Method and apparatus for subscription management

Abstract

The embodiment of the invention provides a method and device for subscription management. A method performed by a first NF includes receiving a first subscription request from a second NF for subscribing to at least one event type. The first subscription request requests the first NF to send an event notification of the at least one event type to a third NF. The method also includes detecting an occurrence of at least one monitored event of the at least one event type. The method further includes sending an event notification of at least one monitored event of the at least one event type to the third NF. The method also includes receiving an event notification response including error information from the third NF. The method further includes transmitting a first message including an event subscription termination notification of the at least one event type to the second NF.

Description

Technical Field

[0001] The non - limiting and exemplary embodiments of the present disclosure generally relate to the field of communication technologies, and more particularly to methods and apparatuses for subscription management. Background Art

[0002] This section introduces several aspects that can help better understand the present disclosure. Therefore, the statements in this section should be read from this perspective and should not be construed as an admission of what is in the prior art or what is not in the prior art.

[0003] In a network, the end - to - end interaction between two network functions (NF service consumer and NF service producer) within the NF service framework can follow two mechanisms, whether using direct communication or indirect communication: "request - response" and "subscription - notification".

[0004] The "subscription - notification" mechanism is described in the 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 23.501 V17.5.0 as follows, the entire disclosure of which is incorporated herein by reference.

[0005] "Subscription - notification": NF_A (NF service consumer) subscribes to an NF service provided by another NF_B (NF service producer). Multiple control - plane NFs can subscribe to the same control - plane NF service. NF_B notifies the result of this NF service to one or more interested NFs that have subscribed to this NF service. The subscription request should include the notification endpoint (i.e., the notification target address) of the NF service consumer to which the event notification from the NF service producer should be sent and the notification association ID (identifier) (e.g., notification URL).

[0006] The notification endpoint URL can include both the notification endpoint and the notification association ID.

[0007] The subscription request can include a notification request for periodic updates or a notification request for notifications triggered by certain events (e.g., a change in the requested information, reaching a specific threshold, etc.). The subscription for notifications can be completed in one of the following ways:

[0008] - Explicit subscription: A separate request / response exchange between the NF service consumer and the NF service producer; or

[0009] - Implicit subscription: The subscription for notifications is included as part of another NF service operation of the same NF service; or

[0010] - Default notification endpoint: During the NF and NF service registration process, register the notification endpoints for each type of notification that the NF consumer is interested in receiving with the NRF, which is used as an NF service parameter as specified in clause 4.17.1 of 3GPP TS 23.502 V17.5.0, the entire disclosure of which is incorporated herein by reference.

[0011] Figure 1a The flowchart showing the first example of the "Subscribe-Notify" NF service, Figure 1a is the same as Figure 7.1.2-2 in 3GPP TS 23.501 V17.5.0.

[0012] NF_A can subscribe to the NF service provided by NF_B by sending a subscription request to NF_B. NF_B can confirm the execution of the subscription request. NF_B detects that a monitored event has occurred and sends an event report to NF_A via a notification message.

[0013] Figure 1b The flowchart showing the second example of the "Subscribe-Notify" NF service, Figure 1b is the same as Figure 7.1.2-3 in 3GPP TS 23.501 V17.5.0.

[0014] NF_A can also subscribe to the NF service provided by NF_B on behalf of NF_C, that is, it requests the NF service producer to send event notifications to one or more other consumers. In this case, NF_A includes the notification endpoint (i.e., the notification target address) of NF_C and the notification association ID in the subscription request. NF_A can also additionally include in the subscription request the notification endpoint and notification association ID of NF_A associated with one or more subscription change related event IDs (such as subscription association ID change) so that NF_A can receive notifications of subscription change related events.

[0015] The security handling of the service operations such as Subscribe-Notify can follow security principles, such as the Service-Based Architecture (SBA) security principles. That is, NF_B as the producer can verify whether NF_A is authorized to use this Subscribe-Notify service operation.

[0016] In some cases, the subscription for a certain event created for the User Equipment (UE) can be stored in the UE context of the serving NF (such as the AMF (Access and Mobility Management Function)). In the case of UE mobility, this subscription can be moved from the source NF to the target NF along with the UE context transfer process. Summary of the Invention

[0017] This Summary of the Invention is provided in a simplified form to introduce a selected concept that is further described below in the Detailed Description. This Summary of the Invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0018] There are some problems with the existing "subscription - notification" mechanism.

[0019] For example, when an NF (such as the AMF) receives a specific response code regarding a notification Uniform Resource Identifier (URI), the NF producer (such as the AMF) can identify that the subscription is no longer valid and terminate the subscription.

[0020] However, when an NF consumer (such as the UDM (Unified Data Management) on behalf of the NEF (Network Exposure Function)) that processes the notification subscribes to such an event subscription, the NF producer (such as the AMF) does not notify the subscription requester that the subscription has been terminated at the NF producer (such as the AMF). The subscription requester cannot trigger a specific local clearance of the invalid subscription based on this notification.

[0021] In addition, in other scenarios, the NF producer (such as the AMF) can terminate an event subscription. For example, after moving between PLMNs (Public Land Mobile Networks), the service authorization for an event subscription created at the source NF producer (such as the AMF) in the source PLMN is no longer valid in the target NF producer (such as the AMF) in the target PLMN. However, in this scenario, the target NF producer (such as the AMF) also does not send a notification about the subscription termination to the subscription requester using a cause IE (Information Element) indicating the reason. Therefore, the subscription requester cannot trigger some necessary actions based on this notification.

[0022] For example, when an NF consumer (NF_A) subscribes to an event subscription on behalf of another NF (NF_C) that processes the notification (such as the UDM as NF_A representing the NEF as NF_C), the original event subscription may be locally deleted or become invalid at the original NF consumer (NF_C), but the subscription is not successfully unsubscribed at the producer (such as the AMF as NF_B).

[0023] In this case, the AMF can pass the notification to NF_C and receive some error codes (such as 404 Not Found) from NF_C. Based on such notification errors, the AMF can trigger appropriate actions, such as clearing the resources reserved for the subscription - notification.

[0024] However, NF_A that requests the subscription - notification from NF_B does not receive any indication and thus will still consume resources to maintain the subscription, which unnecessarily wastes resource usage.

[0025] In another case, for example, after moving between PLMNs, the event subscription can be moved from an NF producer (NF_B_1) known as the source NF to another NF producer (NF_B_1) known as the target NF. The service operation authorization policies for event subscriptions in the source NF and the target NF can be different. That is, the service authorization for the event subscription created at the source AMF / PLMN is no longer valid in the target AMF / PLMN.

[0026] Similarly, NF_A that requests subscription notifications from NF_B is unaware of this situation and will therefore still consume resources to maintain the subscription, which unnecessarily wastes resource usage.

[0027] The subscription terminated by an NF (such as the AMF) cannot be notified to the subscription requester. The NF consumer cannot receive event reports as expected. The NF consumer may attempt to update the subscription and be rejected, which has a negative impact on KPIs (Key Performance Indicators).

[0028] To overcome or mitigate at least one of the above problems or other problems, embodiments of the present disclosure propose an improved solution for subscription management.

[0029] In a first aspect of the present disclosure, a method performed by a first network function (NF) is provided. The method includes receiving, from a second NF, a first subscription request for subscribing to at least one event type. The first subscription request requests the first NF to send event notifications of the at least one event type to a third NF. The method further includes detecting the occurrence of at least one monitoring event of the at least one event type. The method further includes sending, to the third NF, event notifications of the at least one monitoring event of the at least one event type. The method further includes receiving, from the third NF, an event notification response including error information. The method further includes sending, to the second NF, a first message including an event subscription termination notification of the at least one event type.

[0030] In an embodiment, the method further includes terminating the subscription of the at least one event type. The method further includes clearing at least one resource reserved for the subscription of the at least one event type.

[0031] In an embodiment, the first message further includes a cause code.

[0032] In an embodiment, the cause code indicates that the subscription of the at least one event type is terminated because the first NF has identified that the subscription of the at least one event type is no longer valid on the third NF hosting the notification uniform resource identifier (URI).

[0033] In an embodiment, the first NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0034] In an embodiment, the second NF includes the Unified Data Management (UDM).

[0035] In an embodiment, the third NF includes the Network Exposure Function (NEF).

[0036] In a second aspect of the present disclosure, a method performed by a second NF is provided. The method includes receiving, from a third NF, a second subscription request for subscribing to at least one event type. The method further includes: sending, on behalf of the third NF, a first subscription request for subscribing to the at least one event type to a first NF. The first subscription request requests the first NF to send an event notification of the at least one event type to the third NF. The method further includes: receiving, from the first NF, a first message including an event subscription termination notification of the at least one event type. The method further includes: clearing at least one resource reserved for the subscription of the at least one event type.

[0037] In an embodiment, the first message further includes a cause code.

[0038] In an embodiment, the cause code indicates that the subscription of the at least one event type is terminated because the first NF has identified that the subscription of the at least one event type is no longer valid on the third NF hosting the notification Uniform Resource Identifier (URI).

[0039] In an embodiment, the first NF includes at least one of an Access and Mobility Management Function (AMF) or a Session Management Function (SMF).

[0040] In an embodiment, the second NF includes the Unified Data Management (UDM).

[0041] In an embodiment, the third NF includes the Network Exposure Function (NEF).

[0042] In a third aspect of the present disclosure, a method performed by a third Network Function (NF) is provided. The method includes sending a second subscription request for subscribing to at least one event type to a second NF. The method further includes receiving, from a first NF, an event notification of at least one monitoring event of the at least one event type. The method further includes determining that the subscription of the at least one event type is removed or no longer valid at the third NF. The method further includes sending an event notification response including error information to the first NF.

[0043] In an embodiment, the method further, when the subscription of the at least one event type is no longer valid at the third NF, clears at least one resource reserved for the subscription of the at least one event type.

[0044] In an embodiment, the first NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0045] In an embodiment, the second NF includes a unified data management (UDM).

[0046] In an embodiment, the third NF includes a network exposure function (NEF).

[0047] In a fourth aspect of the present disclosure, a method performed by a fourth network function (NF) is provided. The method includes receiving, from a sixth NF, a subscription for at least one event type requested by a fifth NF. The method further includes checking whether the fourth NF supports the at least one event type and / or whether the subscription for the at least one event type requested by the fifth NF is authorized. The method further includes: when the fourth NF does not support the at least one event type and / or the subscription for the at least one event type requested by the fifth NF is not authorized, sending a second message to the fifth NF including an event subscription termination notice for the at least one event type.

[0048] In an embodiment, when the fourth NF does not support the at least one event type and / or the subscription for the at least one event type requested by the fifth NF is not authorized, the method further includes: terminating the subscription for the at least one event type. The method further includes: clearing at least one resource reserved for the subscription for the at least one event type.

[0049] In an embodiment, the second message further includes a cause code.

[0050] In an embodiment, the cause code indicates at least one of the following: the subscription for the at least one event type is terminated because the service access authorization for the fifth NF is no longer valid; the subscription for the at least one event type is terminated because the fourth NF requires a new service authorization; or the subscription for the at least one event type is terminated because the at least one event type is not supported in the fourth NF.

[0051] In an embodiment, during an inter-public land mobile network (PLMN) mobility procedure or a terminal device mobility procedure, the subscription for at least one event type requested by the fifth NF is received from the sixth NF.

[0052] In an embodiment, the fourth NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0053] In an embodiment, the fifth NF includes at least one of a unified data management (UDM) or a network exposure function (NEF).

[0054] In an embodiment, the sixth NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0055] In a fifth aspect of the present disclosure, a method performed by a fifth network function (NF) is provided. The method includes: when a subscription for at least one event type requested by the fifth NF is sent from a sixth NF to a fourth NF, and the fourth NF does not support the at least one event type and / or the subscription for the at least one event type requested by the fifth NF is not authorized, receiving, from the fourth NF, a second message including an event subscription termination notice for the at least one event type. The method further includes: clearing at least one resource reserved for the subscription for the at least one event type.

[0056] In an embodiment, the second message further includes a cause code.

[0057] In an embodiment, the cause code indicates at least one of the following: the subscription for the at least one event type is terminated because the service access authorization for the fifth NF is no longer valid; the subscription for the at least one event type is terminated because the fourth NF requires a new service authorization; or the subscription for the at least one event type is terminated because the at least one event type is not supported in the fourth NF.

[0058] In an embodiment, during an inter-public land mobile network (PLMN) mobility procedure or a terminal device mobility procedure, the subscription for at least one event type requested by the fifth NF is sent from the sixth NF to the fourth NF.

[0059] In an embodiment, the method further includes obtaining an access authorization token for the fourth NF based on the second message.

[0060] In an embodiment, the method further includes sending, based on the second message, a new subscription request for subscribing to one or more event types to the fourth NF. The new subscription request includes an access authorization token for the fourth NF.

[0061] In an embodiment, the fourth NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0062] In an embodiment, the fifth NF includes at least one of a unified data management (UDM) or a network exposure function (NEF).

[0063] In an embodiment, the sixth NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0064] In a sixth aspect of the present disclosure, a first NF is provided. The first NF includes a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The first NF is operable to receive, from a second NF, a first subscription request for subscribing to at least one event type. The first subscription request requests the first NF to send an event notification of the at least one event type to a third NF. The first NF is further operable to detect the occurrence of at least one monitoring event of the at least one event type. The first NF is further operable to send an event notification of the at least one monitoring event of the at least one event type to the third NF. The first NF is further operable to receive, from the third NF, an event notification response including error information. The first NF is further operable to send a first message including an event subscription termination notification of the at least one event type to the second NF.

[0065] In a seventh aspect of the present disclosure, a second NF is provided. The second NF includes a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The second NF is operable to receive, from a third NF, a second subscription request for subscribing to at least one event type. The second NF is further operable to send, on behalf of the third NF, a first subscription request for subscribing to the at least one event type to the first NF. The first subscription request requests the first NF to send an event notification of the at least one event type to the third NF. The second NF is further operable to receive, from the first NF, a first message including an event subscription termination notification of the at least one event type. The second NF is further operable to clear at least one resource reserved for the subscription of the at least one event type.

[0066] In an eighth aspect of the present disclosure, a third NF is provided. The third NF includes a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The third NF is operable to send a second subscription request for subscribing to at least one event type to the second NF. The third NF is further operable to receive, from the first NF, an event notification of at least one monitoring event of the at least one event type. The third NF is further operable to determine that the subscription of the at least one event type is removed or no longer valid at the third NF. The third NF is further operable to send an event notification response including error information to the first NF.

[0067] In a ninth aspect of the present disclosure, a fourth NF is provided. The fourth NF includes a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The fourth NF is operable to receive, from a sixth NF, a subscription for at least one event type requested by a fifth NF. The fourth NF is further operable to check whether the fourth NF supports the at least one event type and / or whether the subscription for the at least one event type requested by the fifth NF is authorized. When the fourth NF does not support the at least one event type and / or the subscription for the at least one event type requested by the fifth NF is not authorized, the fourth NF is further operable to send a second message to the fifth NF, the second message including an event subscription termination notice for the at least one event type.

[0068] In a tenth aspect of the present disclosure, a fifth NF is provided. The fifth NF includes a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The fifth NF is operable to receive, from the fourth NF, a second message including an event subscription termination notice for at least one event type when the subscription for the at least one event type requested by the fifth NF is sent from the sixth NF to the fourth NF and the fourth NF does not support the at least one event type and / or the subscription for the at least one event type requested by the fifth NF is not authorized. The fifth NF is further operable to clear at least one resource reserved for the subscription for the at least one event type.

[0069] In another aspect of the present disclosure, a first NF is provided. The first NF includes a first receiving module configured to receive, from a second NF, a first subscription request for subscribing to at least one event type. The first subscription request requests the first NF to send an event notification of the at least one event type to a third NF. The first NF further includes a detection module configured to detect the occurrence of at least one monitoring event of the at least one event type. The first NF further includes a first sending module configured to send an event notification of the at least one monitoring event of the at least one event type to the third NF. The first NF further includes a second receiving module configured to receive, from the third NF, an event notification response including error information. The first NF further includes a second sending module configured to send a first message including an event subscription termination notice for the at least one event type to the second NF.

[0070] In an embodiment, the first NF further includes a termination module configured to terminate the subscription for the at least one event type.

[0071] In an embodiment, the first NF further includes a clearing module configured to clear at least one resource reserved for the subscription for the at least one event type.

[0072] In another aspect of the present disclosure, a second NF is provided. The second NF includes a first receiving module configured to receive, from a third NF, a second subscription request for subscribing to the at least one event type. The second NF further includes a sending module configured to send, on behalf of the third NF, a first subscription request for subscribing to the at least one event type to a first NF. The first subscription request requests the first NF to send an event notification of the at least one event type to the third NF. The second NF further includes a second receiving module configured to receive, from the first NF, a first message including an event subscription termination notification of the at least one event type. The second NF further includes a clearing module configured to clear at least one resource reserved for the subscription of the at least one event type.

[0073] In another aspect of the present disclosure, a third NF is provided. The third NF includes a first sending module configured to send a second subscription request for subscribing to at least one event type to a second NF. The third NF further includes a receiving module configured to receive, from a first NF, an event notification of at least one monitoring event of the at least one event type. The third NF further includes a determining module configured to determine that the subscription of the at least one event type is removed or no longer valid at the third NF. The third NF further includes a second sending module configured to send an event notification response including an error message to the first NF.

[0074] In an embodiment, the third NF further includes a clearing module configured to clear at least one resource reserved for the subscription of the at least one event type when the subscription of the at least one event type is no longer valid at the third NF.

[0075] In another aspect of the present disclosure, a fourth NF is provided. The fourth NF includes a receiving module configured to receive, from a sixth NF, a subscription of at least one event type requested by a fifth NF. The fourth NF further includes a checking module configured to check whether the fourth NF supports the at least one event type and / or whether the subscription of the at least one event type requested by the fifth NF is authorized. The fourth NF further includes a sending module configured to send, when the fourth NF does not support the at least one event type and / or the subscription of the at least one event type requested by the fifth NF is not authorized, a second message including an event subscription termination notification of the at least one event type to the fifth NF.

[0076] In an embodiment, the fourth NF further includes a termination module configured to terminate the subscription to the at least one event type when the fourth NF does not support the at least one event type and / or the subscription to the at least one event type requested by the fifth NF is not authorized. The fourth NF further includes a clearing module configured to clear at least one resource reserved for the subscription to the at least one event type.

[0077] In another aspect of the present disclosure, a fifth NF is provided. The fifth NF includes a receiving module configured to receive, from the fourth NF, a second message including an event subscription termination notice for the at least one event type when the subscription to the at least one event type requested by the fifth NF is sent from a sixth NF to the fourth NF and the fourth NF does not support the at least one event type and / or the subscription to the at least one event type requested by the fifth NF is not authorized. The fifth NF further includes a clearing module configured to clear at least one resource reserved for the subscription to the at least one event type.

[0078] In an embodiment, the fifth NF further includes an obtaining module configured to obtain an access authorization token for the fourth NF based on the second message.

[0079] In an embodiment, the fifth NF further includes a sending module configured to send, based on the second message, a new subscription request for subscribing to one or more event types to the fourth NF. The new subscription request includes an access authorization token for the fourth NF.

[0080] In another aspect of the present disclosure, a computer program product including instructions is provided, which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of the first, second, third, fourth, or fifth aspects.

[0081] In another aspect of the present disclosure, a computer-readable storage medium storing instructions is provided, which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of the first, second, third, fourth, or fifth aspects.

[0082] Embodiments herein can provide many advantages, and the following is a non-exhaustive list of examples of advantages. In some embodiments herein, based on the new event subscription termination notice, the subscription requester can trigger local clearing of invalid subscriptions to avoid unnecessary resource waste, or trigger other necessary actions to ensure the continuation of the service. Embodiments herein are not limited to the above features and advantages. Those skilled in the art will recognize additional features and advantages after reading the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] From the following detailed description of the reference drawings, by way of example, the above and other aspects, features, and advantages of various embodiments of the present disclosure will become more fully apparent, in which like reference numerals or letters are used to refer to like or equivalent elements. The drawings are shown to facilitate a better understanding of the embodiments of the present disclosure and are not necessarily drawn to scale, wherein:

[0084] Figure 1a A flowchart showing a first example of a "subscription-notification" NF service;

[0085] Figure 1b A flowchart showing a second example of a "subscription-notification" NF service;

[0086] Figure 2 Schematically shows an advanced architecture in a fifth-generation network according to an embodiment of the present disclosure;

[0087] Figure 3a A flowchart showing a method according to an embodiment of the present disclosure;

[0088] Figure 3b A flowchart showing a method according to another embodiment of the present disclosure;

[0089] Figure 4 A flowchart showing a method according to another embodiment of the present disclosure;

[0090] Figure 5 A flowchart showing a method according to another embodiment of the present disclosure;

[0091] Figure 6a A flowchart showing a method according to another embodiment of the present disclosure;

[0092] Figure 6b A flowchart showing a method according to another embodiment of the present disclosure;

[0093] Figure 7a A flowchart showing a method according to another embodiment of the present disclosure;

[0094] Figure 7b A flowchart showing a method according to another embodiment of the present disclosure;

[0095] Figure 7c A flowchart showing an event subscription termination notification according to an embodiment of the present disclosure;

[0096] Figure 7d A flowchart showing an event subscription termination notification according to another embodiment of the present disclosure;

[0097] Figure 7e A flowchart showing a notification according to an embodiment of the present disclosure;

[0098] Figure 8a is a block diagram showing an apparatus suitable for practicing some embodiments of the present disclosure;

[0099] Figure 8b is a block diagram showing a first NF according to an embodiment of the present disclosure;

[0100] Figure 8c is a block diagram showing a second NF according to an embodiment of the present disclosure;

[0101] Figure 8d is a block diagram showing a third NF according to an embodiment of the present disclosure;

[0102] Figure 8e is a block diagram showing a fourth NF according to an embodiment of the present disclosure; and

[0103] Figure 8f is a block diagram showing a fifth NF according to an embodiment of the present disclosure. Detailed Description of Specific Embodiments

[0104] Embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled in the art to better understand and thus implement the present disclosure, rather than suggesting any limitation to the scope of the present disclosure. References to features, advantages, or similar language throughout the specification do not imply that all features and advantages that can be achieved with the present disclosure should be in or in any single embodiment of the present disclosure. On the contrary, language referring to features and advantages should be understood to mean that a particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Additionally, in one or more embodiments, the features, advantages, and characteristics described in the present disclosure may be combined in any suitable manner. Those skilled in the relevant art will recognize that the present disclosure may be practiced without one or more specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments, and the additional features and advantages may not be present in all embodiments of the present disclosure.

[0105] As used herein, the term "network" refers to a network that follows any suitable communication standard, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced, Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), and other wireless networks. CDMA networks may implement radio technologies such as Universal Terrestrial Radio Access (UTRA). UTRA includes WCDMA and other variants of CDMA. TDMA networks may implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks may implement radio technologies such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, Ad-hoc networks, wireless sensor networks, etc. In the following description, the terms "network" and "system" may be used interchangeably. Additionally, communication between two devices in a network may be performed according to any suitable communication protocol, including but not limited to communication protocols defined by standard organizations such as 3GPP. For example, the communication protocol may include first generation (1G), 2G, 3G, 4G, 4.5G, 5G communication protocols and / or any other protocol currently known or developed in the future.

[0106] The term "network device" or "network node" refers to any suitable network function (NF) that can be implemented in a (physical or virtual) network entity of a communication network. For example, a network function can be implemented as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on a suitable platform (e.g., on a cloud infrastructure). For example, a 5G system (5GS) can include multiple NFs such as an access and mobility management function (AMF), a session management function (SMF), an authentication service function (AUSF), a unified data management (UDM), a policy control function (PCF), an application function (AF), a network exposure function (NEF), a user plane function (UPF), and a network repository function (NRF), a radio access network (RAN), a service communication proxy (SCP), a network data analytics function (NWDAF), a network slice selection function (NSSF), a network slice specific authentication and authorization function (NSSAAF), etc. For example, a 4G system (e.g., LTE (Long Term Evolution)) can include a mobility management entity (MME), a home subscriber server (HSS), a PCRF (policy and charging rules function), a packet data network gateway (PGW), a PGW control plane (PGW-C), a serving gateway (SGW), an SGW control plane (SGW-C), an E-UTRAN node B (eNB), etc. In other embodiments, for example, depending on the specific network, the network function can include different types of NFs.

[0107] The term "terminal device" refers to any terminal device that can access a communication network and receive services therefrom. By way of example and not limitation, terminal devices refer to mobile terminals, user equipment (UE), or other suitable devices. A UE can be, for example, a user station (SS), a portable user station, a mobile station (MS), or an access terminal (AT). Terminal devices can include, but are not limited to, portable computers, image capture terminal devices such as digital cameras, game terminal devices, music storage and playback devices, mobile phones, cellular phones, smart phones, IP voice (VoIP) phones, wireless local loop phones, tablet computers, wearable devices, personal digital assistants (PDA), portable computers, desktop computers, wearable terminal devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEE), laptop mounted devices (LME), USB dongles, smart devices, wireless customer premise equipment (CPE), etc. In the following description, the terms "terminal device", "terminal", "user equipment", and "UE" may be used interchangeably. As an example, a terminal device can represent a UE configured to communicate according to one or more communication standards (such as the LTE standard or the NR standard of 3GPP) released by 3GPP (Third Generation Partnership Project). As used herein, a "user equipment" or "UE" may not necessarily have a "user" in terms of a human user who owns and / or operates the relevant device. In some embodiments, a terminal device can be configured to send and / or receive information without direct human interaction. For example, when triggered by an internal or external event, or in response to a request from a communication network, a terminal device can be designed to send information to the network according to a predetermined schedule. Alternatively, a UE can represent a device intended to be sold to or operated by a human user but that may not initially be associated with a specific human user.

[0108] As yet another example, in an Internet of Things (IoT) scenario, a terminal device can represent a machine or other device that performs monitoring and / or measurement and sends the results of such monitoring and / or measurement to another terminal device and / or network device. In this case, the terminal device can be a machine-to-machine (M2M) device, which can be referred to as a machine type communication (MTC) device in the 3GPP context. As a specific example, a terminal device can be a UE that implements the 3GPP narrowband Internet of Things (NB-IoT) standard. Specific examples of such machines or devices are sensors, metering devices (such as electricity meters), industrial machinery, or household or personal appliances such as refrigerators, televisions, personal wearable devices (such as watches), etc. In other scenarios, a terminal device can represent a vehicle or other device capable of monitoring and / or reporting its operating status or other functions related to its operation.

[0109] References to "one embodiment", "an embodiment", "an exemplary embodiment", etc. in the specification indicate that the described embodiments may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Moreover, these phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that, whether or not explicitly described, the influence of combining other embodiments on that feature, structure, or characteristic is within the knowledge of those skilled in the art.

[0110] It should be understood that although terms such as "first" and "second" may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed terms.

[0111] As used herein, the phrase "at least one of A and B" or "at least one of A or B" should be understood to mean "only A, only B, or both A and B". The phrase "A and / or B" should be understood to mean "only A, only B, or both A and B".

[0112] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, as used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms. It will be further understood that when used herein, the terms "comprises", "comprising", "has", "having", "contains", and / or "includes" specify the presence of the stated features, elements, and / or components, etc., but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0113] Note that these terms used herein are only for the convenience of description and for distinguishing between nodes, devices, or networks, etc. As technology develops, other terms with similar / same meanings may also be used.

[0114] In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0115] Although the subject matter described herein may be implemented in any suitable type of system using any suitable components, the embodiments disclosed herein are described with respect to Figure 2 a communication system that conforms to the Figure 2The system architecture only depicts some exemplary elements. In practice, a communication system may further include any additional elements suitable for supporting communication between terminal devices or between a wireless device and another communication device (such as a landline telephone, a service provider, or any other network node or terminal device). The communication system may provide communication and various types of services to one or more terminal devices to facilitate the access and / or use of services provided by or via the communication system by the terminal devices.

[0116] Figure 2 Schematically shows an advanced architecture in a fifth-generation network according to an embodiment of the present disclosure. For example, the fifth-generation network may be 5GS. Figure 2 The architecture is the same as that described in 3GPP TS23.501 V17.5.0 Figure 4 .2.3-1, the disclosure of which is incorporated herein by reference in its entirety. Figure 2 The system architecture may include some exemplary elements, such as AUSF, AMF, DN (data network), NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, UE, (R)AN, SCP (service communication proxy), NSSAAF (network slice-specific authentication and authorization function), NSACF (network slice admission control function), edge application server discovery function (EASDF), etc.

[0117] According to an exemplary embodiment, as Figure 2 shown, the UE may establish a signaling connection with the AMF via reference point N1. This signaling connection may enable NAS (non-access stratum) signaling exchange between the UE and the core network, including the signaling connection between the UE and the (R)AN and the N2 connection for this UE between the (R)AN and the AMF. The (R)AN may communicate with the UPF via reference point N3. The UE may establish a protocol data unit (PDU) session to the DN (data network, such as an operator network or the Internet) via the UPF via reference point N6.

[0118] As Figure 2 further shown, the exemplary system architecture also includes service-based interfaces presented by NFs such as NRF, NEF, AUSF, UDM, PCF, AMF, NSACF, EASDF, and SMF, such as Nnrf, Nnef, Nausf, Nudm, Npcf, Namf, Nnsacf, Neasdf, and Nsmf. In addition, Figure 2Some reference points are also shown, such as N1, N2, N3, N4, N6, and N9, which can support the interaction between NF services in the NF. For example, these reference points can be implemented through corresponding NF service-based interfaces and by specifying some NF service consumers and providers and their interactions to perform specific system processes.

[0119] Figure 2 The various NFs shown in can be responsible for functions such as session management, mobility management, authentication, security, etc. AUSF, AMF, DN, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, UE, (R)AN, SCP, NSACF, EASDF can include, for example, the functions defined in Clause 6.2 of 3GPP TS23.501 V17.5.0.

[0120] Figure 3a A flowchart of a method according to an embodiment of the present disclosure is shown. The method can be executed by a device implemented in a first network function (NF), or a device implemented at the first NF, or a device implemented as the first NF, or a device communicatively coupled to the first NF. Therefore, the device can provide components or modules for implementing various parts of method 300, as well as components or modules for implementing other processes in combination with other components.

[0121] At block 302, the first NF can receive a first subscription request from the second NF for subscribing to at least one event type. The first subscription request requests the first NF to send an event notification of the at least one event type to the third NF.

[0122] The first NF can be any suitable network device, node, entity, or function. For example, the first NF can be any NF (e.g., AUSF, AMF, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, SCP, NSACF, EASDF) described in various 3GPP specifications (e.g., 3GPP TS23.501 V17.5.0).

[0123] In an embodiment, the first NF can include at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0124] The second NF can be any suitable network device, node, entity, or function. For example, the second NF can be any NF (e.g., AUSF, AMF, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, SCP, NSACF, EASDF) described in various 3GPP specifications (e.g., 3GPP TS23.501 V17.5.0).

[0125] In an embodiment, the second NF may include Unified Data Management (UDM).

[0126] The third NF may be any suitable network device, node, entity, or function. For example, the third NF may be any NF (e.g., AUSF, AMF, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, SCP, NSACF, EASDF) described in various 3GPP specifications (e.g., 3GPP TS23.501 V17.5.0).

[0127] In an embodiment, the third NF may include Network Exposure Function (NEF).

[0128] For example, the second NF may receive a second subscription request for subscribing to at least one event type from the third NF and send, on behalf of the third NF, a first subscription request for subscribing to the at least one event type to the first NF.

[0129] The first subscription request may be any suitable subscription request, such as an existing subscription request or a new subscription request.

[0130] In an embodiment, the first subscription request may be a subscription request described in 3GPP TS23.502 V17.5.0. For example, the first subscription request may be a Namf_EventExposure_Subscribe request or an Nsmf_EventExposure_Subscribe request described in 3GPP TS23.502 V17.5.0.

[0131] The at least one event type may be any suitable event type, and the present disclosure places no limitation thereon. In an embodiment, the at least one event type may be the same as the event types described in various 3GPP specifications (e.g., 3GPP TS23.502 V17.5.0). For example, the at least one event type may include PDU session release, UE moving out of the area of interest, etc.

[0132] The first subscription request may include any suitable information. For example, the first subscription request may include the notification endpoint of the third NF and the notification endpoint of the second NF. Each notification endpoint may be associated with a related one or more event IDs (a set of event IDs). This is to ensure that the second NF can receive notifications of subscription change-related events.

[0133] At block 304, the first NF may detect the occurrence of at least one monitoring event of at least one event type.

[0134] At block 306, the first NF may send an event notification of at least one monitoring event of at least one event type to the third NF.

[0135] At block 308, the first NF may receive an event notification response including error information from the third NF.

[0136] The error information may be any suitable error information. For example, when the third NF determines that a subscription of at least one event type has been removed or is no longer valid at the third NF, or cannot be found at the third NF, the third NF may send an event notification response including error information to the first NF. The error information may indicate a specific error, for example, a subscription of at least one event type has been removed or is no longer valid at the third NF, or cannot be found at the third NF.

[0137] At block 310, the first NF may send a first message including an event subscription termination notification of at least one event type to the second NF.

[0138] The first message may be any suitable message, such as an existing message or a new message.

[0139] The event subscription termination notification may be in any suitable form, such as bits, flags, indications, etc.

[0140] In an embodiment, the first message further includes a cause code. The cause code may be in any suitable form, such as bits, flags, indications, etc.

[0141] In an embodiment, the cause code indicates that the subscription of at least one event type is terminated because the first NF has identified that the subscription of at least one event type is no longer valid on the third NF hosting the notification uniform resource identifier (URI).

[0142] Figure 3b A flowchart of a method according to another embodiment of the present disclosure is shown, which may be executed by a device implemented in a first network function (NF), or a device implemented at the first NF, or a device implemented as the first NF, or a device communicatively coupled to the first NF. Thus, the device may provide components or modules for implementing various parts of method 310, as well as components or modules for implementing other processes in combination with other components. For some parts already described in the above embodiments, their descriptions are omitted here for the sake of brevity.

[0143] At block 312, the first NF may terminate the subscription of at least one event type. For example, when the first NF receives an event notification response containing error information from the third NF, it may terminate the subscription of at least one event type.

[0144] At block 314, the first NF may clear at least one resource reserved for subscriptions to the at least one event type. For example, when the first NF receives an event notification response containing error information from the third NF, it may clear at least one resource reserved for subscriptions to the at least one event type.

[0145] Figure 4 A flowchart of a method according to another embodiment of the present disclosure is shown, which may be performed by an apparatus implemented in a second NF, or an apparatus implemented at a second NF, or an apparatus implemented as a second NF, or an apparatus communicatively coupled to the second NF. Thus, the apparatus may provide components or modules for implementing various parts of method 400, as well as components or modules for implementing other processes in combination with other components. For some parts already described in the above embodiments, their descriptions are omitted here for the sake of brevity.

[0146] At block 402, the second NF may receive a second subscription request from the third NF for subscribing to at least one event type.

[0147] In an embodiment, the second NF includes a Unified Data Management (UDM).

[0148] In an embodiment, the third NF includes a Network Exposure Function (NEF).

[0149] The second subscription request may be any suitable subscription request, such as an existing subscription request or a new subscription request.

[0150] In an embodiment, the second subscription request may be a subscription request as described in 3GPP TS 23.502 V17.5.0. For example, the second subscription request may be a Nudm_EventExposure_Subscribe request as described in 3GPP TS 23.502 V17.5.0.

[0151] The at least one event type may be any suitable event type, and the present disclosure places no limitation thereon. In an embodiment, the at least one event type may be the same as the event types described in various 3GPP specifications (such as 3GPP TS 23.502 V17.5.0). For example, the at least one event type may include PDU session release, UE moving out of the area of interest, etc.

[0152] At block 404, the second NF may send a first subscription request for subscribing to at least one event type to the first NF on behalf of the third NF. The first subscription request requests the first NF to send event notifications of the at least one event type to the third NF.

[0153] In an embodiment, the first NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0154] At block 406, the second NF may receive a first message from the first NF that includes an event subscription termination notification for at least one event type.

[0155] For example, the first NF may send the first message at block 310, and then the second NF may receive the first message from the first NF.

[0156] In an embodiment, the first message further includes a cause code.

[0157] In an embodiment, the cause code indicates that the subscription for the at least one event type is terminated because the first NF has identified that the subscription for the at least one event type is no longer valid on a third NF that hosts a notification uniform resource identifier (URI).

[0158] At block 408, the second NF may clear at least one resource reserved for the subscription for the at least one event type.

[0159] In an embodiment, the second NF may send a message to the third NF that includes an event subscription termination notification for the at least one event type.

[0160] In an embodiment, the message may further include a cause code.

[0161] In an embodiment, the cause code may indicate that the subscription for the at least one event type is terminated because the first NF has identified that the subscription for the at least one event type is no longer valid on a third NF that hosts a notification uniform resource identifier (URI).

[0162] Figure 5 A flowchart of a method according to another embodiment of the present disclosure is shown, which may be performed by a device implemented in a third NF, or a device implemented at a third NF, or a device implemented as a third NF, or a device communicatively coupled to a third NF. Thus, the device may provide components or modules for implementing various parts of method 500, as well as components or modules for implementing other processes in combination with other components. For some parts that have been described in the above embodiments, for the sake of brevity, their descriptions are omitted here.

[0163] At block 502, the third NF may send a second subscription request to the second NF for subscribing to at least one event type.

[0164] In an embodiment, the second NF includes a unified data management (UDM).

[0165] In an embodiment, the third NF includes a network exposure function (NEF).

[0166] At block 504, a third NF may receive an event notification of at least one monitoring event of at least one event type from a first NF.

[0167] In an embodiment, the first NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0168] At block 506, the third NF may determine that a subscription of at least one event type is removed or no longer valid at the third NF. For example, the subscription of at least one event type may be removed or no longer valid at the third NF for various reasons, such as the third NF being restarted, a software error, a storage error, etc.

[0169] At block 508, the third NF may send an event notification response including error information to the first NF.

[0170] At block 510, optionally, when the subscription of at least one event type is no longer valid at the third NF, the third NF may clear at least one resource reserved for the subscription of at least one event type.

[0171] In an embodiment, the third NF may receive a message including an event subscription termination notification of at least one event type from a second NF. Then, the third NF may clear at least one resource reserved for the subscription of at least one event type.

[0172] Figure 6a A flowchart of a method according to another embodiment of the present disclosure is shown, and the method may be executed by a device implemented in a fourth NF, or a device implemented at a fourth NF, or a device implemented as a fourth NF, or a device communicatively coupled to a fourth NF. Therefore, the device may provide components or modules for implementing various parts of method 600, as well as components or modules for implementing other processes in combination with other components. For some parts already described in the above embodiments, their descriptions are omitted here for brevity.

[0173] At block 602, the fourth NF may receive a subscription of at least one event type requested by a fifth NF from a sixth NF.

[0174] The fourth NF may be any suitable network device, node, entity, or function. For example, the fourth NF may be any NF (e.g., AUSF, AMF, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, SCP, NSACF, EASDF) described in various 3GPP specifications (e.g., 3GPP TS23.501 V17.5.0).

[0175] In an embodiment, the fourth NF may include at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0176] The fifth NF may be any suitable network device, node, entity, or function. For example, the fifth NF may be any NF (e.g., AUSF, AMF, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, SCP, NSACF, EASDF) described in various 3GPP specifications (e.g., 3GPP TS23.501 V17.5.0).

[0177] In an embodiment, the fifth NF may include a unified data management (UDM) or a network exposure function (NEF).

[0178] The sixth NF may be any suitable network device, node, entity, or function. For example, the sixth NF may be any NF (e.g., AUSF, AMF, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, SCP, NSACF, EASDF) described in various 3GPP specifications (e.g., 3GPP TS23.501 V17.5.0).

[0179] In an embodiment, the sixth NF may include at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0180] The fourth NF may receive a subscription for at least one event type requested by the fifth NF from the sixth NF in various ways. For example, the fourth NF may send a request to the sixth NF to obtain a subscription for at least one event type requested by the fifth NF, and then the fourth NF may receive a subscription for at least one event type requested by the fifth NF from the sixth NF.

[0181] For example, the UE may be served by the sixth NF (e.g., AMF) that stores a subscription for at least one event type requested by the fifth NF (e.g., UDM or NEF). Due to the mobility of the UE, the fourth NF (e.g., AMF) may serve the UE and send a UE context transfer request to the sixth NF. Then, the fourth NF may receive a UE context transfer response from the sixth NF, which includes a subscription for at least one event type requested by the fifth NF.

[0182] In an embodiment, during an inter-public land mobile network (PLMN) mobility procedure or a terminal device mobility procedure, a subscription for at least one event type requested by the fifth NF may be received from the sixth NF.

[0183] At block 604, the fourth NF may check whether the fourth NF supports the at least one event type and / or whether the subscription to the at least one event type requested by the fifth NF is authorized.

[0184] For example, the fourth NF may check whether it supports the event type of the transferred subscription and check whether the received subscription is authorized based on the authorization policy in the fourth NF or its PLMN. For example, the authorization in the sixth NF and its PLMN may be different from the authorization in the fourth NF and its PLMN.

[0185] At block 606, when the fourth NF does not support the at least one event type and / or the subscription to the at least one event type requested by the fifth NF is not authorized, the fourth NF may send a second message to the fifth NF including an event subscription termination notice for the at least one event type.

[0186] The second message may be any suitable message, such as an existing message or a new message.

[0187] The event subscription termination notice may be in any suitable form, such as bits, flags, indications, etc.

[0188] In an embodiment, the second message may also include a cause code. The cause code may be in any suitable form, such as bits, flags, indications, etc.

[0189] In an embodiment, the cause code may indicate at least one of the following: the subscription to the at least one event type is terminated because the service access authorization for the fifth NF is no longer valid; the subscription to the at least one event type is terminated because the fourth NF requires a new service authorization; or the subscription to the at least one event type is terminated because the at least one event type is not supported in the fourth NF.

[0190] Figure 6b A flowchart of a method according to another embodiment of the present disclosure is shown, and the method may be executed by a device implemented in the fourth NF, or a device implemented at the fourth NF, or a device implemented as the fourth NF, or a device communicatively coupled to the fourth NF. Therefore, the device may provide components or modules for implementing various parts of method 610, as well as components or modules for implementing other processes in combination with other components. For some parts that have been described in the above embodiments, their descriptions are omitted here for the sake of brevity.

[0191] At block 612, when the fourth NF does not support the at least one event type and / or the subscription to the at least one event type requested by the fifth NF is not authorized, the fourth NF may terminate the subscription to the at least one event type.

[0192] At block 614, the fourth NF may clear at least one resource reserved for subscriptions to the at least one event type.

[0193] Figure 7a A flowchart of a method according to another embodiment of the present disclosure is shown, which may be performed by a device implemented in a fifth NF, or a device implemented at a fifth NF, or a device implemented as a fifth NF, or a device communicatively coupled to a fifth NF. Thus, the device may provide components or modules for implementing various parts of method 700, as well as components or modules for implementing other processes in combination with other components. For some parts already described in the above embodiments, their descriptions are omitted here for the sake of brevity.

[0194] At block 702, when a subscription to at least one event type requested by the fifth NF is sent from a sixth NF to the fourth NF, and the fourth NF does not support the at least one event type and / or the subscription to the at least one event type requested by the fifth NF is not authorized, the fifth NF may receive a second message from the fourth NF including an event subscription termination notice for the at least one event type.

[0195] In an embodiment, the fourth NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0196] In an embodiment, the fifth NF includes at least one of a unified data management (UDM) or a network exposure function (NEF).

[0197] In an embodiment, the sixth NF includes at least one of an access and mobility management function (AMF) or a session management function (SMF).

[0198] For example, the fifth NF may directly send a subscription request for subscribing to at least one event type to the sixth NF. The fifth NF may send a subscription request for subscribing to at least one event type to an NF, which may send a subscription request for subscribing to at least one event type to the sixth NF on behalf of the third NF. In these cases, the sixth NF may create a subscription to the at least one event type requested by the fifth NF.

[0199] As another example, the sixth NF may obtain a subscription to the at least one event type requested by the fifth NF from another NF.

[0200] In an embodiment, the second message further includes a cause code.

[0201] In an embodiment, the cause code indicates at least one of the following: the subscription for the at least one event type is terminated because the service access authorization for the fifth NF is no longer valid; the subscription for the at least one event type is terminated because the fourth NF requests a new service authorization; or the subscription for the at least one event type is terminated because the at least one event type is not supported in the fourth NF.

[0202] In an embodiment, during an inter-public land mobile network (PLMN) mobility procedure or a terminal device mobility procedure, the subscription for the at least one event type requested by the fifth NF is sent from the sixth NF to the fourth NF.

[0203] At block 704, the fifth NF may clear at least one resource reserved for the subscription for the at least one event type.

[0204] Figure 7b A flowchart of a method according to another embodiment of the present disclosure is shown, which may be executed by a device implemented in the fifth NF, or a device implemented at the fifth NF, or a device implemented as the fifth NF, or a device communicatively coupled to the fifth NF. Thus, the device may provide components or modules for implementing various parts of method 710, as well as components or modules for implementing other processes in combination with other components. For some parts already described in the above embodiments, for the sake of brevity, their descriptions are omitted here.

[0205] At step 712, optionally, the fifth NF may obtain an access authorization token for the fourth NF based on a second message.

[0206] For example, the fifth NF may obtain an access authorization token for the fourth NF through the Nnrf_AccessToken_Get service operation described in 3GPP TS 33.501 V17.7.0.

[0207] For example, when the second message includes a cause code that indicates at least one of the following: the subscription for the at least one event type is terminated because the service access authorization for the fifth NF is no longer valid; the subscription for the at least one event type is terminated because the fourth NF requests a new service authorization; or the subscription for the at least one event type is terminated because the at least one event type is not supported in the fourth NF, the fifth NF may obtain an access authorization token for the fourth NF based on the second message.

[0208] At block 714, optionally, the fifth NF may send a new subscription request for subscribing to one or more event types to the fourth NF based on the second message. The new subscription request includes an access authorization token for the fourth NF.

[0209] For example, when the second message includes a cause code, the cause code indicates at least one of the following: the subscription of the at least one event type is terminated because the service access authorization for the fifth NF is no longer valid; the subscription of the at least one event type is terminated because the fourth NF requests a new service authorization; or the subscription of the at least one event type is terminated because the at least one event type is not supported in the fourth NF. The fifth NF may send a new subscription request for subscribing to one or more event types to the fourth NF. In an embodiment, when the fourth NF requests an access authorization token, the new subscription request may include an access authorization token for the fourth NF. In another embodiment, when the fourth NF does not request an access authorization token, the new subscription request may not include an access authorization token for the fourth NF.

[0210] Figure 7c A flowchart of an event subscription termination notification according to an embodiment of the present disclosure is shown.

[0211] In step 0. The NF service consumer NF_A requests a subscription for an event type on behalf of the NF service consumer NF_C from the NF service producer NF_B, following the process defined in 3GPP TS23.501 V17.5.0 or 3GPP TS23.502 V17.5.0. After success, NF_B sends an event notification of the subscribed event type to NF_C.

[0212] In step 1. Some events occur. For example, the original event subscription may be locally removed or become invalid at the NF service consumer (NF_C). After receiving the notification of the subscribed event type, NF_C sends a response with an error code.

[0213] In step 2. After receiving such a response with an error, NF_B decides to terminate the subscription and clears the resources reserved for the received subscription. If the subscribed event was requested by NF_A on behalf of NF_C, NF_B sends a new event type "event subscription termination notification" to the subscription request NF_A, optionally with a cause code. Table 1 shows examples of cause codes. Table 1

[0214] In step 4. After receiving the event subscription termination notification, NF_A clears the resources reserved for the subscription requested in step 0.

[0215] In step 5. Optionally, if the subscribed event was initially requested by NF_C and was processed by NF_A on behalf of NF_C, NF_A may send an event type "event subscription termination notification" to NF_C, optionally with a cause code.

[0216] In step 6. Optionally, upon receiving the event subscription termination notification, NF_C clears the resources reserved for the subscribed event.

[0217] Figure 7d A flowchart of an event subscription termination notification according to another embodiment of the present disclosure is shown.

[0218] In step 0. The NF service consumer NF_A requests a subscription for an event type from the NF service producer NF_B_1. NF_B_1 authorizes the request and the subscription is created. Following the procedures defined in 3GPP TS23.501 V17.5.0 or 3GPP TS23.502 V17.5.0, event notifications of the subscribed event type are sent to NF_A.

[0219] In step 1. Certain events occur, such as UE mobility, and the UE context for that UE (including the subscription created in step 1) is transferred from NF_B_1 to NF_B_2.

[0220] In step 2. Along with other UE context transfer-related activities, NF_B_2 checks whether it supports the event type of the transferred subscription and checks whether the received subscription is authorized based on the authorization policy in NF_B_2 or its PLMN. For example, the authorization in NF_B_1 and its PLMN may be different from the authorization in NF_B_2 and its PLMN.

[0221] In step 3. If the check in step 2 fails, NF_B_2 decides to terminate the subscription and clears the resources reserved for the received subscription. NF_B_2 sends a new event type notification, such as "event subscription termination notification", optionally with a cause code, to the subscription requesting NF_A. Table 2 shows examples of cause codes. Table 2

[0222] If the cause code suggests that NF_A can take further actions, NF_B_2 may include auxiliary information in this message for further actions in NF_A, such as the NF ID, address, and URL (Uniform Resource Locator) of NF_B_2, which can be used to receive a new subscription from NF_A.

[0223] In step 4. Upon receiving the event subscription termination notification, NF_A clears the resources reserved for the subscription requested in step 0.

[0224] In step 5. If the cause code suggests that NF_A can take further actions, NF_A may send a new subscription request for the event type to NF producer _B_2, possibly based on the auxiliary information received in step 3.

[0225] In an embodiment, NF_A may obtain an access authorization token for NF_B_2, and the new subscription request may include the access authorization token.

[0226] In an embodiment, clause 5.3.2.4.1 of 3GPP TS29.518 V17.7.0 may be modified as follows.

[0227] 5.3.2.4.1 Overview

[0228] When a certain event included in the subscription has occurred, the notification service operation is invoked by the AMF to send a notification to the notification URI.

[0229] The AMF shall use the HTTP method POST and use the notification URI received in the subscription creation as specified in clause 5.3.2.2.2 of 3GPP TS29.518 V17.7.0, including, for example, the subscription ID, one or more event IDs for which the event has occurred, and the notification correlation ID provided by the NF service consumer at the time of event subscription, to send the notification.

[0230] In addition, when there is an AMF change during the UE mobility process, and if the subscription Id changes (i.e., the registration process and the handover process) or the AMF terminates the subscription, the notification service operation shall also be invoked by the AMF.

[0231] Figure 7e A flowchart of a notification according to an embodiment of the present disclosure is shown.

[0232] 1. The AMF shall send a POST request to send the notification.

[0233] 2a. After success, the NF service consumer shall return "204 No Content".

[0234] 2b. After failure or redirection, an appropriate HTTP status code indicating an error (e.g., "403 Forbidden") shall be returned, and appropriate additional error information shall be returned.

[0235] When the AMF receives the following response codes (and application errors), the AMF shall consider the subscription no longer valid and terminate the subscription:

[0236] - "400 Bad Message", with the application error "RESOURCE_CONTEXT_NOT_FOUND"

[0237] - "404 Not Found"

[0238] When the AMF terminates the subscription based on the above response code, and if the subscription is executed by an NF consumer on behalf of another NF (e.g., the UDM subscribes to the AMF on behalf of the NEF), the AMF shall send a notification to the NF consumer (e.g., the UDM) to inform the termination of the subscription.

[0239] In an embodiment, the following data type "SubTerminationReason" can be added to Table 6.2.6.1-1 of 3GPP TS29.518 V17.7.0. Table 6.2.6.1-1: Namf_EventExposure specific data types Data type Defined terms Description SubTerminationReason 6.2.6.3.xx Subscription termination reason

[0240] In an embodiment, the following attribute name "termReason" can be added to Table 6.2.6.2.5-1 of 3GPP TS29.518 V17.7.0. Table 6.2.6.2.5-1: Definition of type AmfEventReport

[0241] In an embodiment, the following enumerated value "SUBSCRIPTION_TERMINATION" can be added to Table 6.2.6.3.3-1 of 3GPP TS29.518 V17.7.0. Table 6.2.6.3.3-1: Enumeration AmfEventType

[0242] In an embodiment, the following Table 6.2.6.3.x-1 can be added to 3GPP TS29.518 V17.7.0. Table 6.2.6.3.x-1: Enumeration SubTerminationReason

[0243] In an embodiment, the Namf_EventExposure API of 3GPP TS29.518 V17.7.0 can be modified as follows.

[0244] In an embodiment, the NF producer (NF_B, such as AMF) supports sending a new event subscription termination notification for notifying the subscription requester NF (NF_A, such as UDM) that the subscription is terminated at the NF producer.

[0245] In an embodiment, the subscription requester (NF_A) is able to trigger a specific local clearing of the invalid subscription based on the notification from the NF producer (NF_B).

[0246] In an embodiment, the NF consumer (NF_A) subscribes to event subscriptions on behalf of another NF (NF_C) that processes the notification. When NF_A receives an event subscription termination notification from the NF producer (NF_B), NF_A also sends an event subscription termination notification to the other NF (NF_C).

[0247] Embodiments herein can provide many advantages, and the following is a non-exhaustive list of examples of advantages. In some embodiments herein, based on the new event subscription termination notification, the subscription requester is able to trigger a local clearing of the invalid subscription to avoid unnecessary resource waste, or trigger other necessary actions to ensure the service continues. Embodiments herein are not limited to the above features and advantages. Those skilled in the art will recognize additional features and advantages after reading the following detailed description.

[0248] Figure 8a is a block diagram showing an apparatus suitable for practicing some embodiments of the present disclosure. For example, any one of the above first NF, second NF, third NF, fourth NF, or fifth NF can be implemented as or by an apparatus 800.

[0249] The apparatus 800 includes at least one processor 821, such as a digital processor (DP), and at least one memory (MEM) 822 coupled to the processor 821. The apparatus 800 may further include a transmitter TX and a receiver RX 823 coupled to the processor 821. The MEM 822 stores a program (PROG) 824. The PROG 824 may include instructions that, when executed on the relevant processor 821, cause the apparatus 800 to operate according to embodiments of the present disclosure. The combination of at least one processor 821 and at least one MEM 822 may form a processing apparatus 825 suitable for implementing various embodiments of the present disclosure.

[0250] Various embodiments of the present disclosure can be implemented by a computer program executable by one or more of the processor 821, software, firmware, hardware, or a combination thereof.

[0251] The MEM 822 can be of any type suitable for the local technical environment and can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory, as non-limiting examples.

[0252] The processor 821 can be of any type suitable for the local technical environment and can include one or more of the following: a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture, as non-limiting examples.

[0253] In an embodiment where the apparatus is implemented as the first NF or at the first NF, the memory 822 stores instructions that can be executed by the processor 821, whereby the first NF operates according to any of the methods related to the first NF as described above.

[0254] In an embodiment where the apparatus is implemented as the second NF or at the second NF, the memory 822 stores instructions that can be executed by the processor 821, whereby the second NF operates according to any of the methods related to the second NF as described above.

[0255] In an embodiment where the apparatus is implemented as the third NF or at the third NF, the memory 822 stores instructions that can be executed by the processor 821, whereby the third NF operates according to any of the methods related to the third NF as described above.

[0256] In an embodiment where the apparatus is implemented as the fourth NF or at the fourth NF, the memory 822 stores instructions that can be executed by the processor 821, whereby the fourth NF operates according to any of the methods related to the fourth NF as described above.

[0257] In an embodiment where the apparatus is implemented as the fifth NF or at the fifth NF, the memory 822 stores instructions that can be executed by the processor 821, whereby the fifth NF operates according to any of the methods related to the fifth NF as described above.

[0258] Figure 8bis a block diagram showing a first NF according to an embodiment of the present disclosure. As shown, the first NF 830 includes a first receiving module 831 configured to receive a first subscription request for subscribing to at least one event type from a second NF. The first subscription request requests the first NF to send an event notification of the at least one event type to a third NF. The first NF 830 further includes a detection module 832 configured to detect the occurrence of at least one monitoring event of the at least one event type. The first NF 830 further includes a first sending module 833 configured to send an event notification of the at least one monitoring event of the at least one event type to the third NF. The first NF 830 further includes a second receiving module 834 configured to receive an event notification response including error information from the third NF. The first NF 830 further includes a second sending module 835 configured to send a first message including an event subscription termination notification of the at least one event type to the second NF.

[0259] In an embodiment, the first NF 830 further includes a termination module 836 configured to terminate the subscription of the at least one event type.

[0260] In an embodiment, the first NF 830 further includes a clearing module 837 configured to clear at least one resource reserved for the subscription of the at least one event type.

[0261] Figure 8c is a block diagram showing a second NF according to an embodiment of the present disclosure. As shown, the second NF 840 includes a first receiving module 841 configured to receive a second subscription request for subscribing to at least one event type from a third NF. The second NF 840 further includes a sending module 842 configured to send, on behalf of the third NF, a first subscription request for subscribing to at least one event type to the first NF. The first subscription request requests the first NF to send an event notification of the at least one event type to the third NF. The second NF 840 further includes a second receiving module 843 configured to receive a first message including an event subscription termination notification of the at least one event type from the first NF. The second NF 840 further includes a clearing module 844 configured to clear at least one resource reserved for the subscription of the at least one event type.

[0262] Figure 8dIt is a block diagram showing a third NF according to an embodiment of the present disclosure. As shown, the third NF 850 includes a first sending module 851 configured to send a second subscription request for subscribing to at least one event type to a second NF. The third NF 850 further includes a receiving module 852 configured to receive an event notification of at least one monitored event of at least one event type from a first NF. The third NF 850 further includes a determining module 853 configured to determine that the subscription of the at least one event type is removed or no longer valid at the third NF. The third NF 850 further includes a second sending module 854 configured to send an event notification response including error information to the first NF.

[0263] In an embodiment, the third NF 850 further includes a clearing module 855 configured to clear at least one resource reserved for the subscription of the at least one event type when the subscription of the at least one event type is no longer valid at the third NF.

[0264] Figure 8e It shows a block diagram of a fourth NF according to an embodiment of the present disclosure. As shown, the fourth NF 860 includes a receiving module 861 configured to receive a subscription of at least one event type requested by a fifth NF from a sixth NF. The fourth NF 860 further includes an inspection module 862 configured to inspect whether the fourth NF supports the at least one event type and / or whether the subscription of the at least one event type requested by the fifth NF is authorized. The fourth NF 860 further includes a sending module 863 configured to send a second message including an event subscription termination notice of the at least one event type to the fifth NF when the fourth NF does not support the at least one event type and / or the subscription of the at least one event type requested by the fifth NF is not authorized.

[0265] In an embodiment, the fourth NF 860 further includes a termination module 864 configured to terminate the subscription of the at least one event type when the fourth NF does not support the at least one event type and / or the subscription of the at least one event type requested by the fifth NF is not authorized. The fourth NF 860 further includes a clearing module 865 configured to clear at least one resource reserved for the subscription of the at least one event type.

[0266] Figure 8fIt is a block diagram showing a fifth NF according to an embodiment of the present disclosure. As shown, the fifth NF 870 includes a receiving module 871 configured to receive, from the fourth NF, a second message including an event subscription termination notice for at least one event type when the subscription for at least one event type requested by the fifth NF is sent from the sixth NF to the fourth NF and the fourth NF does not support the at least one event type and / or the subscription for the at least one event type requested by the fifth NF is not authorized. The fifth NF 870 further includes a clearing module 872 configured to clear at least one resource reserved for the subscription for the at least one event type.

[0267] In an embodiment, the fifth NF 870 further includes an obtaining module 873 configured to obtain an access authorization token for the fourth NF based on the second message.

[0268] In an embodiment, the fifth NF 870 further includes a sending module 874 configured to send, based on the second message, a new subscription request for subscribing to one or more event types to the fourth NF. The new subscription request includes an access authorization token for the fourth NF.

[0269] The term unit or module may have a conventional meaning in the field of electronic, electrical devices and / or electronic devices, and may include, for example, electrical and / or electronic circuits, devices, modules, processors, memories, logic solid-state and / or discrete devices, computer programs or instructions for performing corresponding tasks, processes, calculations, outputs and / or display functions, and the like, such as those described herein.

[0270] Using functional units, the first NF, the second NF, the third NF, the fourth NF or the fifth NF may not require a fixed processor or memory, and any computing resources and storage resources may be arranged from the first NF, the second NF, the third NF, the fourth NF or the fifth NF in the communication system. The introduction of virtualization technology and network computing technology can improve the utilization efficiency of network resources and the flexibility of the network.

[0271] According to one aspect of the present disclosure, there is provided a computer program product tangibly stored on a computer-readable storage medium and including instructions that, when executed on at least one processor, cause the at least one processor to perform any of the above methods.

[0272] According to one aspect of the present disclosure, there is provided a computer-readable storage medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform any of the above methods.

[0273] In addition, the present disclosure may also provide a carrier containing the above computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer-readable storage medium. The computer-readable storage medium may be, for example, an optical disc or an electronic storage device such as RAM (Random Access Memory), ROM (Read-Only Memory), flash memory, magnetic tape, CD-ROM, DVD, Blu-ray Disc, etc.

[0274] The techniques described herein can be implemented in a variety of ways such that an apparatus for implementing one or more functions of the corresponding apparatus described by the embodiments includes not only components of the prior art but also components for implementing one or more functions of the corresponding apparatus described by the embodiments, and it may include separate components for each individual function or may be configured to execute two or more functions. For example, these techniques can be implemented in hardware (one or more apparatuses), firmware (one or more apparatuses), software (one or more modules), or a combination thereof. For firmware or software, the implementation can be accomplished by modules (e.g., procedures, functions, etc.) that execute the functions described herein.

[0275] The exemplary embodiments herein have been described with reference to block diagrams and flowcharts of methods and apparatuses. It will be understood that each block of the block diagrams and flowcharts, and combinations of blocks in the block diagrams and flowcharts, can be implemented by various components including computer program instructions. These computer program instructions can be loaded onto a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, so that the instructions executed on the computer or other programmable data processing device create components for implementing the functions specified in the flowchart block or blocks.

[0276] In addition, although the operations are depicted in a particular order, this should not be construed as requiring that the operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the subject matter described herein, but rather as descriptions of features that may be specific to a particular embodiment. Certain features described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately or in any suitable sub-combination in multiple embodiments.

[0277] Although this specification contains many specific implementation details, these should not be construed as limitations on the scope of any implementation or the scope of what may be claimed, but rather as descriptions of features specific to particular embodiments that may be specific to a particular implementation. Certain features described in the context of separate embodiments in this specification may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination. In addition, although the above features may be described as acting in certain combinations and even initially claimed as such, in some cases one or more features from a claimed combination may be deleted from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination.

[0278] It will be apparent to those skilled in the art that, as technology progresses, the inventive concept can be implemented in various ways. The above embodiments are given for description and not limitation of the disclosure, and it should be understood that modifications and variations can be made without departing from the spirit and scope of the disclosure, as will be readily understood by those skilled in the art. Such modifications and variations are considered to be within the scope of the disclosure and the appended claims. The scope of protection of the disclosure is defined by the appended claims.

Claims

1. A method (300) performed by a first network function NF, comprising: receiving (302) from a second NF a first subscription request for subscribing to at least one event type, wherein the first subscription request requests the first NF to send an event notification of the at least one event type to a third NF; detecting (304) the occurrence of at least one monitored event of the at least one event type; sending (306) to the third NF an event notification of the at least one monitored event of the at least one event type; receiving (308) from the third NF an event notification response including error information; and sending (310) to the second NF a first message including an event subscription termination notification of the at least one event type.

2. The method according to claim 1, further comprising: terminating (312) the subscription of the at least one event type; and clearing (314) at least one resource reserved for the subscription of the at least one event type.

3. The method according to claim 1 or 2, wherein, the first message further includes a cause code.

4. The method according to claim 3, wherein, the cause code indicates that the subscription of the at least one event type is terminated because the first NF has identified that the subscription of the at least one event type is no longer valid on the third NF hosting the notification uniform resource identifier URI.

5. The method according to any one of claims 1-4, wherein, the first NF includes at least one of the following: Access and Mobility Management Function AMF, or Session Management Function SMF.

6. The method according to any one of claims 1-5, wherein, the second NF includes the Unified Data Management UDM.

7. The method according to any one of claims 1-6, wherein, the third NF includes the Network Exposure Function NEF.

8. A method (400) performed by a second network function NF, comprising: receiving (402) from a third NF a second subscription request for subscribing to at least one event type; sending (404) on behalf of the third NF to the first NF a first subscription request for subscribing to the at least one event type, wherein the first subscription request requests the first NF to send an event notification of the at least one event type to the third NF; receiving (406) from the first NF a first message including an event subscription termination notification of the at least one event type; and clearing (408) at least one resource reserved for the subscription of the at least one event type.

9. The method according to claim 8, wherein, the first message further includes a cause code.

10. The method according to claim 9, wherein, the cause code indicates that the subscription of the at least one event type is terminated because the first NF has identified that the subscription of the at least one event type is no longer valid on the third NF hosting the notification uniform resource identifier URI.

11. The method according to any one of claims 8-10, wherein, the first NF includes at least one of the following: Access and Mobility Management Function AMF, or Session Management Function SMF.

12. The method according to any one of claims 8-11, wherein, the second NF includes a Unified Data Management UDM.

13. The method according to any one of claims 8-12, wherein, the third NF includes a Network Exposure Function NEF.

14. A method (500) performed by a third Network Function NF, comprising: sending (502) a second subscription request for subscribing to at least one event type to a second NF; receiving (504) an event notification of at least one monitoring event of the at least one event type from a first NF; determining (506) that the subscription of the at least one event type is removed or no longer valid at the third NF; and sending (508) an event notification response including error information to the first NF.

15. The method according to claim 14, further comprising: when the subscription of the at least one event type is no longer valid at the third NF, clearing (510) at least one resource reserved for the subscription of the at least one event type.

16. The method according to claim 14 or 15, wherein, the first NF includes at least one of the following: Access and Mobility Management Function AMF, or Session Management Function SMF.

17. The method according to any one of claims 14-16, wherein, the second NF includes a Unified Data Management UDM.

18. The method according to any one of claims 14-17, wherein, the third NF includes a Network Exposure Function NEF.

19. A method (600) performed by a fourth Network Function NF, comprising: receiving (602) a subscription for at least one event type requested by a fifth NF from a sixth NF; checking (604) whether the fourth NF supports the at least one event type and / or whether the subscription for the at least one event type requested by the fifth NF is authorized; when the fourth NF does not support the at least one event type and / or the subscription for the at least one event type requested by the fifth NF is not authorized, sending (606) a second message including an event subscription termination notice for the at least one event type to the fifth NF.

20. The method according to claim 19, wherein, when the fourth NF does not support the at least one event type and / or the subscription for the at least one event type requested by the fifth NF is not authorized, the method further comprises: terminating (612) the subscription for the at least one event type; and clearing (614) at least one resource reserved for the subscription for the at least one event type.

21. The method according to claim 19 or 20, wherein, the second message further includes a cause code.

22. The method according to claim 21, wherein, the cause code indicates at least one of the following: the subscription for the at least one event type is terminated because the service access authorization for the fifth NF is no longer valid; Since the fourth NF requests a new service authorization, the subscription of the at least one event type is terminated; Or Since the at least one event type is not supported in the fourth NF, the subscription of the at least one event type is terminated.

23. The method according to any one of claims 19-22, Wherein, During the public land mobile network (PLMN) inter-mobility process or the terminal device mobility process, the subscription of the at least one event type requested by the fifth NF is received from the sixth NF.

24. The method according to any one of claims 19-23, Wherein, The fourth NF includes at least one of the following: Access and Mobility Management Function (AMF), or Session Management Function (SMF).

25. The method according to any one of claims 19-24, Wherein, The fifth NF includes at least one of the following: Unified Data Management (UDM) or Network Exposure Function (NEF).

26. The method according to any one of claims 19-25, Wherein, The sixth NF includes at least one of the following: Access and Mobility Management Function (AMF), or Session Management Function (SMF).

27. A method (700) performed by a fifth network function (NF), Comprising: When the subscription of at least one event type requested by the fifth NF is sent from the sixth NF to the fourth NF, and the fourth NF does not support the at least one event type and / or the subscription of the at least one event type requested by the fifth NF is not authorized, receiving (702) from the fourth NF a second message including an event subscription termination notice for the at least one event type; And Clearing (704) at least one resource reserved for the subscription of the at least one event type.

28. The method according to claim 27, Wherein, The second message further includes a cause code.

29. The method according to claim 28, Wherein, The cause code indicates at least one of the following: Since the service access authorization for the fifth NF is no longer valid, the subscription of the at least one event type is terminated; Since the fourth NF requests a new service authorization, the subscription of the at least one event type is terminated; Or Since the at least one event type is not supported in the fourth NF, the subscription of the at least one event type is terminated.

30. The method according to any one of claims 27-29, Wherein, During the public land mobile network (PLMN) inter-mobility process or the terminal device mobility process, the subscription of the at least one event type requested by the fifth NF is sent from the sixth NF to the fourth NF.

31. The method according to any one of claims 27-30, further Comprising: Based on the second message, obtaining (712) an access authorization token for the fourth NF; And / or Based on the second message, send (714) a new subscription request for subscribing to one or more event types to the fourth NF, where the new subscription request includes the access authorization token for the fourth NF.

32. The method according to any one of claims 27-31, wherein, the fourth NF includes at least one of the following: Access and Mobility Management Function AMF, or Session Management Function SMF.

33. The method according to any one of claims 27-32, wherein, the fifth NF includes at least one of the following: Unified Data Management UDM or Network Exposure Function NEF.

34. The method according to any one of claims 27-33, wherein, the sixth NF includes at least one of the following: Access and Mobility Management Function AMF, or Session Management Function SMF.

35. A first NF (800), comprising: a processor (821); and a memory (822) coupled to the processor (821), the memory (822) storing instructions executable by the processor (821), whereby the first NF (800) is operable to: Receive a first subscription request from a second NF for subscribing to at least one event type, where the first subscription request requests the first NF to send an event notification of the at least one event type to a third NF; Detect the occurrence of at least one monitored event of the at least one event type; Send an event notification of the at least one monitored event of the at least one event type to the third NF; Receive an event notification response including error information from the third NF; and Send a first message including an event subscription termination notification of the at least one event type to the second NF.

36. The first NF according to claim 35, wherein, the first NF is further operable to perform the method according to any one of claims 2 to 7.

37. A second NF (800), comprising: a processor (821); and a memory (822) coupled to the processor (821), the memory (822) storing instructions executable by the processor (821), whereby the second NF (800) is operable to: Receive a second subscription request from a third NF for subscribing to at least one event type; On behalf of the third NF, send a first subscription request for subscribing to the at least one event type to a first NF, where the first subscription request requests the first NF to send an event notification of the at least one event type to the third NF; Receive a first message including an event subscription termination notification of the at least one event type from the first NF; and Release at least one resource reserved for the subscription of the at least one event type.

38. The second NF according to claim 37, wherein, the second NF is further operable to perform the method according to any one of claims 9 to 13.

39. A third NF (800), comprising: a processor (821); and A memory (822) coupled to the processor (821), the memory (822) storing instructions executable by the processor (821), whereby the third NF (800) is operable to: Send a second subscription request to a second NF for subscribing to at least one event type; Receive an event notification of at least one monitoring event of the at least one event type from a first NF; Determine that the subscription of the at least one event type is removed or no longer valid at the third NF; And Send an event notification response including error information to the first NF.

40. The third NF according to claim 39, Wherein, The third NF is further operable to perform the method according to any one of claims 15 to 18.

41. A fourth NF (800), Comprising: A processor (821); And A memory (822) coupled to the processor (821), the memory (822) storing instructions executable by the processor (821), whereby the fourth NF (800) is operable to: Receive a subscription of at least one event type requested by a fifth NF from a sixth NF; Check whether the fourth NF supports the at least one event type and / or whether the subscription of the at least one event type requested by the fifth NF is authorized; When the fourth NF does not support the at least one event type and / or the subscription of the at least one event type requested by the fifth NF is not authorized, send a second message including an event subscription termination notice of the at least one event type to the fifth NF.

42. The fourth NF according to claim 41, Wherein, The fourth NF is further operable to perform the method according to any one of claims 20 to 26.

43. A fifth NF (800), Comprising: A processor (821); And A memory (822) coupled to the processor (821), the memory (822) storing instructions executable by the processor (821), whereby the fifth NF (800) is operable to: When a subscription of at least one event type requested by the fifth NF is sent from a sixth NF to a fourth NF, and the fourth NF does not support the at least one event type and / or the subscription of the at least one event type requested by the fifth NF is not authorized, receive a second message including an event subscription termination notice of the at least one event type from the fourth NF; And Clear at least one resource reserved for the subscription of the at least one event type.

44. The fifth NF according to claim 43, Wherein, The fifth NF is further operable to perform the method according to any one of claims 28 to 34.

45. A computer-readable storage medium storing instructions, which 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 34.

46. A computer program product comprising instructions 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 34.

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