Methods and apparatuses for same event subscription for multi sessions of one ue

Abstract

To provide a method performed by a first NF implementing a consumer of an Event Exposure service provided by a second NF implementing a producer of the Event Exposure service in order to solve a problem such as an increase in a traffic load between a SMF and an AMF in a 5G network, a network function (NF) and a machine-readable medium.SOLUTION: A method includes: receiving a trigger for subscribing an event for a PDU session of a UE; allocating an event ID specific to the UE for the event, and sending a first request for subscribing the event including the event ID to the second NF, if the event has not been allocated with the event ID; and saving mapping between the event ID and the ID of the PDU session. By this method, the waste of resources for the first NF and the second NF can be reduced, for example, the message interaction and the traffic between the two NFs are reduced, and the CPU resources are saved on each of the two NFs.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The non-limiting and exemplary embodiments of the present disclosure generally relate to the technical field of mobile communication networks, and more specifically, to methods and apparatuses for the same event subscription of multiple sessions of one user equipment (UE).

Background Art

[0002] This section introduces aspects that may help deepen the understanding of the disclosure. Therefore, the description in this section should be read from this perspective and should not be understood as an admission of what is in the prior art or what is not in the prior art.

[0003] The network function (NF) of a mobile communication network can provide an event publishing service as a service producer, enabling another NF as a service consumer to subscribe to event notifications and receive notifications regarding the events. For example, the access and mobility management function (AMF) as a producer in a 5G network can provide such a service to another NF as a consumer, such as the session management function (SMF) and the unified data management (UDM).

[0004] The event publishing service may include three basic operations: a subscribe operation, a notify operation, and an unsubscribe operation. As an example, taking the AMF in a 5G network as the producer of the event publishing service and another NF as the consumer of the event publishing service in the 5G network, the three basic operations are described below.

[0005] I. Subscribe Operation The subscribe operation is initiated by the NF service consumer to the AMF when the NF service consumer needs to create a subscription to monitor at least one event related to the AMF. The NF service consumer may subscribe to multiple events in the subscription. The subscription may be associated with one UE, a group of UEs, or any UE. The NF service consumer uses an HTTP POST method specifying the URI of the subscription collection to request the creation of a new subscription.

[0006] An example of the subscribe operation between the NF service consumer and the AMF is shown in Figure 1.

[0007] In step 1 of Figure 1, the NF service consumer (101) sends a POST request to create a subscription resource within the AMF (102). The payload body of the POST request contains the representation of the individual subscription resource to be created. The request represents the time for which it is desired to keep the subscription active, after which the subscribed events will stop generating reports, and may include an expiration time proposed as a hint by the NF service consumer (101).

[0008] If successful, in step 2a of Figure 1, the request is accepted and the AMF (102) includes in the response message an HTTP location header providing the location of the newly created resource (subscription) along with a status code 201 indicating that the requested resource has been created. If the NF service consumer (101) includes multiple events in the event subscription and some events fail to subscribe, the AMF (102) accepts the message and provides in the AmfEventSubscription the events that have been successfully subscribed.

[0009] On failure or redirect, at step 2b of Figure 1, one of the HTTP status codes is returned. In the case of a 4xx / 5xx response, the message body contains a ProblemDetails structure that includes the "cause" attribute set to one of the application errors.

[0010] II. Notification operation The notification service operation is initiated by the AMF to send a notification towards the notification URI when a specific event included in the subscription occurs. The AMF uses the HTTP POST method with, for example, the subscription ID, the event ID of the occurred event, the notification correlation ID provided by the NF service consumer at the time of event subscription, and uses the notification URI received at the time of subscription creation.

[0011] An example of the notification operation between the NF service consumer and the AMF is shown in Figure 2.

[0012] At step 1 of Figure 2, the AMF (202) sends a POST request to send a notification.

[0013] If successful, at step 2a of Figure 2, "204 No content" is returned by the NF service consumer (201).

[0014] On failure or redirect, at step 2b of Figure 2, an appropriate HTTP status code indicating an error (e.g., "403 Forbidden") is returned, and appropriate additional error information is returned.

[0015] III. Unsubscribe operation The unsubscribe service operation is initiated by the NF service consumer to the AMF, and the AMF deletes the existing subscriptions previously created by the NF service consumer. The NF service consumer unsubscribes from the subscription using an HTTP DELETE method specifying the URI of the individual subscription resource to be deleted.

[0016] An example of the notification operation between the NF service consumer and the AMF is shown in Figure 3.

[0017] In step 1 of Figure 3, the NF service consumer (301) sends a delete request to delete the existing subscription resource of the AMF (302).

[0018] If successful, in step 2a of Figure 3, the request is accepted, and the AMF (302) responds with a response message with a status code of 204 indicating that the resource identified by the subscription ID has been successfully deleted.

[0019] In case of failure or redirection, in step 2b of Figure 3, one of the HTTP status codes is returned. In the case of a 4xx / 5xx response, the message body contains a ProblemDetails structure including a "cause" attribute set to one of the application errors.

[0020] In addition to providing the event publishing service, when both the AMF and the UDM support the "ESSYNC" function as defined in 3GPP (registered trademark) Technical Specification (TS) 29.518, if the UE-specific event subscription from the UDM is available in the UE context, the AMF may start synchronizing the event subscription with the UDM for a specific UE during the mobility registration procedure from the Evolved Packet System (EPS) to the 5th Generation System (5GS).

[0021] To start the synchronization of event subscriptions, when sending a notification of subscription change to the UDM, the AMF needs to include event subscription information in the notification request. If a subscription change notification is not required, for example, when the UE registers with the same AMF after moving from the evolved packet system (EPS), the AMF may send the notification to the subscription change notification URI. The notification request in this case includes only the event subscription information and does not include the event report list.

[0022] The AMF includes only the active event subscriptions for a specific UE from the UDM event publishing service in the event subscription information, that is, subscriptions targeting a specific UE (not a group of UEs or any UE) and only each subscribed event with a reference ID (i.e., the "refId" field defined in "Table 6.2.6.2.3-1: Definition of type AmfEvent" in TS29.518). For each active subscription, the following information is included. - The URI of the subscription resource within the AMF; - The notification correlation ID of the subscription; - A list of one reference ID for each event within the subscription; - Optionally, if the subscription ID is changed during a mobility procedure, the URI of the old subscription resource on the source AMF.

[0023] When the UDM receives the event subscription information from the AMF, the UDM uses the reference ID and the notification correlation ID to compare the active event subscriptions of the AMF with the active UDM event publishing subscriptions and performs the following. - If an event is detected by the AMF but does not exist in the AMF, the UDM subscribes to the event in the AMF by creating a new AMF event subscription or updating an existing AMF event subscription. - If the event exists in the AMF but not in the UDM, the UDM unsubscribes from the events from the AMF by deleting or updating the AMF event subscription.

[0024] According to the latest version of TS29.518, the reference ID is specifically designed for event monitoring subscriptions from the UDM, but other NFs cannot be excluded from using it for internal AMF event subscriptions.

Summary of the Invention

Problems to be Solved by the Invention

[0025] In some cases, it is necessary to subscribe to events for the UE's PDU session. Therefore, a first NF operating as a consumer of the event publishing service in a mobile communication network may send a request to a second NF operating as a producer of the event publishing service to subscribe to events for the UE's PDU session. The request to subscribe to events for the PDU session may be triggered by the first NF itself or by another NF according to traffic requirements, operator requirements, and / or other requirements defined by the technical specifications of the mobile communication network.

[0026] However, the inventors of the present disclosure have found that the following problems exist when the first NF wants to subscribe to the same event for multiple PDU sessions of the same UE.

[0027] The first NF operating as a consumer sends requests to the second NF operating as a producer to subscribe to the same event for each of the multiple PDU sessions of the UE, that is, multiple requests are sent from the first NF to the second NF. When an event occurs, the second NF sends multiple reports of the same event to the first NF, which causes waste of resources, for example.

[0028] For example, in a SMF that manages PDU sessions in a 5G network, one UE can have M PDU sessions. When the SMF wants to subscribe to the same events of the M PDU sessions of a UE from the AMF in the 5G network, the SMF sends M requests to the AMF, and the AMF sends M reports of the same event to the SMF, resulting in the following reasons: (1) Increase in the exchange of messages between the SMF and the AMF. (2) Increase in the traffic load between the AMF and the SMF. (3) Increase in the CPU resources consumed by the AMF for generating and sending reports of the same event. (4) Increase in the CPU resources consumed by the SMF for receiving and processing reports of the same event.

[0029] One of the objectives of the present disclosure is to solve or mitigate the above problems.

Means for Solving the Problems

[0030] According to a first aspect of the present disclosure, the objective is achieved by a method in a first NF that implements a consumer of an event publishing service provided by a second network function (NF) that implements a producer of the event publishing service. The method includes receiving a trigger for subscribing to an event of a protocol data unit (PDU) session of a user equipment (UE), assigning a UE-specific event ID to the event if the event does not have an event identifier (ID) assigned thereto, and sending a first request for subscribing to the event, including the event ID, to the second NF, and saving a mapping between the event ID and the ID of the PDU session.

[0031] According to a second aspect of the present disclosure, the object is achieved by a first network function (NF) that implements a consumer of an event publishing service provided by a second NF that implements a producer of the event publishing service. The first NF includes a receiving unit that receives a trigger for subscribing to an event of a protocol data unit (PDU) session of a user equipment (UE), and an assigning and transmitting unit that, when an event identifier (ID) is not assigned to the event, assigns a UE-specific event ID to the event and transmits a first request for subscribing to the event, including the event ID, to the second NF, and a storing unit that stores a mapping between the event ID and the ID of the PDU session.

[0032] According to a third aspect of the present disclosure, the object is achieved by a first NF that includes a processor and a memory storing instructions. When the instructions are executed by the processor, the first NF is caused to receive a trigger for subscribing to an event of a protocol data unit (PDU) session of a user equipment (UE), assign a UE-specific event ID to the event when an event identifier (ID) is not assigned to the event, transmit a first request for subscribing to the event, including the event ID, to the second NF, and store a mapping between the event ID and the ID of the PDU session.

[0033] According to a fourth aspect of the present disclosure, the object is achieved by a machine-readable medium storing instructions that, when executed by the first NF, cause the first NF to execute the method according to the first aspect.

[0034] According to a fifth aspect of the present disclosure, the object is achieved by a method in a second network function (NF) implementing a producer that provides an event publishing service to a first NF implementing a consumer of the event publishing service. The method includes receiving, from the first NF, a request for subscribing to an event, including an event ID of the event; storing the event ID; and when the event occurs, sending, to the first NF, a report of the event including the event ID.

[0035] According to a sixth aspect of the present disclosure, the object is achieved by a second NF implementing a producer that provides an event publishing service to a first NF implementing a consumer of the event publishing service. The second NF includes a receiving unit that receives, from the first NF, a request for subscribing to an event, including an event ID of the event; a storage unit that stores the event ID; and a sending unit that, when the event occurs, sends, to the first NF, a report of the event including the event ID.

[0036] According to a seventh aspect of the present disclosure, the object is achieved by a second NF including a processor and a memory storing instructions. When the instructions are executed by the processor, the second NF is caused to receive, from the first NF, a request for subscribing to an event, including an event ID of the event; store the event ID; and when the event occurs, send, to the first NF, a report of the event including the event ID.

[0037] According to an eighth aspect of the present disclosure, the object is achieved by a machine-readable medium storing instructions that, when executed in the second NF, cause the second NF to execute the method according to the fifth aspect.

[0038] According to a ninth aspect of the present disclosure, the present disclosure also provides a method in a second network function (NF) implementing a producer that provides an event publishing service to a first NF implementing a consumer of the event publishing service. The method includes receiving, from the first NF, a request to subscribe to an event; transmitting, to the first NF, a report of the event when the event occurs; and notifying, to a third NF, subscription information of the event when the third NF operates as a new producer that provides the event publishing service. The first NF is a session management function (SMF) or a first UDM, the second NF is an access and mobility management function (AMF), the third NF is another AMF, and when the another AMF and a second UDM both support an "ESSYNC" function, the subscription information further includes an indicator indicating whether the another AMF needs to synchronize the event subscription with the second UDM, and the second UDM is the first UDM or another UDM.

[0039] According to a tenth aspect of the present disclosure, the present disclosure also provides a second network function (NF) implementing a producer that provides an event publishing service to a first NF implementing a consumer of the event publishing service. The second NF includes a receiving unit configured to receive, from the first NF, a request to subscribe to an event; a transmitting unit configured to transmit, to the first NF, a report of the event when the event occurs; and a notifying unit configured to notify, to a third NF, subscription information of the event when the third NF operates as a new producer that provides the event publishing service. The first NF is a session management function (SMF) or a first UDM, the second NF is an access and mobility management function (AMF), the third NF is another AMF, and when the another AMF and a second UDM both support an "ESSYNC" function, the subscription information further includes an indicator indicating whether the another AMF needs to synchronize the event subscription with the second UDM, and the second UDM is the first UDM or another UDM.

[0040] According to an eleventh aspect of the present disclosure, the present disclosure also provides a second network function (NF) implementing a producer that provides an event publishing service to a first NF implementing a consumer of the event publishing service. The second NF includes a processor and a memory storing instructions. When the instructions are executed by the processor, the second NF is caused to receive, from the first NF, a request to subscribe to an event, send a report of the event to the first NF when the event occurs, and notify a third NF of subscription information of the event when the third NF operates as a new producer providing the event publishing service. The first NF is a session management function (SMF) or a first UDM, the second NF is an access and mobility management function (AMF), the third NF is another AMF, and when the other AMF and a second UDM both support an "ESSYNC" function, the subscription information further includes an indicator indicating whether the other AMF needs to synchronize the event subscription with the second UDM. The second UDM is the first UDM or another UDM.

[0041] According to a twelfth aspect of the present disclosure, the present disclosure also provides a machine-readable medium storing instructions that, when executed in a second NF, cause the second NF to execute the method according to the ninth aspect.

[0042] According to the present invention, when it is necessary to subscribe to the same event in a plurality of sessions, the first NF sends only one request, and the second NF sends only one report of the event when the event occurs. Thus, the exchange of messages and traffic between the two NFs is reduced, and waste of resources such as saving CPU resources in each of the two NFs is reduced.

[0043] The above and other aspects, features, and advantages of the present disclosure will become more fully apparent from the following detailed description with reference to the accompanying drawings. In the drawings, like reference numerals or letters are used to indicate 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.

Brief Description of the Drawings

[0044]

Figure 1

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Modes for Carrying Out the Invention

[0045] With reference to the accompanying drawings, embodiments of the present disclosure will be described in more detail below. However, the embodiments of this specification can be embodied in many different forms and should not be construed as limiting the scope of the appended patent claims.

[0046] The terms used in this specification are for the sole purpose of describing particular embodiments and are not intended to be limiting. The singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used in this specification, the terms "comprising", "including" and / or "having" identify the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0047] Also, the mere use of ordinal numbers such as "first", "second", "third", etc. in this specification to modify elements is not intended to indicate any priority, the rank of one element relative to another, or the chronological order in which method operations are performed, but is used only as a label to distinguish an element having a particular name from another element having the same name for the purpose of differentiating elements (except for the use of ordinal numbers).

[0048] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification have the same meaning as commonly understood. Further, the terms used in this specification should be interpreted as having a meaning consistent with their meaning in the context of this specification and the related art, and should not be interpreted in an ideal or overly formal sense unless clearly defined in this specification.

[0049] A flowchart of the method in the first NF implementing a consumer of the event publishing service provided by the second NF implementing a producer of the event publishing service is shown in FIG. 4. The method 400 includes step 401 of receiving a trigger for subscribing to an event of a PDU session of a UE, and step 402 of, if the event does not have an event ID assigned thereto, assigning a UE-specific event ID to the event and transmitting a first request for subscribing to the event, including the event ID, to the second NF, and step 403 of storing a mapping between the event ID and the ID of the PDU session.

[0050] In one embodiment, method 400 further includes receiving, from a second NF, a report of an event including an event ID, and transferring the report to one or more PDU sessions of a UE subscribing to the event according to a mapping between the event ID and an ID of one or more PDU sessions of the UE.

[0051] In one embodiment, method 400 further includes receiving a trigger for unsubscribing from an event of a PDU session of a UE, deleting a mapping between the event ID and an ID of the PDU session of the unsubscribed event, and if there is no mapping between the event ID and the ID of the PDU session in a first NF, deleting the event ID and sending a second request for unsubscribing from the event to a second NF.

[0052] In one embodiment, the mapping is stored in a mapping table of the first NF.

[0053] In one embodiment, the first NF is an SMF or a UDM, and the second NF is an AMF.

[0054] In a further embodiment, the first request is a Namf_EventExposure_Subscribe request, the report is carried in a Namf_EventExposure_Notify request, and the second request is a Namf_EventExposure_UnSubscribe request.

[0055] In a further embodiment, the event ID is carried in an existing "refId" field or a newly defined field in the Namf_EventExposure_Subscribe request and the report.

[0056] The flowchart of method 500 in the second normal form (2NF) that implements a producer that provides an event publishing service to a consumer that implements an event publishing service in the first normal form (1NF) includes step 501 of receiving, from the 1NF, a request to subscribe to an event that includes the event ID of the event, step 502 of saving the event ID, and step 503 of sending, to the 1NF, a report of the event that includes the event ID when the event occurs.

[0057] In one embodiment, method 500 further includes notifying the third normal form (3NF) of subscription information of an event that includes the event ID when the 3NF operates as a new producer that provides the event publishing service.

[0058] In one embodiment, the 1NF is the session management function (SMF) or the first unified data management (UDM), and the 2NF is the access and mobility management function (AMF).

[0059] In a further embodiment, the request is a Namf_EventExposure_Subscribe request, and the report is carried in a Namf_EventExposure_Notify request.

[0060] In a further embodiment, the event ID is carried in an existing "refId" field or a newly defined field in the Namf_EventExposure_Subscribe request and the report.

[0061] In a further embodiment, the 3NF is another AMF, and the subscription information includes the event ID in an existing "refId" field.

[0062] In a further embodiment, when another AMF and the second unified data management (UDM) both support an "ESSYNC" function, the subscription information further includes an indicator indicating that it is not necessary to synchronize the subscription of the event with the second UDM, and the second UDM may be the first UDM, or the second UDM may be different from the first UDM.

[0063] Both the 1st NF and the 2nd NF can be implemented as network elements on dedicated hardware, as software instances or firmware executed on the hardware, as virtualized functions instantiated on a suitable platform (such as a cloud infrastructure), or as any combination thereof.

[0064] Here, as shown in FIG. 6, further embodiments related to the SMF (as a consumer) and the AMF (as a producer) in a 5G network will be described. Although the further embodiments herein are described in relation to the SMF, the AMF, and the 5G network, it can be understood that if the same problem exists in the mechanism for requesting subscriptions for multiple sessions of one UE, the embodiments can also be applied to other NFs and / or other mobile communication networks. Also, although specific terms are used in the embodiments, it is understood that the embodiments are not limited to those specific terms and can be applied to all similar entities. For example, the "user equipment" / "UE" herein may refer to, for example, a user terminal, a station, a terminal, a terminal node, etc.

[0065] FIG. 6 shows an example of processing and signaling exchange in the 1st NF and the 2nd NF according to the present disclosure. The SMF (601) is an example of the 1st NF, and the AMF (602) is an example of the 2nd NF. Note that in FIG. 6, only two PDU sessions are used as an example, but this does not mean that at most two PDU sessions can be involved in the present invention. The present invention can include more PDU sessions, and the maximum number of PDU sessions of a UE depends on 3GPP (registered trademark) restrictions such as (1) the maximum number of PDU sessions of one UE defined by 3GPP (registered trademark), and (2) the number of PDU sessions of one UE connected to the same SMF at the same time.

[0066] I. An event is subscribed to for the UE's PDU session for the first time. Step 1: The SMF, which is a consumer of the event publishing service, receives a trigger to subscribe to an event of the UE's PDU session (in this example, its ID is "session_id1"). The trigger may come from the SMF itself or from another NF according to traffic requirements, operator requirements, and / or other requirements defined by the technical specifications of the mobile communication network.

[0067] Step 2: The SMF determines whether an event ID is currently assigned to the event. In this example, the event is subscribed for the first time. Therefore, the SMF detects that no event ID is currently assigned to the event, assigns an event ID unique to the UE for that event (in this example, "identifier1"), and saves the mapping between the event ID and the ID of the PDU session, for example, in a mapping table. Each ID of the PDU session uniquely identifies one session of the same UE within the same consumer or one session of the same UE, and is, for example, a PDU session ID defined by 3GPP (registered trademark) or any privately defined identifier. It can be understood that the mapping can be stored in a data structure different from the mapping table. In any case, as is clear from Figure 6, the mapping table stores the mapping between "identifier1" and "session_id1".

[0068] Step 3: The SMF sends a first request to subscribe to the event to the AMF, which is a producer of the event publishing service. The first request includes the event ID. In this example, the first request can be a Namf_EventExposure_Subscribe request. In a further embodiment, the event ID is carried in an existing "refId" field or a newly defined field of the Namf_EventExposure_Subscribe request.

[0069] In the example of FIG. 6, note that although the saving of the mapping between the event ID and the PDU session ID is performed before sending the first request, the saving of the mapping can be performed after sending the first request. The order of saving and sending does not affect the technical effect of the present invention.

[0070] Step 4: The AMF can accept the first request by sending a response to the SMF, and the event ID may or may not be included in the response. In this example, the response can be a Namf_EventExposure_Subscribe response. When the present invention is applied to other mobile communication networks, there may be no such response.

[0071] II. The same event is subscribed in another PDU session of the same UE. Step 5: The SMF receives another trigger for subscribing to the same event in another PDU session of the same UE (in this example, its ID is "session_id2").

[0072] Step 6: The SMF discovers that an event ID is assigned to the event, that is, the SMF previously subscribed to the same event from the AMF for this UE. Therefore, the SMF does not need to send another request to the AMF to subscribe to the event, and only needs to save the mapping between the event ID and the PDU session ID in, for example, a mapping table, which can reduce signaling. As described above, the mapping can be saved in a data structure different from the mapping table. In any case, as is clear from FIG. 6, the mapping table stores the mapping between "identifier1" and {"session_id1", "session_id2"}.

[0073] III. The AMF sends a report of the event to the SMF. Step 7: If an event occurs, the AMF sends a report of the event to the SMF. The report includes an event ID (in this example, "identifer1"). In this example, the report can be carried in a Namf_EventExposure_Notify request. In a further embodiment, the event ID is carried in an existing "refId" field or a newly defined field within the report.

[0074] According to the present disclosure, since the event ID is unique to the UE, it can be understood that if a plurality of event IDs have been previously assigned to events of PDU sessions from a plurality of UEs, there may be a plurality of event IDs in the report.

[0075] Step 8: The SMF can confirm receipt of the report by sending a response to the AMF. In this example, the response can be a Namf_EventExposure_Notify response. When the present invention is applied to other mobile communication networks, there may be no such response.

[0076] IV. The SMF forwards the event report to the corresponding PDU session. Step 9: The SMF uses the event ID (in this example, "identifer1") in the report received from the AMF and the local mapping table to determine the PDU session targeted by the report. In this example, the report containing the event ID "identifer1" is for the PDU sessions with IDs "session_id1" and "sesson_id2" according to the mapping table.

[0077] If there are multiple event IDs in the report, the SMF uses each event ID and the corresponding mapping table to determine the PDU session targeted by the report.

[0078] Step 10: The SMF transfers the report to the corresponding PDU session. In this example, the report is transferred to the PDU session with the ID "session_id1" and the PDU session with the ID "sesson_id2".

[0079] Compared with the per-session subscription, since there is only one report from the AMF for events of multiple PDU sessions of one UE, signaling can be saved. When M PDU sessions share the same event subscription, the signaling overhead of the report can be reduced by only (M - 1) / M.

[0080] V. The event of the UE's PDU session is unsubscribed. Step 11: The SMF receives a trigger to unsubscribe from the events of the UE's PDU session (in this example, its ID is "session_id1"). The trigger may come from the SMF itself or from another NF according to traffic requirements, operator requirements, and / or other requirements defined by the technical specifications of the mobile communication network.

[0081] Step 12: The SMF deletes the mapping between the event ID (in this example, "identifier1") and the ID of the PDU session from which the event is unsubscribed (in this example, "session_id1"), for example, in this example, by deleting the PDU session ID "session_id1" from the mapping table. Thus, only the mapping between the event ID "identifier1" and the session ID "session_id2" is retained in the mapping table.

[0082] Compared with the per-session subscription, in this situation, there is no need to send a request to the AMF to unsubscribe from the event, so the signaling overhead for unsubscription can be reduced.

[0083] VI. The AMF sends further reports of the event to the SMF. Step 13: If the event occurs again, the AMF sends a further report of the event to the SMF. The further report includes an event ID (in this example, "identifer1"). In this example, the further report can be carried in a Namf_EventExposure_Notify request. In a further embodiment, the event ID is carried in an existing "refId" field or a newly defined field within the further report.

[0084] According to the present disclosure, since the event ID is unique to the UE, it can be understood that if multiple event IDs have been previously assigned to events of PDU sessions from multiple UEs, multiple event IDs may exist in the further report.

[0085] Step 14: The SMF can confirm the receipt of the further report by sending a response to the AMF. In this example, the response can be a Namf_EventExposure_Notify response. When the present invention is applied to other mobile communication networks, there may be no such response.

[0086] VII. The SMF forwards the report of the further event to the corresponding PDU session. Step 15: The SMF uses the event ID (in this example, "identifer1") in the further report received from the AMF and the local mapping table to determine the PDU session targeted by the further report. In this example, according to the mapping table, the further report containing the event ID "identifer1" targets only the PDU session with the ID "sesson_id2".

[0087] If there are multiple event IDs in the further report, the SMF uses each event ID and the corresponding mapping table to determine the PDU session targeted by the further report.

[0088] Step 16: The SMF forwards the additional report to the PDU session that corresponds to it. In this example, the additional report is only forwarded to the PDU session with the ID "session_id2". VII. Events of another PDU session of the UE are unsubscribed.

[0089] Step 17: The SMF receives a trigger for unsubscribing events of another PDU session of the UE (in this example, its ID is "session_id2"). The trigger may come from the SMF itself or from another NF according to traffic requirements, operator requirements, and / or other requirements defined by the technical specifications of the mobile communication network.

[0090] Step 18: The SMF deletes the mapping between the event ID (in this example, "identifier1") and the ID of the PDU session for which the event is unsubscribed (in this example, "session_id2"). For example, in this example, the SMF deletes the ID of the PDU session "session_id2" from the mapping table. Thus, there is no mapping regarding the event ID "identifier1" in the mapping table of this example. If the SMF determines that there is no mapping regarding the event ID "identifier1" in the mapping table, the SMF also needs to delete the event ID (in this example, "identifier1").

[0091] Step 19: Since there is no PDU session that needs to subscribe to the event, the SMF sends a second request for unsubscribing the event to the AMF. In this example, the second request may be a Namf_EventExposure_UnSubscribe request.

[0092] Step 20: The AMF may accept the second request by sending a response to the AMF. In this example, the response may be a Namf_EventExposure_UnSubscribe response. When the present invention is applied to other mobile communication networks, there may be no such response.

[0093] It can be understood that when the third NF operates as a new producer providing an event exposure service, the second NF needs to notify the third NF of the subscription information of the event including the event ID. For example, when a new AMF operates as a new producer providing an event exposure service, the AMF needs to notify the new AMF of the subscription information of the event including the event ID. The third NF (i.e., the new producer) may operate in the same manner as the second NF. For example, the new producer also stores the event ID and, when an event occurs, sends a report including the event ID of the event to the first NF.

[0094] However, when the 1st NF is an NF other than the UDM, for example, when the 1st NF is the SMF, if the subscription information includes the event ID in the existing "refId" field and both the new AMF and the UDM support the "ESSYNC" function, and the new AMF determines that the "refId" field is not empty, the new AMF may initiate unnecessary synchronization of event subscriptions with the UDM for a specific UE. To avoid this unnecessary subscription synchronization, the subscription information may further include an indicator for the new AMF indicating that it is not necessary to synchronize the event subscription with the UDM. For example, a new information element (IE) "eventSyncInd" may be defined in the "AmfEventSubscription" type specified in 3GPP (registered trademark) TS29.518 as an indicator. The value "true" of the IE "eventSyncInd" means that event subscription synchronization with the UDM is performed in the subscription, and the absence of the IE "eventSyncInd" or the value "false" of the IE "eventSyncInd" may mean that event subscription synchronization with the UDM is not necessary in the subscription. Therefore, the absence of "eventSyncInd" in the IE or the IE "eventSyncInd" with the value "false" can be used as an indicator to the new AMF indicating that it is not necessary to synchronize the event subscription with the UDM. Further, according to some traffic requirements, when both the new AMF and the UDM support the "ESSYNC" function and the 1st NF is the UDM or another UDM, the new AMF needs to initiate synchronization of event subscriptions with the UDM. In this case, the indicator in the subscription information needs to be set to a value indicating that the new AMF synchronizes the event subscription with the UDM (for example, the value of the IE "eventSyncInd" is set to "true"). In any case, when the 3rd NF is the new AMF, the subscription information may optionally include an indicator indicating whether the new AMF needs to synchronize the event subscription with the UDM.

[0095] FIG. 7 shows a schematic block of the first NF 700 according to the present disclosure. The first NF 700 implements a consumer of an event publishing service provided by a second NF that implements a producer of the event publishing service. The first NF 700 may include a receiving unit 701 that receives a trigger for subscribing to an event of a PDU session of a UE, and an assigning and transmitting unit 702 that, when an event ID is not assigned to an event, assigns a UE-specific event ID to the event and transmits a first request for subscribing to the event, including the event ID, to the second NF, and a storage unit 703 that stores a mapping between the event ID and the ID of the PDU session.

[0096] FIG. 8 shows a schematic block of the second NF 800 according to the present disclosure. The second NF 800 implements a producer that provides an event publishing service to a first NF that implements a consumer of the event publishing service. The second NF 800 may include a receiving unit 801 that receives a request for subscribing to an event, including the event ID of the event, from the first NF, a storage unit 802 that stores the event ID, and a transmitting unit 803 that transmits a report of the event, including the event ID, to the first NF when the event occurs.

[0097] Since the first NF 700 and the second NF 800 described in this specification can be implemented by various units, each of the first NF 700 and the second NF 800 that implements one or more functions described in the embodiments may include not only the units shown in the corresponding figures but also other units for implementing one or more of those functions. Further, each of the first NF 700 and the second NF 800 may include a single unit configured to execute two or more functions, or separate units for separate functions. Further, the units may be implemented in hardware, firmware, software, or any combination thereof.

[0098] It is understood that the blocks of the block diagram and / or flowchart, and the combinations of blocks in the block diagram and / or flowchart, can be implemented by computer program instructions. These computer program instructions are provided to the processor of a general-purpose computer, a special-purpose computer, and / or other programmable data processing devices, and execute the instructions via the processor of the computer and / or other programmable data processing devices to generate a machine that creates means for realizing the functions / operations specified by the block diagram and / or flowchart blocks.

[0099] Furthermore, the solution of the present disclosure may take the form of a computer program on a memory having computer-usable or computer-readable program code incorporated in a medium used by or related to an instruction execution system. In the context of this document, the memory can be any medium adapted to store, contain, or transmit a program used by or related to an instruction execution system, apparatus, or device.

[0100] Therefore, the present disclosure also provides a first NF 900 including a processor 901 and a memory 902, as shown in FIG. 9. In the first NF 900, when the memory 902 is executed by the processor 901, it stores instructions for causing the first NF 900 to execute the method of the first NF described in the above embodiments. The present disclosure also provides a second NF 1000 including a processor 1001 and a memory 1002, as shown in FIG. 10. In the second NF 1000, when the memory 1002 is executed by the processor 1001, it stores instructions for causing the second NF 1000 to execute the method of the second NF described in the above embodiments.

[0101] The present disclosure also provides a machine-readable medium (not shown) that stores instructions for causing the first NF to execute the method of the first NF described in the above embodiments when executed on the first NF. The present disclosure also provides a machine-readable medium (not shown) that stores instructions for causing the second NF to execute the method of the second NF described in the above embodiments when executed on the second NF.

[0102] Although this specification contains many details of specific implementations, these should not be construed as limitations on the scope of the implementation or the claimed subject matter, but rather as descriptions of features specific to particular embodiments of a specific implementation. Specific features described herein in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment can be implemented separately in multiple embodiments or in any suitable sub-combination. Furthermore, features may be described above as acting in a particular combination and may even initially be claimed as such, but one or more features from the claimed combination may, in some cases, be deleted from that combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0103] As technology progresses, it will be apparent to those skilled in the art that the concepts of the present invention can be implemented in various ways. The above-described embodiments are provided for illustration purposes rather than to limit the present disclosure, and it should be understood that those skilled in the art can rely on modifications and changes without departing from the spirit and scope of the present disclosure. Such modifications and variations are considered to be within the scope of the present disclosure and the appended claims. The protection scope of the present disclosure is defined by the appended claims.

[0104] In fact, according to the present disclosure, the inventors have proposed several changes to the following content of 3GPP (registered trademark) TS29.518, and the changes are indicated by bold and underlined text.

[0105] "5.3.2.2.2 Creation of Subscription The subscription service operation is initiated by an NF service consumer, such as the NEF, towards the AMF when there is a need to create a subscription for the NF service consumer to monitor at least one event related to the AMF. The NF service consumer may subscribe to multiple events with a single subscription. The subscription may be associated with one UE, a group of UEs, or any UE. The NF service consumer requests the creation of a new subscription by using an HTTP POST method specifying the URI of the subscription collection. See clause 6.2.3.2. The NF service consumer shall include the following information in the HTTP message body. - NF ID indicating the identifier of the network function instance that starts the subscription; - Subscription target indicating the target to be monitored by one of the following types: - A specific UE identified by SUPI, PEI, or GPSI; - A group of UEs identified by a group identifier; - Any UE identified by the "anyUE" flag. - Notification URI indicating the address to which event notifications generated by the subscription are delivered; - Notification correlation ID indicating the correlation identifier carried in the event notifications generated by the subscription; - A list of events to be subscribed to; - Event type for each event as defined in clause 5.3.1. The NF service consumer may include the following information in the HTTP message body. - Per-event immediate report flag indicating an immediate report generated in the current event state; - Event trigger indicating how the event is reported (one-time report or continuous report); - Report maximum number that defines the maximum number of reports until the event subscription no longer exists; - Expiration date that defines the maximum period until the event subscription no longer exists; - Sampling rate that defines a random subset of UEs among the target UEs, and the AMF will report only events related to the selected subset of UEs; - Per-event periodic report flag indicating that reports are generated periodically; - Repetition period that defines the period of periodic reports; - Per-applicable-event event filter that defines additional options regarding the report method of events; - Per-event reference ID indicating the value of the reference ID associated with the event to be monitored. If specified, the reference ID is included in the report triggered by the event.

[0106]

Table 1

[0107] 1. The NF service consumer sends a POST request to create a subscription resource within the AMF. The payload body of the POST request contains the representation of the individual subscription resources to be created. The request includes the expiration date, which is the time that the subscription is desired to be kept active and after which the subscribed events will stop generating reports, and can be proposed as a hint by the NF service consumer. 2a. If successful, the request is accepted and the AMF includes in the response message an HTTP location header providing the location of the newly created resource (subscription), together with a status code 201 indicating that the requested resource has been created. If the NF service consumer includes multiple events in the event subscription and some of the events fail to subscribe, the AMF accepts the message and provides, in the AmfEventSubscription, the events that have been successfully subscribed. If the NF service consumer includes an immediateFlag with a value of "true" in the event subscription, the AMF includes, if available, the current state of the subscribed events (for example, if the subscribed event is LOCATION_REPORT, the last known location information is included). If an event with immediateFlag set to "true" is subscribed by the NF service consumer instead of the 3NF and the notification is sent directly to the 3NF, that is, if the subsChangeNotifyUri is included in the event subscription, the current state of the subscribed event is not included in the response. The AMF then sends a notification including the current state of the subscribed events to the 3NF. If the NF service consumer sets the event report option to ONE_TIME and the AMF includes the current state of the subscribed events in the response, the AMF shall not perform subsequent event notifications for the events specified in the AmfCreateEventSubscription parameter. If the NF service consumer sets the event report option to ONE_TIME, sets the subscribed event to LOCATION_REPORT, and the immediateFlag is set to false or does not exist, the AMF sends an event notification to notify the current location of the UE after subscription. The response is an expiration determined by the AMF based on the operator's policy and taking into account the expiration included in the request, and the subscription becomes invalid after this expiration. If the NF service consumer wants to continue receiving notifications after the expiration of the subscription, the AMF needs to create a new subscription. The AMF should not set the same expiration for many subscriptions to avoid all subscriptions expiring at the same time and the subscriptions being recreated. If the expiration is not included in the response, the NF service consumer considers the subscription to be valid without an expiration. If the subscription includes a sampling rate ("sampRatio") attribute, the AMF selects a random subset of UEs from the target UEs according to the sampling rate and reports only the events related to the selected subset of UEs. If both the AMF and the NF consumer (i.e., the UDM) support the "ESSYNC" function and the subscription targets a specific UE, the AMF locally includes an "eventSyncInd" IE with the value "true" in the created subscription. The "eventSyncInd" IE is not included in the event subscription sent to the NF consumer. If the new AMF supports the "ESSYNC" function, the "eventSyncInd" IE with the value "true" is included in the UE context during the AMF - to - AMF mobility procedure. 2b. In case of failure or redirect, one of the HTTP status codes listed in Table 6.2.3.2.3.1-3 is returned. In case of a 4xx / 5xx response, the message body includes a ProblemDetails structure with the "cause" attribute set to one of the application errors listed in Table 6.2.3.2.3.1-3. 5.3.2.4.2 Event Subscription Synchronization for a Specific UE When both the AMF and the UDM support the "ESSYNC" function, the AMF can start the synchronization of the event subscription with the UDM for a specific UE during the mobility registration procedure from EPS to 5GS if the UE-specific event subscription from the UDM is available in the UE context (see clause 4.11.5.2 of 3GPP (registered trademark) TS23.502 [3]). To start the synchronization of event subscriptions, when sending a notification of subscription change to the UDM, the AMF shall include the event subscription information in the notification request. If a subscription change notification is not required (e.g., when the UE registers with the same AMF after moving from EPS), the AMF may send the notification to the subscription change notification URI. The notification request in this case shall include only the event subscription information and not include the event report list. The AMF shall include in the event subscription information only the active event subscriptions that are subject to event subscription synchronization with the UDM (determined according to the definition in clause 5.3.2.2.2). For each active subscription, include the following information: - The URI of the subscription resource in the AMF; - The notification correlation ID of the subscription - A list of one reference ID for each event in the subscription - Optionally, if the subscription ID is changed during a mobility procedure, the URI of the old subscription resource on the source AMF. When the UDM receives the event subscription information from the AMF, the UDM shall use the reference ID and the notification correlation ID to compare the active event subscriptions in the AMF with the active UDM event publication subscriptions and perform the following: - If an event is detected by the AMF but does not exist in the AMF, the UDM shall subscribe to the event in the AMF by creating a new AMF event subscription or updating an existing AMF event subscription; - If an event exists in the AMF but does not exist in the UDM, the UDM shall unsubscribe from the event from the AMF by deleting or updating the AMF event subscription.

[0108]

Table 2

Table 3

[0109] 6.2.8 Functional Negotiation The functional negotiation mechanism defined in clause 6.6 of 3GPP (Registered Trademark) TS29.500 [4] is used (if it exists) to negotiate the optional functions applicable to the Namf_EventExposure service between the AMF and the NF service consumer. If the NF service consumer has optional functions supported for the Namf_EventExposure service, it shall indicate them by including the supportedFeatures attribute in the payload of the HTTP request message for subscription resource creation. The AMF determines the functions supported in the service operation and indicates the supported functions by including the supportedFeatures attribute in the payload of the HTTP response for subscription resource creation, as defined in clause 6.6 of 3GPP (Registered Trademark) TS29.500 [4]. The syntax of the supportedFeatures attribute is defined in clause 5.2.2 of 3GPP (Registered Trademark) TS29.571 [6]. The following functions are defined for the Namf_EventExposure service.

[0110]

Table 4

[0111]

Table 5

[0112]

Table 6

Table 7

Table 8

[0113]

Table 9

Table 10

Table 11

Claims

1. A method (400) in a first network function (NF) implementing a consumer of the event publishing service, provided by a second NF implementing a producer of the event publishing service, comprising: Receiving (401) a trigger for subscribing to an event of a protocol data unit (PDU) session of a user equipment (UE); If an event identifier (ID) is not assigned to the event, assigning an event ID unique to the UE to the event, and sending (402) a first request for subscribing to the event, including the event ID, to the second NF; Storing (403) a mapping between the event ID and the ID of the PDU session; A method comprising the above.

2. The method (400) according to claim 1, further comprising: Receiving from the second NF a report of the event, including the event ID; Forwarding the report to one or more PDU sessions of the UE subscribing to the event according to the mapping between the event ID and the ID of the one or more PDU sessions; A method comprising the above.

3. The method (400) according to claim 1 or 2, further comprising: Receiving a trigger for unsubscribing from the event of the PDU session of the UE; Deleting the mapping between the event ID and the ID of the PDU session of the unsubscribed event; If there is no mapping between the event ID and the ID of the PDU session in the first NF, deleting the event ID and sending a second request for unsubscribing from the event to the second NF; A method comprising the above.

4. The method (400) according to any one of claims 1 to 3, wherein The mapping is stored in a mapping table of the first NF.

5. The method (400) according to any one of claims 1 to 4, wherein The first NF is a session management function (SMF) or an integrated data management (UDM), and the second NF is an access and mobility management function (AMF).

6. The method (400) according to claim 5, wherein The first request is a Namf_EventExposure_Subscribe request, the report is carried in a Namf_EventExposure_Notify request, and the second request is a Namf_EventExposure_UnSubscribe request, method.

7. The method (400) according to claim 6, wherein the event ID is carried in an existing "refId" field or a newly defined field of the Namf_EventExposure_Subscribe request and the report, method.

8. A method (500) in a second NF implementing a producer providing the event exposure service to a first NF implementing a consumer of the event exposure service, receiving (501) from the first NF a request for subscribing to the event, including an event ID of the event, storing (502) the event ID, and transmitting (503) to the first NF a report of the event, including the event ID, when the event occurs, method including.

9. The method (500) according to claim 8, further including, notifying the third NF of subscription information of the event, including the event ID, when the third NF operates as a new producer providing the event exposure service, method including.

10. The method (500) according to claim 8 or 9, wherein the first NF is a session management function (SMF) or unified data management (UDM), and the second NF is an access and mobility management function (AMF), method.

11. The method (500) according to claim 10, wherein the request is a Namf_EventExposure_Subscribe request, and the report is carried in a Namf_EventExposure_Notify request, method.

12. The method (500) according to claim 11, wherein the event ID is carried in an existing "refId" field or a newly defined field of the Namf_EventExposure_Subscribe request and the report, method.

13. The method (500) according to any one of claims 10 to 12 when dependent on claim 9, The method wherein the third NF is another AMF, and the subscription information includes the event ID in the existing "refId" field.

14. The method (500) according to claim 13, wherein when the other AMF and the unified data management (UDM) both support the "ESSYNC" function, the subscription information further includes an indicator indicating that it is not necessary to synchronize the subscription of the event with the UDM.

15. A method in a second NF implementing a producer that provides the event publishing service to a first network function (NF) implementing a consumer of the event publishing service, receiving, from the first NF, a request to subscribe to an event; transmitting, when the event occurs, a report of the event to the first NF; notifying, when a third NF operates as a new producer that provides the event publishing service, the subscription information of the event to the third NF; comprising wherein the first NF is a session management function (SMF) or a first UDM, the second NF is an access and mobility management function (AMF), the third NF is another AMF, and when the other AMF and a second UDM both support the "ESSYNC" function, the subscription information further includes an indicator indicating whether the other AMF needs to synchronize the subscription of the event with the second UDM, and the second UDM is the first UDM or another UDM.

16. The method according to claim 15, wherein a first value of the indicator indicates that the other AMF does not need to synchronize the subscription of the event with the second UDM, and a second value of the indicator indicates that the other AMF needs to synchronize the subscription of the event with the second UDM.

17. The method according to claim 16, wherein when the first NF is the SMF, the subscription information includes the indicator having the first value.

18. The method according to claim 16 or 17, wherein when the first NF is the first UDM, the subscription information includes the indicator having the second value.

19. The method according to any one of claims 16 to 18, wherein the indicator is an "eventSyncInd" information element (IE). **Claim 20** The method according to any one of claims 16 to 19, wherein the first value is "false" and the second value is "true". **Claim 21** A first NF (900) implementing a consumer of an event publishing service provided by a second network function (NF) implementing a producer of the event publishing service, comprising a processor (901), and a memory (902) storing instructions that, when executed by the processor, cause the first NF to execute the method according to any one of claims 1 to 7. The first NF comprising the above. **Claim 22** A machine-readable medium storing instructions that, when executed by a first NF, cause the first NF to execute the method according to any one of claims 1 to 7. **Claim 23** A second NF (1000) implementing a producer of an event publishing service that provides the event publishing service to a first NF implementing a consumer of the event publishing service, comprising a processor (1001), and a memory (1002) storing instructions that, when executed by the processor, cause the second NF to execute the method according to any one of claims 8 to 20. The second NF comprising the above. **Claim 24** A machine-readable medium storing instructions that, when executed by a second NF, cause the second NF to execute the method according to any one of claims 8 to 20.

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