WO2022069364A1

WO2022069364A1 - Selection of a smf

Info

Publication number: WO2022069364A1
Application number: PCT/EP2021/076347
Authority: WO
Inventors: Yong Yang; Yunjie Lu
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2020-09-30
Filing date: 2021-09-24
Publication date: 2022-04-07

Abstract

Methods performed by a Session Management Function (SMF) and an Access and Mobility Management Function (AMF) in a Core Network (CN) for reselecting another SMF for a Protocol Data Unit (PDU) session are provided. In examples disclosed herein, the SMF receives a request message from the AMF that includes a binding information related to the another SMF. Accordingly, the SMF selects the another SMF based at least on the binding information received from the AMF. Subsequently, the SMF can send a response message to the AMF that includes a Network Function (NF) Instance Identification of the another SMF. The methods performed by the SMF and the AMF can enable proper reselection of any SMF, thus helping to ensure session continuity in a wireless communication network.

Description

SELECTION OF A SMF

TECHNICAL FIELD

The technology of the disclosure relates generally to selecting a Session Management Function (SMF) in a Core Network (CN).

BACKGROUND

In Rel-16, 3GPP has further broadened the use of a Network Function Set concept to be applicable for all types of Network Function (NF) in 5G Core (5GC). For example, several Session Management Functions (SMFs) can form a SMF Set.

The following is a list of definitions related to NF service, NF service set, NF, and NF Set. (from TS 23.501)

• NF instance: an identifiable instance of the NF.

• NF service: a functionality exposed by a NF through a service based interface and consumed by other authorized NFs.

• NF service instance: an identifiable instance of the NF service.

• NF service operation: An elementary unit a NF service is composed of.

• NF Service Set: A group of interchangeable NF service instances of the same service type within an NF instance. The NF service instances in the same NF Service Set have access to the same context data.

• NF Set: A group of interchangeable NF instances of the same type, supporting the same services and the same Network Slice(s). The NF instances in the same NF Set may be geographically distributed but have access to the same context data.

As specified in 5.21.3.1 of TS 23.501 , an NF instance can be deployed such that several network function instances are present within an NF Set to provide distribution, redundancy and scalability together as a set of NF instances. The same is also supported for NF Services.

Such a network reliability design shall work in both communication modes, (i.e., direct communication and indirect communication).

Equivalent Control Plane NFs may be grouped into NF Sets, e.g., several SMF instances are grouped into an SMF Set. NFs within a NF Set are interchangeable because the NFs share the same context data and may be deployed in different locations (e.g., different data centers). As such, a SMF can be replaced by another SMF within the same SMF Set in such scenarios as failure, load balancing, and load re-balancing.

When an NF (Service) Set is deployed in the network as specified in clauses 5.21.3 and 6.3.1.0 of 3GPP TS 23.501 , an NF Service Producer in the NF (Service) Set creates resource contexts and the context data is shared by all the NF (Service) instances pertaining to the same NF (Service) Set. For example, the resource context is bound to the NF (Service) Set. So, requests targeting the resource may be served by any NF (Service) Instance within the NF (Service) set, unless the shared contexts are lost. Similarly, when a Service Consumer invokes a NF Service, the Service Consumer may create session context for callback (in accordance to the resource context in the NF Service Producer) and make such context data to be shared by any NF (Service) instance, for example, the context is bound to the NF (Service) Set. In this regard, any NF (Service) instance within the NF (Service) set may be able to receive notifications or callback request from the NF Service Producer, until the NF (Service) Set has failed.

Such resilience information for a resource context or session context is denoted as the Binding Indication for a given resource context or session context.

Figures 1 and 2

For a Home Routed (HR) PDU session (with a V-SMF), as shown in Figure 1, or a PDU session with an l-SMF (to support deployments topologies with specific SMF Service Areas, as shown in Figure 2, the V-SMF and l-SMF may be inserted, changed, or removed while the SMF in the Home Public Land Mobile Network (PLMN) (hSmf) or the anchor SMF will remain unchanged functionally.

SUMMARY

Embodiments disclosed herein include methods performed by a Session Management Fu nction (SMF) and an Access and Mobility Management Function (AMF) in a Core Network (CN) for reselecting another SMF(s) for a Protocol Data Unit (PDU) session.

Embodiments disclosed herein include methods performed by a Session Management Function (SMF) and an Access and Mobility Management Function (AMF) in a Core Network (CN) for reselecting another SMF(s) for a Protocol Data Unit (PDU) session. In examples disclosed herein, the SMF receives a request message from the AMF that includes a binding information related to the other SMF(s). Accordingly, the SMF selects the other SMF(s) based at least on the binding information received from the AMF. Subsequently, the SMF can send a response message to the AMF that includes at least a Network Function (NF) Instance Identification of the another SMF(s). The methods performed by the SMF and the AMF can enable proper reselection of any SMF, thus helping to ensure session continuity in a wireless communication network. In one embodiment, a method performed by an SMF in a CN for reselecting another SMF for a PDU session is provided. The method includes receiving a request message from an AMF, wherein the request message comprises binding information related to at least one other SMF. The method also includes selecting the at least one other SMF based at least on the binding information received from the AMF. The method also includes sending a response message to the AMF, wherein the response message comprises at least a Network Function, NF, Instance Identification, ID, of the at least one another SMF.

In one embodiment, the binding information comprises binding information for an SmContext in a first other SMF, where the first other SMF is one of the at least one other SMF. Further, receiving the request message comprises receiving a Nsmf_PDUSession_CreateSMContext Request message comprising the binding information for the SmContext in the first other SMF (e.g., the old l-SMF/V-SMF or hSMF).

In one embodiment, sending the response message to the AMF comprises sending a Nsmf_PDUSession_CreateSMContext Response message or a Nsmf_PDUSession_UpdateSMContext Response message.

In one embodiment, the binding information comprises binding information for an SmContext in a first other SMF, where the first other SMF is one of the at least one other SMF. Further, receiving the request message comprises receiving the request message comprising the binding information for the SmContext in the first other SMF. Selecting the at least one other SMF based on the binding information comprises selecting the first other SMF based on the binding information for the SmContext.

In one embodiment, the first other SMF and an alternate SMF of the first other SMF belong to a same SMF NF (service) Set as indicated by the binding information for SmContext.

In one embodiment, selecting the at least one other SMF comprises selecting a second other SMF based on binding information for a PDU session in the second other SMF, wherein the second other SMF is one of the at least one other SMF.

In one embodiment, selecting the second other SMF (e.g., hSMF) comprises receiving a Nsmf_PDUSession_Context Response message from the first other SMF (e.g., the old I-SMFA/-SMF), wherein the Nsmf_PDUSession_Context Response message comprises the binding information for the PDU session in the second other (e.g., hSMF).

In one embodiment, sending the response message to the AMF further comprises sending a pair of NF IDs corresponding to the first other SMF and the second other SMF, respectively.

In one embodiment, a method performed by an AMF in a CN for reselecting another SMF for a PDU session (e.g., Home Routed PDU session or PDU session with l-SMF) is provided. The method includes sending a request message to an SMF (e.g., I-SMF or V-SMF), wherein the request message comprises a binding information related to at least one other SMF (e.g., old I-SMFA/-SMF, anchor SMF, or hSMF). The method also includes receiving a response message from the SMF, wherein the response message comprises at least a Network Function, NF, Instance Identification, ID, of the at least one other SMF.

In one embodiment, sending the request message comprises sending a Nsmf_PDUSession_CreateSMContext Request message comprising the binding information for an SmContext in the at least one other SMF (e.g., the old l-SMF/V-SMF or hSMF).

In one embodiment, receiving the response message from the SMF comprises receiving a Nsmf_PDUSession_CreateSMContext Response message or a Nsmf_PDUSession_UpdateSMContext Response message.

In one embodiment, sending the request message comprises sending the request message comprising the binding information for an SmContext in a first other SMF and for a PDU session in second other SMF.

In one embodiment, the first other SMF and an alternate SMF of the at least one other SMF belong to a same SMF NF (service) Set as indicated by the binding information for SmContext.

In one embodiment, receiving the response message from the SMF further comprises receiving a pair of NF IDs corresponding to the first other SMF and the second other SMF.

Figure 3

Example l-SMF insertion procedure

Figure 3 is a flow diagram providing an exemplary illustration of UE Triggered Service Request with l-SMF insertion/change/removal as defined in clause 4.23.4.3 of TS 23.502.

When, as part of a UE Triggered Service Request, l-SMF is to be inserted, changed or removed, the procedure in clause 4.23.4.3 is used. It includes the following cases: the UE moves from SMF service area to new l-SMF service area, a new l-SMF is inserted (i.e., I- SMF insertion); or the UE moves from old l-SMF service area to new l-SMF service area, the l-SMF is changed (i.e., I- SMF change); or the UE moves from old l-SMF service area to SMF service area, the old l-SMF is removed (i.e., I- SMF removal).

If the service request is triggered by network due to downlink data and a new l-UPF is selected, forwarding tunnel is established between the old l-UPF, if the old l-UPF is different from Protocol Data Unit (PDU) Session Anchor (PSA), and the new l-UPF to forward buffered data.

For HR Roaming, the l-SMF (old and new) and l-UPF (old and new) are located in Visited PLMN, while the SMF and UPF (PSA) are located in the Home PLMN. In this HR roaming case, only the l-SMF change is applicable as there is always a V-SMF for the PDU Session. Table 6.1.6.2.37-1: Definition of type PduSessionContext.

Table 6.1.6.2.39-1: Definition of type SmContext

BRIEF DESCRIPTION OF THE DRAWINGS

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.

Figure 1 is a block diagram illustrating a roaming Fifth-Generation (5G) architecture as defined in Third-Generation Partnership Project (3GPP) TS 23.501 specification;

Figure 2 is a block diagram illustrating a non-roaming architecture as defined in the 3GPP TS 23.501 specification;

Figure 3 is a flow diagram illustrating a User Equipment (UE) trigger service request procedure as defined in 3GPP TS 23.502 specification;

Figure 4 illustrates one example of a cellular communications system according to some embodiments of the present disclosure;

Figures 5-6 illustrate example embodiments in which the cellular communication system of Figure 4 is a 5G System (5GS);

Figure 7 is a flowchart of method performed by a Session Management Function (SMF) in a Core Network (CN) for reselecting another SMF for a Protocol Data Unit (PDU) session;

Figure 8 is a flowchart of a method performed by an Access and Mobility Management Function (AMF) in a CN for reselecting another SMF for a PDU session;

Figure 9 is a flow diagram providing exemplary signaling of l-SMF change according to embodiments of the present disclosure;

Figure 10 is a flow diagram providing exemplary signaling of l-SMF insertion according to embodiments of the present disclosure; Figure 11 is a flow diagram providing exemplary signaling of SMF reselection according to embodiments of the present disclosure;

Figure 12 is a schematic block diagram of a radio access node according to some embodiments of the present disclosure;

Figure 13 is a schematic block diagram that illustrates a virtualized embodiment of the radio access node of Figure 12 according to some embodiments of the present disclosure;

Figure 14 is a schematic block diagram of the radio access node of Figure 12 according to some other embodiments of the present disclosure;

Figure 15 is a schematic block diagram of a UE according to some embodiments of the present disclosure; and

Figure 16 is a schematic block diagram of the UE of Figure 15 according to some other embodiments of the present disclosure.

DETAILED DESCRIPTION

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.

Radio Node: As used herein, a “radio node” is either a radio access node or a wireless communication device.

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 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.

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. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Home Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing a Access and Mobility Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), 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), or the like.

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 vehicle-mounted mobile device, enabled to communicate voice and/or data via a wireless or wireline connection.

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.

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.

Transmission/Reception Point (TRP): In some embodiments, a TRP may be either a network node, a radio head, a spatial relation, or a Transmission Configuration Indicator (TCI) state. A TRP may be represented by a spatial relation or a TCI state in some embodiments. In some embodiments, a TRP may be using multiple TCI states.

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

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. There currently exist a certain challenge(s) . The SMF Set concept is applicable to both V/I-SMF and the (h)Smf. For example, another SMF in the same SMF Set may take over the SmContext resource context stored in the old V/I-SMF or in the (h)SMF, or take over the (Protocol Data Unit) PDUSession resource context in the (h)SMF for an HR PDU Session, or a PDU Session with a l-SMF. In this regard, there may exist a few issues:

Problem 1 :

In step 4a of Figure 3, when the new l-SMF (for l-SMF insertion or l-SMF change) contacts the SMF or old l-SMF by invoking Nsmf_PDUSession_Context Request, the new l-SMF needs the binding indication of the SmContext for this PDU session, which was provided by the SMF or old-l-SMF earlier, to provide such information that can be used to reselect an equivalent SMF in the same SMF set as the old I- SMF or the SMF, in case the old l-SMF or SMF (as indicated in the target URI or 3gpp-Sbi-target-api Root) is not reachable.

"4a. The new l-SMF retrieves SM Context from the old l-SMF (in the case of l-SMF change) or SMF (in the case of l-SMF insertion) by invoking Nsmf_PDUSession_Context Request (SM context type, SM Context ID). The new l-SMF uses SM Context ID received from AMF for this service operation. SM Context ID is used by the recipient of Nsmf_PDUSession_Context Request in order to determine the targeted PDU Session. SM context type indicates that the requested information is all SM context, i.e. PDN Connection Context and 5G SM context."

Problem 2:

In step 8a of Figure 3, for l-SMF change scenario, when the new l-SMF contacts the SMF by invoking Nsmf_PDUSession_Update Request, the new l-SMF needs the binding indication of the PDUSession resource context for this PDU session, which was provided by the SMF earlier, to provide such information that can be used to reselect an equivalent SMF in the same SMF set as the SMF, in case the SMF (as indicated in the target URI or 3gpp-Sbi-target-apiRoot) is not reachable.

"8a. In the case of l-SMF change, the new l-SMF invokes Nsmf_PDUSession_Update Request (SM Context ID, new l-UPF DL tunnel information, SM Context ID at l-SMF, Access Type, RAT Type, DNAI list supported by the new l-SMF, End Marker Indication) towards the SMF. The new l-SMF uses the SM Context ID at SMF received from old l-SMF for this service operation.

In the case of l-SMF insertion, the new l-SMF invokes Nsmf_PDUSession_Create Request (new l-UPF DL tunnel information, new l-UPF tunnel endpoint for buffered DL data, SM Context ID at l-SMF, Access Type, RAT type, DNAI list supported by the new l-SMF, End marker indication) towards the SMF." Similarly, for an inter V-SMF i nsertion/change procedure, the new V-SMF should be able to reselect a hSmf when the original hSmf is not reachable.

Problem 3:

At any time, when I -/V-SMF re-selects old I-/V-SMF and/or (H-)SMF, the AMF needs to be updated. Otherwise, the AMF cannot perform subsequent operations on the NF hosting the resource, such as to release the SM Context on old I-/V-SMF, or to create SM Context on SMF when I -A/-SMF to be removed.

Embodiments disclosed herein provide a mechanism to populate the Binding Information for SmContext resource context in the old l/V-SMF or (h)SMF, and the Binding Information for PDUSession resource context in the (h)SMF. Specifically, the present disclosure includes the following aspects:

1 . The AMF includes the Binding Information for SmContext resource context in the old l/V-SMF or (h)SMF in the Nsmf_PDUSession_CreateSMContext Request sent to the new l/(V)-SMF (e.g., in step 3 of Figure 3)

2. The old l/(V) SMF includes the Binding Information for PDUSession resource context in the (h)SMF in the Nsmf_PDUSession_Context Response message sent to the new l/(v)-SMF.

3. When a (new) I-/V-SMF re-selects old I-/V-SMF and/or (H-)SMF, the NF instance ID (and service instance Id) information of the re-selected NFs (i.e., the old l/V-SMF and/or (h)Smf) shall be included in Nsmf_PDUSession_CreateSMContext response or Nsmf_PDUSession_UpdateSMContext response to the AMF.

4. Alternative to including the Binding Information for the PDUSession resource context in the (h)SMF in the Nsmf_PDUSession_Context Response message sent, the (old) I-/V-SMF may populate such binding information (of PDUSession resource context in the SMF/H-SMF) to the AMF. Accordingly, the AMF can include such binding information in the Nsmf_PDUSession_CreateSMContext Request (in addition to the SmContext binding information). As such, the new l/V-SMF does not retrieve such information from the old l/V-SMF. Since the binding information (of PDUSession resource in the SMF/H-SMF) is now available in the AMF, the new l/V-SMF may explicitly indicate to AMF that the (H-)SMF is not reachable and the AMF will perform the re-selection of H-SMF according to such binding information already existing in the AMF.

Certain embodiments may provide one or more of the following technical advantage(s). The embodiments disclosed herein enable a new l/V SMF (and a Service Communication Proxy (SCP)) to perform a proper reselection of an old l/V-SMF and (h)SMF, thus helping to ensure session continuity. Figure 4

Figure 4 illustrates one example of a cellular communications system 400 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system 400 is a 5G system (5GS) including a Next Generation RAN (NG-RAN) and a 5G Core (5GC). In this example, the NG-RAN includes base stations 402-1 and 402-2, 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 404-1 and 404-2. The base stations 402-1 and 402-2 are generally referred to herein collectively as base stations 402 and individually as base station 402. Likewise, the (macro) cells 404-1 and 404-2 are generally referred to herein collectively as (macro) cells 404 and individually as (macro) cell 404. The RAN may also include a number of low power nodes 406-1 through 406-4 controlling corresponding small cells 408-1 through 408-4. The low power nodes 406- 1 through 406-4 can be small base stations (such as pico or femto base stations) or Remote Radio Heads (RRHs), or the like. Notably, while not illustrated, one or more of the small cells 408-1 through 408-4 may alternatively be provided by the base stations 402. The low power nodes 406-1 through 406-4 are generally referred to herein collectively as low power nodes 406 and individually as low power node 406. Likewise, the small cells 408-1 through 408-4 are generally referred to herein collectively as small cells 408 and individually as small cell 408. The cellular communications system 400 also includes a core network 410, which in the 5G System (5GS) is referred to as the 5GC. The base stations 402 (and optionally the low power nodes 406) are connected to the core network 410.

The base stations 402 and the low power nodes 406 provide service to wireless communication devices 412-1 through 412-5 in the corresponding cells 404 and 408. The wireless communication devices 412-1 through 412-5 are generally referred to herein collectively as wireless communication devices 412 and individually as wireless communication device 412. In the following description, the wireless communication devices 412 are oftentimes UEs, but the present disclosure is not limited thereto.

Figure 5

Figure 5 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 5 can be viewed as one particular implementation of the system 400 of Figure 4.

Seen from the access side the 5G network architecture shown in Figure 5 comprises a plurality of UEs 412 connected to either a RAN 402 or an Access Network (AN) as well as an AMF 500. Typically, the R(AN) 402 comprises base stations, e.g. such as eNBs or gNBs or similar. Seen from the core network side, the 5GC NFs shown in Figure 5 include a NSSF 502, an AUSF 504, a UDM 506, the AMF 500, a SMF 508, a PCF 510, and an Application Function (AF) 512. 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 412 and AMF 500. The reference points for connecting between the AN 402 and AMF 500 and between the AN 402 and UPF 514 are defined as N2 and N3, respectively. There is a reference point, N11 , between the AMF 500 and SMF 508, which implies that the SMF 508 is at least partly controlled by the AMF 500. N4 is used by the SMF 508 and UPF 514 so that the UPF 514 can be set using the control signal generated by the SMF 508, and the UPF 514 can report its state to the SMF 508. N9 is the reference point for the connection between different UPFs 514, and N14 is the reference point connecting between different AMFs 500, respectively. N15 and N7 are defined since the PCF 510 applies policy to the AMF 500 and SMF 508, respectively. N12 is required for the AMF 500 to perform authentication of the UE 412. N8 and N10 are defined because the subscription data of the UE 412 is required for the AMF 500 and SMF 508.

The 5GC network aims at separating UP and CP. The UP carries user traffic while the CP carries signaling in the network. In Figure 5, the UPF 514 is in the UP and all other NFs, i.e., the AMF 500, SMF 508, PCF 510, AF 512, NSSF 502, AUSF 504, and UDM 506, 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.

The core 5G network architecture is composed of modularized functions. For example, the AMF 500 and SMF 508 are independent functions in the CP. Separated AMF 500 and SMF 508 allow independent evolution and scaling. Other CP functions like the PCF 510 and AUSF 504 can be separated as shown in Figure 5. Modularized function design enables the 5GC network to support various services flexibly.

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.

Figure 6

Figure 6 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 5. However, the NFs described above with reference to Figure 5 correspond to the NFs shown in Figure 6. 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 6 the service based interfaces are indicated by the letter “N” followed by the name of the NF, e.g. Namf for the service based interface of the AMF 500 and Nsmf for the service based interface of the SMF 508, etc. The NEF 600 and the NRF 602 in Figure 6 are not shown in Figure 5 discussed above. However, it should be clarified that all NFs depicted in Figure 5 can interact with the NEF 600 and the NRF 602 of Figure 6 as necessary, though not explicitly indicated in Figure 5.

Some properties of the NFs shown in Figures 5 and 6 may be described in the following manner. The AMF 500 provides UE-based authentication, authorization, mobility management, etc. A UE 412 even using multiple access technologies is basically connected to a single AMF 500 because the AMF 500 is independent of the access technologies. The SMF 508 is responsible for session management and allocates Internet Protocol (IP) addresses to UEs. It also selects and controls the UPF 514 for data transfer. If a UE 412 has multiple sessions, different SMFs 508 may be allocated to each session to manage them individually and possibly provide different functionalities per session. The AF 512 provides information on the packet flow to the PCF 510 responsible for policy control in order to support QoS. Based on the information, the PCF 510 determines policies about mobility and session management to make the AMF 500 and SMF 508 operate properly. The AUSF 504 supports authentication function for UEs or similar and thus stores data for authentication of UEs or similar while the UDM 506 stores subscription data of the UE 412. The Data Network (DN), not part of the 5GC network, provides Internet access or operator services and similar.

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

Before describing exemplary embodiments of the present disclosure, a high-level overview of methods performed by an SMF (e.g., I-SMF, V-SMF) and an AMF for supporting a PDU session are first provided with reference to Figures 7 and 8.

Figure 7

Figure 7 is a flowchart of an exemplary method performed by an SMF (e.g., I-SMF or V-SMF) in a CN for reselecting another SMF for a PDU session (e.g., Home Routed PDU session or PDU session with I- SMF). The SMF (e.g., 508 in Figure 5) is configured to receive a request message from an AMF (e.g., 500 in Figure 5) that includes a binding information related to at least one other SMF (e.g., a different SMF 508 in Figure 5) (e.g., old I-SMFA/-SMF, anchor SMF, or hSMF) (step 700). The SMF is also configured to select the at least one other SMF based at least on the binding information received from the AMF (step 702). The SMF is further configured to send a response message to the AMF that includes at least an NF Instance ID of the at least one other SMF (step 704)

In one embodiment, the SMF may receive the request message as a Nsmf_PDUSession_CreateSMContext Request message comprising the binding information for an SmContext in the at least one other SMF (e.g., I-SMF) (step 700-1). In one embodiment, the SMF may receive the request message from the AMF where the binding information comprised in the request message comprises binding information for an SmContext in a first other SMF. Accordingly, the SMF may select the first other SMF based on the binding information for the SmContext received from the AMF (step 702-1). In a non-limiting example, the first other SMF and an alternate for the first SMF belong to a same SMF NF (service) Set as indicated by a binding information for SmContext (see, e.g., Figure 9). In addition, in some embodiments, the SMF may also select a second other SMF (e.g., hSMF) based on binding information for PDU session (step 702-2).

In another embodiment, the SMF may select the second other SMF based on binding information for the PDU session received from the first other SMF (e.g., old l-SMF/V-SMF) in a Nsmf_PDUSession_UpdateSmContext Request message (step 702-3). See Figure 9 as an example. In a non-limiting example, the second other SMF and an alternate for the second SMF belong to a same SMF NF (service) Set as indicated by a binding information for PDU session (see, e.g., Figure 9).

In another embodiment, the SMF may send the response message to the AMF by a Nsmf_PDUSession_CreateSMContext Response message or a Nsmf_PDUSession_UpdateSMContext Response message (step 704-1).

In another embodiment, the SMF may send the response message to the AMF to include a pair of NF IDs corresponding to the other SMF and the second other SMF, respectively (step 704-2).

Figure 8

Figure 8 is a flowchart of an exemplary method performed by an AMF in a CN for reselecting another SMF for a PDU session (e.g., Home Routed PDU session or PDU session with l-SMF). The AMF (e.g., 500 in Figure 5) is configured to send a request message to an SMF (e.g., 508 in Figure 5) (e.g., I- SMF or V-SMF) that includes a binding information related to at least one other SMF (e.g., a different SMF 508 in Figure 5) (e.g., old I-SMFA/-SMF, anchor SMF, or hSMF) (step 800). Accordingly, the AMF can receive a response message from the SMF that includes at least an NF Instance ID of the at least one other SMF (step 802).

In one embodiment, the AMF may send the request message as a Nsmf_PDUSession_CreateSMContext Request message comprising the binding information for an SmContext in the at least one other SMF (e.g., I-SMF) (step 800-1). The AMF may receive the response message from the SMF as a Nsmf_PDUSession_CreateSMContext Response message or a Nsmf_PDUSession_UpdateSMContext Response message (step 802-1).

In one embodiment, the AMF may send the request message comprising the binding information for an SmContext in a first of the at least one another SMF and for a PDU session in a second of the at least one another SMF (step 800-2). Accordingly, the AMF may receive the response message from the AMF that includes a pair of NF IDs corresponding to the first of the at least one another SMF and the second of the at least one another SMF, respectively (step 802-2).

In a non-limiting example, the binding information (for SmContext) may be provided in a 3GPP Hypertext Transfer Protocol (HTTP) custom header, which has the same format as "3gpp-sbi-binding", or as an attribute (preferably called "binding information for SmContext") that contains several attributes to denote the binding information. In example, the binding information for SmContext resource context in the (h)SMF can be encoded as follows:

In another example, the binding information for SmContext resource context in the old v/(l)SMF may be encoded as follows (underlined texts for v-SMF and italic text for l-SMF:

Similarly, the binding information (for PDU Session) may be provided as a 3gpp HTTP custom header, which has the same format as "3gpp-sbi-binding", or as an attribute (preferably called "binding information for PDUSession ") that contains several attributes to denote the following binding information:

Figure 9

Figure 9 is a flow diagram providing exemplary signaling of l-SMF change according to embodiments of the present disclosure. In this example, the AMF sends the CreateSmContext Request to the new l-SMF 3 that includes the binding information for the SmContext in the old l-SMF 1 (step 1). Notably, this step is equivalent to step 800-1 in Figure 8. The new l-SMF 3 receives the binding information for the PDU session in the hSMF A (step 5). Notably, this step is equivalent to step 702-1 in Figure 7. The new l-SMF 3 sends a Nsmf_PDUSessionCreateSMContext Response to the AMF that includes the NF Instance Id of the re-selected old l/V-SMF and re-selected hSMF (step 10). Notably, this step is equivalent to step 704 in Figure 7.

Figure 10

Figure 10 is a flow diagram providing exemplary signaling of l-SMF insertion according to embodiments of the present disclosure. In this example, the AMF sends the CreateSmContext Request to the new l-SMF that includes the binding information for the SmContext in the anchor SMF A (step 1). Notably, this step is equivalent to step 800-1 in Figure 8. The new l-SMF retrieves the SmContext from the anchor SMF B when the anchor SMF A is deemed not reachable (step 4). Notably, this step is equivalent to step 702-3 in Figure 7. The l-SMF sends a Nsmf_PDUSessionCreateSMContext Response to the AMF that includes the NF Instance Id of the re-selected hSMF (step 8). Notably, this step is equivalent to step 704-1 in Figure 7.

Figure 11

Figure 11 is a flow diagram providing exemplary signaling of SMF reselection according to embodiments of the present disclosure. In this example, the AMF sends an UpdateSmContext Request to the l-SMF (step 1). Notably, this step is equivalent to step 800-2 in Figure 8. Accordingly, the l-SMF updates the PDU session in anchor SMF B (step 4). Notably, this step is equivalent to step 702-4 in Figure 7. The l-SMF then sends a Nsmf_PDUSesssion_UpdateSMContext Response to the AMF that includes the NF Instance ID of the re-slected hSMF (step 6). Notably, this step is equivalent to step 704-1 in Figure 7.

Figure 12

Figure 12 is a schematic block diagram of a radio access node 1200 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The radio access node 1200 may be, for example, a base station 402 or 406 or a network node that implements all or part of the functionality of the base station 402 or gNB described herein. As illustrated, the radio access node 1200 includes a control system 1202 that includes one or more processors 1204 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory 1206, and a network interface 1208. The one or more processors 1204 are also referred to herein as processing circuitry. In addition, the radio access node 1200 may include one or more radio units 1210 that each includes one or more transmitters 1212 and one or more receivers 1214 coupled to one or more antennas 1216. The radio units 1210 may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) 1210 is external to the control system 1202 and connected to the control system 1202 via, e.g., a wired connection (e.g., an optical cable). However, in some other embodiments, the radio unit(s) 1210 and potentially the antenna(s) 1216 are integrated together with the control system 1202. The one or more processors 1204 operate to provide one or more functions of a radio access node 1200 as described herein. In some embodiments, the function(s) is implemented in software that is stored, e.g., in the memory 1206 and executed by the one or more processors 1204.

Figure 13

Figure 13 is a schematic block diagram that illustrates a virtualized embodiment of the radio access node 1200 according to some embodiments of the present disclosure. This discussion is equally applicable to other types of network nodes. Further, other types of network nodes may have similar virtualized architectures. Again, optional features are represented by dashed boxes.

As used herein, a “virtualized” radio access node is an implementation of the radio access node 1200 in which at least a portion of the functionality of the radio access node 1200 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 radio access node 1200 may include the control system 1202 and/or the one or more radio units 1210, as described above. The control system 1202 may be connected to the radio unit(s) 1210 via, for example, an optical cable or the like. The radio access node 1200 includes one or more processing nodes 1300 coupled to or included as part of a network(s) 1302. If present, the control system 1202 or the radio unit(s) is connected to the processing node(s) 1300 via the network 1302. Each processing node 1300 includes one or more processors 1304 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 1306, and a network interface 1308.

In this example, functions 1310 of the radio access node 1200 described herein are implemented at the one or more processing nodes 1300 or distributed across the one or more processing nodes 1300 and the control system 1202 and/or the radio unit(s) 1210 in any desired manner. In some particular embodiments, some or all of the functions 1310 of the radio access node 1200 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) 1300. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 1300 and the control system 1202 is used in order to carry out at least some of the desired functions 1310. Notably, in some embodiments, the control system 1202 may not be included, in which case the radio unit(s) 1210 communicates directly with the processing node(s) 1300 via an appropriate network interface(s).

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 radio access node 1200 or a node (e.g., a processing node 1300) implementing one or more of the functions 1310 of the radio access node 1200 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).

Figure 14

Figure 14 is a schematic block diagram of the radio access node 1200 according to some other embodiments of the present disclosure. The radio access node 1200 includes one or more modules 1400, each of which is implemented in software. The module(s) 1400 provides the functionality of the radio access node 1200 described herein. This discussion is equally applicable to the processing node 1300 of Figure 13 where the modules 1400 may be implemented at one of the processing nodes 1300 or distributed across multiple processing nodes 1300 and/or distributed across the processing node(s) 1300 and the control system 1202.

Figure 15

Figure 15 is a schematic block diagram of a wireless communication device 1500 according to some embodiments of the present disclosure. As illustrated, the wireless communication device 1500 includes one or more processors 1502 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 1504, and one or more transceivers 1506 each including one or more transmitters 1508 and one or more receivers 1510 coupled to one or more antennas 1512. The transceiver(s) 1506 includes radio-front end circuitry connected to the antenna(s) 1512 that is configured to condition signals communicated between the antenna(s) 1512 and the processor(s) 1502, as will be appreciated by one of ordinary skill in the art. The processors 1502 are also referred to herein as processing circuitry. The transceivers 1506 are also referred to herein as radio circuitry. In some embodiments, the functionality of the wireless communication device 1500 described above may be fully or partially implemented in software that is, e.g., stored in the memory 1504 and executed by the processor(s) 1502. Note that the wireless communication device 1500 may include additional components not illustrated in Figure 15 such as, e.g., one or more user interface components (e.g., an input/output interface including a display, buttons, a touch screen, a microphone, a speaker(s), and/or the like and/or any other components for allowing input of information into the wireless communication device 1500 and/or allowing output of information from the wireless communication device 1500), a power supply (e.g., a battery and associated power circuitry), etc.

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 wireless communication device 1500 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).

Figure 16

Figure 16 is a schematic block diagram of the wireless communication device 1500 according to some other embodiments of the present disclosure. The wireless communication device 1500 includes one or more modules 1600, each of which is implemented in software. The module(s) 1600 provide the functionality of the wireless communication device 1500 described herein.

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/or data 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.

Some embodiments described above may be summarized in the following manner:

1 . A method performed by a Session Management Function, SMF (508) (e.g., I-SMF or V-SMF), in a Core Network, CN, (410) for reselecting another SMF (508) for a Protocol Data Unit, PDU, session (e.g., Home Routed PDU session or PDU session with l-SMF), comprising: receiving (700) a request message from an Access and Mobility Management Function, AMF, (500) wherein the request message comprises a binding information related to at least one other SMF (508) (e.g., old l-SMF/V-SMF, anchor SMF, or hSMF); selecting (702) the at least one other SMF (508) based at least on the binding information received from the AMF (500); and sending (704) a response message to the AMF (500), wherein the response message comprises at least a Network Function, NF, Instance Identification, ID, of the at least one other SMF (508).

2. The method of embodiment 1 , wherein: the binding information comprises binding information for an SmContext in a first other SMF, the first other SMF being one of the at least one other SMF (508); and receiving (700) the request message comprises receiving (700-1) a Nsmf_PDUSession_CreateSMContext Request message comprising the binding information for the SmContext in the first other SMF (508) (e.g., the old l-SMF/V-SMF or hSMF).

3. The method of any one of embodiments 1 to 2, wherein sending (704) the response message to the AMF (500) comprises sending (704-1) a Nsmf_PDUSession_CreateSMContext Response message or a Nsmf_PDUSession_UpdateSMContext Response message.

4. The method of embodiment 1 , wherein: the binding information comprises binding information for an SmContext in a first other SMF, the first other SMF being one of the at least one other SMF (508); receiving (700) the request message comprises receiving (700-2) the request message comprising the binding information for the SmContext in the other SMF; and selecting (702) the at least one another SMF (508) based on the binding information comprises: selecting (702-1) the first other SMF (508) based on the binding information for the SmContext.

5. The method of embodiment 4, wherein the first other SMF (508) and an alternative SMF for the first other SMF belong to a same SMF NF (service) Set as indicated by the binding information for the SmContext.

6. The method of embodiment 4 or 5, wherein selecting (702) the at least one another SMF (508) comprises selecting (702-2) a second other SMF based on binding information for a PDU session in the second other SMF, the second other SMF being one of the at least one other SMF.

7. The method of embodiment 6, wherein selecting (702-2) the second other SMF (508) (e.g., hSMF) comprises receiving (702-3) a Nsmf_PDUSession_Context Response message from the first other SMF (508) (e.g., the old l-SMF/V-SMF), wherein the Nsmf_PDUSession_Context Response message comprises the binding information for the PDU session in the second other SMF (508) (e.g., hSMF).

8. The method of embodiment 6 or 7, wherein sending (704) the response message to the AMF (500) further comprises sending (704-2) a pair of NF IDs corresponding to the first other SMF and the second other SMF, respectively.

9. A method performed by an Access and Mobility Management Function, AMF, (500) in a Core Network, CN, (410) for reselecting another Session Management Function (SMF) (508) for a Protocol Data Unit, PDU, session (e.g., Home Routed PDU session or PDU session with l-SMF), comprising: sending (800) a request message to an SMF (508) (e.g., I-SMF or V-SMF), wherein the request message comprises a binding information related to at least one other SMF (508) (e.g., old l-SMF/V-SMF, anchor SMF, or hSMF); and receiving (802) a response message from the SMF (508), wherein the response message comprises at least a Network Function, NF, Instance Identification, ID, of the at least one another SMF (508).

10. The method of embodiment 9, wherein sending (800) the request message comprises sending (800-1) a Nsmf_PDUSession_CreateSMContext Request message comprising the binding information for an SmContext in a first other SMF (508) (e.g., the old l-SMF/V-SMF or hSMF). 11 . The method of embodiment 9 or 10, wherein receiving (802) the response message from the SMF (508) comprises receiving (802-1) a Nsmf_PDUSession_CreateSMContext Response message or a Nsmf_PDUSession_UpdateSMContext Response message.

12. The method of any of embodiments 9 to 11 , sending (800) the request message comprises sending (800-2) the request message comprising the binding information for an SmContext in a first other SMF and for a PDU session in second other SMF.

13. The method of embodiment 10, wherein the first other SMF and an alternate SMF for the first other SMF belong to a same SMF NF (service) Set as indicated by the binding information for SmContext.

14. The method of embodiment 13, wherein receiving (802) the response message from the SMF (508) further comprises receiving (802-2) a pair of NF IDs.

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.).

At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s).

• 3GPP Third Generation Partnership Project

• 5G Fifth Generation

• 5GC Fifth Generation Core

• 5GS Fifth Generation System

• AF Application Function

• AMF Access and Mobility Function

• AN Access Network

• CN Core Network

• DN Data Network

• eNB Enhanced or Evolved Node B

• gNB New Radio Base Station

• HTTP Hypertext Transfer Protocol • loT Internet of Things

• IP Internet Protocol

• LTE Long Term Evolution

• MME Mobility Management Entity

• MTC Machine Type Communication

• NEF Network Exposure Function

• NF Network Function

• NG-RAN Next Generation Radio Access Network

• NR New Radio

• NRF Network Function Repository Function

• PCF Policy Control Function

• PDU Protocol Data Unit

• P-GW Packet Data Network Gateway

• PLMN Public Land Mobile Network

• PSA Protocol Data Unit Session Anchor

• QoS Quality of Service

• RAN Radio Access Network

• SCEF Service Capability Exposure Function

• SMF Session Management Function

• UDM Unified Data Management

• UE User Equipment

• UPF User Plane Function

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 What is claimed is:

1 . A method performed by a Session Management Function, SMF, (508) (e.g., I-SMF or V-SMF), in a Core Network, CN, (410) for selecting another SMF (508) in a set of Session Management Functions, SMFs, for a Protocol Data Unit, PDU, session (e.g., Home Routed PDU session or PDU session with I- SMF), comprising: receiving (700) a request message from an Access and Mobility Management Function, AMF, (500) wherein the request message comprises binding information for a SmContext that indicates biding to the SMF set of the another SMF (508) (e.g., old l-SMF/V-SMF, anchor SMF, or hSMF); selecting (702) the another SMF (508) based at least on the binding information received from the AMF (500) by retrieving (702-3) the SmContext from the another SMF based at least on the binding information; and sending (704) a response message to the AMF (500), wherein the response message comprises at least a Network Function, NF, Instance Identification, ID, of the another SMF (508).

2. The method of claim 1 , wherein sending (704) the response message to the AMF (500) comprises sending (704-1) a Nsmf_PDUSession_CreateSMContext Response message or a Nsmf_PDUSession_UpdateSMContext Response message.

3. The method of claim 1 or 2, wherein: selecting (702) the another SMF (508) based on the binding information comprises: selecting (702-1) the another SMF (508) based on the binding information for the SmContext.

4. A method performed by an Access and Mobility Management Function, AMF, (500) in a Core Network, CN, (410) for selecting another Session Management Function (SMF) (508) in a set of Session Management Functions, SMFs, for a Protocol Data Unit, PDU, session (e.g., Home Routed PDU session or PDU session with l-SMF), comprising: sending (800) a request message to an SMF (508) (e.g., I-SMF or V-SMF), wherein the request message comprises binding information for a SmContext that indicates binding to the SMF set of the another SMF (508) (e.g., old l-SMF/V-SMF, anchor SMF, or hSMF); and receiving (802) a response message from the SMF (508), wherein the response message comprises at least a Network Function, NF, Instance Identification, ID, of the another SMF (508).

5. The method of claim 4, wherein sending (800) the request message comprises sending (800-1 ) a

Nsmf_PDUSession_CreateSMContext Request message comprising the binding information for an SmContext in the another SMF (508) (e.g., the old l-SMF/V-SMF or hSMF).

6 The method of claim 4 or 5, wherein receiving (802) the response message from the SMF (508) comprises receiving (802-1) a Nsmf_PDUSession_CreateSMContext Response message or a Nsmf_PDUSession_UpdateSMContext Response message.