Policy-based access and mobility management function selection using network slice selection assistance information availability information

Abstract

A method for providing policy-based access and mobility management function (AMF) selection using network slice selection assistance information (NSSAI) availability information obtained from a NSSAI availability service, comprising, at a network slice selection function (NSSF) comprising at least one processor, obtaining NSSAI availability information about a plurality of AMFs from an NSSAI availability service. The method further comprises receiving a network slice selection request specifying a network slice service requested by a user equipment (UE) from a first AMF. The method further comprises generating a prioritized list based on the NSSAI availability information and the network slice service requested by the UE, the list comprising an identity of at least one AMF for supporting the network slice service. The method further comprises transmitting the prioritized list to the first AMF.

Description

[0001] Priority claim

[0002] This application claims priority to U.S. patent application serial No. 16 / 676,006, filed on November 6, 2019, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The subject matter described herein relates to network slicing. More specifically, the subject matter described herein relates to methods, systems, and computer-readable media for providing policy-based AMF selection using NSSAI availability information. Background Art

[0004] In 5G telecommunication networks, a network node that provides services is called a producer network function (NF). A network node that consumes services is called a consumer NF. A network function can be both a producer NF and a consumer NF, depending on whether it is consuming or providing services.

[0005] A given producer NF may have many service endpoints, where a service endpoint is a combination of an IP address and a port number on the network node hosting the producer NF. Producer NFs register with the Network Function Repository Function (NRF). NRF maintains NF profiles of available NF instances and the services they support. Consumer NFs can subscribe to receive information about producer NF instances that have registered with NRF.

[0006] An example of a NF that provides services to user equipment (UE) devices such as Internet of Things (IoT) devices is the Access and Mobility Management Function or AMF. The AMF provides registration management, connection management, reachability management, mobility management, and other services for UE devices. The AMF acts as a point of contact between the radio access network and the rest of the nodes in the 5G core network. The AMF also serves as a point of access to network slicing services.

[0007] There may be many AMFs serving a specific transport area (TA) where the UE is located. It is desirable to optimize AMF resource utilization and, in particular, if network slicing is implemented. Network slicing is a service provided in 5G networks where network resources are logically allocated in parts or slices for use by UE devices. Each network slice may provide specific capabilities or services to the UE. Different network slices and capabilities may be accessed via different AMFs. In addition, the same AMF may provide access to different capabilities or network slices.

[0008] When a UE registers with a public land mobile network (PLMN), during the registration process, the UE may transmit requested NSSAI information to the network, which indicates the type of network slice service requested by the UE. If the radio access node that receives the NSSAI information from the UE is able to identify an AMF that can provide access to the requested network slice service, the radio access node forwards the registration request to the AMF, and the AMF provides access to the requested network slice service. However, in some cases, the radio access node may not be able to identify an AMF that can provide access to the requested network slice service. An example of this is when the requested NSSAI from the UE in the non-access stratum (NAS) registration request message is not the NSSAI configured for the PLMN, the NSSAI allowed for the PLMN and access type, or the default configured NSSAI. In such cases, the radio point access node routes the NAS signaling to the default AMF.

[0009] When the UE context in the default AMF does not yet include an allowed NSSAI corresponding to the access type requested by or for the UE, the AMF queries the Network Slice Selection Function (NSSF) to identify an AMF that can provide access to the requested network slice services. In another example, the network may decide to reassign the UE to an AMF different from the AMF that originally received the initial registration request.

[0010] According to 3GPP TS23.501, the network slice selection function provides two different services, called N NSSF _NS Selection Service (hereinafter referred to as "NS Selection Service") and N NSSF _NSSAI Availability Service (hereinafter referred to as "NSSAI Availability Service"). NS selection service includes providing network slice information to the requester. NSSAI Availability Service suggests the availability of subscribed NSSAI (S-NSSAI) to NF consumers on a per TA basis.

[0011] One problem with the existing 3GPP service architecture is the decoupling of the NSSAI availability service and the NS selection service. In other words, 3GPP TS23.501 does not specify how to use the NSSAI availability service to optimize AMF selection in the most efficient way to allocate AMF and network slice resources accessible via AMF.

[0012] For example, clause 5.15.5.2.1 of 3GPP TS23.501 indicates that when multiple network slice instances in the transport area of ​​the UE are capable of providing services based on the operator's NSSAI (S-NSSAI) configured for a given subscription, the NSSF may select one of the network slice instances to serve the UE. A network slice instance is a collection of NF instances and the resources required to constitute a deployed network slice. The AMF is a network node that provides access to a network slice instance. By leaving the selection of a network slice instance and the corresponding AMF to the discretion of the network operator, 3GPP TS23.501 does not define a process to optimize such selection. Therefore, even though the AMF can provide NSSAI availability information to the NSSF, 3GPP TS23.501 does not specify how this information is used. In addition, other information (such as AMF payload) is not specified as part of the NS selection process.

[0013] Thus, what is needed are methods, systems, and computer-readable media for providing policy-based AMF selection based on NSSAI availability information obtained from an NSSAI availability service. Summary of the invention

[0014] A method for providing policy-based access and mobility management function (AMF) selection using network slice selection assistance information (NSSAI) availability information obtained from a NSSAI availability service, comprising, at a network slice selection function (NSSF) comprising at least one processor, obtaining NSSAI availability information about a plurality of AMFs from an NSSAI availability service. The method further comprises receiving a network slice selection request specifying a network slice service requested by a user equipment (UE) from a first AMF. The method further comprises generating a prioritized list based on the NSSAI availability information and the network slice service requested by the UE, the list comprising an identity of at least one AMF for supporting the network slice service. The method further comprises transmitting the prioritized list to the first AMF.

[0015] According to another aspect of the subject matter described herein, obtaining NSSAI availability information includes receiving Hypertext Transfer Protocol (HTTP) messages from the AMF, wherein each HTTP message indicates NSSAI supported for each Transport Area (TA) of one of the AMF.

[0016] According to yet another aspect of the subject matter described herein, receiving a network slice selection request includes receiving a network slice selection request including at least one NSSAI identifying a network slice service requested by the UE.

[0017] According to another aspect of the subject matter described herein, generating a prioritized list includes prioritizing a second AMF that supports a requested network slice service over a third AMF that supports the requested network slice service and that supports a greater number of network slice services other than the requested network slice service than the second AMF.

[0018] According to yet another aspect of the subject matter described herein, prioritizing the second AMF over the third AMF comprises calculating a correlation R for the second and third AMFs, where R is equal to C / T, where C is equal to the number of common NSSAIs between the NSSAI requested by the UE and the NSSAIs supported by the second or third AMF and T is equal to the total number of NSSAIs supported by the second or third AMF.

[0019] According to yet another aspect of the subject matter described herein, a method for providing policy-based AMF selection includes obtaining a load percentage of each AMF.

[0020] According to yet another aspect of the subject matter described herein, obtaining the load percentage includes obtaining the load percentage from a network function repository function (NRF).

[0021] According to yet another aspect of the subject matter described herein, generating the prioritized list includes calculating a weight W for the second and third AMFs, wherein the weight W is equal to R / L, and L is a load percentage of the second or third AMF.

[0022] According to yet another aspect of the subject matter described herein, transmitting the prioritized list to the first AMF comprises transmitting the AMF identities of the second and third AMFs and the weights calculated for the second and third AMFs to the first AMF.

[0023] According to a further aspect of the subject matter described herein, transmitting the prioritized list to the first AMF comprises transmitting the AMF identities of the second and third AMF in an order corresponding to the weights calculated for the second and third AMF.

[0024] According to another aspect of the subject matter described herein, there is provided a system for providing policy-based access and mobility management function (AMF) selection using network slice selection assistance information (NSSAI) availability information obtained from a NSSAI availability service. The system includes a network slice selection function (NSSF) comprising at least one processor. The system also includes an access and mobility management function (AMF) prioritizer implemented by at least one processor for obtaining NSSAI availability information about multiple AMFs using the NSSAI availability service, receiving a network slice selection request specifying a network slice service requested by a user equipment (UE) from a first AMF, generating a prioritized list based on the NSSAI availability information and the network slice service requested by the UE, the list including the identity of at least one AMF for supporting the network slice service, and for transmitting the prioritized list to the first AMF.

[0025] According to yet another aspect of the subject matter described herein, the AMF prioritizer is configured to obtain NSSAI availability information by receiving Hypertext Transfer Protocol (HTTP) messages from the AMF, and each HTTP message indicates NSSAI supported for each Transport Area (TA) of one of the AMFs.

[0026] According to yet another aspect of the subject matter described herein, the network slice selection request includes at least one NSSAI identifying the network slice service requested by the UE.

[0027] According to another aspect of the subject matter described herein, the AMF prioritizer is configured to generate a prioritized list by prioritizing a second AMF that will support a requested network slice service over a third AMF that supports the requested network slice service and supports a greater number of network slice services other than the requested network slice service than the second AMF.

[0028] According to yet another aspect of the subject matter described herein, the AMF prioritizer is configured to prioritize the second AMF over the third AMF by calculating a correlation R of the second and third AMFs, where R=C / T, where C equals the number of common NSSAIs between the NSSAI requested by the UE and the NSSAIs supported by the second or third AMF and T equals the total number of NSSAIs supported by the second or third AMF.

[0029] According to another aspect of the subject matter described herein, the AMF prioritizer is configured to obtain the load percentages of the second and third AMFs and calculate a weight value W for the second and third AMFs, wherein the weight value W for the second or third AMF is equal to R / L and L is the load percentage of the second or third AMF.

[0030] According to yet another aspect of the subject matter described herein, the AMF prioritizer is configured to obtain a load percentage from a network function repository function (NRF).

[0031] According to yet another aspect of the subject matter described herein, the prioritized list of AMFs comprises the AMF identities of the second and third AMFs and weights calculated for the second and third AMFs.

[0032] According to a further aspect of the subject matter described herein, the prioritized list comprises an ordered list of AMF identities of the second and third AMFs, and the order of the AMF identities in the list corresponds to the weights calculated for the second and third AMFs.

[0033] According to another aspect of the subject matter described herein, there is provided a non-transitory computer-readable medium having executable instructions stored thereon, which, when executed by a processor of a computer, control the computer to perform steps. These steps include obtaining NSSAI availability information about multiple AMFs from a network slice selection assistance information (NSSAI) availability service using an NSSAI availability service. These steps also include receiving a network slice selection request specifying a network slice service requested by a user equipment (UE) from a first AMF. These steps also include generating a prioritized list based on the NSSAI availability information and the network slice service requested by the UE, the list including the identity of at least one AMF for supporting the network slice service. These steps also include transmitting the prioritized list to the first AMF.

[0034] The subject matter described herein can be implemented in hardware, software, firmware, or any combination thereof. Thus, the terms "function," "node," or "module," as used herein, refer to hardware for implementing the described features, which may also include software and / or firmware components. In an exemplary embodiment, the subject matter described herein may be implemented using a computer-readable medium having computer-executable instructions stored thereon, which, when executed by a processor of a computer, controls the computer to perform steps. Exemplary computer-readable media suitable for implementing the subject matter described herein include non-transitory computer-readable media, such as disk storage devices, chip memory devices, programmable logic devices, and application-specific integrated circuits. In addition, the computer-readable medium that implements the subject matter described herein may be located on a single device or computing platform, or may be distributed across multiple devices or computing platforms. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The subject matter described herein will now be explained with reference to the accompanying drawings, in which:

[0036] Figure 1 is a network diagram illustrating an exemplary 5G network architecture;

[0037] Figure 2is a network diagram illustrating an exemplary NSSF service;

[0038] Figure 3 is a message flow diagram illustrating NS selection of a service without using NSSAI availability information;

[0039] Figure 4 is a message flow diagram illustrating messages exchanged between the NSSF and the AMF according to the NSSAI availability service;

[0040] Figure 5 is a message flow diagram illustrating an example of NSSF providing policy-based AMF selection based on NSSAI availability information and AMF payload information;

[0041] Figure 6 is a message flow diagram illustrating an alternative example of an NSSF providing policy-based AMF selection based on NSSAI availability information and AMF payload information;

[0042] Figure 7 is a block diagram illustrating an exemplary NSSF providing policy-based AMF selection based on NSSAI availability information; and

[0043] Figure 8 is a flow chart illustrating an exemplary process for policy-based AMF selection using NSSAI availability information. DETAILED DESCRIPTION

[0044] Figure 1 is a block diagram illustrating an exemplary 5G system network architecture. Figure 1 In the embodiment, the network includes NRF 100 and service communication proxy (SCP) 101. As described above, NRF 100 can maintain the profile of available producer NF service instances and the services they support, and allow consumer NF or SCP to subscribe and be notified of the registration of new / updated producer NF service instances. SCP 101 can also support service discovery and selection of producer NF. In addition, SCP 101 can load balance the connection between consumer NF and producer NF.

[0045] NRF 100 is a repository of NF profiles. In order to communicate with producer NF, consumer NF or SCP must obtain NF profile from NRF 100. NF profile is a JavaScript Object Notation (JSON) data structure defined in 3GPP TS 29.510. NF profile definition includes at least one of a fully qualified domain name (FQDN), an Internet Protocol (IP) version 4 (IPv4) address, or an IP version 6 (IPv6) address.

[0046] exist Figure 1In the example shown, any of the nodes (except SCP 101 and NRF 100) can be a consumer NF or a producer NF, depending on whether they are requesting services or providing services. In the example shown, the nodes include a policy control function (PCF) 102 that performs policy-related operations in the network, a user data management (UDM) function 104 that manages user data, and an application function (AF) 106 that provides application services. Figure 1 The nodes shown in FIG. 1 also include a session management function (SMF) 108 that manages sessions between AMF 110 and PCF 102. AMF 110 performs mobility and registration management operations similar to those performed by a mobility management entity (MME) in a 4G network. AMF 110 also serves as an access point for network slice services. AMF 110 may also perform AMF selection to select a serving AMF that will provide access to the network slice services requested by the UE during registration.

[0047] Authentication server function (AUSF) 112 performs authentication services for user equipment (UE), such as UE 114, seeking to access the network.

[0048] The network slice selection function (NSSF) 116 provides the above-mentioned NSSAI availability and NS selection services for devices seeking access to specific network capabilities. As will be described in further detail below, the NSSF 116 may obtain AMF payload information from the NRF and obtain NSSAI availability information from the AMF. The NSSF 116 may store the AMF payload information and the NSSAI availability information in an AMF selection database maintained by the NSSF 116. When the NSSF 116 receives an NSSAI selection request from the AMF, the NSSF 116 may use the stored AMF payload and NSSAI availability information to calculate the AMF relevance score and weight for each AMF that can support the network slice service requested by the UE seeking access to the network slice service. The NSSF 116 may generate a prioritized list of AMFs and corresponding weights that can provide the requested service and transmit the list to the requesting AMF. The requesting AMF may then use the prioritized list and weights of the AMF to select an AMF to provide access to the requested network slice service.

[0049] The Network Exposure Function (NEF) 118 provides an Application Programming Interface (API) for application functions seeking to obtain information about Internet of Things (IoT) devices and other UEs attached to the network. The NEF 118 performs functions similar to the Service Capability Exposure Function (SCEF) in 4G networks.

[0050] Radio access network (RAN) 120 connects UE 114 to the network via a wireless link. A g-Node B (gNB) ( Figure 1 The UE 114 may use a wireless access point (not shown) or other wireless access point to access the radio access network 120. The user plane function (UPF) 122 may support various proxy functions for user plane services. An example of such a proxy function is a multipath transmission control protocol (MPTCP) proxy function. The UPF 122 may also support a performance measurement function that may be used by the UE 114 to obtain network performance measurements. Figure 1 Also shown is a data network (DN) 124 through which the UE accesses data network services, such as Internet services.

[0051] A service edge protection proxy (SEPP) 126 filters incoming traffic from another PLMN and performs topology hiding for traffic leaving the home PLMN. The SEPP 126 can communicate with a SEPP in an external PLMN that manages security for the external PLMN. Thus, traffic between NFs in different PLMNs may pass through a minimum of two SEPP functions, one for the local PLMN and another for the external PLMN.

[0052] As mentioned above, one problem with the existing 3GPP network architecture is that it does not provide for the use of NSSAI availability or AMF load information in the AMF selection process. For example, Table 7.2.14 (renumbered as Table 1) of 3GPP TS23.501 is set as follows:

[0053]

[0054] Table 1: Services provided by NSSF

[0055] In Table 1 above, NSSF provides two different services. The first service provides network slice information to the requester, and the second service provides NSSAI availability information on a per-TA basis. However, there is no connection between these two services in 3GPP TS23.501 or 3GPP TS23.502, which define the service.

[0056] For example, as described above, when there are multiple AMFs that can provide access to the network slice service requested by the UE or when the network decides to reassign the registration to an AMF other than the AMF that initially received the registration message, the AMF may consult the NSSF to identify the AMF that can provide the requested service. According to 3GPP TS23.501, as part of the initial registration process, a 5G UE can request up to 8 S-NSSAIs. The AMF selected for the UE shall support all S-NSSAIs requested by the UE (see clause 5.15.2.1 of 3GPP TS23.501). NSSAI is a set of S-NSSAIs. NSSAI can be a configured NSSAI, a requested NSSAI, or an allowed NSSAI. There can be up to 8 S-NSSAIs among the allowed and requested NSSAIs sent in signaling messages between the UE and the network. The requested NSSAI signaled by the UE to the network allows the network to select a serving AMF, network slice(s) and network slice instance(s) for the UE as specified in clause 5.15.5 of 3GPP TS 23.501.

[0057] As described above, AMF reallocation can occur due to network slicing support. During the registration process in the PLMN, if the network decides that the UE should be served by a different AMF based on network slicing aspects, the AMF that first receives the registration request redirects the registration request to another AMF via RAN or via direct signaling between the initial AMF and the target AMF. If the target AMF(s) are returned from the NSSF and identified by a list of candidate AMF(s), the redirection message can only be sent via direct signaling between the initial AMF and the target AMF. If the redirection message is sent by the AMF via RAN, the message includes information for selecting a new AMF to serve the UE.

[0058] For registered UEs, the system supports network initiated redirection of the UE from its serving AMF to the target AMF for network slicing considerations (e.g. the operator has changed the mapping between network slice instances and their corresponding (one or more) serving AMFs). Operator policy determines whether redirection between AMFs is allowed.

[0059] The subject matter described herein provides for using NSSAI availability information and AMF payload information to generate a prioritized list of AMFs that can provide access to a requested network slice service, and providing the prioritized list to the AMF to facilitate selection of the optimal AMF to access the requested network slice service. When the AMF is required to select a serving AMF for the UE, the prioritized list of AMFs can be used to select the serving AMF in any of the above cases.

[0060] Figure 2 is a network diagram illustrating the services provided by NSSF in more detail. Figure 2 , the NSSF is shown as a physical NSSF 116A and a virtual NSSF (V-NSSF) 116B. The NSSF 116A and 116B communicate with the AMF 110 and the NRF 100. The NSSF 116A or 116B can register with the NRF 100 to receive updates about the NF (such as the AMF 110) when the AMF is added to the network and the network slice or other services supported by the AMF 110 change. The NSSF 116A and 116B can also receive load information of the NF (such as the AMF 110) subscribed by the NSSF 116A or 116B from the NRF 100. In operation, the NSSF 116A or 116B selects a network slice instance (NSI), determines the allowed NSSAI information, and determines the AMF that will serve the UE. The AMF 110 may retrieve the NRF, NSI ID, and target AMF as part of the UE initial registration and packet data unit (PDU) session establishment process.

[0061] As mentioned above, the two services provided by NSSF 116 are the NSSAI availability service and the NS selection service. The NS selection service is used by the NF service consumer (i.e., AMF) to retrieve information related to network slicing. The NS selection service also enables the NSSF to provide the AMF with the allowed NSSAI and configured NSSAI for the serving PLMN. The NSSAI availability service enables the NSSF to be updated with the S-NSSAI(s) supported by the NF service consumer (e.g., AMF) based on each TA. The NSSAI availability service allows the AMF to subscribe to the S-NSSAI(s) available per TA (unrestricted) and the restricted S-NSSAI(s) for each PLMN in the TA of the UE's serving PLMN on a per TA basis, and be notified of any changes in their status.

[0062] 3GPP TS23.502 allows NSSF to obtain NSSAI availability information from AMF, but does not specify the use of NSSAI availability information for AMF selection. The subject matter described herein includes using NSSAI availability information obtained through the NSSAI availability service to determine weights for candidate AMFs, providing the weights to a requesting AMF, and using the weights by the requesting AMF to select an AMF to serve a session involving a UE (such as an IoT device).

[0063] Figure 3 is a message flow diagram illustrating the NS selection service performed without NSSAI availability information. Figure 3, in line 1, the AMF 200, which may be the default AMF to which the initial registration of the UE is routed or the AMF that decides that the initial registration should be routed to a different AMF for network slicing reasons, sends a Hypertext Transfer Protocol (HTTP) GET message to the NSSF 116. The HTTP GET message specifies a list of requested NSSAIs, a list of subscribed NSSAIs, a Transport Area Identifier (TAI), a PLMN Identifier, and a Network Function Identifier identifying the AMF 200. Based on the requested and subscribed NSSAIs, PLMNID, TA ID, and the identity of the requesting AMF, the NSSF 116 determines the Network Slice Identifier (NSI) and the target AMF that provides access to the service identified by the NSI, and, in line 2, sends a NF Discovery Request to the NRF 100. The NF Discovery Request specifies a set of target AMFs that provide access to the requested network slice services.

[0064] In line 3, the NRF 100 responds with a list of AMFs that belong to the target AMF set identified in the request in line 2. In line 4, the NSSF 116 sends a response with a list of candidate AMFs to the requesting AMF. The AMF 200 then selects one of the AMFs to provide access to the requested network slice service. It should be noted that the NSSAI availability information obtained from the NSSAI availability service is not used in Figure 3 AMF selection in progress.

[0065] Figure 4 is a message flow diagram illustrating the NSSF 116 receiving NSSAI availability information via the NSSAI availability service. Figure 4 , in line 1, NSSF 116 receives an HTTP PUT / PATCH message from AMF1 200. The HTTP PUT / PATCH message contains the NSSAIs supported by each TA. In the illustrated example, the supported NSSAIs are embedded battery (eMBBATT) and massive IoT (mIOT). The mIOT NSSAI can be requested by a large number of IoT devices or on behalf of a large number of IoT devices requesting the same service from the network. The eMBBATT NSSAI can be requested by a UE with an embedded battery (such as an IoT device). Parameter 0x2345 is an identifier of the TA. Another example of an NSSAI that can be specified is ultra-reliable low-latency communication (URLLC). URLLC can be used for industrial automation and remote control applications that require low latency, ultra-reliable communication. Another NSSAI that can be specified is enhanced mobile broadband (emBB) for mobile broadband services (such as streaming video).

[0066] According to the subject matter described herein, NSSF 116 may store and utilize NSSAI availability information to provide information to Figure 3 The query AMF for the NF selection service shown in FIG. 1 provides a list of AMFs. Therefore, after line 1, the NSSF 116 stores the identifier for the AMF1 200 and the NSSAI supported by each TA for the AMF 200, and this data can be used to respond to the NS selection query. In line 2 of the message flow diagram, the NSSF 116 responds to the AMF1 200 with an authorized NSSAI availability data message confirming the receipt of the NSSAI availability information.

[0067] In line 3 of the message flow diagram, AMF2 202 sends an HTTP PUT message to NSSF 116, identifying the mIOT service for the transport area identified by the identifier 0x2345. In response to the HTTP PUT message, NSSF 116 stores the identifier for AMF2 202, TA ID, and NSSAI. Table 2 shown below illustrates the information provided by NSSF 116 in Figure 4 An example of NSSAI availability information that may be stored following the call flow shown in FIG.

[0068]

[0069] Table 2: NSSAI availability information stored by NSSF In Table 2, it can be seen that the NSSF 116 stores the AMF identifier, the corresponding TA identifier and the NSSAI for each TA ID. In the example shown, the AMF identifier is the identifier of the TA ID. Figure 4 The AMF1 200 and AMF2 202 shown in the figure are AMF1 and AMF2. For both AMF1 and AMF2, the TA identifier is 0x2345. It will be appreciated that a given AMF may support multiple TAs, and in this case, multiple TA IDs may be stored in the AMF selection database maintained by the NSSF 116. The third column in Table 2 is the NSSAI for each TA and each AMF. In the example shown, the NSSAI for AMF1 and TA 0x2345 is eMBBATT and mIOT. The NSSAI for AMF2 202, TA ID 0x2345 is mIOT, indicating that AMF2 202 and TA ID 0x2345 provide access to mIOT services.

[0070] Once NSSF 116 stores NSSAI availability information such as shown in Table 2, NSSF 116 may respond to NS selection requests using the NSSAI availability information. Figure 5is a message flow diagram illustrating the use of NSSAI availability information to respond to an NS selection request. Figure 5 , in line 1 of the message flow diagram, AMF1 200 sends an HTTP PUT / PATCH message to NSSF 116. The HTTP PUT / PATCH message contains the NSSAI supported by each TA. In the example shown, the supported NSSAI are eMBBATT and mIOT. The TA is identified by the number 0x2345. NSSF 116 receives the HTTP PUT / PATCH message and stores the NSSAI supported by each TA, as shown in Table 2. In line 2 of the message flow diagram, NSSF 116 responds to the HTTP PUT / PATCH message with an authorized NSSAI availability data message.

[0071] In line 3 of the message flow diagram, AMF2 202 sends an HTTP PUT message containing NSSAI availability data mIOT for TA 0x2345 to NSSF 116. NSSF 116 receives the HTTP PUT message and stores the NSSAI availability data in its local AMF selection database. In line 4, NSSF 116 responds to AMF2 202 with an authorized NSSAI availability data response message.

[0072] In line 5 of the message flow diagram, AMF1 200 sends a NSSelect GET request message to NSSF 116. The NSSelect GET request message specifies the requested NSSAI, which in the example shown is mIOT and TA ID 0x2345. NSSF 116 receives the NSSelect GET request message and executes a most relevant AMF selection algorithm to generate a prioritized list of AMFs that can provide access to the requested one or more network slice services. In one example, the most relevant AMF selection algorithm may calculate the relative AMF priority using at least the following two factors:

[0073] 1.AMF load.

[0074] 2. Correlation of AMF.

[0075] The first factor is the load of the AMF, which in one example is a measure of the current processing load of the AMF. The load of the AMF can be expressed in terms similar to Figure 3 The second factor is the relevance of the AMF, which can be determined using the list of S-NSSAIs supported by the AMF. In one example, a weight W is calculated for each AMF present in the NRF discovery response. The higher the weight, the higher the priority of the AMF's response to the NSSAI selection GET request. The weight W can be calculated using the following formula:

[0076] W = R / L, where

[0077] W = weight,

[0078] R = correlation in percentage of AMF, and

[0079] L = percentage of load in AMF.

[0080] AMF relevance is defined as the ratio of the minimum number of S-NSSAIs required to serve the selected slice to the total number of S-NSSAIs supported by the AMF. AMF relevance is calculated using the following formula:

[0081] R=C / T,

[0082] C = the number of S-NSSAIs in common between the selected NSSAI list and the requested NSSAI list, and

[0083] T = the total number of S-NSSAIs supported by AMF.

[0084] use Figure 5 In the example shown in , there is a requested NSSAI, mIOT, in the NS Select GET request in row 5. Both AMF1 and AMF2 have a NSSAI, mIOT, that is shared with the requested NSSAI. Thus, the C value in the correlation equation is equal to 1 for both AMF1 200 and AMF2 202. The total number of NSSAIs supported by AMF1 200 is 2 (eMBBATT and mIOT). The total number of NSSAIs supported by AMF2 202 is 1 (mIOT). Thus, the correlation score for AMF1 200 is calculated as follows:

[0085] R=C / T

[0086] =1 / 2

[0087] =0.5.

[0088] The relevance score for AMF2 202 can be calculated using the following expression:

[0089] R=C / T

[0090] =1 / 1

[0091] =1.0.

[0092] If the loads of AMF1 200 and AMF2 202 are equal, for example 50%, then the weight of AMF1 200 can be calculated as follows:

[0093] W=R / L

[0094] =0.5 / (0.5)

[0095] =1.0.

[0096] The weight used for AMF2 202 is determined using the following expression:

[0097] W=R / L

[0098] =1 / (0.5)

[0099] =2.0.

[0100] Return to Figure 5 , in line 6, NSSF 116 returns AMF2 202 as the responding candidate AMF because the most relevant selection algorithm results in AMF2 202 as the AMF with the highest weight value. In an alternative embodiment, NSSF 116 may return a prioritized list of AMFs that can provide the requested service and the corresponding weights. For example, in Figure 5 , the list will include the identities of AMF1 200 with a weight of 1 and AMF2 202 with a weight of 2.0.

[0101] From About Figure 5 As can be seen in the described example, the AMF relevance determination algorithm results in preferential assignment of the AMF that provides the smallest set of matching network slice services to the UE session. Figure 5 In the example, both AMF1 200 and AMF2 202 support the requested mIOT service. However, AMF1 200 also supports eMBBATT service. Therefore, if the UE session is assigned to AMF1, then the UE that needs to access AMF1 200 to implement its emBBATT service may not be able to access the resources of AMF1 200. Because AMF2 202 only provides mIOT services, assuming that the payload of AMF1 200 and AMF2 202 is the same, it is more efficient to assign the UE requesting mIOT service to AMF2 202.

[0102] Figure 6 Another example of providing AMF selection based on NSSAI availability is illustrated, where the AMF payload is taken into account in the AMF selection process. Figure 6 , in line 1, AMF1 200 sends an HTTP PUT / PATCH message to NSSF 116 indicating the network slicing capabilities of AMF1 200. In the example shown, AMF1 200 supports mIOT services for transport area 0x2345. In line 2, NSSF 116 responds to the HTTP PUT / PATCH message.

[0103] In line 3, AMF2 202 sends an HTTP PUT message to NSSF 116, which indicates that AMF2 202 provides mIOT service for transport zone U0x2345. In line 4, NSSF 116 responds to the HTTP PUT message from AMF2 202. Therefore, after line 4, NSSF 116 stores the supported NSSAI availability information of AMF1 200 and AMF2 202 for transport zone 0x2345.

[0104] In line 5 of the message flow diagram, NSSF 116 receives a NS select request from AMF1 200 requesting mIOT service for the UE. In response to the NS select GET request message, NSSF 116 calculates the relevance and waits for AMF1 200 and AMF2 202. Using the above formula, the relevance score for AMF1 200 is calculated as follows:

[0105] R=C / T

[0106] =1 / 1

[0107] =1.0

[0108] The relevance score for AMF2 202 is calculated using the following expression:

[0109] R=C / T

[0110] =1 / 1

[0111] =1.0.

[0112] Therefore, the relevance scores of AMF1 200 and AMF2 202 are equal. In this example, it is assumed that AMF1 loading is 10% and AMF2 loading is 50%. Thus, the weight of AMF1 200 is calculated as follows:

[0113] W=R / L

[0114] =1.0 / (0.1)

[0115] =10.0

[0116] The weight of AMF2 202 is determined as follows:

[0117] W=R / L

[0118] =1 / 0.5

[0119] =2.0

[0120] Therefore, in this example, AMF1 200 has a higher weight than AMF2 202. Thus, in row 6, NSSF 116 returns a list including AMF1 200 and AMF2 202, with AMF1 200 being preferred due to its higher weight.

[0121] Figure 7 is a block diagram illustrating an exemplary NSSF capable of using NSSAI availability information to perform NSSAI relevance determination and facilitate AMF selection. Figure 7 , the NSSF 116 includes at least one processor 700 and a memory 702. An AMF prioritizer 704 may be executed by the processor 700 and reside in the memory 702. The AMF prioritizer 704 obtains NSSAI availability information using the above-described NSSAI availability process. The AMF prioritizer 704 may also obtain AMF payload information by communicating with the NRF. The AMF prioritizer 704 may store the NSSAI availability information and the AMF payload information in an AMF selection database 706. Using Table 2 above as an example, the AMF selection database 706 may include NSSAI availability information based on each TA, as shown in Table 2. In addition, the AMF payload information may be added to each database entry as a third column or field.

[0122] The AMF prioritizer 704 may receive a NS selection GET request message from the AMF, identify the requested NSSAI information in the request message, and use the NSSAI availability and AMF payload information stored in the AMF selection database 706 to determine the relevance and weight of each AMF that can provide the requested network slice service. The AMF prioritizer 704 may return a prioritized list of one or more AMFs that can provide access to the requested network slice service. The receiving AMF may use the prioritized list to select an AMF and forward the registration request for the user session to the selected AMF.

[0123] Figure 8 is a flow chart illustrating an exemplary process for providing policy-based AMF selection using NSSAI availability information. Figure 8 The steps shown in may be performed at a network slice selection function comprising at least one processor. Figure 8 , at step 800, NSSF 116 obtains NSSAI availability information about multiple AMFs using the NSSAI availability service. For example, NSSF 116 may receive NSSAI availability information from AMFs via an HTTP PUT / PATCH message that specifies the NSSAI supported by each transport zone.

[0124] In step 802, the process includes obtaining AMF payload information. The NSSF 116 may obtain the AMF payload information from the NRF 100 by sending a NF discovery request to the NRF 100, wherein the NF discovery request identifies the AMF for which the NSSF 116 desires to obtain the AMF payload information. The NRF 100 may respond to the NF discovery request with a list of AMF identities and corresponding payload information. In one example, the AMF payload information may indicate a percentage of the processing capacity of the AMF currently being used.

[0125] At step 804, the process includes receiving a network slice selection request message specifying a network slice service requested by a user equipment. For example, the NSSF 116 may receive a NS selection GET request message identifying one or more requested NSSAIs and corresponding transport areas.

[0126] In step 806, the processing includes generating a prioritized list including at least one AMF for supporting network slice services based on NSSAI availability information, AMF load information, and the network slice service requested by the UE. For example, NSSF116 may identify a list of AMFs capable of providing the requested (one or more) NS services based on the NSSAI in the NS selection request and the supported NSSAI obtained from the NSSAI availability service. In the above example, the priority is based on the ratio of the number of requested network slice services provided by the AMF to the total number of services provided by the AMF and the relative load of the AMF. In another example, the prioritized list may include only the AMF with the highest relative priority.

[0127] In step 808, the prioritized list is provided to the requesting AMF. In one example, the NSSF 116 may send the list and the corresponding weights to the requesting AMF, where the weights are calculated based on the relevance and load percentage of the AMF calculated using the above formula. In another example, the NSSF 116 may send a list of AMF identities, where the order of the AMFs in the list indicates their relative priority.

[0128] The list is used to select an AMF for handling the user session at step 810. For example, the requesting AMF may receive a prioritized list of AMFs and select the AMF with the highest weight (based on relevance and load assignment) in the list to provide access to the requested network slice service.

[0129] The subject matter described herein allows the NSSF to select and prioritize a list of candidate AMFs using NSSAI availability information. Using NSSAI availability information to select and prioritize a list of candidate AMFs, especially when AMF relevance is considered as a prioritization criterion, the UE session is more likely to be forwarded to the most specialized AMF to provide the network slice service requested by the UE rather than to a general AMF supporting a larger set of network slice services. The subject matter described herein enables quality of service (QoS) based traffic isolation by prioritizing candidate AMFs based on the S-NSSAI information they support. The subject matter described herein reduces the possibility of overloading AMFs supporting larger S-NSSAI sets by preferentially selecting AMFs with smaller S-NSSAI sets that match the NSSAI requested by the UE.

[0130] The disclosures of each of the following references are incorporated herein by reference in their entirety:

[0131] 1.3GPP TS23.501, “Technical Specification Group Services and SystemAspects; System Architecture for the 5G System (5GS)”, Stage 2 (Release 16), V16.2.0 (2019-09).

[0132] 2.3GPP TS23.502, “Technical Specification Group Services and SystemAspects; Procedures for the 5G System (5GS)”, Stage 2 (Release 16) V16.2.0 (2019-09).

[0133] 3. 3GPP TS 29.510, “Technical Specification Group Core Network and Terminals; 5G System; Network Function Repository Services”, Stage 3 (Release 16), V16.1.1 (2019-10).

[0134] It will be understood that various details of the presently disclosed subject matter may be varied without departing from the scope of the presently disclosed subject matter.In addition, the foregoing description is for the purpose of illustration only and not for the purpose of limitation.

Claims

1. A method for providing policy-based access and mobility management function (AMF) selection using NSSAI availability information obtained from a Network Slice Selection Assistance Information (NSSAI) availability service, the method comprising: At a network slice selection function NSSF comprising at least one processor: obtaining NSSAI availability information about a plurality of AMFs using an NSSAI availability service, wherein obtaining the NSSAI availability information comprises receiving Hypertext Transfer Protocol (HTTP) messages from the AMFs, wherein each HTTP message indicates an NSSAI supported by each transport area (TA) of one of the AMFs; receiving, from the first AMF, a network slice selection request specifying a network slice service requested by a user equipment UE, wherein receiving the network slice selection request comprises receiving a network slice selection request including at least one NSSAI identifying the network slice service requested by the UE; generating a prioritized list based on the NSSAI availability information and the network slice service requested by the UE, the list comprising the identity of at least one AMF for supporting the network slice service; as well as The prioritized list is transmitted to the first AMF, Wherein generating the prioritized list includes prioritizing a second AMF that supports a requested network slice service over a third AMF that supports the requested network slice service and supports a greater number of network slice services other than the requested network slice service than the second AMF.

2. The method of claim 1, wherein prioritizing the second AMF over the third AMF comprises calculating a correlation R for the second AMF and the third AMF, wherein R is equal to C / T, wherein C is equal to the number of common NSSAIs between the NSSAI requested by the UE and the NSSAIs supported by the second AMF or the third AMF and T is equal to the total number of NSSAIs supported by the second AMF or the third AMF.

3. The method of claim 2, comprising obtaining a load percentage of each AMF.

4. The method of claim 3, wherein obtaining the load percentage comprises obtaining the load percentage from a network function repository function (NRF).

5. The method of claim 3 or claim 4, wherein generating the prioritized list comprises calculating a weight W for the second AMF and the third AMF, wherein the weight W is equal to R / L, and L is a load percentage of the second AMF or the third AMF.

6. The method of claim 5, wherein transmitting the prioritized list to the first AMF comprises transmitting the AMF identities of the second AMF and the third AMF and the weights calculated for the second AMF and the third AMF to the first AMF.

7. The method of claim 5, wherein transmitting the prioritized list to the first AMF comprises transmitting the AMF identities of the second AMF and the third AMF in an order corresponding to the weights calculated for the second AMF and the third AMF.

8. A system for providing policy-based access and mobility management function (AMF) selection using NSSAI availability information obtained from a Network Slice Selection Assistance Information (NSSAI) availability service, the system comprising: A network slice selection function NSSF, comprising at least one processor; as well as An access and mobility management function AMF prioritizer implemented by the at least one processor, configured to: obtaining NSSAI availability information about a plurality of AMFs using an NSSAI availability service, wherein obtaining the NSSAI availability information comprises receiving Hypertext Transfer Protocol HTTP messages from the AMFs, wherein each HTTP message indicates an NSSAI supported by each transport area TA for one of the AMFs, receiving, from the first AMF, a network slice selection request specifying a network slice service requested by a user equipment UE, wherein receiving the network slice selection request comprises receiving a network slice selection request including at least one NSSAI identifying the network slice service requested by the UE, generating a prioritized list based on the NSSAI availability information and the network slice service requested by the UE, the list comprising the identity of at least one AMF for supporting the network slice service, and for transmitting the prioritized list to the first AMF, Wherein generating the prioritized list includes prioritizing a second AMF that supports a requested network slice service over a third AMF that supports the requested network slice service and supports a greater number of network slice services other than the requested network slice service than the second AMF.

9. The system of claim 8, wherein the AMF prioritizer is configured to prioritize the second AMF over the third AMF by calculating a correlation R of the second AMF and the third AMF, where R=C / T, where C equals the number of common NSSAIs between the NSSAI requested by the UE and the NSSAIs supported by the second AMF or the third AMF and T equals the total number of NSSAIs supported by the second AMF or the third AMF.

10. The system of claim 9, wherein the AMF prioritizer is configured to obtain the load percentages of the second AMF and the third AMF and calculate a weight value W for the second AMF and the third AMF, wherein the weight value W for the second AMF or the third AMF is equal to R / L and L is the load percentage of the second AMF or the third AMF.

11. The system of claim 10, wherein the AMF prioritizer is configured to obtain the load percentage from a network function repository function (NRF).

12. The system of claim 10 or claim 11, wherein the prioritized list of AMFs comprises the AMF identities of the second AMF and the third AMF and weights calculated for the second AMF and the third AMF.

13. The system of claim 10, wherein the prioritized list comprises an ordered list of AMF identities of the second AMF and the third AMF, and an order of the AMF identities in the list corresponds to weights calculated for the second AMF and the third AMF.

14. A non-transitory computer readable medium having executable instructions stored thereon, which instructions, when executed by a processor of a computer, control the computer to perform steps comprising: At the network slice selection function NSSF: obtaining NSSAI availability information about a plurality of AMFs using a network slice selection assistance information (NSSAI) availability service, wherein obtaining the NSSAI availability information comprises receiving hypertext transfer protocol (HTTP) messages from the AMFs, wherein each HTTP message indicates an NSSAI supported by each transport area (TA) of one of the AMFs; receiving, from the first AMF, a network slice selection request specifying a network slice service requested by a user equipment UE, wherein receiving the network slice selection request comprises receiving a network slice selection request including at least one NSSAI identifying the network slice service requested by the UE; generating a prioritized list based on the NSSAI availability information and the network slice service requested by the UE, the list comprising the identity of at least one AMF for supporting the network slice service; as well as The prioritized list is transmitted to the first AMF, Wherein generating the prioritized list includes prioritizing a second AMF that supports a requested network slice service over a third AMF that supports the requested network slice service and supports a greater number of network slice services other than the requested network slice service than the second AMF.

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