CN117882433A

CN117882433A - Intermediate session management function failure and recovery

Info

Publication number: CN117882433A
Application number: CN202180101874.4A
Authority: CN
Inventors: 李志军; 朱进国; 于阳
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2021-09-22
Filing date: 2021-09-22
Publication date: 2024-04-12
Also published as: EP4406284A1; WO2023044616A1

Abstract

A wireless communication method for use in an intermediate session management function, SMF, is disclosed. The method includes transmitting recovery information for recovering an intermediate SMF of the protocol data unit PDU session to the anchor SMF.

Description

Intermediate session management function failure and recovery

Technical Field

This document relates generally to wireless communications.

Background

After accessing the fifth generation (5G) network, a user terminal (UE) may request to establish a Protocol Data Unit (PDU) session to obtain an Internet Protocol (IP) connection service. For a PDU session, a Session Management Function (SMF) is selected to control the PDU session and is also referred to as an anchor SMF, and a User Plane Function (UPF) controlled by the anchor SMF to assign the UE IP address is also referred to as a PDU Session Anchor (PSA) or PSA UPF.

In general, anchor SMF and PSA UPF have their own service areas and cannot serve the entire Public Land Mobile Network (PLMN). To support PDU session services when a UE leaves a service area supported by anchor SMF and PSA UPF, an intermediate SMF (I-SMF) and an intermediate UPF (I-UPF) are inserted to serve the location area where the UE is located.

In a PDU session involving an I-SMF, the I-SMF is located in an intermediate path between an access mobility management function (AMF) and an anchor SMF, and connects the AMF and the anchor SMF. The intermediate SMF maintains a Session Management (SM) context for the PDU session, wherein the SM context includes, for example, AMF information, N3 tunnel information, and the like. The anchor SMF maintains PDU session context including, for example, UE Internet Protocol (IP) address, PDU session policy information, N6 tunnel information, etc. The I-SMF assigns an SM context Identifier (ID) for locating an SM context in the I-SMF. If the I-SMF fails, neither the AMF nor the anchor SMF can use the SM context ID to locate the SM context in the I-SMF. In this case, the AMF signaling cannot reach the anchor SMF even via another I-SMF, and vice versa.

Network Function (NF) set concepts are designed in 5G systems to support stateless deployment of NFs and are commonly used in NF failure and recovery situations. Each NF within the same NF set shares a resource (e.g., UE IP address resource) and a session context (e.g., UE PDU session context). If one NF is detected as failed by another NF, the NF that detected the failure may select another NF in the same NF set to continue the relevant service flow.

However, NF sets may not always be available, especially at an early stage of 5G network deployment. Furthermore, the NF set concept is not widely supported in PLMNs.

If the NF set is not deployed, the AMF and anchor SMF cannot continue the service flow by using another I-SMF because the SM context information stored in the failed I-SMF cannot be retrieved from elsewhere.

Disclosure of Invention

This document relates to methods, systems, and devices for I-SMF restoration, and in particular to methods, systems, and devices for allowing AMFs and/or anchor SMFs to select alternative I-SMFs upon detection of an I-SMF failure.

The present disclosure relates to a wireless communication method for use in an intermediate Session Management Function (SMF). The method comprises the following steps:

the recovery information for recovering the intermediate SMF of the Protocol Data Unit (PDU) session is transmitted to the anchor SMF.

Various embodiments may preferably implement the following features:

preferably, the recovery information includes at least one of: information of an access and mobility management function (AMF) associated with the PDU session, information of a radio access network node associated with the PDU session, or information associated with an intermediate User Plane Function (UPF).

Preferably, the information of the AMF comprises at least one of: an AMF instance identifier, an application program interface Uniform resource identifier of an AMF service, or a callback Uniform resource identifier that receives a session management context status notification.

Preferably, the information of the radio access network node includes radio access network N3 tunnel information.

Preferably, the information associated with the intermediate UPF includes at least one of: a UPF instance identifier, UPF N3 tunnel information, UPF N9 tunnel information, or an N4 session identifier.

Preferably, the wireless communication method further comprises:

transmitting to the anchor SMF a resume indication of an intermediate SMF associated with the PDU session, an

The recovery information is received from the anchor SMF.

Preferably, the wireless communication method further comprises receiving a resume indication of an intermediate SMF associated with the PDU session from the access and mobility management function.

Preferably, the wireless communication method further includes performing an intermediate SMF restoration procedure based on the restoration information.

Preferably, performing the intermediate SMF recovery procedure based on the recovery information includes:

the intermediate UPF indicated by the resume information is selected for servicing the PDU session.

Preferably, the intermediate SMF is selected to serve the PDU session after an intermediate SMF serving the PDU session fails.

Preferably, the intermediate SMF is selected to serve the PDU session during the PDU session establishment.

The present disclosure relates to a wireless communication method for use in an anchor Session Management Function (SMF). The method comprises the following steps:

recovery information for recovering an intermediate SMF of a Protocol Data Unit (PDU) session is received from a first intermediate SMF.

Various embodiments may preferably implement the following features:

Preferably, the wireless communication method further comprises:

receiving a resume indication of an intermediate SMF associated with the PDU session from a second intermediate SMF, an

The recovery information is sent to the second intermediate SMF.

Preferably, the wireless communication method further comprises:

a restoration instruction of the intermediate SMF triggering the restoration procedure of the intermediate SMF is sent to the access and mobility management function indicated by the restoration information.

Preferably, the wireless communication method further comprises:

a PDU session release request including a reactivation indication is sent to the access and mobility management function indicated by the resume information.

The present disclosure relates to a wireless communication method for use in access and mobility management functions. The method comprises the following steps:

receiving a resume indication of an intermediate Session Management Function (SMF) associated with a Protocol Data Unit (PDU) session from an anchor SMF, and

a resume procedure for resuming the intermediate SMF of the PDU session is triggered.

Various embodiments may preferably implement the following features:

preferably, triggering a recovery procedure of the intermediate SMF for recovering the PDU session includes:

selecting an intermediate SMF for the PDU session

A session management context creation message for the PDU session is sent to the selected SMF,

preferably, the session management context creation message includes at least one of: a PDU session identifier, an anchor SMF instance identifier, or an intermediate SMF restoration indication.

The present disclosure relates to a wireless device including an intermediate Session Management Function (SMF), the wireless device comprising:

a communication unit configured to transmit recovery information for recovering an intermediate SMF of a Protocol Data Unit (PDU) session to an anchor SMF.

Various embodiments may preferably implement the following features:

preferably, the wireless device further comprises a processor configured to perform any of the aforementioned wireless communication methods.

The present disclosure relates to a wireless device including an anchor Session Management Function (SMF). The wireless device includes:

a communication unit configured to receive recovery information for recovering an intermediate SMF of a Protocol Data Unit (PDU) session from the intermediate SMF.

Various embodiments may preferably implement the following features:

The present disclosure relates to a wireless device including access and mobility management functions. The wireless device includes:

a communication unit configured to receive a resume indication of an intermediate Session Management Function (SMF) associated with a Protocol Data Unit (PDU) session from an SMF, and

a processor configured to trigger a resume procedure for resuming the intermediate SMF of the PDU session.

Various embodiments may preferably implement the following features:

preferably, the processor is further configured to perform any of the aforementioned wireless communication methods.

The present disclosure relates to a computer program product comprising computer readable program medium code stored thereon, which, when executed by a processor, causes the processor to implement a wireless communication method as described in any of the preceding methods.

The exemplary embodiments disclosed herein are intended to provide features that will become apparent by reference to the following description in conjunction with the accompanying drawings. According to various embodiments, exemplary systems, methods, devices, and computer program products are disclosed herein. However, it should be understood that these embodiments are presented by way of example and not limitation, and that various modifications of the disclosed embodiments may be made while remaining within the scope of the disclosure, as will be apparent to those of ordinary skill in the art from reading the disclosure.

Thus, the disclosure is not limited to the exemplary embodiments and applications described and illustrated herein. Additionally, the particular order and/or hierarchy of steps in the methods disclosed herein is merely exemplary. Based on design preferences, the specific order or hierarchy of steps in the disclosed methods or processes may be rearranged while remaining within the scope of the present disclosure. Accordingly, those of ordinary skill in the art will understand that the methods and techniques disclosed herein present various steps or acts in an example order, and that the present disclosure is not limited to the particular order or hierarchy presented, unless specifically stated otherwise.

Drawings

The above and other aspects and implementations thereof are described in more detail in the accompanying drawings, description and claims.

Fig. 1 shows a schematic diagram of a 5G home routing roaming architecture according to an embodiment of the disclosure.

Fig. 2 shows a schematic diagram of a 5G non-roaming architecture according to an embodiment of the disclosure.

Fig. 3 shows a schematic diagram of a PDU session establishment procedure according to an embodiment of the present disclosure.

Fig. 4 shows a schematic diagram of a PDU session establishment procedure according to an embodiment of the present disclosure.

Fig. 5A and 5B illustrate schematic diagrams of an intermediate SMF recovery procedure according to an embodiment of the present disclosure.

Fig. 6 shows a schematic diagram of an intermediate SMF recovery procedure according to an embodiment of the present disclosure.

Fig. 7 illustrates a schematic diagram of PDU session release with reactivation procedure, according to an embodiment of the disclosure.

Fig. 8 shows an example of a schematic diagram of a wireless terminal according to an embodiment of the disclosure.

Fig. 9 shows an example of a schematic diagram of a wireless network node according to an embodiment of the disclosure.

Fig. 10 shows a flow chart of a method according to an embodiment of the present disclosure.

Fig. 11 shows a flow chart of a method according to an embodiment of the present disclosure.

Fig. 12 shows a flow chart of a method according to an embodiment of the present disclosure.

Detailed Description

In the present disclosure, the term "information" is equal to or has the same meaning as "info".

Fig. 1 illustrates a 5G home routing roaming architecture according to an embodiment of the disclosure. In fig. 1, the anchor SMF and PSA UPF cannot directly serve the Visited PLMN (VPLMN) where the UE resides. Fig. 2 illustrates a 5G non-roaming architecture according to an embodiment of the disclosure. In fig. 2, anchor SMF and PSA UPF cannot directly serve the region where the UE is located (i.e., UE location region). In fig. 1 and 2, the following network functions and network entities exist:

1) UE (user terminal)

2) RAN (radio access network (node)):

in a 5G network, the RAN may be a new air interface (NR) base station.

3) AMF (access and mobility management function):

the AMF includes the following functions: registration management, connection management, reachability management, and mobility management. The AMF also performs access authentication and access authorization. The AMF is a NAS security terminal, and relays SM NAS or the like between the UE and the SMF.

4) SMF (session management function)

The SMF includes the following functions: session establishment, modification and release, UE IP address allocation and management (including optional authorization functions), selection and control of UP functions, downlink data notification, etc. The SMF controls the UPF via the N4 association.

5) UPF (user plane function)

The UPF includes the following functions: serving as anchor points for intra-radio/inter-Radio Access Technology (RAT) mobility, packet routing and forwarding, traffic usage reporting, qoS handling for the user plane, downlink packet buffering, and downlink data notification triggering, etc. The UPF can be deployed as an intermediate UPF (I-UPF) or as a PSA. The PSA/UPF is the UPF that interfaces to the data network termination (terminating) N6. The I-UPF provides traffic forwarding between the RAN and the PSA/UPF. The I-UPF may support "ULCL" (upstream classifier: offload upstream traffic based on destination IP address) or "BP" (branching point: offload upstream traffic based on source IP address) to offload (off load) some traffic to the local PSA/UPF.

6) PCF (policy control function)

The PCF provides QoS policy rules for the control plane functions to enforce the rules. The PCF(s) convert the AF request into a policy applicable to the PDU session. The PCF provides the AF-affected traffic steering enforcement control to the SMF in PCC rules, so the SMF may establish a data path to offload traffic to the local data network.

7) AF (application function)

The AF interacts with the 3GPP core network to provide services, e.g. to support the impact of applications on traffic routing. Depending on the deployment of the operator, the AF, which is considered trusted by the operator, may be allowed to interact directly with the relevant network functions. An AF that the operator does not allow direct access to network functions should interact with the relevant network functions using an external exposure framework via a Network Exposure Function (NEF).

In the PDU session establishment procedure, if the selected anchor SMF and PSA UPF cannot serve the area occupied by the UE, I-SMF and I-UPF need to be inserted (see fig. 2). The visited SMF (V-SMF) (i.e., home routed roaming scenario) shown in fig. 1 plays a similar role as the I-SMF (i.e., non-roaming scenario) shown in fig. 2. Thus, in the present disclosure, I-SMF may be equal to V-SMF. Similarly, the I-UPF may be equal to the accessed UPF (V-UPF) shown in FIG. 1 of the present disclosure.

Fig. 3 shows a schematic diagram of a PDU session establishment procedure according to an embodiment of the present disclosure. The PDU session establishment procedure in fig. 3 involves I-SMF insertion. Specifically, after the UE registers with the 5G network, the UE may request a PDU session establishment procedure including the steps of:

step 301: the UE sends a PDU session establishment request to the AMF.

The PDU session establishment request is included in a non-access stratum (NAS) message and encapsulated in an N1 SM container. The NAS message may include single network slice selection assistance information (S-nsai), a Data Network Name (DNN) requested by the UE, a PDU session ID, a request type, and an N1 SM container (including a PDU session establishment request). NAS messages sent by the UE are encapsulated by the RAN in AMF-oriented N2 messages.

Step 302: the AMF selects an appropriate SMF (i.e., anchor SMF) to serve the PDU session based on the requested DNN, S-nsai, and current UE location information. If the anchor SMF is unable to service the current location of the UE, the AMF determines to also select an I-SMF for the PDU session.

Step 303: the AMF sends an Nsmf_PDUSion_CreateMContext request to the I-SMF, where the Nsmf_PDUSion_CreateMContext request includes a subscription permanent identifier (SUPI), a selected DNN, a DNN of the UE request, S-NSSAI (S), PDU session ID, AMF ID, request type, N1 SM container (PDU session establishment request), user location information, access type, RAT type, permanent device identifier (PEI), general Public Subscription Identifier (GPSI), AMF callback URI for receiving SM context status notification, and the like. SUPI uniquely identifies the UE subscription. The AMF ID carries a globally unique AMF ID (GUAMI) that uniquely identifies the AMF serving the UE. The AMF callback URI for receiving the SM context notification is used by the SMF (e.g., I-SMF, anchor SMF) to send a notification of the SM context state to the AMF.

Step 304: the I-SMF sends an Nsmf_PDUSion_CreateSMContext response to the AMF, wherein the Nsmf_PDUSion_CreateSMContext response comprises a reason and an SM context ID. The SM context ID identifies the SM context for the UE created in the I-SMF.

Step 305: the I-SMF selects an I-UPF to serve the PDU session based on the UE location.

Step 306: the I-SMF initiates an N4 session establishment procedure with the selected I-UPF.

Step 307: the I-SMF sends an Nsmf_PDUSation_Create request to the anchor SMF, wherein the Nsmf_PDUSation_Create request comprises DNN, S-NSSAI, PDU session ID, I-SMF instance ID, I-SMF SM context ID and Intermediate Core Network (ICN) tunnel information. The ICN tunnel information carries an I-UPF Downlink (DL) fully defined tunnel endpoint identifier (F-TEID) that identifies the GTP-U (GPRS tunneling protocol user plane) tunnel information of the I-UPF to receive downlink traffic.

Step 308: the anchor SMF sends a nudm_sdm_get request to the UDM to retrieve session management subscription data. The UDM sends back the requested data in a response message.

Step 309: the anchor SMF selects the UPF that acts as the PSA.

Step 310: the anchor SMF initiates an N4 session establishment procedure with the selected UPF.

Step 311: the anchor SMF sends a Nsm _PDUSation_Create response to the I-SMF, wherein the Nsm _PDUSation_Create response includes quality of service (QoS) rules, qoS flow levels, qoS parameters, qoS Flow ID (QFI), qoS configuration file, session Maximum Bit Rate (MBR), and H-UPF tunnel information. The H-UPF tunnel information carries H-UPF GTP-U tunnel information of PSA UPF for receiving UL traffic.

Step 312: the I-SMF initiates an N4 session modification procedure with the I-UPF to update GTP-U tunnel information (i.e., UPF UL F-TEID) of the PSA UPF.

Step 313: the I-SMF sends a namf_communication_n1n2message transfer request to the AMF, wherein the namf_communication_n1n2message transfer request includes PDU session ID, N2 SM information (PDU session ID, QFI(s), qoS profile(s), N3 CN tunnel information), N1 SM container (PDU session establishment accept).

The N2 SM information carries information that the AMF will forward to the RAN, including N3 CN tunnel information carrying I-UPF UL F-TEID, QFI and QoS profile used by the RAN to set QoS flows. In an embodiment, the N1 SM container contains PDU session establishment acceptance that the AMF should provide to the UE.

Step 314: the AMF sends an N2 PDU session request to the RAN, wherein the N2 PDU session request includes N2 SM information, NAS message (PDU session ID, N1 SM container (PDU session establishment accept)). The AMF sends NAS messages containing PDU session ID and PDU session establishment accept for the UE and N2 SM information received from the SMF to the RAN within an N2 PDU session request.

Step 315: the RAN may issue AN-specific signaling exchange with the UE that is related to the information received from the SMF. For example, in the case of a 3GPP RAN, RRC connection reconfiguration may occur as the UE establishes the necessary RAN resources associated with the QoS rules for the PDU session request. The RAN forwards NAS messages (PDU session ID, N1 SM container (PDU session establishment accept)) to the UE. The RAN also allocates N3 tunnel information for the PDU session.

Step 316: the RAN sends a PDU session response to the AMF, wherein the N2 PDU session response includes a PDU session ID, a cause, N2 SM information (PDU session ID, AN tunnel information, list of accept/reject QFI (s)).

The AN tunnel information corresponds to AN access network address of the N3 tunnel corresponding to the PDU session.

Step 317: AMF sends Nsmf_PDUSion_UpdateSMContext to I-SMF, wherein the Nsmf_PDUSion_UpdateSMContext request includes N2 SM information.

The AMF forwards the N2 SM information received from the RAN to the I-SMF. If the list of rejected QFI(s) is included in the N2 SM information, the SMF should release the QoS profile associated with the rejected QFI(s).

Step 318: the I-SMF initiates an N4 session modification procedure using the I-UPF. The I-SMF provides RAN tunnel information and corresponding forwarding rules to the I-UPF.

Step 319: the I-SMF sends an Nsmf_PDUSess_UpdateSMContext response to the AMF.

Fig. 4 shows a schematic diagram of a PDU session establishment procedure according to an embodiment of the present disclosure. In fig. 4, the PDU session establishment procedure includes I-SMF insertion, and the I-SMF stores I-SMF restoration container information to the anchor SMF. Specifically, the PDU session establishment procedure includes the following steps:

Step 401: the UE initiates a PDU session establishment procedure (e.g., fig. 3). Since the anchor SMF cannot serve the current UE location, an I-SMF is inserted. The I-SMF selects an I-UPF to serve the PDU session.

Step 402: the I-SMF sends a PDU session Update request (i.e., nsmf_pduse_update) to the anchor SMF. In this message, the I-SMF includes I-SMF restoration container information (i.e., ivres container information shown in fig. 4).

In an embodiment, the I-SMF restoration container information includes at least one of AMF information, RAN information, I-UPF information.

In an embodiment, the AMF information comprises at least one of: AMF instance ID, application program interface Uniform resource identifier (API URI) of AMF service, callback URI for SM context status notification.

In an embodiment, the AMF instance ID uniquely identifies the AMF and may be used by other NFs to retrieve AMF configuration files from a Network Repository Function (NRF).

In an embodiment, the API URI of the AMF service indicates (or is) the API URI of the service provided by the AMF. For example, the API URI of the AMF service may indicate an API URI of the namf_communication service that the SMF may use to send the N1/N2 message(s) to the AMF.

In an embodiment, the callback URI for the SM context state notification is a callback URI belonging to the AMF to receive any SM context state notification from the SMF (e.g., I-SMF), e.g., to notify that the SM context is transferred to another I-SMF, or to notify that the SM context is released, etc.

In an embodiment, the RAN information includes N3 tunnel information (RAN DL F-TEID).

In an embodiment, the RAN N3 tunnel information may indicate whether an N3 tunnel of the RAN node is allocated.

In an embodiment, the I-UPF information includes at least one of: UPF instance ID, UP connection status (ACTIVATED, RELEASED), N3 tunnel information (I-UPF UL F-TEID), N9 tunnel information (I-UPF DL F-TEID), N4 session ID of N4 session between I-SMF and I-UPF.

In an embodiment, a UPF instance ID is used to uniquely identify the I-UPF.

In an embodiment, the UP connection state is used to indicate the N3 connection state with the RAN node. The ACTIVATED state indicates that the N3 connection is ACTIVATED and the RELEASE state indicates that the N3 connection is released.

In an embodiment, the N3 tunnel information indicates I-UPF UL F-TEID used by the RAN to transmit upstream traffic.

In an embodiment, the N9 tunnel information indicates I-UPF DL F-TEID used by the PSA UPF to send downstream traffic.

Step 403: the anchor SMF stores the I-SMF restoration container information in its local storage device.

Step 404: the anchor SMF sends a PDU session Update response (i.e., a response message to the nsmf_pduse_update request message) to the I-SMF.

Once the I-SMF restoration container information is stored in (or sent to) the anchor SMF, it may be used by the new I-SMF to select the old I-UPF in the I-SMF restoration procedure (see, e.g., fig. 5A and 5B), by the anchor SMF to look up the serving AMF and request the serving AMF to trigger the I-SMF restoration procedure (see, e.g., fig. 6), or by the anchor SMF to look up the serving AMF via which a PDU session release command is sent to the UE (see, e.g., fig. 7).

Fig. 5A and 5B depict schematic diagrams of an AMF initiating an I-SMF recovery procedure according to an embodiment of the present disclosure. Note that in this embodiment, a PDU session has been established and the I-SMF restoration container information associated with that PDU session is sent and stored in the anchor SMF (see fig. 4). In fig. 5A and 5B, the AMF performs an I-SMF restoration procedure by means of the I-SMF restoration container information. During an AMF-initiated I-SMF restoration procedure, the anchor SMF returns I-SMF restoration container information to the newly selected I-SMF (i.e., the new I-SMF shown in FIGS. 5A and 5B) to allow the newly selected SMF to select the old I-UPF.

Step 501 (fig. 5A): the UE sends Mobile Originated (MO) signaling to the AMF.

For example, when the UE is in the IDLE state, the UE transmits a service request. Instead, the UE sends non-access stratum (NAS) SM signaling (e.g., PDU session modification request) to the AMF for the SMF.

Step 502: the AMF detects that the old I-SMF is not reachable (i.e., detects an I-SMF failure). That is, the old I-SMF failed.

Step 503: the AMF reselects a new I-SMF for this PDU session.

Step 504: AMF sends (PDU session) CreateSMontext request (i.e. Nsmf_PDUSess_CreateSMontext request) to new I-SMF, wherein CreateSMontext request carries the following information: PDU session ID, NF instance ID of anchor SMF, API URI of anchor SMF. In addition, an I-SMF resume indication (i.e., an ivres indication) is also included in the message.

If a User Plane (UP) connection needs to be activated, e.g., as requested by a UE-initiated service request, the UP connection status attribute is included in the message and set to ACTIVATING.

The NF instance ID of the anchor SMF and the API URI of the anchor SMF may be used by the new I-SMF to find the anchor SMF and to locate the PDU session context in the anchor SMF.

In an embodiment, if an I-SMF resume indication is detected in the CreateSMContext request, the new I-SMF may not retrieve the SM context from the anchor SMF or from the old I-SMF.

In an embodiment, to assist the new I-SMF in re-establishing the SM context, the AMF may provide other relevant information (e.g., selected PCF information) in the CreateSMContext request.

Step 505: the new I-SMF sends (PDU session) a CreateSMContext response (i.e., a response to the nsmf_pduse ion_createsmcontext request) to the AMF.

Step 506: the new I-SMF may select a new I-UPF to serve the PDU session.

Step 507: the new I-SMF initiates an N4 session setup procedure with the newly selected I-UPF.

Step 508: the new I-SMF sends a (PDU session) creation request (i.e., nsmf_pduse ion_create request) to the anchor SMF, wherein the creation request includes an I-SMF restoration indication (i.e., the ivres indication shown in fig. 5A). In an embodiment, the creation request further carries at least one of the following information: PDU session ID, NF instance ID of I-SMF, callback URI of I-SMF, N9 tunnel information of I-UPF.

Step 509: the anchor SMF detection creation request is used to trigger an I-SMF restoration procedure based on the I-SMF restoration indication. Thus, the anchor SMF updates the I-SMF information for the PDU session, prepares SM context-related information (e.g., at least a portion of the I-SMF restoration container information) and sends it back to the new I-SMF.

Step 510: if the N9 tunnel information of the I-UPF is provided in the creation request, the anchor SMF triggers the N4 session modification procedure with the PSA UPF to update the N9 tunnel information of the I-UPF.

Step 511: the anchor SMF sends a (PDU session) creation response (i.e., a response corresponding to the nsmf_pduse ion_create request) to the new I-SMF. In an embodiment, if the anchor SMF detects that an I-SMF restoration indication (i.e., ivres indication) is present in the corresponding request message (see step 508), and the anchor SMF has stored I-SMF restoration container information (i.e., ivres container information) in the previous flow, the I-SMF restoration container information (i.e., ivres container information) is also included in the message.

In an embodiment, creating the response further comprises at least one of the following information: SM context information and N9 tunnel information for PSA UPF.

Step 512: the new I-SMF stores in its storage device the I-SMF restoration container information (i.e., ivres container information) received from the anchor SMF. The new I-SMF obtains the old I-UPF information from the I-SMF restoration container information. The new I-SMF may use the stored information for subsequent flows.

In an embodiment, if a UPF instance ID exists in the I-SMF restoration container information, the new I-SMF may reselect the old I-UPF identified by the UPF instance ID.

In an embodiment, if the new I-SMF determines to reuse the old I-UPF to service the PDU session, the new I-SMF may further recover the N3 tunnel and the N9 tunnel using UPF information (e.g., UP connection state, N3 tunnel information, N9 tunnel information) included in the I-SMF recovery container information. For example, if the stored UP connection status indicates ACTIVATED, the new I-SMF restores the N3 tunnel, e.g., by using the stored I-SMF to restore the N3 tunnel information in the container information. Alternatively or additionally, if N9 tunnel information is stored (i.e., included in the I-SMF restoration container information), the new I-SMF restores the N9 tunnel, for example, by using the stored N9 tunnel information.

Step 513 (fig. 5B): the new I-SMF initiates an N4 session release procedure with the new I-UPF.

Step 514: the new I-SMF initiates the N4 session modification procedure with the old I-UPF.

In step 514, if the new I-SMF determines to reuse the old I-UPF to service the PDU session, the new I-SMF may use UPF information (e.g., UPF instance ID, N4 session ID) included in the I-SMF restoration container information to construct an N4 session modification request that is sent to the old I-UPF.

Step 515: the new I-SMF sends a (PDU session) update request to the anchor SMF to update the N9 tunnel information of the I-UPF (which is changed back to the old I-UPF). The anchor SMF updates the N9 tunnel information of the I-UPF and sends (PDU session) update response to the I-SMF.

In step 515, if the new I-SMF determines to reuse the old I-UPF to service the PDU session, the new I-SMF may resume the N9 tunnel using UPF information (e.g., N9 tunnel information) included in the I-SMF resume container information.

Step 516: the new I-SMF sends an N1N2message transfer request (i.e., namf_communication_n1n2message transfer request) to the AMF. In an embodiment, the N1N2MessageTransfer request may carry at least one of the following information: UP connection state, N2 SM information.

If the UP connection state (i.e., upCnxState) is set to active in the CreateSMContext request (which means that the requested user plane connection will be activated by the UE according to the service request), the new I-SMF establishes the N3 tunnel user plane resources for the PDU session and includes the following information in the response message: the upCnxState attribute is set to active, N3 tunnel information of I-UPF, N2 SM information carrying PDU session resource setup request transfer I E to request the RAN to allocate resources for the PDU session.

If the new I-SMF detects that the stored UP connection state is active (which means that the user plane connection is pre-ACTIVATED before the I-SMF resume procedure), the new I-SMF re-establishes the N3 tunnel user plane resources for the PDU session and includes the following information in the response message: the upCnxState attribute is set to active, N3 tunnel information for I-UPF, N2 SM information carrying PDU session resource modification request transport I E to request the RAN to allocate resources for the PDU session. In step 516, if the new I-SMF decides to reuse the old I-UPF and restore the original N3 tunnel, the original N3 tunnel (hosted by the old I-UPF) is restored and PDU session resource modification request transmission sent to the RAN is constructed using UPF information (e.g., UP connection state, N3 tunnel information) and RAN information (e.g., RAN N3 tunnel information) included in the I-SMF restoration container information. Otherwise, the new I-SMF requests the new I-UPF to establish the N3 tunnel and constructs the PDU session modification request transmission sent to the RAN accordingly.

Step 517: the AMF sends an N2 PDU session request message to the RAN. The N2 SM information received from the SMF is included in the N2 PDU session request message. The RAN allocates RAN resources for the PDU session and returns an N2 PDU session request Ack (acknowledgement) to the AMF.

Step 518 to step 520: the AMF sends a (PDU session) UpdateSMContext request to the I-SMF, wherein the PDU session UpdateSMContext request carries RAN N3 tunnel information (RAN DL F-TEID), and the RAN N3 tunnel information triggers the I-SMF to update the RAN N3 tunnel information in the I-UPF.

Step 521: the I-SMF sends an (PDU session) UpdateSMContext request (i.e., a Nsmf_PDUSation_UpdateSMContext request) to the anchor SMF, wherein the PDU session UpdateSMContext request carries updated I-SMF restoration container information. The anchor SMF updates the stored I-SMF restoration container information based on the received I-SMF restoration container.

Step 522: subsequent procedures are performed to handle MO signaling initiated by the UE. Note that step 522 may be performed before step 521 or not later than step 521.

Fig. 6 shows a schematic diagram of an I-SMF recovery flow according to an embodiment of the present disclosure. In fig. 6, an anchor SMF receives and/or stores I-SMF restoration container information from an old I-SMF serving a PDU session. Based on the I-SMF restoration container information, the anchor SMF searches for the AMF and triggers the AMF to initiate an I-SMF restoration flow.

In this embodiment, after steps 601a, 601b, or 601c, the anchor SMF is triggered to request the AMF to initiate an I-SMF (i.e., I-SMF/V-SMF) resume procedure:

Step 601a: the anchor SMF itself needs to send Mobile Terminal (MT) signaling to the AMF or to the UE.

Step 601b: the anchor SMF receives MT signaling towards the AMF or towards the UE.

Step 601c: the anchor SMF receives the GTP-U error report from the PSA UPF.

In an embodiment, the PSA UPF may receive a GTP-U error indication from the I-UPF. For example, when the UE is in IDLE state and the downstream traffic arrives at the old I-UPF, if the I-SMF is in failure, the I-UPF cannot trigger the I-SMF to send a downstream data notification to the AMF. In this case, the I-UPF may send a GTP-U error indication to the PSA UPF, and the PSA UPF may trigger a GTP-U error report to the anchor SMF.

Step 602: the anchor SMF detects a failure of the I-SMF.

Step 603: the anchor SMF determines to notify the AMF about the I-SMF failure.

In some embodiments, the anchor SMF may notify the AMF using the following method:

a) If the AMF instance ID exists in the I-SMF restoration container information, the anchor SMF uses the AMF instance ID to look up an AMF configuration file from a Network Repository Function (NRF) and obtains an API URI to send a notification to the AMF.

b) If the API URI of the AMF service exists in the I-SMF restoration container information, the anchor SMF uses the stored API URI to send a notification to the AMF.

c) If the callback URI of the SM context notification is present in the I-SMF restoration container information, the anchor SMF sends the SM context notification to the AMF using the stored callback URI.

Step 604: the anchor SMF sends a notification to the AMF, wherein the notification carries an I-SMF restoration indication (i.e., an ivres indication) or an I-SMF failure indication (i.e., an ivfai l indication).

In some embodiments, the anchor SMF may send a notification to the AMF using the following message:

a) Namf_Commun communication_N1N2Messagetransfer request carrying I-SMF restoration indication (ivres indication) or I-SMF failure indication (ivfai indication).

b) Namf_Commun communication_ SMContextStatusNot ify request carrying SM resource failure indication (ivres indication) or I-SMF failure indication (ivfai l indication).

c) Newly defined namf_communication_ IvSmfRestorat ion request.

Step 605: responsive to receiving the indication from the anchor SMF, the AMF may perform one of the following actions:

a) If the UE is in the IDLE state, initiating an I-SMF recovery procedure:

the AMF reselects a new I-SMF and performs an I-SMF restoration procedure (e.g., steps 502/503 through 522 shown in FIG. 5A and FIG. 5B). For a UE in IDLE state, no N3 tunnel activation is required in the I-SMF recovery procedure. Therefore, even if the anchor SMF does not return the stored UP connection state to the newly selected I-SMF, the I-SMF restoration procedure is not damaged.

B) Even if the UE is in CONNECTED state, initiate I-SMF recovery procedure:

the AMF reselects a new I-SMF and performs the I-SMF restoration process shown in FIGS. 5A and 5B (e.g., steps 502/503 through 522). For a UE in CONNECTED state, N3 tunnel activation is required in the I-SMF recovery procedure. If the old I-UPF is reused for the PDU session, the new I-SMF may request the new I-UPF to establish the N3 tunnel or request the old I-UPF to recover the original N3 tunnel. In this case, the anchor SMF may return the stored UPF information (i.e., UP connection state, and optionally other UPF information (i.e., UPF instance ID, N3 tunnel information, N9 tunnel N4 session)) to the newly selected I-SMF (e.g., step 511). If the new I-SMF cannot acquire the UP connection state, the N3 tunnel cannot be activated, resulting in I-SMF restoration flow failure.

C) If the UE is in the CONNECTED state, then the N2 connection associated with the UE is released:

when the N2 connection is released, the UE is forced from the CONNECTED state into the IDLE state. In this embodiment, the AMF may trigger the I-SMF restoration procedure until/after receiving the UE-initiated service request (e.g., fig. 5A and 5B). Alternative C may be a simple replacement for alternative B because alternative C only requires the new I-SMF to store AMF information and UP connection state in the anchor SMF, while alternative B requires the I-SMF to store more information from the anchor SMF (e.g., UPF information such as UP connection state, UPF instance ID, N3 tunnel information, N9 tunnel information, N4 session ID).

Fig. 7 illustrates a schematic diagram of PDU session release with reactivation procedure, according to an embodiment of the disclosure. In fig. 7, the anchor SMF detects an I-SMF failure and triggers PDU session release using a reactivation procedure.

Specifically, after steps 701a, 701b, or 701c, the anchor SMF is triggered to request the AMF to initiate a PDU session release with reactivation procedure. Steps 701a, 701b, and 701c are similar to steps 601a, 601b, and 601c, respectively, and are not described here for brevity.

Step 702: the anchor SMF detects a failure of the I-SMF.

Step 703: the anchor SMF determines to release and re-activate the PDU session.

In step 703, the anchor SMF constructs a PDU session release message, wherein a reactivation indication is included in the PDU session release message.

Step 704: the anchor SMF sends an N1N2message transfer (i.e., namf_communication_nf1n2message transfer) carrying an N1 SM container (with a re-activated PDU session release message) to the AMF.

In step 704, the anchor SMF uses the AMF information stored in the intermediate recovery container information to find the AMF to which the N1N2MessageTransfer request was sent.

Step 705: after performing the PDU session release with reactivation procedure, the PDU session is reactivated. During PDU session release with reactivation procedure, the AMF detects failure of the old I-SMF and selects a new I-SMF to service the PDU session.

Fig. 8 relates to a schematic diagram of a wireless terminal 80 according to an embodiment of the present disclosure. The wireless terminal 80 may be a user terminal (UE), a mobile phone, a laptop computer, a tablet computer, an electronic book, or a portable computer system, and is not limited thereto. The wireless terminal 80 may include a processor 800, such as a microprocessor or an Application Specific Integrated Circuit (ASIC), a storage unit 810, and a communication unit 820. The memory unit 810 may be any data storage device that stores program code 812 that is accessed and executed by the processor 800. Examples of storage unit 812 include, but are not limited to, a Subscriber Identity Module (SIM), read Only Memory (ROM), flash memory, random Access Memory (RAM), hard disk, and optical data storage devices. The communication unit 820 may be a transceiver and is configured to transmit and receive signals (e.g., messages or data packets) according to the processing result of the processor 800. In an embodiment, communication unit 820 transmits and receives signals via at least one antenna 822 shown in fig. 8.

In an embodiment, the memory unit 810 and the program code 812 may be omitted, and the processor 800 may include a memory unit having stored program code.

Processor 800 may implement any of the steps of the exemplary embodiments on wireless terminal 80, for example, by executing program code 812.

The communication unit 820 may be a transceiver. Alternatively or additionally, the communication unit 820 may combine a transmitting unit and a receiving unit configured to transmit and receive signals to and from a radio network node (e.g., a base station), respectively.

Fig. 9 relates to a schematic diagram of a wireless network node 90 according to an embodiment of the present disclosure. The radio network node 90 may be a satellite, a Base Station (BS), a network entity, a Mobility Management Entity (MME), a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), a Radio Access Network (RAN) node, a next generation RAN (NG-RAN) node, a gNB, eNB, gNB central unit (gNB-CU), a gNB distributed unit (gNB-DU), a data network, a core network, or a Radio Network Controller (RNC), without limitation herein. Further, the wireless network node 90 may include (perform) at least one network function, such as an access and mobility management function (AMF), a Session Management Function (SMF), a User Plane Function (UPF), a Policy Control Function (PCF), an Application Function (AF), etc. The radio network node 90 may comprise a processor 900, such as a microprocessor or ASIC, a storage unit 910 and a communication unit 920. The storage unit 910 may be any data storage device that stores program code 912 that is accessed and executed by the processor 900. Examples of storage units 912 include, but are not limited to, SIM, ROM, flash memory, RAM, hard disk, and optical data storage devices. The communication unit 920 may be a transceiver and is configured to transmit and receive signals (e.g., messages or data packets) according to the processing result of the processor 900. In an example, the communication unit 920 transmits and receives signals via at least one antenna 922 shown in fig. 9.

In an embodiment, the storage unit 910 and the program code 912 may be omitted. Processor 900 may include a memory unit with stored program code.

Processor 900 may implement any of the steps described in the exemplary embodiments on radio network node 90, for example, by executing program code 912.

The communication unit 920 may be a transceiver. Alternatively or additionally, the communication unit 920 may combine a transmitting unit and a receiving unit configured to transmit and receive signals to and from a wireless terminal (e.g., a user terminal or another wireless network node), respectively.

Fig. 10 shows a schematic diagram of a method according to an embodiment of the present disclosure. The method shown in fig. 10 may be used in an I-SMF (e.g., the V-SMF shown in fig. 1 or the I-SMF shown in fig. 2, a wireless device comprising the I-SMF, a wireless device performing (part or all of) the functionality of the I-SMF), and comprises the steps of:

step 1001: and transmitting recovery information of the I-SMF for recovering the PDU session to the anchor SMF.

In the embodiment of fig. 10, the PDU session is established with an insert I-SMF. To be able to resume the I-SMF of a PDU session, the I-SMF transmits resume information (i.e., I-SMF resume container information or ivres container information) of the I-SMF for resuming the PDU session to an anchor SMF (of the PDU session). Note that if the container information changes or updates, the I-SMF may send the container information to the anchor SMF in order to keep the container information up-to-date. If the anchor SMF detects a failure of the I-SMF, the transmission of the resume information enables the anchor SMF to trigger a procedure for resuming the I-SMF of the PDU session.

In an embodiment, the recovery information includes at least one of: information of an AMF associated with the PDU session (i.e., AMF information), information of a RAN node associated with the PDU session (i.e., RAN information), or information associated with an I-UPF (i.e., I-UPF information).

In an embodiment, the AMF information comprises at least one of: AMF instance ID, API URI of AMF service, callback URI for (receiving) SM context status notification.

In an embodiment, the AMF instance ID uniquely identifies the AMF and may be used by other NFs to retrieve the AMF profile from the NRF.

In an embodiment, the API URI of the AMF service indicates the API URI of the service provided by the AMF. For example, the API URI of the AMF service may indicate an API URI of the namf_communication service that the SMF may use to send the N1/N2 message(s) to the AMF.

In an embodiment, the callback URI for the SM context state notification is a callback URI belonging to the AMF and is used to receive any SM context state notification from the SMF (e.g., I-SMF), where the SM context state notification may notify, for example, that the SM context is transferred to another I-SMF, that the SM context is released, etc.

In an embodiment, a UPF instance ID is used to uniquely identify the I-UPF.

In an embodiment, the I-SMF may send a resume indication of an intermediate SMF associated with the PDU session to the anchor SMF and receive resume information from the anchor SMF. For example, the I-SMF may be a newly selected I-SMF for a PDU session (e.g., the new I-SMF shown in FIGS. 5A and 5B). The I-SMF may send a create request to the anchor SMF including a resume indication of the intermediate SMF and receive a create response from the anchor SMF including resume information (see, e.g., step 508 and step 511 shown in fig. 5A). In this embodiment, the I-SMF may perform step 1001 after the resume information is changed (e.g., step 521). Further, in this embodiment, the I-SMF may further receive a resume indication of the intermediate SMF from the AMF of the PDU session (e.g., step 504).

In an embodiment, the I-SMF may perform an intermediate SMF recovery procedure based on the (received) recovery information. For example, the I-SMF may select an I-UPF indicated by the resume information (e.g., the old I-UPF shown in FIGS. 5A and 5B) to serve the PDU session. Alternatively or additionally, the I-SMF may use/reuse tunnel information (e.g., N3 tunnel information and/or N9 tunnel information) in the restoration information to restore the corresponding tunnel(s) (e.g., N3 tunnel and/or N9 tunnel).

In an embodiment, the I-SMF is selected to serve the PDU session after an I-SMF failure of the serving PDU session (e.g., after a failure of an intermediate SMF of the serving PDU session is detected). That is, the I-SMF may be a new I-SMF shown in FIG. 5A, FIG. 5B, FIG. 6 or FIG. 7.

In an embodiment, during PDU session establishment, I-SMF may be selected to serve the PDU session. In other words, the I-SMF may be the I-SMF shown in FIG. 4 or the old I-SMF shown in FIG. 5A, FIG. 5B, FIG. 6 or FIG. 7.

Fig. 11 shows a schematic diagram of a method according to an embodiment of the present disclosure. The method shown in fig. 11 may be used in an anchor SMF (e.g., a wireless device that includes the anchor SMF, a wireless device that performs (part or all of) the functions of an I-SMF), and comprises the steps of:

Step 1101: recovery information for recovering an intermediate SMF of the PDU session is received from the first I-SMF.

In fig. 11, an anchor SMF (of a PDU session) may receive resume information from a first I-SMF (serving the PDU session), where the resume information is associated with (e.g., for) the I-SMF of the PDU session. The anchor SMF may receive resume information during or after PDU session establishment.

In an embodiment, a UPF instance ID is used to uniquely identify the I-UPF.

In an embodiment, the anchor SMF receives a resume indication of an intermediate SMF associated with the PDU session from a second I-SMF (e.g., the new I-SMF shown in fig. 5A and 5B). The anchor SMF transmits the received (or stored) resume information to the second I-SMF.

In an embodiment, the anchor SMF may trigger a resume procedure for resuming the I-SMF of the PDU session based on the resume information. Specifically, the anchor SMF may find (e.g., determine) the AMF indicated by the resume information and send an indication to the AMF to trigger a resume procedure of the I-SMF for resuming the PDU session. For example, the anchor SMF may send a resume indication of the intermediate SMF that triggered the intermediate SMF resume procedure to the AMF indicated by the resume information (see, e.g., fig. 6). Alternatively, the anchor SMF may send a PDU session release request including a reactivation indication to the AMF indicated by the resume information. That is, the triggered procedure may be a PDU session release with reactivation procedure (see e.g., fig. 7).

Note that the anchor SMF may trigger a resume procedure if at least one of the following is detected/determined:

-failure of an I-SMF serving PDU session;

-an I-SMF failure of a service PDU session;

-an I-SMF that cannot reach or is not able to reach a service PDU session;

The I-SMF serving the PDU session cannot (successfully) process the request.

Fig. 12 shows a schematic diagram of a method according to an embodiment of the present disclosure. The method shown in fig. 12 may be used in an AMF (e.g., a wireless device including the AMF or a wireless device performing (part or all of) the functions of the AMF), and comprises the steps of:

step 1201: a resume indication of an intermediate SMF associated with the PDU session is received from the anchor SMF.

Step 1202: a resume procedure for resuming the intermediate SMF of the PDU session is triggered.

In fig. 12, the AMF receives a resume indication of an intermediate SMF associated with a PDU session and triggers a resume procedure of the intermediate SMF for resuming the PDU session (e.g., based on or responsive to the resume indication of the intermediate SMF).

In an embodiment, the AMF triggers the resume flow by:

selecting an I-SMF (e.g., new I-SMF) for a (serving) PDU session, and

SM context creation messages associated with the PDU session are sent to the selected SMF (e.g., steps 503 and 504).

Note that the context creation message includes at least one of the following: a PDU session identifier, an anchor SMF instance identifier, or an intermediate SMF restoration indication.

In an embodiment, if the UE associated with the PDU session is in IDLE state, the AMF triggers an I-SMF recovery procedure (e.g., steps 502/503 to 522) as the recovery procedure. In this embodiment, the UPF information sent from the anchor AMF to the new I-SMF (e.g., at step 511) may not include the UP connection state.

In an embodiment, if the UE associated with the PDU session is in the CONNECTED state, the AMF triggers an I-SMF recovery procedure (e.g., steps 502/503 to 522) as the recovery procedure. In the I-SMF restoration procedure, the newly selected I-SMF may receive UPF information from the anchor SMF, wherein the UPF information includes an UP connection state. The UPF information in this embodiment may further include at least one of a UPF instance ID, N3 tunnel information, N9 tunnel N4 session.

In an embodiment, the triggered resume procedure includes releasing an N2 connection associated with the UE of the PDU session. For example, the N2 connection associated with a UE is a connection between the AMF and the RAN node serving the UE and established for the UE. In this embodiment, the new I-SMF receives UPF information from the anchor SMF including (only) UP connection status. In this embodiment, the UPF information may not include other information.

While various embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example only, and not limitation. Likewise, the various figures may depict exemplary architectures or configurations provided to enable those of ordinary skill in the art to understand the exemplary features and functions of the present disclosure. However, those skilled in the art will appreciate that the present disclosure is not limited to the example architectures or configurations shown, but may be implemented using a variety of alternative architectures and configurations. Furthermore, as will be appreciated by one of ordinary skill in the art, one or more features of one embodiment may be combined with one or more features of another embodiment described herein. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments.

It will be further understood that any reference herein to elements using designations such as "first," "second," etc. generally does not limit the number or order of such elements. Rather, these reference names may be used herein as a convenient means of distinguishing between two or more elements or multiple instances of an element. Thus, references to first and second elements do not mean that only two elements can be used or that the first element must somehow precede the second element.

Furthermore, those of ordinary skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, and symbols that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof, for example.

Those of skill would further appreciate that any of the various illustrative logical blocks, units, processors, devices, circuits, methods, and functions described in connection with the aspects disclosed herein may be implemented with electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of both), firmware, various forms of program or design code incorporating instructions (which may be referred to herein as "software" or "a software unit" for convenience), or any combination of these techniques.

To clearly illustrate this interchangeability of hardware, firmware, and software, various illustrative components, blocks, units, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware, or software, or as a combination of such techniques, depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. According to various embodiments, processors, devices, components, circuits, structures, machines, units, etc. may be configured to perform one or more of the functions described herein. The term "configured" or "configured for" as used herein with respect to a specified operation or function refers to a processor, device, component, circuit, structure, machine, unit, etc. that is physically constructed, programmed and/or arranged to perform the specified operation or function.

Moreover, those of skill in the art will appreciate that the various illustrative logical blocks, units, devices, components, and circuits described herein may be implemented within or performed by an Integrated Circuit (IC) that may comprise a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, or any combination thereof. Logic blocks, units, and circuits may also include antennas and/or transceivers to communicate with various components within the network or within the device. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration to perform the functions described herein. If implemented in software, these functions may be stored on a computer-readable medium as one or more instructions or code. Thus, the steps of a method or algorithm disclosed herein may be embodied as software stored on a computer readable medium.

Computer-readable media includes both computer storage media and communication media including any medium that can transfer a computer program or code from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.

In this document, the term "unit" as used herein refers to software, firmware, hardware, and any combination of these elements for performing the associated functions described herein. In addition, for purposes of discussion, the various units are described as discrete units; however, as will be apparent to one of ordinary skill in the art, two or more units may be combined to form a single unit that performs the associated function in accordance with embodiments of the disclosure.

Additionally, memory or other storage and communication components may be used in embodiments of the present disclosure. It should be appreciated that for clarity, the above description has described embodiments of the disclosure with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality may be applied between different functional units, processing logic elements, or domains without departing from the present disclosure. For example, functions illustrated as being performed by separate processing logic elements or controllers may be performed by the same processing logic element or controller. Thus, references to specific functional units are only references to suitable means for providing the functionality, and do not represent strict logical or physical structures or organization.

Various modifications to the implementations described in this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the scope of this disclosure. Thus, the present disclosure is not limited to the implementations shown herein but is to be accorded the widest scope consistent with the novel features and principles disclosed herein as described in the following claims.

Claims

1. A wireless communication method for use in an intermediate session management function, SMF, the method comprising:

the recovery information for recovering the intermediate SMF of the protocol data unit PDU session is sent to the anchor SMF.

2. The wireless communication method of claim 1, wherein the recovery information comprises at least one of: information of an access and mobility management function, AMF, associated with the PDU session, information of a radio access network node associated with the PDU session, or information associated with an intermediate user plane function, UPF.

3. The wireless communication method of claim 2, wherein the information of the AMF comprises at least one of: an AMF instance identifier, an application program interface Uniform resource identifier of an AMF service, or a callback Uniform resource identifier that receives a session management context status notification.

4. A wireless communication method according to claim 2 or 3, wherein the information of the radio access network node comprises radio access network N3 tunnel information.

5. The wireless communication method of any of claims 2-4, wherein the information associated with the intermediate UPF comprises at least one of: a UPF instance identifier, UPF N3 tunnel information, UPF N9 tunnel information, or an N4 session identifier.

6. The wireless communication method according to any one of claims 1 to 5, further comprising:

transmitting a resume indication of an intermediate SMF associated with the PDU session to the anchor SMF, an

The recovery information is received from the anchor SMF.

7. The wireless communication method of claim 6, further comprising:

a resume indication of an intermediate SMF associated with the PDU session is received from an access and mobility management function.

8. The wireless communication method according to claim 6 or 7, further comprising:

and executing an intermediate SMF recovery flow based on the recovery information.

9. The wireless communication method of claim 8, wherein performing the intermediate SMF recovery procedure based on the recovery information comprises:

an intermediate UPF indicated by the resume information is selected for servicing the PDU session.

10. The wireless communication method of any of claims 1-9, wherein the intermediate SMF is selected to service the PDU session after an intermediate SMF serving the PDU session fails.

11. The wireless communication method of any of claims 1-5, wherein the intermediate SMF is selected to serve the PDU session during the PDU session establishment.

12. A wireless communication method for use in an anchor session management function, SMF, the method comprising:

recovery information for recovering the intermediate SMF of the protocol data unit PDU session is received from the first intermediate SMF.

13. The wireless communication method of claim 12, wherein the recovery information comprises at least one of: information of an access and mobility management function, AMF, associated with the PDU session, information of a radio access network node associated with the PDU session, or information associated with an intermediate user plane function, UPF.

14. The wireless communication method of claim 13, wherein the information of the AMF comprises at least one of: an AMF instance identifier, an application program interface Uniform resource identifier of an AMF service, or a callback Uniform resource identifier of a session management context state notification.

15. The wireless communication method according to claim 13 or 14, wherein the information of the radio access network node comprises radio access network N3 tunnel information.

16. The wireless communication method of any of claims 13-15, wherein the information associated with the intermediate UPF comprises at least one of: a UPF instance identifier, UPF N3 tunnel information, UPF N9 tunnel information, or an N4 session identifier.

17. The wireless communication method according to any one of claims 12 to 16, further comprising:

And sending the recovery information to a second intermediate SMF.

18. The wireless communication method according to any one of claims 12 to 16, further comprising:

and sending a recovery instruction of the intermediate SMF triggering the recovery flow of the intermediate SMF to the access and mobility management function indicated by the recovery information.

19. The wireless communication method according to any one of claims 12 to 16, further comprising:

sending a PDU session release request including a reactivation indication to the access and mobility management function indicated by the resume information.

20. A wireless communication method for use in access and mobility management functions, the method comprising:

receiving a resume indication of an intermediate SMF associated with a protocol data unit PDU session from an anchor session management function SMF, an

Triggering a recovery procedure for recovering the intermediate SMF of the PDU session.

21. The wireless communication method of claim 20, wherein triggering a recovery procedure for recovering the intermediate SMF of the PDU session comprises:

selecting an intermediate SMF for the PDU session, an

And sending a session management context creation message of the PDU session to the selected SMF.

22. The wireless communication method of claim 21, wherein the session management context creation message comprises at least one of: a PDU session identifier, an anchor SMF instance identifier, or an intermediate SMF restoration indication.

23. A wireless device comprising an intermediate session management function, SMF, the wireless device comprising:

a communication unit configured to send recovery information for recovering an intermediate SMF of a protocol data unit, PDU, session to an anchor SMF.

24. The wireless device of claim 23, further comprising a processor configured to perform the wireless communication method of any of claims 2-11.

25. A wireless device comprising an anchor session management function, SMF, the wireless device comprising:

a communication unit configured to receive recovery information for recovering the intermediate SMF of the protocol data unit PDU session from the intermediate SMF.

26. The wireless device of claim 25, further comprising a processor configured to perform the wireless communication method of any of claims 13-19.

27. A wireless device comprising access and mobility management functions, the wireless device comprising:

a communication unit configured to receive a resume indication of an intermediate SMF associated with a protocol data unit, PDU, session from an anchor session management function, SMF, and

a processor configured to trigger a resume procedure for resuming an intermediate SMF of the PDU session.

28. The wireless device of claim 27, wherein the processor is further configured to perform the wireless communication method of claim 21 or 22.

29. A computer program product comprising computer readable program medium code stored on the computer program product, which when executed by a processor causes the processor to implement the wireless communication method according to any one of claims 1 to 22.