A mechanism to improve home routing of sessions

Abstract

Method and apparatus are provided for improving establishment of a home routed PDU session or home routed policy association by a visited NF instance and a home NF instance, when the home NF instance has failed. The method comprises receiving one of a message to establish a home routed PDU session establishment for a User Equipment (UE), or a message to establish a home routed policy association for the UE, the message comprising a URI of a selected home NF instance of same type as visited NF instance, a set identifier of the selected home NF instance and a URI of the selected home NF instance and in response to determining the selected home NF instance is unreachable during the establishment procedure, selecting an alternative home NF instance based on the received set id of the selected home NF instance.

Description

1A mechanism to improve Home Routing of sessionsRelated Applications5

[0001] This application claims the benefit of provisional patent application serial number 63 / 651463, filed on 5 / 24 / 2024, the disclosure of which is hereby incorporated herein by reference in its entirety.Technical Field10

[0002] The present disclosure relates to a cellular communications system and, more particularly, PDU session management and policy association management in home routed sessions scenarios.Background15 PDU Session Establishment procedure

[0003] In Home-Routed roaming scenario in a 3GPP 5G system illustrated in Figure 4, during Packet Data Unit (PDU) Session establishment, the Access and mobility Management Function (AMF) performs the following steps:1. AMF receives PDU Session Establishment Request from a User Equipment (UE).20 2. AMF uses NRF discovery mechanism to discover home Session Management function (H-SMF) (in the home Public Land Mobile Network).3. AMF uses NRF discovery mechanism to discover a visited SMF (V-SMF) (in the visited PLMN)4. While sending Nsmf_PDUSession_ CreateSMContext request to V-SMF, AMF25 includes from information obtained in step 3 (Refer to sections 5.2.2.2.1 and 6.1.6.2.2 in 3GPP IS 29.502) in "SmContextCreateData" - hSmfURI (API URI of the Nsmf_PDUSession service of the selected H-SMF) and hSmfld (NF instance ID of the selected H-SMF)5. When V-SMF needs to send Nsmf_PDUSession_ Create request to H-SMF, V-30 SMF uses the hSmfURI as the R-URI for the request destination.UE Policy Association Establishment procedure

[0004] In Home-Routed roaming scenario illustrated in Figure 5, during UE Policy Association establishment, AMF performs the following steps:1 . UE performs Registration with the 5G Core network (5GC).2. AMF uses NRF discovery mechanism to discover Home Policy Control Function (H-PCF) (in the home PLMN)3. AMF uses NRF discovery mechanism to discover a Visited PCF (V-PCF) (in the visited PLMN)4. While sending Npcf_UEPolicyControl_Create request to V-PCF, AMF includes from information obtained in step 3 (Refer to sections 4.2.2.1 and 5.6.2.3 in 3GPP TS 29.525) in “PolicyAssociationRequest” -(i) hPcfURI (API URI of the Npcf_UEPolicyControl_Create service of the selected H-PCF) and(ii) hPcfld (NF instance ID of the selected H-PCF)Note: Currently the standard does not allow including hPcfUR! as shown above. This necessitates another NRF discovery by V-PCF. Unfortunately, this has already been discussed with Ericsson standards delegates and they agree to take a CR to 3GPP to fic this. It was my idea, can we still include this as part of invention step?5. When V-PCF needs to send Npcf_UEPolicyControl_Create request to H-PCF, V- PCF uses hPcfUR I as the R-URI for the request destination.Summary

[0005] Certain aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges.According to some embodiments described in the context of 5G Service Based Architecture, a method performed by a network function such as AMF is provided where:1) During PDU Session Establishment Procedure, the AMF includes SMF NF Set Id information to the V-SMF. a. In case V-SMF needs to perform failover, it only needs one NRF Discovery to find an alternate H-SMF b. For Indirect Communication, V-SMF sends received SMF Set Id in 3gpp- Sbi-Discovery-target-nf-set id header to SCP to enable SCP to perform failover when needed.2) During UE Policy Association Establishment Procedure, AMF includes PCF NFSet Id information to V-PCF.a. In case V-PCF needs to perform failover, it only needs one NRF Discovery to find an alternate H-PCF b. For Indirect Communication, V-PCF sends received PCF Set Id in 3gpp- Sbi-Discovery-target-nf-set id header to SCP to enable SCP to perform failover when needed.

[0006] In some embodiments, a method performed by an access and mobility management in a visited Public Land Mobile Network (PLMN), during a home routed Packet Data Unit (PDU) session establishment procedure for a User Equipment (UE) is provided. The method comprises the step of receiving as part of a discovery procedure with a home PLMN, at least one home Session Management function (SMF) instance of a home SMF and a home SMF set identifier(id) of the at least one home SMF instance; and the step of transmitting to a visited SMF instance a message to establish a home routed PDU session for the UE, the message comprising a URI of a home SMF instance selected based on the received at least one home SMF instance, an identifier of the selected home SMF instance and the home SMF set id of the selected home SMF instance.

[0007] For example, the message comprises an SmContextCreateData data type that includes the URI of a selected home SMF instance, the identifier of the selected home SMF instance identifier and the home SMF set id of the selected home SMF instance.

[0008] For example, the step of receiving as part of a discovery procedure with a home PLMN comprises sending a discovery request to a home Network Registry Function (H-NRF) to discover home SMF instances and receiving a discovery response comprising the at least one home SMF instance of the home SMF and the corresponding home SMF set id of the at least one home SMF instance.

[0009] In some aspect, the home SMF set id is to be used by the visited SMF instance to initiate failover procedure to a second home SMF instance in the event the selected home SMF instance has failed.

[0010] According to some embodiment, a method performed by an access and mobility management in a visited Public Land Mobile Network (PLMN) during a home routed policy association establishment procedure for a User Equipment (UE) is provided, the method comprises the step of receiving as part of a discovery procedure with a home PLMN, at least one home Policy Control function (PCF) instance of a home PCF and a home PCF set identif ier(id) of the at least one home PCF instance and thestep of transmiting to a visited PCF instance a message to create a home routed policy association for the LIE (for e.g., Npcf_UEPolicyControl_Create request), the message comprising a URI of a home PCF instance selected based on the received at least one home PCF instance, an identifier of the selected home PCF instance and the home PCF set id of the selected home PCF instance.

[0011] In some aspect, the home PCF set id is to be used by the visited PCF instance to initiate failover procedure to a second home PCF instance in the event the selected home PCF instance has failed.

[0012] For example, the step of receiving as part of a discovery procedure with a home PLMN comprises sending a discovery request to a home Network Registry Function (H-NRF) to discover home PCF instances and receiving a discovery response comprising the at least one home PCF instance of the home PCF and the corresponding home PCF set id of the at least one home PCF instance.

[0013] According to some other embodiments, a method performed by a Network Function (NF) instance in a visited Public Land Mobile Network (PLMN) is provided, the method comprises the step of receiving one of a message to establish a home routed PDU session establishment for a User Equipment (UE), or a message to establish a home routed policy association for the UE, the message comprising a URI of a selected home NF instance in a home PLMN where the selected home NF instance is of a same type as the NF instance in the visited PLMN, a set identifier of the selected home NF instance and a URI of the selected home NF instance and the step of in response to determining the selected home NF instance is unreachable while establishing one of home routed PDU session or home routed policy association with the selected home NF instance, selecting an alternative home NF instance based on the received set id of the selected home NF instance.

[0014] For example, the visited NF instance is a visited session management function (SMF) instance, the selected home NF instance is the selected home SMF instance or when the visited NF instance is a visited policy control function (PCF) instance, the selected home NF instance is the selected home PCF instance.

[0015] In some aspects, prior to determining the selected home NF instance is unreachable, using the selected home NF instance and the URI of the selected home NF instance to request establishment of a home routed PDU session or establishment of a home routed policy association.

[0016] For exampie, the selected home NF instance is unreachable is determine dif the visited NF instance fails to receive a response to the request for establishment of a home routed PDU session or home routed policy association.

[0017] In some embodiments, a network node configured to perform any of the embodiments herein is provided.

[0018] In some embodiments, a network node comprising one or more processors and memory comprising instructions which when executed by the one or more processors enable the network node to perform any of the embodiments herein is provided.

[0019] In some embodiments, a computer readable memory comprising instructions which when executed by one or more processors of one or more servers configures the one or more servers to perform any of the embodiments herein is provided.Brief Description of the Drawings

[0020] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0021] Figure 1 illustrates one example of a cellular communications system 100 in which embodiments of the present disclosure may be implemented;

[0022] Figures 2 and 3 illustrate example embodiments of the cellular communication system of Figure 1;

[0023] Figure 3A illustrates a roaming 5G System architecture - home routed scenario in service-based interface representation;

[0024] Figure 4 illustrates a flow diagram of Home routed PDU session establishment according to the prior art;

[0025] Figure 5 illustrates a flow diagram of Home routed policy association establishment according to the prior art;

[0026] Figure 6 illustrates a problem of Home routed PDU session establishment of Figure 4;

[0027] Figure 7 illustrates a problem of Home routed policy association establishment of Figure 5;

[0028] Figures 8 illustrates a problem of Home routed PDU session establishment using indirect communication;

[0029] Figure 9A illustrates a flow diagram of home routed PDU session establishment in accordance with some embodiments;

[0030] Figure 9B illustrates a flow diagram of home routed PDU session establishment using indirect communications in accordance with some embodiments;

[0031] Figure 10 illustrates a flow diagram of Home routed policy association establishment in accordance with some embodiments;

[0032] Figure 11 illustrate a flow chart for NF (e.g., AMF) performing the method in accordance with some embodiments;

[0033] Figures 12, 13, and 14 are schematic block diagrams of example embodiments of a network node.

[0034] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure.

[0035] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0036] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a stepmust follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features, and advantages of the enclosed embodiments will be apparent from the following description.

[0037] Radio Node: As used herein, a "radio node" is either a radio access node or a wireless communication device.

[0038] Radio Access Node: As used herein, a "radio access node" or "radio network node" or "radio access network node" is any node in a Radio Access Network (RAN) of a cellular communications network that operates to wirelessly transmit and / or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a base station (e.g., a network node that implements a gNB Central Unit (gNB-CU) or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node.

[0039] Core Network Node: As used herein, a "core network node" is any type of node in a core network or any node that implements a core network function (NF). The node can be a server or system of distributed servers. Some examples of a core network functions implemented in a core network node include, e.g., an Access and Mobility Management Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), and an SMF-packet data gateway control and user plane (SMF+PGW-C, SMF+PGW-U) to support interworking between 5G core network, a Short message service function (SMSF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), a Network slice Admission Control function (NSACF), an Non-3GPP Interworking function (N3IWF) to support untrusted non-3GPP access or the like, a trusted non-3GPP access network function (TNGF) to support trusted non-3GPP accessnetworks. The core network node also includes a Service Communications Proxy (SCP) can be used for indirect communication between NFs and NF services within the visited public Land Mobile network (VPLMN), within the Home PLMN (HPLMN), or in within both VPLMN and HPLMN. The Core network functions may be virtualized / containerized on a node, server, distributed servers, or implemented as a dedicated function on a dedicated physical node (compute, memory, and network). Other future core network functions in future core networks such as 6G and beyond are also applicable for this invention.

[0040] Communication Device: As used herein, a "communication device" is any type of device that has access to an access network. Some examples of a communication device include, but are not limited to: mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or Personal Computer (PC). The communication device may be a portable, hand-held, computer-comprised, or vehiclemounted mobile device, enabled to communicate voice and / or data via a wireless or wireline connection.

[0041] Wireless Communication Device: One type of communication device is a wireless communication device, which may be any type of wireless device that has access to (i.e., is served by) a wireless network (e.g., a cellular network). Some examples of a wireless communication device include but are not limited to: a User Equipment device (UE) in a 3GPP network, a Machine Type Communication (MTC) device, and an Internet of Things (loT) device. Such wireless communication devices may be, or may be integrated into, a mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or PC. The wireless communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and / or data via a wireless connection.

[0042] Network Node: As used herein, a "network node" is any node that is either part of the RAN or the core network of a cellular communications network / system.

[0043] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPPterminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system.

[0044] Note that, in the description herein, reference may be made to the term "cell"; however, particularly with respect to 5G NR concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams.

[0045] Figure 1 illustrates one example of a cellular communications system 100 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system 100 is a 5G system (5GS) including a Next Generation RAN (NG-RAN) and a 5G Core (5GC); however, the present disclosure is not limited thereto. In this example, the RAN includes base stations 102-1 and 102-2, which in the 5GS include NR base stations (gNBs) and optionally next generation eNBs (ng-eNBs) (e.g., LTE RAN nodes connected to the 5GC), controlling corresponding (macro) cells 104-1 and 104-2. The base stations 102- 1 and 102-2 are generally referred to herein collectively as base stations 102 and individually as base station 102. Likewise, the (macro) cells 104-1 and 104-2 are generally referred to herein collectively as (macro) cells 104 and individually as (macro) cell 104. The RAN may also include a number of low power nodes 106-1 through 106-4 controlling corresponding small cells 108-1 through 108-4. The low power nodes 106-1 through 106-4 can be small base stations (such as pico or femto base stations) or RRHs, or the like. Notably, while not illustrated, one or more of the small cells 108-1 through 108-4 may alternatively be provided by the base stations 102. The low power nodes 106-1 through 106-4 are generally referred to herein collectively as low power nodes 106 and individually as low power node 106. Likewise, the small cells 108-1 through 108-4 are generally referred to herein collectively as small cells 108 and individually as small cell 108. The cellular communications system 100 also includes a core network 110, which in the 5G System (5GS) is referred to as the 5GC. The base stations 102 (and optionally the low power nodes 106) are connected to the core network 110.

[0046] The base stations 102 and the low power nodes 106 provide service to wireless communication devices 112-1 through 112-5 in the corresponding cells 104 and 108. The wireless communication devices 112-1 through 112-5 are generally referred to herein collectively as wireless communication devices 112 and individually as wireless communication device 112. In the following description, the wireless communicationdevices 112 are oftentimes UEs and as such sometimes referred to herein as UEs 112, but the present disclosure is not limited thereto.

[0047] Figure 2 illustrates a wireless communication system represented as a 5G network architecture composed of core Network Functions (NFs), where interaction between any two NFs is represented by a point-to-point reference point / interface. Figure 2 can be viewed as one particular implementation of the system 100 of Figure 1. The embodiments in the reminder of these document are described within the context of 5G network architecture using the 5G terminology, but the embodiments are also applicable to other systems / networks using network slicing, admission control of network slicing and on-demand network slicing can. Example of those systems / networks may be 6G systems / networks and beyond.

[0048] Seen from the access side the 5G network architecture shown in Figure 2 comprises a plurality of UEs 112 connected to either a RAN 102 or an Access Network (AN) as well as an AMF 200. Typically, the R(AN) 102 comprises base stations, e.g. such as eNBs or gNBs or similar. Seen from the core network side, the 5GC NFs shown in Figure 2 include a NSSF 202, an AUSF 204, a UDM 206, the AMF 200, a SMSF 220, a SMF 208, a SMF-PGW-C, N3IWF, TNGF, ePDG, a PCF 210, and an Application Function (AF) 212.

[0049] Reference point representations of the 5G network architecture are used to develop detailed call flows in the normative standardization. The N1 reference point is defined to carry signaling between the UE 112 and AMF 200. The reference points for connecting between the AN 102 and AMF 200 and between the AN 102 and UPF 214 are defined as N2 and N3, respectively. There is a reference point, Nil, between the AMF 200 and SMF 208, which implies that the SMF 208 is at least partly controlled by the AMF 200. N4 is used by the SMF 208 and UPF 214 so that the UPF 214 can be set using the control signal generated by the SMF 208, and the UPF 214 can report its state to the SMF 208. The SMSF 220 communicates with the AMF 200 over the N20 reference point, and with UDM 206 over the N21 reference point, and AMF 200 communicates with UDM 206 over the N8 reference point as illustrated in Figure 2. N9 is the reference point for the connection between different UPFs 214, and N14 is the reference point connecting between different AMFs 200, respectively. N15 and N7 are defined since the PCF 210 applies policy to the AMF 200 and SMF 208, respectively. N12 is required forthe AMF 200 to perform authentication of the UE 112. N8 and N10 are defined because the subscription data of the UE 112 is required for the AMF 200 and SMF 208.

[0050] The 5GC network aims at separating UP and CP. The UP carries user traffic white the CP carries signaling in the network. In Figure 2, the UPF 214 is in the UP and all other NFs, i.e., the AMF 200, SMF 208, SMF-PGW-C, PCF 210, AF 212, NSSF 202, AUSF 204, and UDM 206, are in the CP. Separating the UP and CP guarantees each plane resource to be scaled independently. It also allows UPFs to be deployed separately from CP functions in a distributed fashion. In this architecture, UPFs may be deployed very close to UEs to shorten the Round Trip Time (RTT) between UEs and data network for some applications requiring low latency. To support non-3GPP access networks N3IWF, TNGF, ePDG are special functions that provide access to core network resources and services and they handle both User plane and control plane capabilities.

[0051] The 5G core network architecture is composed of modularized functions. For example, the AMF 200, SMF 208 / SMF+PGW-C are independent functions in the CP. Separated AMF 200 and SMF 208 / SMF+PGW-C allow independent evolution and scaling. Other CP functions like the PCF 210 and AUSF 204 can be separated as shown in Figure 2. Modularized function design enables the 5GC network to support various services flexibly.

[0052] Each NF interacts with another NF directly. It is possible to use intermediate functions to route messages from one NF to another NF. In the CP, a set of interactions between two NFs is defined as service so that its reuse is possible. This service enables support for modularity. The UP supports interactions such as forwarding operations between different UPFs.

[0053] Figure 3 illustrates a 5G network architecture using service-based interfaces between the NFs in the CP, instead of the point-to-point reference points / interfaces used in the 5G network architecture of Figure 2. However, the NFs described above with reference to Figure 2 correspond to the NFs shown in Figure 3. The service(s) etc. that a NF provides to other authorized NFs can be exposed to the authorized NFs through the service-based interface. In Figure 3 the service based interfaces are indicated by the tetter "N" followed by the name of the NF, e.g. Namf for the service based interface of the AMF 200 and Nsmf for the service based interface of the SMF 208, Nsmsf for service based interface exposing services of SMSF 220, etc. Any NFsdepicted in Figure 2 can interact with the NEF 216 and / or NRF 218 of Figure 3 as necessary, though not explicitly indicated in Figure 2.

[0054] Some properties of the NFs shown in Figures 2 and 3 may be described in the foilowing manner. The AMF 200 provides UE-based authentication, authorization, mobility management, etc. A UE 112 even using multiple access technologies is basically connected to a single AMF 200 because the AMF 200 is independent of the access technologies. The AMF 200 selects an SMF when the communication device (e.g., UE) requests establishment of a PDU session. The AMF can select an SMF or an SMF+PGW-C (when potential interworking with 4G system such as Evolved Packet System, EPS is required). The SMF 208 and SMF-PGW-C are responsible for session management and allocates Internet Protocol (IP) addresses to UEs. It also selects and controls the UPF 214 for data transfer. More particularly the SMF+PGW-C supports session management interworking between 5G core network and evolved packet core (4G) to support session continuity for a UE moving between 5G core network and 4G core network (EPC) including between NR and LTE access networks. If a UE 112 has multiple sessions, different SMFs 208 may be allocated to each session to manage them individually and possibly provide different functionalities per session. The AUSF 204 supports authentication function for UEs or similar and thus stores data for authentication of UEs or similar while the UDM 206 stores subscription data of the UE 112. The functionality of N3IWF in the case of untrusted non-3GPP access includes support of IPsec tunnel establishment with the UE where the N3IWF terminates the IKEv2 / IPsec protocols with the UE over NWu and relays over N2 the information needed to authenticate the UE and authorize its access to the 5G Core Network, it also terminates N2 and N3 interfaces to 5G Core Network for control - plane and user-plane respectively, relay uplink and downlink control-plane NAS (Nl) signalling between the UE and AMF, Handling of N2 signalling from SMF (relayed by AMF) related to PDU Sessions and QoS. The N3IWF also establishment the IPsec Security Association (IPsec SA) to support PDU Session traffic as well as relays uplink and downlink user-plane packets between the UE and UPF.

[0055] Many NFs including AMF 200, SMF 208 communicate with UDM 206 to obtain subscription data and / or notification of UE availability for reachability or SMS availability. The Data Network (DN), not part of the 5GC network, provides Internet access or operator services and similar.

[0056] Figure 3A illustrates a Roaming 5G System architecture - home routed scenario in service-based interface representation illustrated in Figure 3. The architecture supports roaming UEs establishing a PDU session anchored in the home PLMN, herein referred to as "Home-Routed" HR PDU session establishment. In "Home Routed" (HR), the PDU Session is supported by a SMF function under control of the HPLMN, by a SMF function under control of the VPLMN, by at least one UPF under control of the HPLMN and by at least one UPF under control of the VPLMN. In this case the SMF in HPLMN (H-SMF) selects the UPF(s) in the HPLMN and the SMF in VPLMN (V- SMF) selects the UPF(s) in the VPLMN. In home routed roaming case, the AMF selects an SMF in the VPLMN and a SMF in the HPLMN as described in clause 6.3.2 and in clause 4.3.2.2.3.3 of 3GPP TS 23.502 and provides the identifier of the selected SMF in the HPLMN to the selected SMF in the VPLMN.

[0057] An NF may be implemented either as a network element on a dedicated hardware, as a software instance (NF instance) running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., a cloud infrastructure.

[0058] The Network Function instance can be deployed as distributed, redundant, stateless, and scalable NF instance that provides the services from several locations and several execution instances in each location. The NF instance can also be deployed such that several NF instances are present within a NF set provide distributed, redundant, stateless and scalability together as a set of NF instances. The same is also supported for NF Services. This can be achieved when the equivalent NFs and NF Services share the same context data. Therefore, an NF can be replaced by an alternative NF within the same NF Set in the case of scenarios such as failure, load balancing, load rebalancing.

[0059] Such a network reliability design as implemented in the 5G SBA system work in both communication modes, i.e. Direct Communication and Indirect Communication. In the Direct Communication mode, the NF Service consumer is involved in the reliability related procedures (e.g., such reselecting an NF instance or NF service instance of the same set in the event failure of previously selected NF instance or NF service instance). In Indirect Communication mode, the SCP is involved in the reliability related procedures instead of the NF consumer.

[0060] As described in 3GPP TS 23.501, Equivalent Control Plane NFs such as SMF or PCF may be grouped into NF Sets, e.g., several SMF instances are grouped into an SMF Set including H-SMF and H-PCF in the roaming architecture of Figure 3A. NFs within a NF Set are interchangeable because they share the same context data, and may be deployed in different locations, e.g. different data centers. In the case of SMF, multiple instances of SMFs within an SMF Set need to be connected to the same UPF.

[0061] A Control Plane NF such as SMF or PCF is composed of one or multiple NF Services. Within a NF, a NF service may have multiple instances. These multiple NF Service instances can also be grouped into NF Service Set if they are interchangeable with each other because they share the same context data.

[0062] The NF producer instance (such as SMF instance or PCF instance) is the NF instance which host the NF Service Producer. When the NF producer instance is not available, another NF producer instance within the same NF Set is selected. In the case of home routed PDU session the H-SMF is the NF producer while the V-SMF behaves as the NF consumer when interacting the H-SMF. Similarly, in the case of home routed policy association the H- PCF is the NF producer while the V-PCF behaves as the NF consumer when interacting the H-PCF.

[0063] For Direct Communication mode, if the NF Service consumer detects that the NF producer instance is not available anymore, another available NF producer instance within the same NF Set is selected by the NF Service consumer.

[0064] For Indirect Communication mode, the SCP may need to select another NF producer instance within the same NF Set if the original NF producer instance serving the UE is not available anymore.

[0065] Figure 6 and Figure 7 illustrates the problem with the current procedures described in Figures 4 and 5 above.

[0066] In Figure 6, even though AMF holds NF Set Id information of SMF NF Set to which H-SMF1 belongs (obtained in step 2b), AMF does not include the SMF NF Set Id in step 4.

[0067] Therefore, if, for some reason, step 5 in Figure 6 fails (the request either times out or a failure response is received in V-SMF), V-SMF needs to perform two NRF discoveries with H-NRF to obtain an alternate H-SMF instance. More specifically,

[0068] Step 6a) V-SMF performs NRF Discovery using home SMF1 identifier (hSmflld) received in step 4.

[0069] Step 6b) V-SMF receives SMF NF Set Id from to which H-SMF1 belongs.

[0070] Step 7a) V-SMF performs NRF Discovery using SMF NF Set Id received in step 6b.

[0071] Step 7b) V-SMF receives a!! SMF profiles belonging to that SMF NF Set (as an example, H-SMF1 and H-SMF2).

[0072] Now V-SMF can send Nsmf_PDUSession_ Create request to H-SMF2 (Step 8).

[0073] Similarly in Figure 7, even though AMF had NF Set Id information of PCF NF Set to which H-PCF1 belongs (obtained in step 2b), AMF does not include PCF NF Set Id in step 4.

[0074] Therefore, if, for some reason, step 5 in Figure 7 fails (the request either times out or a failure response is received in V-PCF), V-PCF needs to perform 2 NRF discoveries with H-NRF to obtain an alternate H-PCF instance.

[0075] Step 6a) V-PCF performs NRF Discovery using hPcflld received in step 4

[0076] Step 6b) V-PCF receives PCF NF Set Id from to which H-PCF1 belongs

[0077] Step 7a) V-PCF performs NRF Discovery using PCF NF Set Id received in step 6b

[0078] Step 7b) V-PCF receives all PCF profiles belonging to that PCF NF Set (as an example, H-PCF1 and H-PCF2)

[0079] Now V-PCF can send Npcf_UEPolicyControl_Create request to H-PCF2 (Step 8).Issue with Indirect Communication

[0080] Most operators are deploying indirect communication where there could be one or more SCPs in the calf path between V-SMF and H-SMF. In this case:

[0081] Even though AMF had NF Set Id information of SMF NF Set to which H-SMF1 belongs (obtained in step 2b), AMF does not include SMF NF Set Id in step 4 to V-SMF. Consequently, V-SMF cannot include H-SMF NF Set Id in 3gpp-Sbi-Discovery-target-nf- set id

[0082] If SCP fails to send the request to H-SMF, SCP cannot perform failover to an alternate H-SMF instance. The problem is further highlighted in Figure 8.

[0083] In Step 5 of Figure 8, V-SMF sends Nsmf_PDUSession_ Create. In this step, R-URI is SCP URI and 3gpp-Sbi-Target-apiRoot header contains hSmflURI (as API URI). V-SMF cannot include 3gpp-Sbi-Discovery-target-nf-set id, since it did not receive SMF NF Set Id from AMFStep 6): SCP forwards the request to H-SMF1 . But it is unsuccessful (the request either times out or a failure response is received in SCP)Result: SCP cannot send the request to an alternate SMF (i.e., H-SMF2) The same issue exists with indirect communication for UE Policy Association Establishment. Not elaborated further since the issue is identical as above.

[0084] Certain aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges. According to some embodiments and in light of the problem illustrated in Figures 6, 7 and 8, at home-routed PDU Session Establishment, the AMF provides "H-SMF NF Set Id information" to V-SMF. This allows V-SMF to perform failover operation (if needed) to an alternate H-SMF belonging to same set by performing NRF Discovery using "target-nf-set-id" as Discovery query attribute. Additionally, if indirect communication via SCP is applicable, V-SMF can populate 3gpp-Sbi-Discovery-target-nf-set id header to SCP to enable SCP to perform failover when needed.

[0085] At home-routed UE Policy Association Establishment, AMF provides "H-PCF NF Set Id information" to V-PCF. This allows V-PCF to perform failover operation (if needed) to an alternate H-PCF belonging to same set by performing NRF Discovery using "target-nf-set-id" as Discovery query attribute. Additionally, if indirect communication via SCP is applicable, V-PCF can populate 3gpp-Sbi-Discovery-target-nf- set id header to SCP to enable SCP to perform failover when needed.

[0086] The embodiments presented herein enables:1 ) In case of failover by V-SMF / V-PCF to alternate H-SMF / H-PCF, only one NRF Discovery is needed.2) In case of indirect communication, it allows SCP to failover to alternate H-SMF / H- PCF

[0087] Further details will now be elaborated addressing the challenges above. Figure 9A illustrates a flow diagram of home routed PDU session establishment procedure using direct communication in accordance with some embodiments.

[0088] Step 1 of Figure 9 is identical to step 1 in Figure 4. AMF receives a PDU session establishment request from the UE (included in a NAS transport message).

[0089] Steps 2a-2b AMF uses NRF discovery mechanism to discover H-SMF (in the home PLMN) using H-NRF. H-NRF provides H-SMF instance(s) (e.g., H-SMF1, H-SMF2) and the H-SMF Set Id of each of the H-SMF1 and H-SMF-2 instances. AMF then selectsan H-SMF instance (e.g., H-SMF1 instance) based on the resuit of the discovery procedure.

[0090] Step 3a-3b. The AMF may interact with NRF in the visited PLMN (V-NRF) to discover one or more V-SMF instances and selects a V-SMF instance.

[0091] Step 4: to proceed with establishment of the home routed PDU session, the AMF sends a request to the selected V-SMF instance (e.g., a Nsmf_PDUSession_CreateSMContext request) to request establishment of the home routed PDU session and includes the URI of H-SMF1 and the H-SMF1 instance id and the H-SMF Set Id of H-SMF1 (hSmfl NF Set id) (received in step 2b).

[0092] Step 5: the V-SMF initiates interaction with H-SMF1 using the received URI, but the interaction fails (e.g., not available, not responsive).

[0093] Step 6a: When V-SMF is unable to reach H-SMF1 and needs to find an alternate H-SMF, instead of failing the establishment of the PDU session, the V-SMF will now be able to uses hSmfl NF Set id (received at step 4) to perform NRF Discovery.

[0094] This solves the problem that V-SMF needs to perform 2 NRF Discovery as shown in Figure 6. Only one NRF Discovery is needed for the failover.

[0095] Figure 9B illustrates a flow diagram of home routed PDU session establishment procedure using Indirect-communication in accordance with some embodiments.

[0096] Step 1 of Figure 9B is identical to step 1 in Figure 9A. AMF receives a PDU session establishment request from the UE (included in a NAS transport message).

[0097] Steps 2a-2b AMF uses NRF discovery mechanism to discover H-SMF (in the home PLMN) using H-NRF. H-NRF provides H-SMF instance(s) (e.g., H-SMF1, H-SMF2) and the H-SMF Set Id of each of the H-SMF1 and H-SMF-2 instances. AMF then selects an H-SMF instance (e.g., H-SMF1 instance) based on the resuit of the discovery procedure.

[0098] Steps 3a-3b. The AMF may interact with NRF in the visited PLMN (V-NRF) to discover one or more V-SMF instances and selects a V-SMF instance.

[0099] Step 4: to proceed with establishment of the home routed PDU session, the AMF sends a request to the selected V-SMF instance (e.g., a Nsmf_PDUSession_CreateSMContext request) to request establishment of the home routed PDU session and includes the URI of H-SMF1 and the H-SMF1 instance id and the H-SMF Set Id of H-SMF1 (hSmfl NF Set id) (received in step 2b).

[0100] Step 5: the V-SMF sends Nsmf_PDUSession_CreateSMContext request to the SCP using the hSMFlURI (Received in step 4) as API URI and the H-SMF1 set id (hSmfl NF Set id). The V-SMF includes hSmfl NF Set id (received in step 4) in 3gpp-Sbi- Discovery-target-nf-set id header.

[0101] Step 6. The SCP forwards the request to H-SMF1 to establish the home routed PDU session using the hSMFlURI, but the interaction fails (e.g., H-SMF1 instance not available, not responsive).

[0102] Step 7a: When SCP is unable to reach H-SMF1 and needs to find an alternate H-SMF, it uses hSmfl NF Set id (received in step 5) to perform NRF Discovery.

[0103] Step 7b: SCP receives alternate H-SMF2 belonging to same NF Set from H- NRF.

[0104] Step 8: SCP forwards the request to alternate H-SMF2. This solves the problem that SCP cannot do failover as shown in Figure 8.

[0105] Figure 10 illustrates a flow diagram of home routed policy association establishment procedure using Direct-communication in accordance with some embodiments.

[0106] Step 1 of Figure 10 is identical to step 1 in Figure 5. AMF receives a registration request from the UE.

[0107] Steps 2a-2b AMF uses NRF discovery mechanism to discover H-PCF (in the home PLMN) using H-NRF. H-NRF provides H-PCF instance(s) (e.g., H-PCF1, H-PCF2) instances and the H-PCF Set Id of each of the H-PCF1 and H-PCF2 instances. AMF then selects an H-PCF instance (e.g., H-PCF1 instance) based on the result of the discovery procedure.

[0108] Steps 3a-3b. The AMF may interact with NRF in the visited PLMN (V-NRF) to discover one or more V-PCF instances and selects a V-PCF instance.

[0109] Step 4: to proceed with establishment of the home routed policy association, the AMF sends a request to the selected V-PCF instance (e.g., a Npcf_UEPolicyControl_Create request) to request establishment of the home routed Policy association and includes the URI of H-PCF1 and the H-PCF1 instance id and the H-PCF Set Id of H-PCF1 (hPCFl NF Set id) (received in step 2b).

[0110] Step 5: the V-PCF initiates interaction with H-PCF1 using the received URI, but the interaction fails (e.g., not available, not responsive).

[0111] Step 6a: When V-PCF is unable to reach H-PCF1 and needs to find an alternate H-PCF, instead of failing the establishment of the policy association, the V-PCF will now be able to uses hPCFl NF Set id (received at step 4) to perform NRF Discovery.

[0112] This solves the problem that V-PCF needs to perform 2 NRF Discovery as shown in Figure 7. Only one NRF Discovery is needed for the failover.

[0113] Although Figure 10 illustrates the scenario for Direct communication, the same scenario described in 9B for indirect communication applies for home routed policy association establishment using SCP as well, replacing SMF with PCF.

[0114] The above embodiments are described based on the standard procedures described in 3GPP standards. The following are examples of proposed changes to the 3GPP standards to support the above embodiments illustrated in Figures 9A, 9B and 10.

[0115] For example, 3GPP TS 23.502 Section 5.2.5.6.2 can be amended as (change in bold / underlined):5.2.5.6.2 Npcf_UEPolicyControl_Create service operation- Some parts not shownInputs, Optional: H-PCF ID and H-PCF NF Set Id (if the NF service producer is V- PCF and AMF is NF service consumer), information provided by the AMF as define in clause 6.2.1.2 of TS 23.503 ..., such as Access Type, Permanent Equipment Identifier, GPSI, User Location Information, UE Time Zone, Serving Network (PLMN ID, or PLMN ID and NID, see clause 5.34 of TS 23.501 ...), RAT type, LBO Information (see clause 6.1 .2.2.4 of TS 23.503 ...), UE policy container including the list of PSIs, OS id, the indication of UE support for ANDSP, UE capability of reporting URSP rule enforcement to network (see clause 6.6.2.4 of TS 23.503 ...), UE indication of support of URSP delivery in EPS and Internal Group (see TS 23.501 ...), Satellite backhaul category (see clause 5.43 of TS 23.501 ...), ”5GS to EPS Mobility” indication, request to update the UE policies, request to be notified when updated UE policies have been provided to the UE.

[0116] For example, 3GPP TS 23.502 Section 5.2.8.2.5 can be amended as (change in bold / underlined):5.2.8.2.5 Nsmf_PDUSession_CreateSMContext service operation- Some parts not shownInput, Optional: PEI, S-NSSAI(s), Alternative S-NSSAI, Slice Area Restriction indication, PDU Session Id, N1 SM container, UE location information, UE Time Zone, AN type, H-SMF identifier / address. H-SMF NF Set id. list of alternative H-SMF(s) ifavailable, old PDU Session ID (if the AMF also received an old PDU Session ID from the UE as specified in clause 4.3.5.2), Subscription For PDU Session Status Notification, Subscription for DON Failure Notification, NEF Correlation ID, indication that the SUPI has not been authenticated, PCF ID, PCF Group ID, Same PCF Selection Indication, DNN Selection Mode, UE PDN Connection Context, GPSI, UE presence in LADN service area, indication that "the PDU Session is subject to LADN per LADN DNN and S-NSSAI", GUAM!, backup AMF(s) (if NF Type is AMF), Trace Requirements, Control Plane CloT 5GS Optimisation indication, Small Data Rate Control Status, APN Rate Control Status. Backup AMF(s) sent only once by the AMF to the SMF in its first interaction with the SMF, UE's Routing Indicator optionally with Home Network Public Key identifier or UDM Group ID for the UE, EPS Interworking indication, EPS Bearer Status. Target ID (for EPS to 5GS handover), "Invoke NEF" flag, target DNAI, additional following for SM context transfer: SMF transfer indication, Old SMF ID, SM context ID in old SMF (see clause 4.26.5.3), HO Preparation Indication, indication of no NG-RAN change. MA PDU request indication, MA PDU Network-Upgrade Allowed indication, Indication on whether the UE is registered in both accesses, Satellite backhaul category, GEO Satellite ID, PVS FQDN(s) and / or PVS IP address(es) and Onboarding Indication in the case of ON-SNPN, Disaster Roaming service indication, HR-SBO allowed indication, Indication of UE supports non-3GPP access path switching.

[0117] For example, 3GPP TS 29.502 Section 5.2.2.2.1 can be amended as (change in bold / underlined):5.2.2.2.1 General- Some parts not shownFor the UE requested PDU Session Establishment procedure in home routed roaming scenario (see clause 4.3.2.2.2 of 3GPP TS 23.502 ...), the NF Service Consumer shall provide the URI of the Nsmf_PDUSession service of the H-SMF in the hSmfUri IE and optionally the corresponding SMF ID and NF Set Id of the SMF. and may provide the URI of the Nsmf_PDUSession service of additional H- SMF(s) with the corresponding SMF ID(s). The V-SMF shall try to create the PDU session using the hSmfUri IE. If due to communication failure on the N16 interface the V-SMF does not receive any response from the H-SMF, then:

[0118] For example, 3GPP TS 29.502 Section 6.1.6.2.2 can be amended as following (new IE as shown in bold text)6.1 .6.2.2 Type: SmContextCreateDataTable 6.1.6.2.2-1: Definition of type SmContextCreateData- Some parts not shown

[0119] For example, 3GPP TS 29.525 Section 4.2.2.1 can be amended as following (bold / underlined)4.2.2.1 General- Some parts not shown- the received UE policy delivery protocol message defined in Annex D of 3GPP TS 24.501

[0015] encoded as "uePolReq" attribute;- for the roaming scenario, if the NF service consumer is an AMF, the H-PCF ID encoded as "hPcfld" attribute and the H-PCF NF Set ID encoded as "hPcfSetld" attribute:- the Internal Group Identifier(s) encoded as “grouplds" attribute:

[0120] For example, 3GPP TS 29.525 Section 5.0.2.3 (include new IE as shown in bold text)- Some parts not shown

[0121] Figure 11 illustrates a flow chart for a method in an Access and Mobility Management function (AMF) for improving home routed PDU session establishment or policy association establishment for a roaming UE.

[0122] The AMF receives an access request (e.g., a registration request or a PDU0 session establishment request). The AMF determines the UE is roaming (e.g., based on subscription) and home-routing PDU session or policy association establishment needs to be performed.

[0123] At step 11A1, the AMF discovers (via a home NRF) the Home NF producer instance (SMF or PCF) for PDU session establishment (SMF) or policy association5 establishment (PCF) and obtains one or more NF instances in the home PLMN and the NF set IDs of each of the NF instances in the home PLMN (NF instances in the home are home SMF or home PCF).

[0124] The AMF selects an NF instance in the home PLMN (herein referred to as home NF instance) and determines another NF instance in the visited network (herein0 referred to as visited NF instance)

[0125] At step 11A2, the AMF invokes a service operation with the visited NF instance (e.g., Nsmf_PDUSession_CreateSMContext service operation, Npcf_UEPolicyControl_Create service operation) by sending respective request messages and includes the URI of the selected home NF instance, the home NFinstance id and the Home NF Set id of the selected home NF instance (e.g., H-SMF or H-PCF) to enable the visited NF instance to use the home NF Set ID to discover an alternative home NF instance in the event the selected home NF instance is unreachable instead of the visited NF instance failing in establishing the PDU session or policy association.

[0126] Figure 12 is a schematic block diagram of a network node 1100 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The network node 1100 may be, for example, a core network node that implements a NF (e.g., AMF 200, SMF 206, SMSF220, NSACF 207, UDM 406, or the like). As illustrated, the network node 1100 includes a one or more processors 1104 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and / or the like), memory 1106, and a network interface 1108. The one or more processors 1104 are also referred to herein as processing circuitry. The one or more processors 1104 operate to provide one or more functions of the network node 1100 as described herein (e.g., one or more functions of the AMF 200, SMF 206, SMSF220, NSACF 207, UDM 406, ePDG, N3IWF, TNGF or the like, as described herein. In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 1106 and executed by the one or more processors 1104.

[0127] Figure 13 is a schematic block diagram that illustrates a virtualized embodiment of the network node 1100 according to some embodiments of the present disclosure. Again, optional features are represented by dashed boxes. As used herein, a "virtualized" network node is an implementation of the network node 1100 in which at least a portion of the functionality of the network node 1100 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the network node 1100 includes one or more processing nodes 1200 coupled to or included as part of a network(s) 1202. Each processing node 1200 includes one or more processors 1204 (e.g., CPUs, ASICs, FPGAs, and / or the like), memory 1206, and a network interface 1208. In this example, functions 1210 of the network node 1100 described herein (e.g., one or more functions of the AMF 200, SMF 206, SMSF220, NSACF 207, UDM 406, ePDG, N3IWF, TNGF or thelike, as described herein) are implemented at the one or more processing nodes 1200 or distributed across the two or more processing nodes 1200 in any desired manner. In some particular embodiments, some or all of the functions 1210 of the network node 1100 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 1200.

[0128] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the network node 1100 or a node (e.g., a processing node 1200) implementing one or more of the functions 1210 of the network node 1100 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0129] Figure 14 is a schematic block diagram of the network node 1100 according to some other embodiments of the present disclosure. The network node 1100 includes one or more modules 1300, each of which is implemented in software. The module(s) 1300 provide the functionality of the network node 1100 described herein. This discussion is equally applicable to the processing node 1200 of Figure 13 where the modules 1300 may be implemented at one of the processing nodes 1200 or distributed across multiple processing nodes 1200.

[0130] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / ordata communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure.

[0131] While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

[0132] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

[0133] Some example embodiments of the present disclosure are as follows: Embodiment 1. A method performed by an access and mobility management in a visited PLMN, the method comprising:- determining whether to initiate one of a home routed PDU session establishment procedure or a home routed policy association procedure;- receiving as part of a discovery procedure with a home PLMN, one or more home SMF instances of a home SMF and the corresponding one or more home SMF set identifier for the home routed PDU session establishment procedure or one or more home PCF instances of a home PCF and the corresponding one or more home PCF set id for the home routed policy association establishment procedure; and- one of transmitting to a visited SMF instance a message as part of the home routed PDU session establishment procedure, the message comprising a URI of a selected home SMF instance, a home SMF instance identifier and the home SMF set id of the selected home SMF instance or transmitting to a visited PCF instance a message as part of the home routed policy association establishment procedure, the message comprising a URI of a selected home PCF instance, a home PCF instance identifier and the home PCF set id of the selected home SMF instance.Embodiment 2. The method of embodiment 1 wherein the step of determining further comprises receiving a registration request from a UE or a PDU session establishment request.Embodiment 3. A method performed by an NF instance in a visited PLMN, the method comprising:- one of receiving a message as part of a home routed PDU session establishment procedure, the message comprising a URI of a selected home NF instance of a same type in the Home PLMN, and a home SMF set id of the selected home SMF instance or receiving a message as part of the home routed policy association establishment procedure, the message comprising a URI of a selected home PCF instance and a home PCF set id of the selected home PCF instance;- in response to determining one of the selected home SMF instance or home PCF instance is unreachable, selecting an alternative one of home SMF instance or home PCF instance based on the received home SMF set id of the selected home SMF instance or the received home PCF set id of the selected home PCF instance.Embodiment 4. The method of any one of embodiments 3 wherein the NF instance in the visited PLMN is a visited SMF instance for home routed PDU session establishment procedure or a visited PCF instance for the home routed policy association establishment procedure or an SCP regardless of the procedure when indirect communication is used.Embodiment 5. The method of embodiment 4 wherein the message is one of Nsmf_PDUSession_CreateSMContext request or Nsmf_UEPolicyControl_Create request message.Embodiment 6. A network node configured to perform the method of any of embodiments 1 to 5.Embodiment 7. A network node comprising one or more processors and memory comprising instructions which when executed by the one or more processors enable the network node to perform the method of any of embodiments 1 to 5. Embodiment 8. A computer readable memory comprising instructions which when executed by one or more processors of one or more servers configures the one or more servers to perform any of the embodiments 1 to 5.

[0134] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

Claims:

1. A method performed by an access and mobility management in a visited Public Land Mobile Network (PLMN), during a home routed Packet Data Unit (PDU) session establishment procedure for a User Equipment (UE), the method comprising:- receiving as part of a discovery procedure with a home PLMN, at least one home Session Management function (SMF) instance of a home SMF and a home SMF set identifier(id) of the at least one home SMF instance; and- transmitting to a visited SMF instance a message to establish a home routed PDU session for the UE, the message comprising a URI of a home SMF instance selected based on the received at least one home SMF instance, an identifier of the selected home SMF instance and the home SMF set id of the selected home SMF instance.

2. The method of claim 1 wherein the message comprises an SmContextCreateData data type and the SmContextCreateData data type includes the URI of a selected home SMF instance, the identifier of the selected home SMF instance identifier and the home SMF set id of the selected home SMF instance.

3. The method of claim 1 wherein the step of receiving as part of a discovery procedure with a home PLMN comprises sending a discovery request to a home Network Registry Function (H-NRF) to discover home SMF instances and receiving a discovery response comprising the at least one home SMF instance of the home SMF and the corresponding home SMF set id of the at least one home SMF instance.

4. The method of claim 1 wherein the home SMF set id is to be used by the visited SMF instance to initiate failover procedure to a second home SMF instance in the event the selected home SMF instance has failed.

5. A method performed by an access and mobility management in a visited Public Land Mobile Network (PLMN) during a home routed policy association establishment procedure for a User Equipment (UE), the method comprising:- receiving as part of a discovery procedure with a home PLMN, at least one home Policy Control function (PCF) instance of a home PCF and a home PCF set identifier(id) of the at least one home PCF instance; and- transmitting to a visited PCF instance a message to create a home routed policy association for the UE, the message comprising a URI of a home PCF instance selected based on the received at least one home PCF instance, an identifier of the selected home PCF instance and the home PCF set id of the selected home PCF instance.

6. The method of claim 5 wherein the message is a Npcf_UEPolicyControl_Create request.

7. The method of claim 5 wherein the home PCF set id is to be used by the visited PCF instance to initiate failover procedure to a second home PCF instance in the event the selected home PCF instance has failed.

8. The method of claim 5 wherein the step of receiving as part of a discovery procedure with a home PLMN comprises sending a discovery request to a home Network Registry Function (H-NRF) to discover home PCF instances and receiving a discovery response comprising the at least one home PCF instance of the home PCF and the corresponding home PCF set id of the at least one home PCF instance.

9. A method performed by a Network Function (NF) instance in a visited Public Land Mobile Network (PLMN), the method comprising: receiving one of a message to establish a home routed PDU session establishment for a User Equipment (UE), or a message to establish a home routed policy association for the UE, the message comprising a URI of a selected home NF instance in a home PLMN where the selected home NF instance is of a same type as the NF instance in the visited PLMN, a set identifier of the selected home NF instance and a URI of the selected home NF instance;- in response to determining the selected home NF instance is unreachable while establishing one of home routed PDU session or home routed policy association with the selected home NF instance , selecting an alternative home NF instance based on the received set id of the selected home NF instance.

10. The method of claim 9 wherein when the visited NF instance is a visited session management function (SMF) instance, the selected home NF instance is the selected home SMF instance.

11. The method of claim 9 wherein when the visited NF instance is a visited policy control function (PCF) instance, the selected home NF instance is the selected home PCF instance.

12. The method of claim 9 wherein prior to determining the selected home NF instance is unreachable, using the selected home NF instance and the URI of the selected home NF instance to request establishment of a home routed PDU session or establishment of a home routed policy association.

13. The method of claim 9 or 12 wherein the step of determining the selected home NF instance is unreachable further comprises failing to receive a response to the request for establishment of a home routed PDU session or home routed policy association.

14. A network node configured to perform the method of any one of claims 1 to 13.

15. A network node comprising one or more processors and memory comprising instructions which when executed by the one or more processors enable the network node to perform the method of any one of claims 1 to 13.

16. A computer readable memory comprising instructions which when executed by one or more processors of one or more servers configures the one or more servers to perform any one of the claims 1 to 13.

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