. 5 is an architecture diagram of a roaming site NSSF according to a fifth embodiment of the present disclosure;

fig. 6 is an architecture diagram of a computer device according to a sixth embodiment of the present disclosure.

Detailed Description

In order to make the technical solutions of the present disclosure better understood by those skilled in the art, the present disclosure is further described in detail below with reference to the accompanying drawings and examples.

In which the terminology used in the embodiments of the disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used in the disclosed embodiments and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

In the prior art, the user can use the non-standard S-NSSAI in the roaming place network only when a mapping protocol between the non-standard S-NSSAI values exists between the home network of the user and the roaming place network where the user is located. In the roaming area network, the mapping relationship between the S-NSSAI between the roaming area network and the user home network is stored and managed by the NSSF of the roaming area network, and the allowed NSSAI which can be obtained by the user after the user registers in the roaming area network is determined (by the NSSF of the roaming area network). This determines that when a user needs to use a non-standard (in the roaming network) S-NSSAI in the roaming network, the user must subscribe to the mapping (in the home network) S-NSSAI in the home network in advance. However, in the current situation where smart phones are popularized, after entering a roaming area network, applications that do not exist in a home area network are downloaded and used, which is a common situation. This creates a new demand for S-NSSAI for the user after entering into a roaming network. I.e. requiring S-NSSAI allowed in the roaming network (S), but not subscribing to the corresponding S-NSSAI in the home network in advance; or require that the (one or more) S-NSSAIs allowed in the roaming network, but not subscribe to the corresponding S-NSSAI in the home network (e.g., there is no S-NSSAI in the home network at all that corresponds to the desired S-NSSAI).

The following describes the technical solutions of the present disclosure and how to solve the above problems in detail with specific examples. The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments.

Fig. 1 is a flowchart illustrating a method for establishing a roaming user session based on an access and mobility management function entity AMF according to an embodiment of the present disclosure, where the method is applied to an AMF at a roaming location, as shown in fig. 1, and the method includes:

step S101: receiving a PDU session request initiated after a user UE is registered in a roaming place network;

step S102: judging whether the PDU session request meets a first preset condition, wherein the first preset condition is that the UE cannot use a first S-NSSAI which needs to be used in a roaming place;

step S103: if yes, initiating a request of home network mapping S-NSSAI to the roaming place NSSF, wherein the request of home network mapping S-NSSAI comprises a first S-NSSAI value, so that the roaming place NSSF initiates a request of allocating a second S-NSSAI corresponding to the first S-NSSAI and applied to the UE home network to the NSSF of the home network according to the first S-NSSAI value, so that the NSSF of the home network allocates a second S-NSSAI and returns the second S-NSSAI to the roaming place AMF through the roaming place NSSF, and the service configuration of the second S-NSSAI is completed in a home core network;

step S104: receiving the second S-NSSAI;

step S105: and sending a message for attempting to reinitiate the PDU session by using the second S-NSSAI to the UE so that the UE subscribes to the second S-NSSAI from the UDM of the home network, and reinitiating a PDU session request to the AMF of the roaming place by using the second S-NSSAI after successful subscription, wherein the reinitiated PDU session request comprises the first S-NSSAI corresponding to the second S-NSSAI.

The 5G core Network supports a PDU connection service, which is a service for exchanging PDU packets between the UE and a DN (Data Network, such as an operator service, internet or third party service, etc.); the PDU connection service is implemented by the UE initiating the establishment of a PDU session. After a PDU session is established, a data transmission channel between the UE and the DN is established.

The NSSF of the roaming PLMN maps the subscribed S-NSSAI value to a corresponding S-NSSAI value to be used in the roaming PLMN if the roaming PLMN and the home PLMN have an SLA (Service-Level Agreement) supporting the non-standard S-NSSAI value in the roaming PLMN; the S-NSSAI value to be used in the roaming PLMN is determined by the NSSF of the roaming PLMN based on the SLA.

After the UE is registered in the roaming network, a PDU session request is initiated, wherein the PDU session request comprises user information and slice information. After receiving a PDU session request initiated by a UE after network registration in a roaming area, the AMF in the roaming area identifies, according to parameters carried in the PDU session request, that the UE cannot use a first S-NSSAI session request that needs to be used in the roaming area, that is, there is no S-NSSAI in the home network that directly corresponds to the S-NSSAI (first S-NSSAI) needed for using a specific application in the roaming area, or the AMF in the home network cannot subscribe to the S-NSSAI corresponding to the first S-NSSAI.

In step S103, if the AMF at the roaming location determines that the PDU session request is the first preset condition, the AMF initiates a request for requesting a home network mapping S-NSSAI to the NSSF at the roaming location, where the request includes a first S-NSSAI value. And the roaming NSSF finds out a network slicing parameter corresponding to the first S-NSSAI value and a corresponding Traffic Descriptor (TD) according to the first S-NSSAI value in the AMF request. And sending the first S-NSSAI value, the corresponding flow descriptor and the corresponding network fragmentation parameter to the NSSF of the home network to request the NSSF of the home network to allocate a second S-NSSAI which corresponds to the first S-NSSAI value and is applied to the UE home network. The NSSF of the home network allocates a second S-NSSAI according to the request of the roaming place NSSF, and then interacts with PCF, CHF and UDM of the home network to complete service configuration aiming at the second S-NSSAI, including tariff information and the like. The home network' S NSSF then returns the second S-NSSAI to the roaming destination NSSF. The roaming site NSSF returns the second S-NSSAI to the roaming site AMF.

The AMF of the roaming place receives a second S-NSSAI sent by the NSSF of the roaming place; the UE may be prompted to attempt to re-initiate the PDU session using the second S-NSSAI.

The UE initiates a request for subscribing the second S-NSSAI to the UDM of the home network according to the indication from the AMF of the roaming place, after receiving the request of the UE, the UDM can complete the subsequent NSSAI updating of the UE according to the normal standard flow after completing the subscription of the second S-NSSAI of the UE, and a mapping protocol between the non-standard S-NSSAI values, namely a mapping protocol between the second S-NSSAI value of the home network and the first S-NSSAI value of the roaming place, is formed between the home network of the UE and the network of the roaming place where the UE is located.

If the mapping relationship already exists on the UE, the UE provides a mapping of the S-NSSAI of the Requested NSSAI and the configured S-NSSAI of the home PLMN when constructing the Requested NSSAI.

The Allowed NSSAI carried by the Registration Accept message contains the S-NSSAI used under the roaming-site PLMN.

In the PDU session establishment procedure, the UE includes the following two S-NSSAIs:

(a) S-NSSAI (a); S-NSSAI (a) is the S-NSSAI that matches the application that triggered the PDU session setup request, and (a) is the S-NSSAI value used under the home PLMN.

(b) S-NSSAI (b); S-NSSAI (b) belongs to Allowed NSSAI, S-NSSAI (a) and S-NSSAI (b) are mapping relations, and S-NSSAI (b) is the S-NSSAI value used under the roaming PLMN.

And the UE re-initiates the PDU session, the session comprises a first S-NSSAI, and the roaming AMF selects a network fragment instance and an SMF responsible for session management for the UE according to the first S-NSSAI in the request. When the roaming user is temporarily downloaded in the roaming network and does not subscribe the application corresponding to the S-NSSAI in advance, the establishment of the session corresponding to the S-NSSAI by using the application is realized.

alternatively, the first and second electrodes may be,

Specifically, the AMF determines that the PDU session request does not carry S-NSSAI (i.e., the PDU session is not corresponding to any S-NSSAI) or that the S-NSSAI carried in the session request is a default S-NSSAI (i.e., the UE uses the S-NSSAI mapped to the default S-NSSAI subscribed in the home network), and that an opposite end of the session request (the other end performing the PDU session with the UE) meets a second preset condition, where the second preset condition includes: and the UE which has a session with the opposite terminal and exceeds a preset proportion adopts the first S-NSSAI which is different from the default S-NSSAI carried in the session request, and the value of the first S-NSSAI is a non-standard S-NSSAI value. The preset ratio indicates that the UEs performing sessions with the opposite end generally all use one same S-NSSAI (i.e., the first S-NSSAI), and may specifically be 70%, 80%, 90%, or other numerical values. For example, 90% of the terminals that have a PDU session with an application server have an S-NSSAI value of 0x07FFFFFF (hexadecimal). And the value of the first S-NSSAI is a non-standard S-NSSAI value, and the first S-NSSAI is different from the S-NSSAI carried in the PDU session request, and the AMF at the roaming location cannot establish a data transmission channel between the UE and the opposite end of the session request for the user in the network at the roaming location according to the PUD session.

Further, the message for re-initiating the PDU session request includes indication information that the second S-NSSAI is an S-NSSAI in the UE home network.

And the roaming AMF sends a message for attempting to reinitiate the PDU session by using the second S-NSSAI to the UE, and the UE subscribes the second S-NSSAI to the home core network after receiving the message because the message comprises that the second S-NSSAI is the S-NSSAI in the home network of the UE.

Further, the method further comprises:

receiving a message sent by a UDM of a home network and indicating that S-NSSAI subscription information of the UE is updated, wherein the message sent by the UDM of the home network and indicating that the S-NSSAI subscription information of the UE is updated is used for informing a PCF of the home network to update a URSP of the UE after receiving a request initiated by the UE for subscribing the second S-NSSAI, so that the PCF of the home network sends the updated URSP to the UE and then sends the updated URSP to a roaming AMF;

and receiving a PDU session request reinitiated by the UE, and selecting a network fragment instance and an SMF (simple message format) responsible for session management for the UE according to a first S-NSSAI in the reinitiated PDU session request.

After the AMF at the roaming place sends a message to the UE to enable the UE to subscribe the second S-NSSAI, the UDM of the home network returns a successful subscription message to the UE; the UDM of the home network informs PCF of the home network to update URSP of the UE; PCF of home network sends updated URSP to UE; the URSP comprises NSSP, and the NSSP comprises the corresponding relation between a flow descriptor corresponding to the first S-NSSAI value and the second S-NSSAI; the UDM of the home network informs the roaming AMF UE that the S-NSSAI subscription information is updated. The roaming AMF initiates a configuration update procedure to the UE. The UE allowed NSSAI update is done according to the procedure defined in section 4.2.4 of 3GPP TS 23.502. Wherein the updated allowed NSSAI of the UE comprises the first S-NSSAI and the mapping relation between the first S-NSSAI and the second S-NSSAI. And after the UE completes the configuration updating, the UE re-initiates a PDU session request, wherein the PDU session request comprises the first S-NSSAI. And the roaming AMF selects a roaming area network fragmentation example and an SMF responsible for session management for the UE according to the S-NSSAI in the request so as to establish a data transmission channel between the UE and the session request opposite end in the roaming area network.

In another embodiment of the present disclosure, if steps S103-S104 have been performed for other UEs (belonging to the same network as the current UE) before, and the roaming AMF stores the mapping relationship between the first S-NSSAI requested in step S103 and the second S-NSSAI in the network to which the UE belongs, the roaming AMF determines that the PDU session request satisfies the first preset condition. The AMF directly prompts the UE that it can attempt to re-initiate the PDU session using the second S-NSSAI 1. Which comprises the following steps: the "second S-NSSAI is an indication of the S-NSSAI in the UE' S home network".

According to the embodiment of the disclosure, when the user enters the new S-NSSAI requirement generated after entering the roaming place network, the session corresponding to the new S-NSSAI requirement is created for the user, so that the problem that the user cannot obtain the corresponding network fragment in the roaming place because the home network does not select auxiliary information for the network fragment of the specific application program is solved, and the user experience is improved

Fig. 2 is a flowchart of a roaming user session establishment method based on AMF according to a second embodiment of the present disclosure, which is applied to a roaming site NSSF, and as shown in fig. 2, the method includes:

step S201: receiving a home network mapping S-NSSAI request initiated by a roaming AMF, wherein the home network mapping S-NSSAI request is sent by the roaming AMF after receiving a PDU session request initiated by user UE after the roaming AMF registers in a roaming network, and judging that the PDU session request meets a first preset condition; the home network mapping S-NSSAI request includes a value of the first S-NSSAI; the first preset condition is that the UE cannot use the first S-NSSAI which needs to be used in a roaming place;

step S202: initiating a request for allocating a second S-NSSAI corresponding to the first S-NSSAI and applied to the UE home network to the NSSF of the home network according to the value of the first S-NSSAI, so that the NSSF of the home network allocates the second S-NSSAI and returns the second S-NSSAI to the NSSF of the roaming place, and completing the service configuration of the second S-NSSAI in the core network of the home place;

step S203: and sending the second S-NSSAI to a roaming AMF, so that the roaming AMF receives the second S-NSSAI, sending a message for attempting to reinitiate the PDU session by using the second S-NSSAI to the UE, and enabling the UE to subscribe the second S-NSSAI to the UDM of the home network, and reinitiating the PDU session request to the roaming AMF by using the second S-NSSAI after the subscription is successful, wherein the reinitiated PDU session request comprises the first S-NSSAI corresponding to the second S-NSSAI.

NSSF supports the following functions: selecting a set of network slice instances serving the UE; determining allowed NSSAIs, and if necessary, a mapping to subscribed S-NSSAIs; determining configured NSSAI, and if necessary, a mapping to subscribed S-NSSAI; determining a set of AMFs that may be used to query the UE, or determining a list of candidate AMFs (possibly through query NRFs) based on the configuration; in the embodiment of the present disclosure, after receiving a request for requesting a home network to map S-NSSAI initiated by a roaming AMF, a roaming NSSF determines information such as a session parameter suitable for the first S-NSSAI based on a value of the first S-NSSAI, and requests the NSSF of the home network to allocate an S-NSSAI that is applied to the UE home network and corresponds to the first S-NSSAI value.

The S-NSSAI value contains two parts, an allocation/Service type (SST) and an allocation discriminator (SD). SST takes 1 byte and SD takes 3 bytes. The standard values for the current 5G specification for the team SST are defined:

Slice/Service type	SST value
		eMBB
	1
		URLLC	2
MIoT	3
		V2X	4

namely, only four standard values of 1, 2, 3 and 4 are defined. While SD has no standard value definition. And specifies that when standard SST values are used, there are no SD values. And at the same time, it is stipulated that when the SD value is not used, 3 bytes occupied by SD need to be filled in with 0 xFFFFF. Therefore, for a certain application server, terminals conducting PDU sessions, more than a certain percentage of terminals have adopted an S-NSSAI value of 0x07FFFFFF (hexadecimal), which 0x07FFFFFF actually represents a non-standard S-NSSAI with SST value 0x07 and SD value.

And the NSSF of the home network allocates a second S-NSSAI to return to the NSSF of the roaming place according to the request of the NSSF of the roaming place, and completes the service configuration of the second S-NSSAI in the core network of the home place. Wherein the second S-NSSAI allocated by the NSSF of the home network may be an S-NSSAI that is not applicable to the home network itself, but is specifically set for the corresponding roaming-destination network. The roaming AMF sends the second S-NSSAI to the roaming AMF, the roaming AMF prompts the UE to subscribe the corresponding second S-NSSAI, a configuration updating process is initiated, the UE updated allowed NSSAI comprises the first S-NSSAI and the mapping relation between the first S-NSSAI and the second S-NSSAI, after the UE re-initiates the PDU session, the roaming AMF uses the updated allowed NSSAI to create the session for the UE, as the UE subscribes the second S-NSSAI in the home network which has the mapping relation with the first S-NSSAI in the home network, the roaming AMF can enable the user to use the first S-NSSAI which is not standard in the roaming network to establish the data transmission channel between the UE and the opposite terminal server through the retransmitted PDU session.

Further, the first preset condition includes:

the PDU session request does not carry S-NSSAI;

alternatively, the first and second electrodes may be,

Because the value of the first S-NSSAI that the UE needs to use in the roaming area is a non-standard S-NSSAI value, and the first S-NSSAI is different from the S-NSSAI carried in the PDU session request, the AMF in the roaming area cannot establish a data transmission channel between the UE and the session request peer end in the network in the roaming area according to the PUD session.

The NSSF of the roaming place finds out a network slicing parameter corresponding to the S-NSSAI value and a corresponding Traffic Descriptor (TD) according to the first S-NSSAI value in the AMF request of the roaming place; sending the S-NSSAI value, the corresponding flow descriptor and the corresponding network fragmentation parameter to NSSF of the home network to request the NSSF of the home network to allocate a second S-NSSAI which corresponds to the S-NSSAI value and is applied to the UE home network; the correspondence between the traffic descriptor and the S-NSSAI may be regarded as assigning a corresponding S-NSSAI to a specific traffic descriptor. Specifically, if one traffic descriptor is (OSid, APPid) and the corresponding S-NSSAI value is 0x07FFFFFF, it indicates that the application identified as APPid under the os identified as OSid selects the network slice with the auxiliary information of 0x07ffff when the 5G mobile communication network is used by the application identified as APPid. After the home network allocates a second S-NSSAI, the UE may subscribe to the second S-NSSAI in the home network, and the updated allowed NSSAI of the UE includes the first S-NSSAI and the mapping relationship between the first S-NSSAI and the second S-NSSAI; the UE is enabled to use the non-standard first S-NSSAI in the roaming network.

a resource type, the resource type comprising: guaranteed bit rate, delay sensitive GBR, non-GBR; a resource scheduling priority; a packet delay tolerance; error rate; an averaging window; a maximum burst tolerance; time delay jitter; packet loss rate; whether reflective QoS is used; assigning and retaining priorities.

Specific parameters may include one or more (combinations of) of the following:

resource type: GBR, delay sensitive GBR, non-GBR;

a resource scheduling priority;

a packet delay tolerance;

error rate;

averaging window (valid only for GBR and delay sensitive GBR resource types);

maximum burst tolerance (valid only for delay sensitive GBR resource types);

time delay jitter;

packet loss rate;

whether Reflective QoS Attribute (RQA) is used;

allocation and Retention Priority (ARP);

according to the value of the first S-NSSAI, the network fragmentation parameter corresponding to the value of the first S-NSSAI and the corresponding traffic descriptor are found, so that the NSSF of the home network can find a second S-NSSAI corresponding to the first S-NSSAI value and applied to the UE home network according to the corresponding network fragmentation parameter, and the first S-NSSAI and the second S-NSSAI form a mapping, and the second S-NSSAI can subscribe in the home network, and in particular, the second S-NSSAI may be an S-NSSAI that cannot be applied to the home network itself and is specifically set only for the corresponding roaming network.

In another implementation manner of the embodiment of the present disclosure, if the NSSF of the home network has selected a suitable second S-NSSAI for the first S-NSSAI, and the roaming AMF stores a mapping relationship between the first S-NSSAI and the second S-NSSAI in the UE home network, after the other user sends the PDU session, the roaming AMF determines that the PDU session request of the other user meets the first preset condition. The AMF directly prompts the UE that it can attempt to re-initiate the PDU session using the second S-NSSAI. Which comprises the following steps: the "second S-NSSAI is an indication of the S-NSSAI in the UE' S home network".

According to the embodiment of the disclosure, by selecting the appropriate second S-NSSAI in the home network corresponding to the first S-NSSAI required by the user, when the user enters a new S-NSSAI requirement generated after entering the roaming network, a session corresponding to the new S-NSSAI requirement can be created for the user, and the problem that the user cannot obtain the corresponding network fragment in the roaming place because the home network does not select auxiliary information for the network fragment of the specific application program is solved.

In order to more clearly and completely describe the technical solution of the present disclosure, a third embodiment of the present disclosure further provides an AMF-based roaming user session establishment method, as shown in fig. 3, where the method includes:

step (1): after the UE is registered in a roaming network, a PDU session request is initiated;

step (2): the AMF identifies according to the parameters carried in the session request:

a) the S-NSSAI not carried in the session request (i.e., the PDU session is not mapped to any one S-NSSAI) or carried in the session request is the default S-NSSAI (i.e., the UE uses the S-NSSAI mapped to the default S-NSSAI to which it subscribes in the home network); and the number of the first and second electrodes,

b) the opposite end of the session request (the other end which carries out PDU session with the UE) meets the preset condition; wherein the preset conditions are as follows: in general, a certain same first S-NSSAI is adopted by the UE which carries out conversation with the opposite terminal; for example, among terminals performing a PDU session with an application server, 90% of the terminals adopt an S-NSSAI value of 0x07FFFFFF (hexadecimal); and the number of the first and second electrodes,

c) the values of one and the same first S-NSSAI are adopted in the step b), and are non-standard S-NSSAI values;

d) and all 'in b) adopt a certain same first S-NSSAI' value, which is different from the default S-NSSAI in a);

and (3): the AMF initiates a request to NSSF-V for a home network mapping S-NSSAI with the first S-NSSAI value in (2) b);

and (4): the NSSF-V finds out a network slicing parameter corresponding to a first S-NSSAI value and a corresponding Traffic Descriptor (TD) according to the first S-NSSAI value in the AMF request; sending the first S-NSSAI value, the corresponding flow descriptor and the corresponding network fragmentation parameter to NSSF-H for requesting the NSSF-H to allocate a second S-NSSAI which is corresponding to the first S-NSSAI value and is applied to the UE home network; wherein the specific parameters may include one or more (combination of) of the following:

a) resource type: guaranteed Bit Rate (GBR), delay sensitive GBR, non-GBR;

b) a resource scheduling priority;

c) a packet delay tolerance;

d) error rate;

e) averaging window (valid only for GBR and delay sensitive GBR resource types);

f) maximum burst tolerance (valid only for delay sensitive GBR resource types);

g) time delay jitter;

h) packet loss rate;

i) whether Reflective QoS Attribute (RQA) is used;

j) allocation and Retention Priority (ARP);

and (5): the NSSF-H allocates a second S-NSSAI according to the request of the NSSF-V, and then interacts with the PCF, the CHF and the UDM to complete service configuration aiming at the second S-NSSAI, wherein the service configuration comprises tariff information and the like;

and (6): NSSF-H returns the second S-NSSAI to NSSF-V;

and (7): NSSF-V returns the second S-NSSAI to AMF;

and (8): the AMF prompts the UE to attempt to re-initiate the PDU session using the second S-NSSAI. Which comprises the following steps: "second S-NSSAI is an indication of S-NSSAI in the UE home network";

and (9): the UE initiates a request for subscribing the second S-NSSAI to the UDM according to the indication from the AMF;

step (10): the UDM returns a successful subscription message to the UE;

step (11): the UDM informs PCF to update URSP of UE;

step (12): PCF sends updated URSP to UE;

step (13): the UDM informs the AMF UE that S-NSSAI subscription information is updated;

step (14): the AMF initiates a configuration updating process to the UE;

step (15): the UE allowed NSSAI update is done according to the procedure defined in section 4.2.4 of 3GPP TS 23.502. Wherein, the updated allowed NSSAI of the UE includes the first S-NSSAI in step (4) and the mapping relationship between the first S-NSSAI in step (4) and the second S-NSSAI1 in step (5);

step (16): after the UE completes the configuration update, the UE re-initiates the session request in (1), wherein the session request comprises the first S-NSSAI in (4);

step (17): the AMF selects a network fragment instance and an SMF responsible for session management (session management function entity in the roaming network, not shown in the figure) for the UE according to the first S-NSSAI in the request.

Description of the drawings: the "-V" in fig. 3 indicates a device in the roaming network where the UE is currently located, and the "-H" indicates a device in the home network of the UE. The text description of the working process is for convenience, without "-V" and "-H".

NSSAI is a set of one or more S-NSSAIs.

In step (2), the S-NSSAI value includes two parts, namely, an allocation/Service type (SST) and an allocation discriminator (SD). SST takes 1 byte and SD takes 3 bytes. The standard values for the current 5G specification for the team SST are defined:

Slice/Service type	SST value
		eMBB
	1
		URLLC	2
MIoT	3
		V2X	4

namely, only four standard values of 1, 2, 3 and 4 are defined. While SD has no standard value definition. And specifies that when standard SST values are used, there are no SD values. And at the same time, it is stipulated that when the SD value is not used, 3 bytes occupied by SD need to be filled in with 0 xFFFFF. Thus 0x07FFFFFF in step (2) b) actually represents a non-standard S-NSSAI with SST value 0x07 and with SD value.

In step (3), if step (3) has been performed for other UEs (belonging to the same network as the current UE) and the AMF stores the mapping relationship between the first S-NSSAI (in step (2) b) and the second S-NSSAI in the network to which the UE belongs, which is requested in step (3), step (3) to step (7) are skipped and step (8) is directly performed.

In the step (4), the correspondence between the traffic descriptor and the S-NSSAI may be regarded as allocating a corresponding S-NSSAI to a specific traffic descriptor. Specifically, if one traffic descriptor is (OSid, APPid) and the corresponding S-NSSAI value is 0x07FFFFFF, it indicates that the application identified as APPid under the os identified as OSid selects the network slice with the auxiliary information of 0x07ffff when the 5G mobile communication network is used by the application identified as APPid.

The second S-NSSAI allocated in step (5) may not be applicable to the home network itself, and is specifically set only for the corresponding roaming-destination network.

The URSPs in step (11) and step (12) include NSSP, and the NSSP includes the correspondence between the traffic descriptor in step (4) and the second S-NSSAI in step (5).

Fig. 4 is an architecture diagram of a roaming-place AMF according to a fourth embodiment of the present disclosure, as shown in fig. 4, the roaming-place AMF includes:

a first receiving module 11, configured to receive a protocol data unit PDU session request initiated by a user UE after roaming local network registration;

a determining module 12, configured to determine whether the PDU session request meets a first preset condition, where the first preset condition is that the UE cannot use a first single network segment that the UE needs to use in a roaming area to select an auxiliary information S-NSSAI;

a first sending module 13, configured to initiate a home network mapping S-NSSAI request to a roaming-location network fragment selection function entity NSSF if the PDU session request meets the first preset condition, where the home network mapping S-NSSAI request includes a value of a first S-NSSAI, so that the roaming-location NSSF initiates a request for allocating, to the NSSF of the home network, a second S-NSSAI corresponding to the first S-NSSAI and applied to a second S-NSSAI in the UE home network according to the value of the first S-NSSAI, so that the NSSF of the home network allocates a second S-NSSAI and returns the second S-NSSAI to the AMF of the roaming-location via the NSSF, and completes service configuration of the second S-NSSAI in the core network of the roaming-location;

the first receiving module 11 is further configured to receive the second S-NSSAI;

the first sending module 13 is further configured to send a message attempting to re-initiate the PDU session using the second S-NSSAI to the UE, so that the UE subscribes to the second S-NSSAI to a unified data management function entity, UDM, of the home network, and re-initiate a PDU session request to the roaming AMF using the second S-NSSAI after successful subscription, where the re-initiated PDU session request includes a first S-NSSAI corresponding to the second S-NSSAI.

Further, the first preset condition includes:

the PDU session request does not carry S-NSSAI;

alternatively, the first and second electrodes may be,

Further, the roaming AMF further comprises a selection module 14;

the first receiving module 11 is further configured to receive a message that S-NSSAI subscription information of the UE is updated, where the message that S-NSSAI subscription information of the UE is updated is sent by the UDM of the home network, and after receiving a request for subscribing to the second S-NSSAI, initiated by the UE, the UDM of the home network notifies the PCF of the home network to update the URSP of the UE, so that the PCF of the home network sends the updated URSP to the UE and then sends the updated URSP to the AMF of the roaming destination;

the first sending module 13 is further configured to initiate a configuration update process to the UE, where the updated allowed network segment selection auxiliary information configured by the UE includes the first S-NSSAI and a mapping relationship between the first S-NSSAI and the second S-NSSAI, so that the UE uses the second S-NSSAI to reinitiate a PDU session request to the roaming AMF after completing the configuration update, where the reinitiated PDU session request includes the first S-NSSAI corresponding to the second S-NSSAI;

the selecting module 14 is configured to select a network fragmentation instance and an SMF responsible for session management for the UE according to a first S-NSSAI in the re-initiated PDU session request after the first receiving module 11 receives the PDU session request re-initiated by the UE.

Fig. 5 is an architecture diagram of a roaming location NSSF according to a fifth embodiment of the present disclosure, and as shown in fig. 5, the roaming location NSSF includes:

a second receiving module 21, configured to receive a request for home network mapping single network segment selection auxiliary information S-NSSAI initiated by a roaming AMF, where the request for home network mapping S-NSSAI is sent by the roaming AMF after receiving a protocol data unit PDU session request initiated by a user UE after roaming network registration, and determining that the PDU session request satisfies a first preset condition; the home network mapping S-NSSAI request includes a value of the first S-NSSAI; the first preset condition is that the UE cannot use the first S-NSSAI which needs to be used in a roaming place;

a second sending module 22, configured to initiate, according to the value of the first S-NSSAI, a request for allocating a second S-NSSAI, which corresponds to the first S-NSSAI and is applied to the UE in the home network, to the NSSF of the home network, so that the NSSF of the home network allocates a second S-NSSAI and returns the second S-NSSAI to the roaming NSSF, and complete service configuration of the second S-NSSAI in the home core network;

the second sending module 22 is further configured to send the second S-NSSAI to the roaming AMF, so that the roaming AMF receives the second S-NSSAI, and send a message to the UE, where the message attempts to re-initiate the PDU session using the second S-NSSAI, so that the UE subscribes to the second S-NSSAI to a unified data management function entity UDM of a home network, and re-initiates a PDU session request to the roaming AMF using the second S-NSSAI after the subscription is successful, where the re-initiated PDU session request includes the first S-NSSAI corresponding to the second S-NSSAI.

Further, the first preset condition includes:

the PDU session request does not carry S-NSSAI;

alternatively, the first and second electrodes may be,

Further, the second sending module 22 includes:

a searching unit, configured to find out a network fragmentation parameter corresponding to the value of the first S-NSSAI and a corresponding traffic descriptor according to the value of the first S-NSSAI;

a sending unit configured to send the value of the first S-NSSAI, the corresponding traffic descriptor, and the corresponding network fragmentation parameter to the NSSF of the home network to request the NSSF of the home network to allocate a second S-NSSAI applied to the UE home network corresponding to the value of the first S-NSSAI.

a resource type, the resource type comprising: guaranteed bit rate GBR, delay sensitive GBR, non-GBR; a resource scheduling priority; a packet delay tolerance; error rate; an averaging window; a maximum burst tolerance; time delay jitter; packet loss rate; whether to use a reflective quality of service QoS; assigning and retaining priorities.

The roaming AMF and the roaming NSSF in the embodiment of the present disclosure are used to implement the method for establishing a roaming user session based on the AMF in the first method embodiment and the second method embodiment, so that description is simple, and reference may be specifically made to the related descriptions in the first to third method embodiments, and details are not repeated here.

Furthermore, as shown in fig. 6, a computer device according to a sixth embodiment of the present disclosure is further provided, which includes a memory 10 and a processor 20, where the memory 10 stores a computer program, and when the processor 20 runs the computer program stored in the memory 10, the processor 20 executes the above-mentioned various possible AMF-based roaming user session establishment methods.

In addition, the embodiments of the present disclosure also provide a computer-readable storage medium, in which computer-executable instructions are stored, and when at least one processor of the user equipment executes the computer-executable instructions, the user equipment executes the above-mentioned various possible methods.

Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. Of course, the storage medium may also be integral to the processor. The processor and the storage medium may reside in an ASIC (Application Specific Integrated Circuit). Additionally, the ASIC may reside in user equipment. Of course, the processor and the storage medium may reside as discrete components in a communication device.

It is to be understood that the above embodiments are merely exemplary embodiments that are employed to illustrate the principles of the present disclosure, and that the present disclosure is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the disclosure, and these are to be considered as the scope of the disclosure.

Claims

1. A roaming user session establishment method based on an access and mobility management function (AMF) is applied to a roaming AMF, and is characterized in that the method comprises the following steps:

receiving a Protocol Data Unit (PDU) session request initiated by User Equipment (UE) after roaming network registration;

judging whether the PDU session request meets a first preset condition, wherein the first preset condition is that the UE cannot use a first single network fragment which needs to be used by the UE in a roaming place to select auxiliary information S-NSSAI;

if yes, initiating a request of home network mapping S-NSSAI to a roaming place network fragment selection function entity NSSF, wherein the request of home network mapping S-NSSAI comprises a first S-NSSAI value, so that a roaming place NSSF initiates a request of allocating a second S-NSSAI corresponding to the first S-NSSAI and applied to the UE home network to the NSSF of the home network according to the first S-NSSAI value, so that the NSSF of the home network allocates a second S-NSSAI and returns the second S-NSSAI to the roaming place AMF through the roaming place NSSF, and completing service configuration of the second S-NSSAI in a home place core network;

receiving the second S-NSSAI;

and sending a message for attempting to reinitiate the PDU session by using the second S-NSSAI to the UE so that the UE subscribes to the second S-NSSAI from a unified data management function entity (UDM) of a home network, and reinitiating a PDU session request to the roaming AMF by using the second S-NSSAI after successful subscription, wherein the reinitiated PDU session request comprises a first S-NSSAI corresponding to the second S-NSSAI.

2. The method for establishing a session of a roaming user as claimed in claim 1, wherein the first preset condition comprises: the PDU session request does not carry S-NSSAI;

alternatively, the first and second electrodes may be,

3. The method of claim 1, wherein the message for re-initiating the PDU session request comprises: the "second S-NSSAI is an indication of the S-NSSAI in the UE' S home network".

4. The method of claim 1, wherein the method further comprises:

receiving a message sent by a UDM of a home network and indicating that S-NSSAI subscription information of UE is updated, wherein the message sent by the UDM of the home network and indicating that the S-NSSAI subscription information of the UE is updated is used for informing a policy control function entity PCF of the home network to update a UE routing policy URSP of the UE after receiving a request initiated by the UE for subscribing the second S-NSSAI, so that the PCF of the home network sends the updated URSP to the UE and then sends the updated URSP to a roaming place AMF;

and receiving a PDU session request reinitiated by the UE, and selecting a network fragment instance and a session management function entity (SMF) responsible for session management for the UE according to a first S-NSSAI in the reinitiated PDU session request.

5. A roaming user session establishment method based on access and mobility management function (AMF) is applied to a roaming area network fragmentation selection function (NSSF), and is characterized in that the method comprises the following steps:

receiving a request of home network mapping single network fragmentation selection auxiliary information S-NSSAI initiated by a roaming place AMF, wherein the request of home network mapping S-NSSAI is sent by the roaming place AMF after receiving a Protocol Data Unit (PDU) session request initiated by user UE after roaming place network registration and judging that the PDU session request meets a first preset condition; the request for mapping S-NSSAI by the home network comprises a value of a first S-NSSAI; the first preset condition is that the UE cannot use the first S-NSSAI which needs to be used in a roaming place;

and sending the second S-NSSAI to a roaming AMF, so that the roaming AMF receives the second S-NSSAI, sending a message for attempting to reinitiate the PDU session by using the second S-NSSAI to the UE, and enabling the UE to subscribe the second S-NSSAI to a unified data management function entity (UDM) of a home network, and reinitiating the PDU session request to the roaming AMF by using the second S-NSSAI after the subscription is successful, wherein the reinitiated PDU session request comprises the first S-NSSAI corresponding to the second S-NSSAI.

6. The method for establishing a session of a roaming user as claimed in claim 5, wherein the first preset condition comprises:

the PDU session request does not carry S-NSSAI;

alternatively, the first and second electrodes may be,

7. The method of claim 5, wherein the initiating a request to assign a second S-NSSAI corresponding to the first S-NSSAI and applicable to the UE home network to the home network NSSF according to the value of the first S-NSSAI comprises:

8. The method of claim 7, wherein the corresponding network fragmentation parameters include one or more of the following:

9. A roaming access and mobility management function, AMF, comprising:

the first receiving module is further configured to receive the second S-NSSAI;

10. A roaming-home network segment selection function entity NSSF, comprising:

a second receiving module, configured to receive a request for home network mapping single network segment selection auxiliary information S-NSSAI initiated by a roaming AMF, where the request for home network mapping S-NSSAI is sent by the roaming AMF after receiving a protocol data unit PDU session request initiated by a user UE after roaming network registration, and determining that the PDU session request satisfies a first preset condition; the request for mapping S-NSSAI by the home network comprises a value of a first S-NSSAI; the first preset condition is that the UE cannot use the first S-NSSAI which needs to be used in a roaming place;

11. A computer arrangement, characterized in that it comprises a memory in which a computer program is stored and a processor, which, when executing the computer program stored by the memory, executes the access and mobility management function entity, AMF, roaming user session establishment method according to any of claims 1-4 and claims 5-8.

12. A computer-readable storage medium, comprising: computer program which, when run on a computer, causes the computer to perform a method for roaming user session establishment based on an access and mobility management function entity, AMF, according to any of claims 1-4 and claims 5-8.