Method, network node and medium for implicit event subscription removal

Abstract

The present disclosure provides a first network node and a method (200) performed by the first network node. The method (200) comprises: receiving (S201) a request message from a second network node for subscribing to an event of a user equipment (UE) served by a first network node; and sending (S203) a first indication to the second network node, the first indication indicating that the first network node is able to locally remove the subscribed events of the UE stored as at least part of the UE context during a logout of the first network node from the second network node due to the UE releasing the last session of the UE in the first network node. The disclosure also provides a corresponding second network node and a method (300) performed by the second network node.

Description

Technical Field

[0001] The present disclosure relates to wireless communication, and particularly to a method, a network node, and a computer-readable storage medium for implicit event subscription removal during a deregistration process from a first network node to a second network node due to the release of the last Protocol Data Unit (PDU) session of a User Equipment (UE) in the first network node. Background Art

[0002] This section is intended to provide background for various embodiments of the technology described in the present disclosure. The descriptions in this section may include concepts that can be studied, but are not necessarily concepts that have been previously conceived or studied. Thus, unless otherwise stated herein, the content described in this section is not prior art to the specification and / or claims of the present disclosure and is not admitted to be prior art merely by virtue of being included in this section.

[0003] An Application Function (AF) may subscribe to events (event opening) notified by a Session Management Function (SMF) (e.g., PDU session state).

[0004] Currently, the handling of the last PDU session of a given UE being deregistered in the SMF (i.e., the SMF does not provide PDU session service for the UE) is under discussion. In this case, the SMF deregisters the last PDU session from the UDM (via the Nudm_UEContextManagement service), and when removing the ongoing event subscriptions stored in the Unified Data Repository (UDR) for this SMF, the UDM needs to cancel the subscriptions of the removed events to the SMF.

[0005] To ensure the removal / cleanup of event subscriptions in the SMF, the UDM sends an unsubscribe (e.g., HTTP DELETE) request to the SMF. However, the SMF may have previously decided to add the events requested for the UE as part of the UE context. This would mean that when the UE context terminates, the events / resources in the SMF no longer exist in the SMF. Therefore, the HTTP DELETE request from the UDM will result in an HTTP response 404 Not Found from the SMF, which the Mobile Network Operator (MNO) may interpret as a failure situation, while in fact it is not a failure. Even if the SMF returns 200 OK (instead of 404 Not Found) to fix this problem, unnecessary signaling (involving potential failover and / or retry) cannot be avoided.

[0006] Therefore, it is desirable to solve or alleviate at least the above problems and the like. Summary of the Invention

[0007] Certain aspects of the present disclosure and its embodiments can provide solutions to the above or other problems. In particular, embodiments of the present disclosure propose that the SMF indicates to the UDM (which has subscribed to events of the UE served by the SMF) that during the deregistration process of the SMF from the UDM due to the release of the last PDU session of the UE in the SMF, the SMF can locally remove the events of the UE stored as at least a part of the UE context.

[0008] According to a first aspect of the present disclosure, a method performed by a first network node is provided. The method includes: receiving a request message from a second network node for subscribing to events of a UE served by the first network node; and sending a first indication to the second network node, the first indication indicating that during the deregistration process of the first network node from the second network node due to the release of the last session of the UE in the first network node, the first network node can locally remove the subscribed events of the UE stored as at least a part of the UE context.

[0009] In an exemplary embodiment, the method further includes: locally removing the UE context in the first network node.

[0010] In an exemplary embodiment, the first indication is sent to the second network node in a response message for subscribing to events of the UE.

[0011] In an exemplary embodiment, the request message for subscribing to events of the UE includes a second indication, the second indication indicating that during the deregistration process of the first network node from the second network node due to the release of the last session of the UE in the first network node, the second network node can skip the request message for unsubscribing / deleting the subscribed events of the UE.

[0012] In an exemplary embodiment, the method further includes: based on the second indication, determining that the subscribed events of the UE can be securely stored and removed as at least a part of the UE context; and storing the subscribed events of the UE as at least a part of the UE context.

[0013] In an exemplary embodiment, the first indication is sent to the second network node in a deregistration request message sent during the deregistration process of the first network node from the second network node due to the release of the last session of the UE in the first network node.

[0014] In an exemplary embodiment, the first network node is an SMF node and the second network node is a UDM node.

[0015] According to a second aspect of the present disclosure, a method performed by a second network node is provided. The method includes: sending a request message to a first network node for subscribing to events of a UE served by the first network node; and receiving a first indication from the first network node, the first indication indicating that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the first network node can locally remove the subscribed events of the UE stored as at least a part of the UE context.

[0016] In an exemplary embodiment, the method further includes: during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, skipping a request message for unsubscribing / deleting the subscribed events of the UE.

[0017] In an exemplary embodiment, receive the first indication from the first network node in a response message for subscribing to events of the UE.

[0018] In an exemplary embodiment, the request message for subscribing to events of the UE includes a second indication, the second indication indicating that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the second network node can skip a request message for unsubscribing / deleting the events of the UE.

[0019] In an exemplary embodiment, receive the first indication from the first network node in a deregistration request message received during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node.

[0020] In an exemplary embodiment, the first network node is an SMF node and the second network node is a UDM node.

[0021] According to a third aspect of the present disclosure, a first network node is provided. The UE includes: at least one processor, and at least one memory storing instructions, which when executed on the at least one processor, cause the first network node to perform any method according to the first aspect of the present disclosure.

[0022] According to a fourth aspect of the present disclosure, a second network node is provided. The second network node includes: at least one processor, and at least one memory storing instructions, which when executed on the at least one processor, cause the second network node to perform any method according to the second aspect of the present disclosure.

[0023] According to a fifth aspect of the present disclosure, a computer-readable storage medium is provided. The computer-readable storage medium has computer program instructions stored thereon, which, when executed by at least one processor, cause the at least one processor to execute any method according to any one of the first aspect to the second aspect of the present disclosure.

[0024] Certain embodiments of the present disclosure may provide one or more technical advantages.

[0025] Through this indication from the SMF to the UDM: During the deregistration process from the SMF to the UDM due to the UE releasing the UE's last PDU session in the SMF, the SMF can locally remove the UE's events stored as at least a part of the UE context, allowing the UDM to be aware of the SMF event storage and processing through a new feature (indication) in the response message for subscribing to the UE's events or in the deregistration request message sent during the deregistration process from the first network node to the second network node due to the UE releasing the UE's last session in the first network node. In this way, the UDM can securely determine its own handling of events and related signaling to the SMF. For example, during the deregistration process from the first network node to the second network node due to the UE releasing the UE's last session in the first network node, the request message for explicitly canceling the subscription / deleting the subscribed events of the UE can be skipped.

[0026] Therefore, the embodiments of the present disclosure can avoid unnecessary signaling between the UDM and the SMF, and can also improve network monitoring, because it avoids the degradation of key performance indicators (KPIs) associated with frequent and normal operation errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] When considered in conjunction with the accompanying drawings, a more complete understanding of the embodiments of the present disclosure and their attendant advantages and features will be more readily understood by reference to the following detailed description, in which:

[0028] Figure 1 An exemplary signaling sequence diagram showing a process for explicit event subscription removal during the deregistration process from the SMF to the UDM due to the UE releasing the UE's last PDU session in the SMF is schematically shown;

[0029] Figure 2 A method for implicit event subscription removal executed by the first network node during the deregistration process from the first network node to the second network node due to the UE releasing the UE's last PDU session in the first network node according to an exemplary embodiment of the present disclosure is schematically shown;

[0030] Figure 3Schematically shows a method for implicit event subscription removal performed by a second network node during the deregistration process of a first network node to a second network node due to the release of the last PDU session of a UE in the first network node according to an exemplary embodiment of the present disclosure;

[0031] Figure 4 Schematically shows an exemplary signaling sequence diagram of a process for implicit event subscription removal during the deregistration process of a first network node to a second network node due to the release of the last PDU session of a UE in the first network node, where methods performed by the first network node and the second network node according to an exemplary embodiment of the present disclosure are applied;

[0032] Figure 5 Schematically shows another exemplary signaling sequence diagram of a process for implicit event subscription removal during the deregistration process of a first network node to a second network node due to the release of the last PDU session of a UE in the first network node, where methods performed by the first network node and the second network node according to an exemplary embodiment of the present disclosure are applied;

[0033] Figure 6 Schematically shows a structural block diagram of a first network node according to an exemplary embodiment of the present disclosure;

[0034] Figure 7 Schematically shows a structural block diagram of a first network node according to another exemplary embodiment of the present disclosure;

[0035] Figure 8 Schematically shows a structural block diagram of a second network node according to an exemplary embodiment of the present disclosure; and

[0036] Figure 9 Schematically shows a structural block diagram of a second network node according to another exemplary embodiment of the present disclosure. Detailed Description

[0037] Hereinafter, the principles and spirit of the present disclosure will be described with reference to illustrative embodiments. Some embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. However, other embodiments are within the scope of the subject matter disclosed herein, and the disclosed subject matter should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. Additional information can be referred to the following documents, which are incorporated herein by reference in their entirety:

[0038] 3GPP TS29.522 V17.5.0, "3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; 5G System; Network Exposure Function Northbound API; Phase 3 (Release 17)", March 2022;

[0039] 3GPP TS29.122 V17.5.0, "3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; T8 Reference Point for Northbound APIs; (Release 17)", March 2022; and

[0040] 3GPP TS29.503 V17.7.0, "3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; 5G System; Unified Data Management Service; Phase 3 (Release 17)", June 2022.

[0041] Those skilled in the art will understand that the term "exemplary" is used herein to mean "illustrative" or "serving as an example", and is not intended to imply that a particular embodiment is superior to another or that a particular feature is essential. Similarly, terms such as "first" and "second" may be used only to distinguish one entity or element from another, and do not necessarily require or imply any physical or logical relationship or order between such entities or elements. The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the concepts described herein. As used herein, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms as well. It will be further understood that when used herein, the terms "comprises", "comprising", "includes" and / or "including" specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0042] In the embodiments described herein, connection terms such as "communicating with" may be used to indicate electrical communication or data communication, which may be achieved, for example, by physical contact, induction, electromagnetic radiation, radio signals, infrared signals, or optical signals. Those of ordinary skill in the art will understand that multiple components may interoperate and may be modified and varied to achieve electrical and data communication.

[0043] In some embodiments described herein, terms such as "coupled", "connected", etc. may be used herein to indicate a connection, although not necessarily direct, and may include wired connections and / or wireless connections.

[0044] The term "network node" as used herein can be any type of network node included in a radio network, which can also include any one of the following: base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g-node B (gNB), evolved node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node (e.g., MSR BS), multi-cell / multicast coordination entity (MCE), integrated access and backhaul (IAB) node, relay node, donor node controlled relay, radio access point (AP), transmission point, transmission node, remote radio unit (RRU), remote radio head (RRH), core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, coordination node, positioning node, MDT node, etc.), external node (e.g., third-party node, node external to the current network), node in a distributed antenna system (DAS), spectrum access system (SAS) node, element management system (EMS), etc. A network node can also include test equipment. The term "radio node" as used herein can also be used to denote a wireless device, such as a wireless device or a radio network node.

[0045] In some embodiments, the non - restrictive terms wireless device or UE may be used interchangeably. A UE here can be any type of wireless device capable of communicating with a network node or another wireless device via radio signals, such as a wireless device. A UE can also be a radio communication device, a target device, a D2D wireless device, a machine - type wireless device or a wireless device capable of machine - to - machine communication (M2M), a low - cost and / or low - complexity wireless device, a sensor equipped with a wireless device, a tablet, a mobile terminal, a smartphone, a laptop embedded equipped (LEE), a laptop mounted equipment (LME), a USB dongle, a customer premises equipment (CPE), an Internet of Things (IoT) device or a narrowband Internet of Things (NB - IoT) device, etc.

[0046] Furthermore, in some embodiments, the general term "radio network node" is used. It can be any type of radio network node and can include any one of the following: base station, radio base station, base station transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, multi - cell / multicast coordination entity (MCE), IAB node, relay node, access point, radio access point, remote radio unit (RRU), remote radio head (RRH).

[0047] The term "radio access technology" or RAT can refer to any RAT, such as Universal Terrestrial Radio Access (UTRA), evolved UTRA (E - UTRA), NarrowBand Internet Of Things (NB - IoT), Wireless Fidelity (WiFi), Bluetooth, next - generation RAT, New Radio (NR), 4G, 5G, etc. Any device represented by the terms node, network node or radio network node is capable of supporting a single or multiple RATs.

[0048] The term "signal" or "radio signal" as used herein can be any physical signal or physical channel. Examples of DL physical signals are reference signals (RS), such as primary synchronization signal (PSS), secondary synchronization signal (SSS), CSI-RS, demodulation reference signal (DMRS) in synchronization signal (SS) / physical broadcast channel (PBCH) block (SSB), discovery reference signal (DRS), cell reference signal (CRS), position reference signal (PRS), etc. The RS can be periodic. For example, the RS occasion carrying one or more RSs can occur with a specific periodicity, such as 20 ms, 40 ms, etc. The RS can also be aperiodic. Each SSB carries NR-PSS, NR-SSS, and NR-PBCH in 4 consecutive symbols. One or more SSBs are transmitted in an SSB burst, and the SSB burst repeats with a specific periodicity, such as 5 ms, 10 ms, 20 ms, 40 ms, 80 ms, and 160 ms. The UE is configured with information about SSBs on a cell of a specific carrier frequency through one or more SS / PBCH block-based measurement timing configuration (SMTC). The SMTC configuration includes parameters such as the SMTC period, the time length or duration of the SMTC occasion, the SMTC time offset relative to a reference time (e.g., the system frame number (SFN) of the serving cell), etc. Therefore, the SMTC occasion can also occur with a specific periodicity, such as 5 ms, 10 ms, 20 ms, 40 ms, 80 ms, and 160 ms. Examples of UL physical signals are reference signals, such as SRS, DMRS, etc. The term "physical channel" refers to any channel that carries higher layer information (such as data, control, etc.). Examples of physical channels are PBCH, narrowband PBCH (NPBCH), PDCCH, PDSCH, short PUCCH (sPUCCH), sPDSCH, sPUCCH, sPUSCH, machine type communication (MTC) PDCCH (MPDCCH), NPDCCH, NPDSCH, E-PDCCH, PUSCH, PUCCH, NPUSCH, etc.

[0049] Note that although terms from a specific wireless system (e.g., 3GPP LTE and / or New Radio (NR)) may be used in this disclosure, this should not be construed as limiting the scope of the disclosure to only the above systems. Other wireless systems, including but not limited to Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB), and Global System for Mobile Communications (GSM), may also benefit from leveraging the concepts covered in this disclosure.

[0050] It should also be noted that the functions described herein as being performed by a UE or a network node may be distributed across multiple UEs and / or network nodes. In other words, it is contemplated that the functions of the network nodes and UEs described herein are not limited to being performed by a single physical device and may in fact be distributed among several physical devices.

[0051] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It should also be understood that the terms used herein shall be interpreted as having a meaning that is consistent with the context of this specification and the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0052] As previously mentioned, to ensure the removal / cleanup of event subscriptions in the SMF, the UDM sends an unsubscribe (e.g., HTTP DELETE) request to the SMF, i.e., an explicit event subscription removal request. However, the SMF may have previously decided to add the events requested for the UE as part of the UE context. This would mean that when the UE context terminates, the events / resources in the SMF no longer exist in the SMF. Consequently, the HTTP DELETE request from the UDM will result in an HTTP response 404 Not Found from the SMF, which may be interpreted by a Mobile Network Operator (MNO) as a failure situation, while in fact it is not a failure. Even if the SMF returns 200 OK (instead of 404 Not Found) to fix this issue, unnecessary signaling (involving potential failover and / or retry) is still inevitable.

[0053] From Figure 1 it can be clearly seen the above related issues, Figure 1Schematically shows an exemplary signaling sequence diagram of a process for explicit event subscription removal during the deregistration process of the SMF to the UDM due to the UE releasing the last PDU session of the UE in the SMF.

[0054] In the following, it will be combined with Figure 1 Describe in detail how this problem occurs in the current process for explicit event subscription removal. For simplicity, the description of unnecessary signaling is omitted here.

[0055] In S1_1, the AF subscribes to events detected and reported by the SMF (such as PDU session status), and there is a serving SMF registered for the UE (i.e., the UE has a PDU session established in the serving SMF).

[0056] In S1_2, the UDM subscribes to the serving SMF via a request message for subscribing to events of the UE served by the serving SMF, for example, the Nsmf_EventExposure_Subscribe request, which includes, for example, the UE ID, monitoring type = PDU_SESSION_STATUS, etc.

[0057] In S1_3, the SMF decides to store the requested one or more events as part of the UE context (new resource ID).

[0058] In S1_4, the SMF sends a response message to the UDM in response to the request message sent in S1_2, for example, the Nsmf_EventExposure_Subscribe response, which includes, for example, success, one or more resource IDs created in the SMF, etc.

[0059] In S1_5, the UDM stores the resource ID allocated in the SMF in the UDR.

[0060] In S1_6, the UE releases the last PDU session in the SMF, and the SMF triggers the deregistration process to the UDM.

[0061] In S1_7, the SMF sends a deregistration request message sent during the deregistration process of the SMF to the UDM due to the UE releasing the last PDU session of the UE in the SMF, for example, the Nudm_uecm_deregistration_request, which includes, for example, the UE ID, session ID, etc.

[0062] In S1_8, the UDM sends a corresponding deregistration response message to the SMF.

[0063] In S1_9-1, since the UE context is removed in the SMF that has stored the event as part of the UE context, all resource IDs associated with the UE context are removed.

[0064] On the other hand, in S1_9-2, since the SMF no longer serves the UE, the UDM decides to remove all resource IDs allocated in the SMF in the UDR; thus, the UDM cancels the subscription to the event to ensure that the resources are also cleared in the SMF.

[0065] Therefore, in S1_10, the UDM sends a request message to the SMF for unsubscribing / deleting the subscribed events of the UE, such as the Nsmf_EventExposure_Unsubscribe request, which includes the UE ID, resource ID, and monitoring type = PDU_SESSION_STATUS.

[0066] However, in S1_11, the SMF cannot find the resource ID because the resource ID was removed when the UE context was removed.

[0067] Therefore, in S1_12, the SMF sends a corresponding response message to the UDM for unsubscribing / deleting the subscribed events of the UE, such as the Nsmf_EventExposure_Unsubscribe response, which includes, for example, the error: 404 Not Found.

[0068] This "404 Not Found" response may be understood by the MNO as a failure situation, but in fact, this is not a failure. Even if the SMF returns 200 OK (instead of 404 Not Found) to fix this problem, unnecessary signaling (involving potential failover and / or retry) is still inevitable. Therefore, the network KPIs are contaminated by a large number of errors associated with normal and frequent traffic situations. On the other hand, unnecessary signaling (involving potential failover and / or retry) is inevitable.

[0069] To at least address or mitigate the above problems exemplified in Figure 1 embodiments of the present disclosure propose that the SMF indicates to the UDM (which has subscribed to the events of the UE served by the SMF) that: during the deregistration process of the SMF to the UDM due to the UE releasing the last PDU session of the UE in the SMF, the SMF can locally remove the events of the UE subscribed by the UDM and stored as at least part of the UE context.

[0070] The basic concept of the present disclosure lies in

[0071] 1) The SMFUDM (event of the UE subscribed to the SMF service) sends an indication that indicates that during the deregistration process of the SMF from the UDM due to the UE releasing the last PDU session of the UE in the SMF, the SMF can locally remove the events of the UE stored as at least part of the UE context;

[0072] Alternatively or additionally, the SMF can include a new feature in the response message for subscribing to the events of the UE. For example, include a new Information Element (IE) IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL_LAST_SMF_REGISTRATION in the Nsmf_EventExposure_Subscribe response, so that the UDM is aware that during the deregistration process of the SMF from the UDM due to the UE releasing the last PDU session of the UE in the SMF, the SMF can locally remove the events of the UE stored as at least part of the UE context. In this way, when the UE context is terminated, the UDM can skip the explicit unsubscription / deletion of the events at the SMF;

[0073] As an alternative, the SMF can include a new indication in the deregistration request message. For example, include a new IE IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL in the Nudm_UECM_deregistration_request sent during the deregistration process of the SMF from the UDM due to the UE releasing the last PDU session of the UE in the SMF, to notify the UDM that the events are implicitly removed because they are stored as part of the UE context; this makes the UDM aware of this so that the UDM can skip the explicit unsubscription / deletion of the events at the SMF; and

[0074] 2) After receiving such an indication, the UDM knows the handling of the events by the SMF and its relationship with the UE context at the SMF instance, and thus determines that after removing the events in the UDR, there is no need to explicitly unsubscribe from the SMF because the cleanup at the SMF has been implicitly completed; therefore, during the deregistration process of the SMF from the UDM due to the UE releasing the last PDU session of the UE in the SMF, the UDM skips the request message for unsubscribing / deleting the subscribed events of the UE;

[0075] Alternatively or additionally, when subscribing to the SMF service, the UDM may include new features in the request message for subscribing to UE events. For example, include the new IE IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL_LAST_SMF_REGISTRATION in the Nsmf_EventExposure_Subscribe request to enable the SMF to know that UE events can be safely stored as part of the UE context. In this way, when the UE context is terminated, the UDM can skip the request message for unsubscribing / deleting the subscribed events of the UE.

[0076] In the following, reference will be made to Figure 2 Describe method 200 performed by a first network node according to an exemplary embodiment of the present disclosure for implicit event subscription removal during the deregistration process of the first network node to the second network node due to the UE releasing the last PDU session of the UE in the first network node.

[0077] In an exemplary embodiment, the first network node may be an SMF. It should be understood that the first network node may also be any other suitable entity that can be configured to perform method 200 described below, including virtualized entities that can be implemented on the cloud. Accordingly, the second network node may be a UDM.

[0078] As Figure 2 shown, method 200 may at least include step S201 and step S203.

[0079] In step S201, the first network node may receive a request message from the second network node for subscribing to events of the UE served by the first network node.

[0080] Alternatively or additionally, in an exemplary embodiment, the request message for subscribing to UE events may include an indication that indicates that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the second network node may skip the request message for unsubscribing / deleting the subscribed events of the UE.

[0081] For example, the request message for subscribing to events of a UE may be an Nsmf_EventExposure_Subscribe request, and a new IE (e.g., IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL_LAST_SMF_REGISTRATION) may be included in the Nsmf_EventExposure_Subscribe request to indicate to the first network node that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the second network node may skip the request message for unsubscribing / deleting the subscribed events of the UE.

[0082] That is, the first network node may be notified that the subscribed events of the UE can be securely stored as part of the UE context, and the second network node has the ability to skip the request message for unsubscribing / deleting the subscribed events of the UE when the UE context is terminated.

[0083] Therefore, the first network node may determine based on the indication from the second network node that the subscribed events of the UE can be securely stored and removed as at least part of the UE context; and then store the subscribed events of the UE as at least part of the UE context.

[0084] It can be understood that such an indication in the request message for subscribing to events of a UE may be optional.

[0085] Then, in step S203, the first network node may send an indication to the second network node, which indicates that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least part of the UE context.

[0086] In an exemplary embodiment, the indication may be sent to a second network node in a response message for subscribing to events of a UE. For example, the response message for subscribing to events of a UE may be an Nsmf_EventExposure_Subscribe response, and a new IE (such as IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL_LAST_SMF_REGISTRATION) may be included in the Nsmf_EventExposure_Subscribe response to indicate to the second network node that, during the deregistration process of the first network node from the second network node due to the UE releasing its last session in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least part of the UE context.

[0087] Alternatively, in another exemplary embodiment, the indication may be sent to the second network node in a deregistration request message sent during the deregistration process of the first network node from the second network node due to the UE releasing its last session in the first network node. For example, the deregistration request message may be an Nudm_UECM_deregistration_request, and a new IE (such as IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL) may be included in the Nudm_UECM_deregistration_request to indicate to the second network node that, during the deregistration process of the first network node from the second network node due to the UE releasing its last session in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least part of the UE context.

[0088] Accordingly, the first network node may locally remove the UE context. On the other hand, since the second network node is informed that, during the deregistration process of the first network node from the second network node due to the UE releasing its last session in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least part of the UE context, the second network node may skip the explicit request message for unsubscribing / deleting the subscribed events of the UE during the deregistration process.

[0089] Therefore, unnecessary signaling between network nodes can be avoided, and network monitoring can be improved because it can avoid a decrease in KPIs associated with frequent and normal operation errors.

[0090] Hereinafter, reference will be made to Figure 3Describe method 300 performed by a second network node according to an exemplary embodiment of the present disclosure for implicit event subscription removal during the deregistration process of a first network node from a second network node due to the release of the last PDU session of a UE in the first network node. It should be understood that method 300 at the second network node corresponds to method 200 at the first network node as described above. Therefore, some descriptions of method 300 may refer to the description of method 200 and will be omitted for simplicity.

[0091] In an exemplary embodiment, the second network node may be a UDM. It should be understood that the second network node may also be any other suitable entity that can be configured to perform method 300 as described below, including virtualized entities that can be implemented on the cloud. Correspondingly, the first network node may be an SMF.

[0092] As Figure 3 shown, method 300 may at least include step S301 and step S303.

[0093] In step S301, the second network node may send a request message to the first network node for subscribing to events of a UE served by the first network node.

[0094] Alternatively or additionally, in an exemplary embodiment, the request message for subscribing to events of a UE may include an indication that indicates that during the deregistration process of the first network node from the second network node due to the release of the last session of the UE in the first network node, the second network node may skip the request message for unsubscribing / deleting the subscribed events of the UE.

[0095] For example, the request message for subscribing to events of a UE may be an Nsmf_EventExposure_Subscribe request, and a new IE (e.g., IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL_LAST_SMF_REGISTRATION) may be included in the Nsmf_EventExposure_Subscribe request to indicate to the first network node that during the deregistration process of the first network node from the second network node due to the release of the last session of the UE in the first network node, the second network node may skip the request message for unsubscribing / deleting the subscribed events of the UE.

[0096] That is, the second network node may notify the first network node that the first network node may safely store the subscribed events of the UE as part of the UE context, and the second network node has the ability to skip the request message for unsubscribing / deleting the subscribed events of the UE when the UE context is terminated.

[0097] It can be understood that such an indication in the request message for subscribing to the UE's event may not be necessary.

[0098] Then, in step S303, the second network node may receive an indication from the first network node, which indicates that during the deregistration process of the first network node from the second network node due to the UE releasing the UE's last session in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least part of the UE context.

[0099] In an exemplary embodiment, this indication from the first network node may be received in the response message for subscribing to the UE's event. For example, the response message for subscribing to the UE's event may be an Nsmf_EventExposure_Subscribe response, and a new IE (such as IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL_LAST_SMF_REGISTRATION) may be included in the Nsmf_EventExposure_Subscribe response to indicate to the second network node that during the deregistration process of the first network node from the second network node due to the UE releasing the UE's last session in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least part of the UE context.

[0100] Alternatively, in another exemplary embodiment, this indication from the first network node may be received in the deregistration request message sent during the deregistration process of the first network node from the second network node due to the UE releasing the UE's last session in the first network node. For example, the deregistration request message may be an Nudm_UECM_deregistration_request, and a new IE (such as IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL) may be included in the Nudm_UECM_deregistration_request to indicate to the second network node that during the deregistration process of the first network node from the second network node due to the UE releasing the UE's last session in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least part of the UE context.

[0101] Since the first network node notifies the second network node that, in the deregistration process of the first network node from the second network node due to the UE releasing the last session of the UE in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least a part of the UE context, and the second network node may skip the explicit request message for unsubscribing / deleting the subscribed events of the UE during the deregistration process.

[0102] Therefore, unnecessary signaling between network nodes can be avoided, and network monitoring can be improved because it can avoid the KPI degradation associated with errors in frequent and normal operations.

[0103] Figure 4 An exemplary signaling sequence diagram of a process for implicit event subscription removal during the deregistration process of the first network node from the second network node due to the UE releasing the last PDU session of the UE in the first network node is schematically shown, where the method performed by the first network node and the second network node according to an exemplary embodiment of the present disclosure is applied. As Figure 4 Some descriptions of the exemplary signaling sequence diagram shown in may refer to the descriptions of methods 200 and 300 as described above, and thus will be omitted here for simplicity.

[0104] In the following description of Figure 4 the exemplary signaling sequence diagram, the SMF is used as an example of the first network node as described above, and the UDM is used as an example of the second network node as described above.

[0105] It should be noted that the following description mainly focuses on the signaling related to methods 200 and 300, and some other signaling is not described in detail to avoid obscuring the principles of the present disclosure. In Figure 4 the modifications to the signaling related to methods 200 and 300 are shown in bold italics, which involve, for example, signaling S4_3, S4_9-2, and optionally S4_2.

[0106] In S4_1: The AF subscribes to events (such as PDU session status) detected and reported by the SMF, and there is a serving SMF registered for the UE (i.e., the UE has a PDU session established in the serving SMF).

[0107] In S4_2, the UDM subscribes to the serving SMF via a request message for subscribing to events of the UE served by the serving SMF, for example, the Nsmf_EventExposure_Subscribe request, which includes, for example, UEID, monitoring type = PDU_SESSION_STATUS, etc. It can be understood that S4_2 corresponds to S201 in Figure 2 and S301 in Figure 3 respectively.

[0108] As an alternative, a request message for subscribing to events of a UE served by the service SMF may further include an indication that indicates that during the deregistration process of the SMF to the UDM due to the UE releasing the UE's last session in the SMF, the UDM can skip the request message for unsubscribing / deleting the subscribed events of the UE. For example, the Nsmf_EventExposure_Subscribe request may include a new IE, such as IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL_LAST_SMF_REGISTRATION. In this case, the UDM may indicate to the SMF that during the deregistration process of the SMF to the UDM due to the UE releasing the UE's last session in the SMF, the UDM can skip the request message for unsubscribing / deleting the subscribed events of the UE.

[0109] Then in S4_3, the SMF may determine, based on the indication received from the UDM, that the subscribed events of the UE can be securely stored and removed as at least part of the UE context; then store the subscribed events of the UE as at least part of the UE context and decide to store the requested events as part of the UE context (new resource ID).

[0110] It can be understood that S4_3 is only executed when the UDM indicates to the SMF that it can skip the request message for unsubscribing / deleting the subscribed events of the UE during the deregistration process of the SMF to the UDM due to the UE releasing the UE's last session in the SMF.

[0111] If the SMF receives a request message for subscribing to events of a UE served by the service SMF in S4_2 without such an indication from the UDM (i.e., the same as in Figure 1 S1_2), then the SMF may decide to store the requested events as part of the UE context (new resource ID), i.e., the same as in Figure 1 S1_3.

[0112] In S4_4, in response to the request message sent in S4_2, the SMF sends a corresponding response message for subscribing to the events of the UE to the UDM, such as the Nsmf_EventExposure_Subscribe response. In addition to general IEs (such as success, resource ID created in the SMF, etc.), the response message may include an indication that indicates that during the deregistration process of the SMF to the UDM due to the UE releasing the last session of the UE in the SMF, the SMF can locally remove the subscribed events of the UE stored as at least a part of the UE context. For example, the indication can be a new IE in the response message, such as IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL_LAST_SMF_REGISTRATION.

[0113] It can be understood that S4_4 corresponds to Figure 2 S203 in Figure 3 and S303 in

[0114] In S4_5, the UDM stores the resource ID allocated in the SMF in the UDR.

[0115] In S4_6, the UE releases the last PDU session in the SMF, and the SMF triggers a deregistration process to the UDM.

[0116] In S4_7, the SMF sends a deregistration request message sent during the deregistration process of the SMF to the UDM due to the UE releasing the last PDU session of the UE in the SMF, such as Nudm_UECM_deregistration_request, which includes, for example, the UE ID, session ID, etc.

[0117] In S4_8, the UDM sends a corresponding deregistration response message to the SMF.

[0118] In S4_9-1, since the UE context is removed in the SMF that has stored the events as a part of the UE context, all resource IDs associated with the UE context are removed.

[0119] On the other hand, in S4_9-2, since the UDM has been informed that during the deregistration process of the SMF to the UDM due to the UE releasing the last session of the UE in the SMF, the SMF can locally remove the subscribed events of the UE stored as at least a part of the UE context, it skips the explicit request message for unsubscribing / deleting the subscribed events of the UE during the deregistration process.

[0120] Therefore, unnecessary signaling between network nodes (such as SMF and UDM) can be avoided, and network monitoring can be improved because it avoids the KPI degradation associated with errors in frequent and normal operations.

[0121] Figure 5 Another exemplary signaling sequence diagram for implicit event subscription removal in the deregistration process of a first network node to a second network node due to the UE releasing the last PDU session of the UE in the first network node is schematically shown, where the methods performed by the first network node and the second network node according to the exemplary embodiments of the present disclosure are applied. As Figure 4 Some descriptions of the exemplary signaling sequence diagram shown can refer to the descriptions of methods 200 and 300 as described above, and thus will be omitted here for simplicity.

[0122] In the following description of Figure 5 the exemplary signaling sequence diagram, SMF is used as an example of the first network node as described above, and UDM is used as an example of the second network node as described above.

[0123] It should be noted that the following description mainly focuses on the signaling related to methods 200 and 300, and some other signaling is not described in detail to avoid obscuring the principles of the present disclosure. In Figure 5 the modifications of the signaling related to methods 200 and 300 are shown in bold italics, which involve, for example, signaling S5_7 and S5_9-2.

[0124] In S5_1: AF subscribes to events (such as PDU session status) detected and reported by SMF, and there is a serving SMF registered for the UE (i.e., the UE has a PDU session established in the serving SMF).

[0125] In S5_2, the UDM subscribes to the serving SMF via a request message for subscribing to events of the UE served by the serving SMF, such as the Nsmf_EventExposure_Subscribe request, which includes, for example, UE ID, monitoring type = PDU_SESSION_STATUS, etc. It can be understood that S5_2 corresponds to Figure 2 S201 in Figure 3 and S301 in

[0126] In S5_3, the SMF decides to store the requested one or more events as part of the UE context (new resource ID), i.e., the same as Figure 1 S1_3 in

[0127] In S5_4, in response to the request message sent in S1_2, the SMF sends a response message to the UDM, such as an Nsmf_EventExposure_Subscribe response, which includes, for example, success, one or more resource IDs created in the SMF, etc.

[0128] In S5_5, the UDM stores the resource ID allocated in the SMF in the UDR.

[0129] In S5_6, the UE releases the last PDU session in the SMF, and the SMF triggers a deregistration process to the UDM.

[0130] In S5_7, the SMF sends a deregistration request message sent during the SMF-to-UDM deregistration process due to the UE releasing the UE's last PDU session in the SMF to the UDM, such as an Nudm_UECM_deregistration_request. In addition to general IEs (such as success, session ID, etc.), this deregistration request message may include an indication that indicates that during the SMF-to-UDM deregistration process due to the UE releasing the UE's last session in the SMF, the SMF can locally remove the subscribed events of the UE stored as at least part of the UE context. For example, this indication may be a new IE in the response message, such as IMPLICIT_EVENT_SUBSCRIPTION_REMOVAL.

[0131] It can be understood that S5_7 corresponds respectively to Figure 2 S203 in Figure 3 and S303 in

[0132] In S5_8, the UDM sends a corresponding deregistration response message to the SMF.

[0133] In S5_9-1, since the UE context is removed in the SMF that has stored the event as part of the UE context, all resource IDs associated with the UE context are removed.

[0134] On the other hand, in S5_9-2, since the UDM has been informed that during the SMF-to-UDM deregistration process due to the UE releasing the UE's last session in the SMF, the SMF can locally remove the subscribed events of the UE stored as at least part of the UE context, it skips the explicit request message for unsubscribing / deleting the subscribed events of the UE during the deregistration process.

[0135] Therefore, unnecessary signaling between network nodes (such as the SMF and UDM) can be avoided, and network monitoring can be improved because it avoids the KPI degradation associated with errors in frequent and normal operations.

[0136] In the following, reference will be made to Figure 6 describe the structure of a first network node according to an exemplary embodiment of the present disclosure. Figure 6 A block diagram schematically showing a first network node 600 according to an exemplary embodiment of the present disclosure is shown. Figure 6 The first network node 600 in Figure 2 can execute the method 200 with reference to Figure 2 Therefore, some detailed descriptions of the first network node 600 can be referred to the corresponding descriptions of the method 200 in Figure 4 and Figure 5 and the signaling sequence diagrams in

[0137] As Figure 6 shown, the first network node 600 may at least include a receiving unit 601 and a transmitting unit 603.

[0138] In an exemplary embodiment, the receiving unit 601 may be configured to receive a request message from a second network node for subscribing to events of a UE served by the first network node.

[0139] Then, the transmitting unit 603 may be configured to send a first indication to the second network node, which indicates that in the deregistration process of the first network node from the second network node due to the release of the last session of the UE in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least a part of the UE context.

[0140] In an exemplary embodiment, the first network node 600 may further include a removing unit (not shown), which may be configured to locally remove the UE context in the first network node.

[0141] In an exemplary embodiment, the first indication may be sent to the second network node in a response message for subscribing to events of the UE.

[0142] In an exemplary embodiment, the request message for subscribing to events of the UE may include a second indication, which indicates that in the deregistration process of the first network node from the second network node due to the release of the last session of the UE in the first network node, the second network node may skip the request message for unsubscribing / deleting the subscribed events of the UE.

[0143] In an exemplary embodiment, the first network node 600 may further include a determination unit (not shown), which may be configured to determine, based on a second indication, that the subscribed events of the UE can be securely stored and removed as at least a part of the UE context; and store the subscribed events of the UE as at least a part of the UE context.

[0144] In an exemplary embodiment, a first indication may be sent to a second network node in a deregistration request message sent during a deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node.

[0145] In an exemplary embodiment, the first network node may be an SMF node, and the second network node may be a UDM node.

[0146] Hereinafter, reference will be made to Figure 7 describe the structure of the first network node according to another exemplary embodiment of the present disclosure. Figure 7 A block diagram of a first network node 700 according to an exemplary embodiment of the present disclosure is schematically shown. Figure 7 The first network node 700 in Figure 2 can perform the method 200 as previously described with reference to Figure 2 Therefore, some detailed descriptions of the first network node 700 can refer to Figure 4 and Figure 5 and the signaling sequence diagrams of

[0147] As Figure 7 shown, the first network node 700 includes at least one processor 701 and at least one memory 703. The at least one processor 701 includes, for example, any suitable CPU (Central Processing Unit), microcontroller, DSP (Digital Signal Processor), etc. that can execute computer program instructions. The at least one memory 703 can be any combination of RAM (Random Access Memory) and ROM (Read Only Memory). The at least one memory 703 may further include persistent storage, which may be, for example, any single or combination of magnetic memory, optical memory, or solid-state memory or even remotely installed memory.

[0148] The at least one memory 703 stores instructions executable by the at least one processor 701. When loaded from the at least one memory 703 and executed on the at least one processor 701, the instructions may cause the first network node 700 to perform actions of, for example, the process previously described in conjunction with Figure 2 description.

[0149] In an exemplary embodiment, when loaded from at least one memory 703 and executed on at least one processor 701, the instruction may cause the first network node 700 to receive a request message from a second network node for subscribing to events of a UE served by the first network node; and send a first indication to the second network node, the first indication indicating that during the deregistration process of the first network node from the second network node due to the UE releasing its last session in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least a part of the UE context.

[0150] In an exemplary embodiment, when loaded from at least one memory 703 and executed on at least one processor 701, the instruction may cause the first network node 700 to locally remove the UE context in the first network node.

[0151] In an exemplary embodiment, the first indication may be sent to the second network node in a response message for subscribing to events of the UE.

[0152] In an exemplary embodiment, the request message for subscribing to events of the UE may include a second indication, the second indication indicating that during the deregistration process of the first network node from the second network node due to the UE releasing its last session in the first network node, the second network node may skip the request message for unsubscribing / deleting the subscribed events of the UE.

[0153] In an exemplary embodiment, when loaded from at least one memory 703 and executed on at least one processor 701, the instruction may cause the first network node 700 to determine that the subscribed events of the UE can be safely stored and removed as at least a part of the UE context based on the second indication; and store the subscribed events of the UE as at least a part of the UE context.

[0154] In an exemplary embodiment, the first indication may be sent to the second network node in a deregistration request message sent during the deregistration process of the first network node from the second network node due to the UE releasing its last session in the first network node.

[0155] In an exemplary embodiment, the first network node may be an SMF node, and the second network node may be a UDM node.

[0156] Hereinafter, reference will be made to Figure 8 Describe the structure of a second network node according to another exemplary embodiment of the present disclosure. Figure 8 A block diagram of a second network node 800 according to an exemplary embodiment of the present disclosure is schematically shown. Figure 8 The second network node 800 in Figure 3The described method 300. Therefore, some detailed descriptions regarding the second network node 800 can be referred to the corresponding description of the method 300 in Figure 3 and the signaling sequence diagrams in Figure 4 and Figure 5 which will be omitted here for simplicity.

[0157] As Figure 8 shown, the second network node 800 may at least include a sending unit 801 and a receiving unit 803.

[0158] In an exemplary embodiment, the sending unit 801 may be configured to send a request message to the first network node for subscribing to events of a UE served by the first network node.

[0159] Correspondingly, the receiving unit 803 may be configured to receive a first indication from the first network node, which indicates that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the first network node may locally remove the subscribed events of the UE stored as at least a part of the UE context.

[0160] In an exemplary embodiment, the second network node 800 may further include a skipping unit (not shown), which may be configured to skip a request message for unsubscribing / deleting the subscribed events of the UE during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node.

[0161] In an exemplary embodiment, the first indication from the first network node may be received in a response message for subscribing to events of the UE.

[0162] In an exemplary embodiment, the request message for subscribing to events of the UE may include a second indication, which indicates that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the second network node may skip a request message for unsubscribing / deleting the events of the UE.

[0163] In an exemplary embodiment, the first indication from the first network node is received in a deregistration request message received during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node.

[0164] In an exemplary embodiment, the first network node may be an SMF node, and the second network node may be a UDM node.

[0165] Hereinafter, reference will be made to Figure 9Describe the structure of a second network node according to another exemplary embodiment of the present disclosure. Figure 9 A block diagram of a second network node 900 according to an exemplary embodiment of the present disclosure is schematically shown. Figure 9 The second network node 900 in Figure 3 can execute the method 300 as previously referred to Figure 3 in. Therefore, some detailed descriptions of the second network node 900 can refer to Figure 4 and Figure 5 the corresponding descriptions of the method 300 in and

[0166] As Figure 9 shown, the second network node 900 includes at least one processor 901 and at least one memory 903. The at least one processor 901 includes, for example, any suitable CPU (Central Processing Unit), microcontroller, DSP (Digital Signal Processor), etc. that can execute computer program instructions. The at least one memory 903 can be any combination of RAM (Random Access Memory) and ROM (Read-Only Memory). The at least one memory 903 can also include persistent storage, which can be, for example, any single or a combination of magnetic memory, optical memory, or solid-state memory, or even remotely installed memory.

[0167] The at least one memory 903 stores instructions executable by the at least one processor 901. When loaded from the at least one memory 903 and executed on the at least one processor 901, the instructions can cause the second network node 900 to perform actions of, for example, the processes previously described separately in conjunction with Figure 3 in.

[0168] In an exemplary embodiment, when loaded from the at least one memory 903 and executed on the at least one processor 901, the instructions can cause the second network node 900 to send a request message to the first network node for subscribing to events of UEs served by the first network node; and receive a first indication from the first network node, the first indication indicating that in the deregistration process from the first network node to the second network node due to the release of the last session of the UE in the first network node, the first network node can locally remove the subscribed events of the UE stored as at least a part of the UE context.

[0169] In an exemplary embodiment, when loaded from the at least one memory 903 and executed on the at least one processor 901, the instructions can cause the second network node 900 to skip the request message for unsubscribing / deleting the subscribed events of the UE in the deregistration process from the first network node to the second network node due to the release of the last session of the UE in the first network node.

[0170] In an exemplary embodiment, a first indication from a first network node may be received in a response message for subscribing to an event of a UE.

[0171] In an exemplary embodiment, a request message for subscribing to an event of a UE may include a second indication indicating that, during a deregistration process of the first network node from the second network node due to the UE releasing the last session of the UE in the first network node, the second network node may skip a request message for canceling / removing the event of the UE.

[0172] In an exemplary embodiment, a first indication from the first network node is received in a deregistration request message received during a deregistration process of the first network node from the second network node due to the UE releasing the last session of the UE in the first network node.

[0173] In an exemplary embodiment, the first network node may be a SMF node, and the second network node may be a UDM node.

[0174] The present disclosure also provides at least one computer program product in the form of a non-volatile or volatile memory, such as a non-transitory computer-readable storage medium, an Electrically Erasable Programmable Read-Only Memory (EEPROM), a flash memory, and a drive. The computer program product includes a computer program.

[0175] The computer program includes: code / computer-readable instructions that, when executed by at least one processor 701, cause the first network node 700 to perform actions of a process described, for example, previously in conjunction with Figure 2 the described process; or code / computer-readable instructions that, when executed by at least one processor 901, cause the second network node 900 to perform actions of a process described, for example, previously in conjunction with Figure 3 the described process.

[0176] The computer program product may be configured as computer program code structured in a computer program module. The computer program module may substantially perform Figures 4 to 5 the actions of any of the illustrated processes.

[0177] The processor can be a single CPU (Central Processing Unit), but can also include two or more processing units. For example, the processor can include a general - purpose microprocessor; an instruction - set processor and / or a related chipset and / or a dedicated microprocessor, such as an Application Specific Integrated Circuit (ASIC). The processor can also include on - board memory for cache purposes. The computer program can be carried by a computer program product connected to the processor. The computer program product can include a non - transitory computer - readable storage medium on which the computer program is stored. For example, the computer program product can be a flash memory, a Random Access Memory (RAM), a Read - Only Memory (ROM) or an EEPROM, and in alternative embodiments, the above - mentioned computer program modules can be distributed in the form of memories on different computer program products.

[0178] Although the computing devices described herein (e.g., UEs, network nodes, hosts) can include combinations of the hardware components shown, other embodiments can include computing devices with different combinations of components. It should be understood that these computing devices can include any suitable combination of hardware and / or software required to perform the tasks, features, functions, and methods disclosed herein. The determinations, calculations, acquisitions, or similar operations described herein can be performed by a processing circuit, which can process information by, for example, converting the acquired information into other information, comparing the acquired information or the converted information with the information stored in the network node, and / or performing one or more operations based on the acquired information or the converted information and making a determination based on the processed result. Additionally, although components are depicted as single boxes within larger boxes, or nested within multiple boxes, in reality, a computing device can include multiple different physical components that make up a single - shown component, and the functions can be divided among separate components. For example, the communication interface can be configured to include any of the components described herein, and / or the functions of the components can be divided between the processing circuit and the communication interface. In another example, the non - computationally intensive functions of any such component can be implemented in software or firmware, while the computationally intensive functions can be implemented in hardware.

[0179] In some embodiments, some or all of the functions described herein may be provided by a processing circuit that executes instructions stored in a memory, which in some embodiments may be a computer program product in the form of a non-transitory computer-readable storage medium. In alternative embodiments, some or all of the functions may be provided by the processing circuit without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hardwired manner. In any of those particular embodiments, whether or not instructions are executed on a non-transitory computer-readable storage medium, the processing circuit may be configured to perform the functions described. The benefits provided by such functions are not limited to the processing circuit alone or other components of a computing device, but are enjoyed by the entire computing device and / or by the end user and the wireless network generally.

[0180] Many different embodiments are disclosed herein in connection with the above description and drawings. It should be understood that a literal description and illustration of every combination and sub-combination of these embodiments would be overly repetitive and confusing. Accordingly, all embodiments may be combined in any manner and / or combination, and this specification (including the drawings) should be construed as constituting a complete written description of all combinations and sub-combinations of the embodiments described herein and the manner and process of making and using them, and should support claims to any such combination or sub-combination.

[0181] Those skilled in the art will understand that the embodiments described herein are not limited to what has been particularly shown and described above. Further, unless the contrary is mentioned above, it should be noted that all of the drawings are not drawn to scale. Various modifications and variations are possible in light of the above teachings.

Claims

1. A method (200) performed by a first network node, comprising: Receiving (S201) a request message from a second network node for subscribing to events of a user equipment UE served by the first network node; And Sending (S203) a first indication to the second network node, the first indication indicating that during the deregistration process of the first network node from the second network node due to the UE releasing the last session of the UE in the first network node, the first network node can locally remove the subscribed events of the UE stored as at least a part of the UE context.

2. The method (200) according to claim 1, further comprising: Locally removing the UE context in the first network node.

3. The method (200) according to claim 1 or 2, wherein The first indication is sent to the second network node in a response message for subscribing to events of the UE.

4. The method (200) according to any one of claims 1 to 3, wherein, The request message for subscribing to events of the UE includes a second indication, the second indication indicating that during the deregistration process of the first network node from the second network node due to the UE releasing the last session of the UE in the first network node, the second network node can skip the request message for unsubscribing / deleting the subscribed events of the UE.

5. The method (200) according to claim 4, further comprising: Based on the second indication, determining that the subscribed events of the UE can be securely stored and removed as at least a part of the UE context; And Storing the subscribed events of the UE as at least a part of the UE context.

6. The method (200) according to claim 1 or 2, wherein, Sending the first indication to the second network node in a deregistration request message sent during the deregistration process of the first network node from the second network node due to the UE releasing the last session of the UE in the first network node.

7. The method (200) according to any one of claims 1 to 6, wherein The first network node is a session management function SMF node, and The second network node is a unified data management UDM node.

8. A method (300) performed by a second network node, comprising: Sending (S301) a request message to a first network node for subscribing to events of a user equipment UE served by the first network node; And Receiving (S303) a first indication from the first network node, the first indication indicating that during the deregistration process of the first network node from the second network node due to the UE releasing the last session of the UE in the first network node, the first network node can locally remove the subscribed events of the UE stored as at least a part of the UE context.

9. The method (300) according to claim 8, further comprising: During the deregistration process of the first network node from the second network node due to the UE releasing the last session of the UE in the first network node, skipping the request message for unsubscribing / deleting the subscribed events of the UE.

10. The method (300) according to claim 8 or 9, wherein, Receiving the first indication from the first network node in a response message for subscribing to events of the UE.

11. The method (300) according to any one of claims 8 to 10, wherein, The request message for subscribing to events of a UE includes a second indication, and the second indication indicates that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the second network node can skip the request message for canceling the subscription / deleting the events of the UE.

12. The method (300) according to claim 8 or 9, wherein, Receive the first indication from the first network node in a deregistration request message received during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node.

13. The method (200) according to any one of claims 8 to 12, wherein the first network node is a session management function (SMF) node, and the second network node is a unified data management (UDM) node.

14. A first network node (700), comprising: at least one processor (701), and at least one memory (703) storing instructions that, when executed on the at least one processor (701), cause the first network node (700) to: Receive a request message from a second network node for subscribing to events of a user equipment (UE) served by the first network node; and Send a first indication to the second network node, the first indication indicating that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the first network node can locally remove the subscribed events of the UE stored as at least a part of the UE context.

15. The first network node (700) according to claim 14, wherein, When executed on the at least one processor (701), the instructions further cause the first network node (700) to perform the method according to any one of claims 2 to 7.

16. A second network node (900), comprising: at least one processor (901), and at least one memory (903) storing instructions that, when executed on the at least one processor (901), cause the second network node (900) to: Send a request message to a first network node for subscribing to events of a user equipment (UE) served by the first network node; and Receive a first indication from the first network node, the first indication indicating that during the deregistration process of the first network node to the second network node due to the UE releasing the last session of the UE in the first network node, the first network node can locally remove the subscribed events of the UE stored as at least a part of the UE context.

17. The second network node (900) according to claim 16, wherein, When executed on the at least one processor (901), the instructions further cause the second network node (900) to perform the method according to any one of claims 9 to 13.

18. A computer-readable storage medium having computer program instructions stored thereon that, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 7.

19. A computer-readable storage medium having computer program instructions stored thereon that, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 8 to 13.

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