WO2022214695A1

WO2022214695A1 - Network nodes and methods therein for handling group event

Info

Publication number: WO2022214695A1
Application number: PCT/EP2022/059538
Authority: WO
Inventors: Qian Chen; Yunjie Lu; Juying GAN
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-04-09
Filing date: 2022-04-08
Publication date: 2022-10-13
Also published as: AR125671A1

Abstract

The present disclosure provides a method (200) in a Network Exposure Function, NEF. The method (200) includes: transmitting (210), to a Unified Data Management, UDM, a first request to modify a subscription for an event associated with a group of User Equipments, UEs. The first request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

Description

NETWORK NODES AND METHODS THEREIN FOR HANDLING GROUP

EVENT

TECHNICAL FIELD The present disclosure relates to communication technology, and more particularly, to network nodes and methods therein for handling a group event.

BACKGROUND

The 3^rd Generation Partnership Project (3GPP) Technical Specification (TS) 23.501 , V17.0.0, which is incorporated herein by reference in its entirety, specifies the 5^th Generation (5G) system architecture. Fig. 1 A shows the 5G system architecture with service-based interfaces and Fig. 1 B shows the 5G system architecture using the reference point representation. As shown, the 5G system architecture includes, but not limited to, the following Network Functions (NFs): - Authentication Server Function (AUSF)

Access and Mobility Management Function (AMF)

Data Network (DN), e.g. operator services, Internet access or 3rd party services

Network Exposure Function (NEF) - Network Repository Function (NRF)

Network Slice Specific Authentication and Authorization Function (NSSAAF) Network Slice Selection Function (NSSF)

Policy Control Function (PCF)

Session Management Function (SMF) - Unified Data Management (UDM)

User Plane Function (UPF)

Application Function (AF)

User Equipment (UE)

(Radio) Access Network ((R)AN) - Service Communication Proxy (SCP).

For further details of the NFs, services, and reference points shown in Figs. 1A and 1 B, reference can be made to Section 4.2 of TS 23.501. The 3GPP TS 23.502, V17.0.0, which is incorporated herein by reference in its entirety, specifies subscription, cancellation, and reporting for a group event in Section 4.15.3.2.3. In the case of a group event, the same event is monitored for a group of UEs. For a UE belonging to a group configured with an active monitoring event, the UE’s event monitoring may be cancelled or terminated due to reasons such as: the UEs’ subscription is deleted from a UDM while the monitoring event is active, the UE’s authorization for the monitoring event is revoked, the UE’s event monitoring is cancelled (e.g., cancellation initiated by an AF or cancellation as a result of the UE moving to an AMF not supporting the event monitoring), or the UE is removed from the group.

It is desired to provide dynamic group management in this case, such that the group event can be handled properly.

SUMMARY

It is an object of the present disclosure to provide network nodes and methods therein, capable of handling a group event properly, e.g., when a UE belonging to a group configured with the group event has its event monitoring cancelled or terminated.

According to a first aspect of the present disclosure, a method performed by an NEF is provided. The method includes: transmitting, to a UDM, a first request to modify a subscription for an event associated with a group of UEs. The first request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

In an embodiment, the first request may be an Nudm_EventExposure_Subscribe request.

In an embodiment, the method may further include: receiving, from the UDM, a first response containing a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained; and updating a total remaining number of reports for the group based on the total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained.

In an embodiment, the first response may be an Nudm_EventExposure_Subscribe response.

In an embodiment, the method may further include: receiving, from the UDM or an AMF, a notification message containing a remaining number of reports for one of the one or more UEs for which the event is to be terminated; and updating a total remaining number of reports for the group based on the remaining number of reports for the one UE.

In an embodiment, the notification message may be an Nudm_EventExposure_Notify message or an Namf_EventExposure_Notify message.

In an embodiment, the method may further include: receiving, from an AF, a second request to modify the subscription for the event associated with the group of UEs, the second request indicating the one or more UEs in the group for which the event is to be terminated or the one or more UEs in the group for which the event is to be maintained. The first request may be transmitted in response to receiving the second request.

In an embodiment, the second request may be an Nnef_EventExposure_Subscribe request.

According to a second aspect of the present disclosure, a method performed by a UDM is provided. The method includes: receiving, from an NEF, a first request to modify a subscription for an event associated with a group of UEs. The first request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

In an embodiment, the first request may be an Nudm_EventExposure_Subscribe request. In an embodiment, the method may further include: transmitting, to the NEF, a first response containing a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained.

In an embodiment, the method may further include: transmitting, to each of one or more AMFs, a third request to modify the subscription for the event associated with the group of UEs, the third request indicating the one or more UEs in the group for which the event is to be terminated or the one or more UEs in the group for which the event is to be maintained.

In an embodiment, the method may further include: receiving, from each of the one or more AMFs, a third response containing a total remaining number of reports for at least one UE served by the AMF in the group for which the event is to be terminated or at least one UE served by the AMF in the group for which the event is to be maintained; determining a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained, based on the total remaining number of reports received from each of the one or more AMFs; and transmitting, to the NEF, a first response containing the total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained.

In an embodiment, the third request may be an Namf_EventExposure_Subscribe request.

In an embodiment, the third response may be an Namf_EventExposure_Subscribe response.

In an embodiment, the method may further include: transmitting, to the NEF, a notification message containing a remaining number of reports for one of the one or more UEs for which the event is to be terminated. In an embodiment, the notification message may be an Nudm_EventExposure_Notify message.

According to a third aspect of the present disclosure, a method performed by an AMF is provided. The method includes: receiving, from a UDM, a third request to modify a subscription for an event associated with a group of UEs. The third request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

In an embodiment, the method may further include: transmitting, to the UDM, a third response containing a total remaining number of reports for at least one UE served by the AMF in the group for which the event is to be terminated or at least one UE served by the AMF in the group for which the event is to be maintained.

In an embodiment, the method may further include: transmitting, to an NEF, a notification message containing a remaining number of reports for one UE served by the AMF, out of the one or more UEs, for which the event is to be terminated.

In an embodiment, the notification message may be an Namf_EventExposure_Notify message.

According to a fourth aspect of the present disclosure, a method performed by an AF is provided. The method includes: transmitting, to an NEF, a second request to modify a subscription for an event associated with a group of UEs. The second request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained. In an embodiment, the second request may be an Nnef_EventExposure_Subscribe request.

According to a fifth aspect of the present disclosure, a method performed by a UDM is provided. The method includes: transmitting, to an AMF, a request to modify a subscription for an event associated with a group of UEs, the request indicating one UE served by the AMF in the group for which the event is to be terminated; and transmitting, to an NEF, a notification message containing a remaining number of reports for the one UE for which an event associated with the group event is to be terminated.

In an embodiment, the request may be an Nudm_SDM_Notification request or an Nudm_UECM_DeregistrationNotification request, and/or the notification message may be an Nudm_EventExposure_Notify message.

According to a sixth aspect of the present disclosure, a method performed by an AMF is provided. The method includes: receiving, from a UDM, a request to modify a subscription for an event associated with a group of UEs, the request indicating one UE served by the AMF in the group for which the event is to be terminated; and transmitting, to an NEF, a notification message containing a remaining number of reports for the one UE.

In an embodiment, the request may be an Nudm_SDM_Notification request or an Nudm_UECM_DeregistrationNotification request, and/or the notification message may be an Namf_EventExposure_Notify message.

According to a seventh aspect of the present disclosure, a method performed by an NEF is provided. The method includes: receiving, from a UDM or an AMF, a notification message containing a remaining number of reports for a UE, in a group of UEs, for which an event associated with the group is to be terminated; and updating a total remaining number of reports for the group based on the remaining number of reports for the UE.

In an embodiment, the notification message may be an Nudm_EventExposure_Notify message or an Namf_EventExposure_Notify message. According to an eighth aspect of the present disclosure, a network node is provided. The network node includes a communication interface, a processor and a memory. The memory contains instructions executable by the processor whereby the network node is operative to, when implementing an NEF, perform the method according to the above first or seventh aspect, or when implementing a UDM, perform the method according to the above second or fifth aspect, or when implementing an AMF, perform the method according to the above third or sixth aspect, or when implementing an AF, perform the method according to the above fourth aspect.

According to a ninth aspect of the present disclosure, a computer-readable storage medium is provided. The computer-readable storage medium has computer-readable instructions stored thereon. The computer-readable instructions, when executed by a processor of a network node, configure the network node to, when implementing an NEF, perform the method according to the above first or seventh aspect, or when implementing a UDM, perform the method according to the above second or fifth aspect, or when implementing an AMF, perform the method according to the above third or sixth aspect, or when implementing an AF, perform the method according to the above fourth aspect.

With the embodiments of the present disclosure, a request to modify a subscription for an event associated with a group of UEs can indicate one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained, such that a network node receiving the request can handle the event properly, e.g., without cancelling the entire group event.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages will be more apparent from the following description of embodiments with reference to the figures, in which:

Figs. 1 A and 1 B are schematic diagrams showing 5G system architectures;

Fig. 2 is a flowchart illustrating a method in an NEF according to an embodiment of the present disclosure; Fig. 3 is a flowchart illustrating a method in a UDM according to an embodiment of the present disclosure;

Fig. 4 is a flowchart illustrating a method in an AMF according to an embodiment of the present disclosure;

Fig. 5 is a sequence diagram showing an exemplary information flow according to an embodiment of the present disclosure;

Fig. 6 is a flowchart illustrating a method in an AF according to an embodiment of the present disclosure;

Fig. 7 is a sequence diagram showing an exemplary information flow according to an embodiment of the present disclosure;

Fig. 8 is a flowchart illustrating a method in a UDM according to another embodiment of the present disclosure;

Fig. 9 is a flowchart illustrating a method in an AMF according to another embodiment of the present disclosure;

Fig. 10 is a flowchart illustrating a method in an NEF according to another embodiment of the present disclosure;

Fig. 11 is a sequence diagram showing an information flow according to another embodiment of the present disclosure;

Fig. 12 is a block diagram of a network node according to an embodiment of the present disclosure;

Fig. 13 is a sequence diagram showing a procedure for an NF service consumer to subscribe to notifications;

Fig. 14 is a sequence diagram showing a procedure for an NF service consumer to update a subscription; and Fig. 15 is a sequence diagram showing a procedure for subscription for creation.

DETAILED DESCRIPTION

References in the specification to "one embodiment," "an embodiment," "an example embodiment," and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic.

Moreover, such phrases are not necessarily referring to the same embodiment.

Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It shall be understood that although the terms "first" and "second" etc. 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, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed terms. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "has", "having", "includes" and/or "including", when used herein, specify the presence of 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.

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

Fig. 2 is a flowchart illustrating a method 200 according to an embodiment of the present disclosure. The method 200 can be performed in an NEF.

At block 210, a first request (e.g., an Nudm_EventExposure_Subscribe request) to modify a subscription for an event associated with a group of UEs is transmitted to a UDM. The first request indicates one or more UEs in the group for which the event is to be terminated. Alternatively, the first request indicates one or more UEs in the group for which the event is to be maintained (meaning that the event is to be terminated for other UEs in the group).

In an example, the NEF may then receive, from the UDM, a first response (e.g., an Nudm_EventExposure_Subscribe response) containing a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained. The NEF can then update a total remaining number of reports for the group based on the total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained. For example, assuming the total remaining number of reports for the group currently maintained at the NEF is Cnef and the first response contains the total remaining number, Ct, of reports for the one or more UEs for which the event is to be terminated, the NEF can update Cnef as Cnef=Cnef-Ct. When the first response contains the total remaining number, Cm, of reports for the one or more UEs for which the event is to be maintained, the NEF can update Cnef as Cnef=Cm.

In another example, the NEF may receive, from the UDM (e.g., when the event is monitored by the UDM itself) or an AMF (e.g., when the event is monitored by the AMF), a notification message containing a remaining number of reports for one of the one or more UEs for which the event is to be terminated. Here, the notification message may be an Nudm_EventExposure_Notify message (from the UDM) or an Namf_EventExposure_Notify message (from the AMF). The NEF can then update a total remaining number of reports for the group based on the remaining number of reports for the one UE, e.g., each time such notification message is received. For example, assuming the total remaining number of reports for the group currently maintained at the NEF is Cnef and the notification message indicates the remaining number Ctp of reports for the one UE, the NEF can update Cnef as Cnef=Cnef-Ctp.

In an example, the NEF may receive, from an AF, a second request (an Nnef_EventExposure_Subscribe request) to modify the subscription for the event associated with the group of UEs. The second request may indicate the one or more UEs in the group for which the event is to be terminated or the one or more UEs in the group for which the event is to be maintained (meaning that the event is to be terminated for other UEs in the group). The first request in the block 210 may be transmitted in response to receiving the second request. In other words, the modification is initiated by the AF in this case.

Fig. 3 is a flowchart illustrating a method 300 according to an embodiment of the present disclosure. The method 300 can be performed in a UDM. At block 310, a first request (e.g., an Nudm_EventExposure_Subscribe request) to modify a subscription for an event associated with a group of UEs is received from an NEF. The first request indicates one or more UEs in the group for which the event is to be terminated. Alternatively, the first request indicates one or more UEs in the group for which the event is to be maintained (meaning that the event is to be terminated for other UEs in the group).

In an example, e.g., when the event is monitored by one or more AMFs (e.g., each serving at least one of the UEs in the group), the UDM may transmit, to each of the one or more AMFs, a third request (e.g., an

Namf_EventExposure_Subscribe request) to modify the subscription for the event associated with the group of UEs. The third request indicates the one or more UEs in the group for which the event is to be terminated or the one or more UEs in the group for which the event is to be maintained.

In an example, the UDM may then transmit, to the NEF, a first response (e.g., an Nudm_EventExposure_Subscribe response) containing a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained. For example, when the event is monitored by the UDM itself, the UDM can determine the total remaining number of reports and notify the NEF of the total remaining number of reports directly. Alternatively, when the event is monitored by the one or more AMFs, the UDM may receive, from each of the one or more AMFs, a third response (e.g., an Namf_EventExposure_Subscribe response) containing a total remaining number of reports for at least one UE served by the AMF in the group for which the event is to be terminated or at least one UE served by the AMF in the group for which the event is to be maintained. The UDM can then determine a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained, based on the total remaining number of reports received from each of the one or more AMFs, and transmit, to the NEF, a first response (e.g., an Nudm_EventExposure_Subscribe response) containing the total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained. For example, assuming the total remaining number of reports for the group currently maintained at the UDM is Cudm, and the total remaining number of reports for the UE(s) served by AMF (for i=l, 2, K, where K is the number of AMFs to which the third request is transmitted) in the group for which the event is to be terminated is Ct the UDM can determine the total remaining number of reports for the one or more UEs for which the event is to be terminated as Ct =

Ct and transmit to the NEF the first response containing Ct (or containing Cm=Cudm-Ct ). In another example, assuming the total remaining number of reports for the UE(s) served by AMF/ (for i=l, 2, K, where K is the number of AMFs to which the third request is transmitted) in the group for which the event is to be maintained is Cm the UDM can determine the total remaining number of reports for the one or more UEs for which the event is to be terminated as Ct =

Ct and transmit to the NEF the first response containing Cm (or containing Ct=Cudm-Cm).

In another example, e.g., when the event is monitored by the UDM itself, the UDM may transmit, to the NEF, a notification message (e.g., an Nudm_EventExposure_Notify message) containing a remaining number of reports for one of the one or more UEs for which the event is to be terminated.

Fig. 4 is a flowchart illustrating a method 400 according to an embodiment of the present disclosure. The method 400 can be performed in an AMF.

At block 410, a third request (e.g., an Namf_EventExposure_Subscribe request) to modify a subscription for an event associated with a group of UEs is received from a UDM. The third request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained (meaning that the event is to be terminated for other UEs in the group).

In an example, the AMF may transmit, to the UDM, a third response (e.g., an Namf_EventExposure_Subscribe response) containing a total remaining number of reports for at least one UE served by the AMF in the group for which the event is to be terminated or at least one UE served by the AMF in the group for which the event is to be maintained.

In another example, the AMF can transmit, to an NEF, a notification message (e.g., an Namf_EventExposure_Notify message) containing a remaining number of reports for one UE served by the AMF, out of the one or more UEs, for which the event is to be terminated.

The above methods 200-400 will be further explained with reference to Fig. 5, which shows an exemplary information flow according to an embodiment of the present disclosure. The procedure is used by the NEF to subscribe to or modify event notifications and to explicitly cancel a previous subscription. Cancelling is done by sending Nudm_EventExposure_Unsubscribe request identifying the subscription to cancel. The notification steps 4 and 5 are not applicable in cancellation case.

Step 1. The NEF subscribes to one or several monitoring events by sending Nudm_EventExposure_Subscribe request. The NEF subscribes to one or several Event(s) (identified by Event ID) and provides the associated notification endpoint of the NEF.

Event Reporting Information defines the type of reporting requested. If the reporting event subscription is authorized by the UDM, the UDM records the association of the event trigger and the requester identity.

The subscription may include Maximum number of reports and/or Maximum duration of reporting IE.

If event notifications for some group members of a previously accepted group event are removed (e.g., AF removes certain UEs from a group), the NEF provides impacted (removed or retained) UE information (e.g., Subscriber Permanent Identifier (SUPI), Mobile Station Integrated Services Digital Network Number (MSISDN) or External Identity) to the UDM via

Nudm_EventExposure_Subscribe without cancelling the entire group event. The UDM shall trigger an extra Nudm_EventExposure_Notify as described in Step 4a to report the remaining number of reports for the impacted UEs. As an alternative, the UDM may include the remaining number of reports for the impacted UEs in the Nudm_EventExposure_Subscribe response as specified in Step 3 and skip 4a. Step 2a. [Conditional] Some events require that the UDM sends Namf_EventExposure_Subscribe request to the AMF serving that UE. As the UDM itself is not the Event Receiving NF, the UDM shall additionally provide the notification endpoint of itself besides the notification endpoint of NEF. Each notification endpoint is associated with the related (set of) Event ID(s). This is to assure the UDM can receive the notification of subscription change related event

The UDM sends the Namf_EventExposure_Subscribe request to all serving AMF(s) (if subscription applies to a UE or a group of UE(s)), or to all the AMF(s) in the same Public Land Mobile Network (PLMN) as the UDM (if subscription applies to any UE).

If the subscription applies to a group of UE(s), the UDM shall include the same notification endpoint of itself, i.e., Notification Target Address (+ Notification Correlation ID), in the subscriptions to all UE's serving AMF(s).

If event notifications for some group members of a previously accepted group event are removed (e.g., the NEF removes certain UEs from a group), the NEF provides impacted (removed or retained) UE information (e.g. SUPI, MSISDN or External Identity) to the UDM via Nnef_EventExposure_Subscribe and Nudm_EventExposure_Subscribe without cancelling the entire group event. The UDM sends Namf_EventExposure_Subscribe with update to the AMF, including the impacted UE information (e.g., SUPI).

Step 2b. [Conditional] The AMF acknowledges the execution of Namf_EventExposure_Subscribe.

The AMF acknowledges the event subscription or update. In case of Namf_EventExposure_Subscribe with update indicating the removal of event notifications for some group members of a previous accepted group event which includes Maximum number of Reports, the AMF shall trigger an extra Namf_EventExposure_Notify as described in Step 4c to report the remaining number of reports for the impacted UEs. As an alternative, the AMF may include the remaining number of reports for the impacted UEs in this Namf_EventExposure_Subscribe response and skip Step 4c. Step 3. The UDM acknowledges the execution of Nudm_EventExposure_Subscribe.

If the subscription is applicable to a group of UE(s) and the Maximum number of reports is included in the Event Report information in Step 1 , the Number of UEs within this group is included in the acknowledgement. As an alternative, the UDM may include the remaining number of reports for the impacted UEs in the Nudm_EventExposure_Subscribe response (either based on the alternative information from the AM F in Step 2b for AM F generated event, or its own local information for UDM generated event).

Steps 4a - 4b. [Conditional - depending on the Event] The UDM detects the monitored event occurs and sends the event report, by means of Nudm_EventExposure_Notify message, to the associated notification endpoint of the NEF, along with the time stamp. The NEF may store the information in the Unified Data Repository (UDR) along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.

In case of removal of event notifications for some group members of a previous accepted group event which includes Maximum number of Reports, the UDM shall cancel the event notification for the impacted UEs and trigger Nudm_EventExposure_Notify to report the remaining number of reports for the impacted UEs.

Step 4c - 4d. [Conditional - depending on the Event] The AMF detects the monitored event occurs and sends the event report, by means of Namf_EventExposure_Notify message, to the associated notification endpoint of the NEF, along with the time stamp. The NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.

If the AMF has a maximum number of reports stored for the UE, the AMF shall decrease its value by one for the reported event.

In a case where Namf_EventExposure_Subscribe with update is received in Step 2a indicating removal of event notifications for some group members of a previous accepted group event which includes Maximum number of Reports, the AMF shall cancel the event notification for the impacted UEs and trigger the Namf_EventExposure_Notify to report the remaining number of reports for the impacted UEs.

For both Step 4a and Step 4c, when the maximum number of reports is reached and if the subscription is applied to a UE, the NEF unsubscribes the monitoring event(s) to the UDM and the UDM unsubscribes the monitoring event(s) to the AMF serving that UE.

For both Step 4a and Step 4c, when the maximum number of reports is reached for an individual group member UE, the NEF uses the Number of UEs received in Step 3 to determine if reporting for the group is complete. If the NEF determines that reporting for the group is complete, the NEF unsubscribes the monitoring event(s) to the UDM and the UDM unsubscribes the monitoring event(s) to all AMF(s) serving the UEs belonging to that group. If the NEF receives the remaining number for reports from the UDM or the AMF in Step 4a or 4c, or alternatively from Step 3, the NEF reduces/recalculates the maximum number of reports for the group events based on the received remaining number of reports for the impacted UEs.

When the Maximum duration of reporting expires in the NEF, the UDM and the AMF, then each of these nodes shall locally unsubscribe the monitoring event.

Step 5. [Conditional - depending on the Event] The AMF detects the subscription change related event occurs, e.g., Subscription Correlation ID change due to AMF reallocation or addition of new Subscription Correlation ID due to a new group UE registered, it sends the event report by means of Namf_EventExposure_Notify message to the associated notification endpoint of the UDM.

Fig. 6 is a flowchart illustrating a method 600 according to an embodiment of the present disclosure. The method 600 can be performed in an AF.

At block 610, a second request (e.g., an Nnef_EventExposure_Subscribe request) to modify a subscription for an event associated with a group of UEs is transmitted to an NEF. The second request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained (meaning that the event is to be terminated for other UEs in the group).

The above methods 200-400 and 600 will be further explained with reference to Fig. 7, which shows an exemplary information flow according to an embodiment of the present disclosure. The procedure is used by the AF to subscribe to or modify event notifications and to explicitly cancel a previous subscription. Cancelling is done by sending Nnef_EventExposure_Unsubscribe request identifying the subscription to cancel with Subscription Correlation ID. The notification steps 6 to 8 are not applicable in cancellation case.

Step 1. The AF subscribes to one or several Event(s) (identified by Event ID) and provides the associated notification endpoint of the AF by sending Nnef_EventExposure_Subscribe request.

Event Reporting Information defines the type of reporting requested (e.g. one time reporting, periodic reporting or event based reporting, for Monitoring Events). If the reporting event subscription is authorized by the NEF, the NEF records the association of the event trigger and the requester identity. The subscription may also include Maximum number of reports and/or Maximum duration of reporting IE.

Step 2. [Conditional - depending on authorization in Step 1] The NEF subscribes to received Event(s) (identified by Event ID) and provides the associated notification endpoint of the NEF to the UDM by sending Nudm_EventExposure_Subscribe request. The NEF maps the AF-ldentifier into Data Network Name (DNN) and Single Network Slice Selection Assistance Information (S-NSSAI) combination based on local configuration, and include DNN, S-NSSAI in the request.

If the reporting event subscription is authorized by the UDM, the UDM records the association of the event trigger and the requester identity. Otherwise, the UDM continues in Step 4 indicating failure. If event notifications for some group members of a previously accepted group event are removed (e.g., the AF removes certain UEs from a group), the AF provides impacted (removed or retained) UE information (e.g. MSISDN or External Identity) to the UDM via Nnef_EventExposure_Subscription and Nudm_EventExposure_Subscribe without cancelling the entire group event. The UDM shall trigger an extra Nudm_EventExposure_Notify as described in Step 6a to report the remaining number of reports for the impacted UEs. As an alternative, the UDM may include the remaining number of reports for the impacted UEs in the Nudm_EventExposure_Subscribe response as specified Step 4 and Skip 6a.

Step 3a. [Conditional] If the requested event (e.g. monitoring of Loss of Connectivity) requires AMF assistance, then the UDM sends the Namf_EventExposure_Subscribe to the AMF serving the requested user. The UDM sends the Namf_EventExposure_Subscribe request to the all serving AMF(s) (if subscription applies to a UE or a group of UE(s)), or all the AMF in the same PLMN as the UDM (if subscription applies to any UE).

As the UDM itself is not the Event Receiving NF, the UDM shall additionally provide the notification endpoint of itself besides the notification endpoint of the NEF. Each notification endpoint is associated with the related (set of) Event ID(s). This is to assure the UDM can receive the notification of subscription change related event.

If the subscription applies to a group of UE(s), the UDM shall include the same notification endpoint of itself, i.e., Notification Target Address (+ Notification Correlation Id), in the subscriptions to all UE's serving AM F(s).

If event notifications for some group members of a previously accepted group event are removed (e.g., the AF removes certain UEs from a group), the AF provides impacted (removed or retained) UE information (e.g. MSISDN or External Identity) to the UDM via Nnef_EventExposure_Subscribe and Nudm_EventExposure_Subscribe without cancelling the entire group event. The UDM sends Namf_EventExposure_Subscribe with update, including the impacted UE information (e.g., SUPI). Step 3b. [Conditional] The AMF acknowledges the execution of Namf_EventExposure_Subscribe.

The AMF acknowledges the event subscription or update. In case of Namf_EventExposure_Subscribe with update indicating the removal of event notifications for some group members of a previous accepted group event which includes Maximum number of Reports, the AMF shall trigger an extra Namf_EventExposure_Notify as described in Step 6c to report the remaining number of reports for the impacted UEs. As an alternative, the AMF may include the remaining number of reports for the impacted UEs in the Namf_EventExposure_Subscribe response and skip Step 6c.

Step 3c. [Conditional] If the requested event (e.g. Protocol Data Unit (PDU) Session Status) requires SMF assistance, then the UDM sends the Nsmf_EventExposure_Subscribe Request message to each SMF where at least one UE identified in Step 2 has a PDU session established. The NEF notification endpoint received in Step 2 is included in the message.

Step 3d. [Conditional] The SMF acknowledges the execution of Nsmf_EventExposure_Subscribe.

Step 4. [Conditional] The UDM acknowledges the execution of Nudm_EventExposure_Subscribe.

If the subscription is applicable to a group of UE(s) and the Maximum number of reports is included in the Event Report information in Step 1 , the Number of UEs is included in the acknowledgement. As an alternative, the UDM may include the remaining number of reports for the impacted UEs in the Nudm_EventExposure_Subscribe response (either based on the alternative information from the AMF in Step 3b for AMF generated event, or its own local information for UDM generated event).

Step 5. The NEF acknowledges the execution of Nnef_EventExposure_Subscribe to the requester that initiated the request. Step 6a - 6b. [Conditional - depending on the Event] The UDM (depending on the Event) detects the event occurs and sends the event report, by means of Nudm_EventExposure_Notify message to the associated notification endpoint of the NEF along with the time stamp. The NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.

Step 6c - 6d. [Conditional - depending on the Event] The AMF detects the event occurs and sends the event report, by means of

Namf_EventExposure_Notify message to associated notification endpoint of the NEF along with the time stamp. The NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.

If the AMF has a maximum number of reports stored for the UE or the individual member UE, the AMF shall decrease its value by one for the reported event.

In a case where Namf_EventExposure_Subscribe with update is received in Step 3a indicating removal of event notifications for some group members of a previous accepted group event which includes Maximum number of Reports, the AMF shall cancel the event notification for the impacted UEs and trigger the Namf_EventExposure_Notify to report the remaining number of reports for the impacted UEs.

For both Step 6a and Step 6c, when the maximum number of reports is reached and if the subscription is applied to a UE, the NEF unsubscribes the monitoring event(s) to the UDM and the UDM unsubscribes the monitoring event(s) to AMF serving for that UE. For both Step 6a and Step 6c, when the maximum number of reports is reached for an individual group member UE, the NEF uses the Number of UEs received in Step 4 to determine if reporting for the group is complete. If the NEF determines that reporting for the group is complete, the NEF unsubscribes the monitoring event(s) to the UDM and the UDM unsubscribes the monitoring event(s) to all AMF(s) serving the UEs belonging to that group. If the NEF receives remaining number for reports from the UDM or the AMF in Step 6a or 6c, or alternatively from Step 4, the NEF reduces/recalculates the maximum number of reports for the group events based on the received remaining number of reports for the impacted UEs.

Step 6e - 6f. [Conditional - depending on the Event] When the SMF detects a subscribed event, the SMF sends the event report, by means of Nsmf_EventExposure_Notify message, to the associated notification endpoint of the NEF provided in Step 3c. The NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.

Step 7. [Conditional - depending on the Event in Steps 6a-6f] The NEF forwards to the AF the reporting event received by either Nudm_EventExposure_Notify and/or Namf_EventExposure_Notify. In the case of the PDU Session Status event, the NEF maps it to a PDN Connectivity Status notification when reporting to the AF.

Step 8. [Conditional - depending on the Event] The AMF detects the subscription change related event occurs, e.g., Subscription Correlation ID change due to AMF reallocation or addition of new Subscription Correlation ID due to a new group UE registered, it sends the event report, by means of Namf_EventExposure_Notify message to the associated notification endpoint of the UDM.

Fig. 8 is a flowchart illustrating a method 800 according to an embodiment of the present disclosure. The method 800 can be performed in a UDM. At block 810, a request to modify a subscription for an event associated with a group of UEs is transmitted to an AMF. The request indicates one UE served by the AMF in the group for which the event is to be terminated. Here, the request may be an Nudm_SDM_Notification request (e.g., when the UE is changed from one internal group to another due to e.g., Operation and Maintenance (O&M) reasons) or an Nudm_UECM_DeregistrationNotification request (e.g., when subscription data of the UE is removed from the UDM).

At block 820, a notification message (e.g., an Nudm_EventExposure_Notify message) is transmitted to an NEF. The notification message contains a remaining number of reports for the one UE for which an event associated with the group event is to be terminated.

Fig. 9 is a flowchart illustrating a method 900 according to an embodiment of the present disclosure. The method 900 can be performed in an AMF.

At block 910, a request to modify a subscription for an event associated with a group of UEs is received from a UDM. The request indicates one UE served by the AMF in the group for which the event is to be terminated. Here, the request may be an Nudm_SDM_Notification request (e.g., when the UE is changed from one internal group to another due to e.g., Operation and Maintenance (O&M) reasons) or an Nudm_UECM_DeregistrationNotification request (e.g., when subscription data of the UE is removed from the UDM).

At block 920, a notification message (e.g., an Namf_EventExposure_Notify message) containing a remaining number of reports for the one UE is transmitted to an NEF.

Fig. 10 is a flowchart illustrating a method 1000 according to an embodiment of the present disclosure. The method 1000 can be performed in an NEF.

At block 1010, a notification message is received from a UDM or an AMF. The notification message contains a remaining number of reports for a UE, in a group of UEs, for which an event associated with the group is to be terminated. Here, the notification message may be an Nudm_EventExposure_Notify message (from the UDM) or an Namf_EventExposure_Notify message (from the AMF).

At block 1020, a total remaining number of reports for the group is updated based on the remaining number of reports for the UE. For example, assuming the total remaining number of reports for the group currently maintained at the NEF is Cnef and the notification message indicates the remaining number Ctp of reports for the UE, the NEF can update Cnef as Cnef=Cnef-Ctp.

The above methods 800-1000 will be further explained with reference to Fig. 11 , which shows an exemplary information flow according to an embodiment of the present disclosure. The procedure is used by the AF to subscribe to or modify event notifications and to explicitly cancel a previous subscription for loss of connectivity and UE reachability.

Step 1. Step 1 to Step 3b of Fig. 7 are performed with the following differences:

For Loss of Connectivity, the subscription request may include Maximum Detection Time.

For UE reachability, the subscription request may include Maximum Latency, Maximum Response Time and/or Suggested number of downlink packets. In Step 3a of Fig. 7, the UDM may include Maximum Response Time in the subscription request to the AMF.

Step 2. [Conditional] If the subscribed periodic registration timer has not been set according to any subscription request, or a Network Configuration, the UDM shall set the subscribed periodic registration timer using the Maximum Detection Time or Maximum Latency; otherwise if the subscribed periodic registration timer was previously set by a different subscription identified by a different Notification Target Address (+ Notification Correlation ID), or set by a different Network Configuration identified by a different NEF reference ID for the same UE, and if the newly received Maximum Detection Time or Maximum Latency is lower than the provided subscribed periodic registration timer, the UDM shall set the subscribed periodic registration timer using the newly received Maximum Detection Time or Maximum Latency. If Nudm_EventExposure_Unsubscribe request is performed in Step 1 , the UDM shall recalculate the subscribed periodic registration timer based on the remaining event subscriptions and/or Network Configurations.

In addition for UE reachability subscription, if the newly received Maximum Response Time is longer than the provided subscribed Active Time (i.e. previously provided Maximum Response Time), the UDM shall set the subscribed Active Time using the newly received Maximum Response Time. If the suggested number of downlink packets is newly received, the UDM shall add the newly received suggested number of downlink packets to the currently used value of suggested number of downlink packets if the aggregated value is within the operator defined range.

If Nudm_EventExposure_Unsubscribe request is performed in Step 1 , the UDM shall recalculate the subscribed Active Time and/or Suggested Number of Downlink Packets based on the remaining event subscriptions and/or Network Configurations.

If the subscribed periodic registration timer or the subscribed Active Time are set or modified, the UDM sends the Nudm_SDM_Notification request to related serving AMF(s). If the AMF receives a subscribed periodic registration timer value from the UDM, it allocates the received value to the UE as the periodic registration timer at subsequent Registration procedure. The AMF starts monitoring of the expiration of the mobile reachable timer for Loss of Connectivity (if required) and starts monitoring of the UE entering connected mode for UE reachability (if required).

If the suggested number of downlink packets are set or modified, the UDM sends the Nudm_SDM_Notification request to related serving SMF(s). The SMF configures the data buffer at the SMF/UPF according the suggested number of downlink packets.

If the provided value is updated by the UDM, the UDM may notify the NEF (which then notifies the AF) of the actual value that is being applied in the 3GPP network. When the UDM changes UE group information (e.g., due to O&M a UE is changed from one internal group to another one), it sends the Nudm_SDM_Notification request to related serving AMF(s) to update the UE group information. In a case where the UE is a group member of a previous accepted group event which includes Maximum number of Reports, the AMF shall cancel the event notification for the impacted UE(s) and trigger the Namf_EventExposure_Notify to report the remaining number of reports for the impacted UE(s) in Step 4 (or Step 6c in Fig. 7) below. In a case where the previous accepted group event is related to the UDM, the UDM can trigger the Nudm_EventExposure_Notify to report the remaining number of reports for the impacted UEs.

When the UDM withdraws subscription data of a UE, it sends the Nudm_UECM_DeregistrationNotification request to related serving AMF(s) to remove the UE. In a case where the UE is a group member of a previous accepted group event which includes Maximum number of Reports, the AMF shall cancel the event notification for the impacted UE(s) and trigger the Namf_EventExposure_Notify to report the remaining number of reports for the impacted UE(s) in Step 4 (or Step 6c in Fig. 7) below, before the UE is removed in AMF. In a case where the previous accepted group event is related to the UDM, the UDM can trigger the Nudm_EventExposure_Notify to report the remaining number of reports for the impacted (UEs).

Step 3. Step 4 to step 5 of Fig. 7 are performed.

Step 4. Step 6c to Step 6d of Fig. 7 are performed with the following differences:

For Loss of Connectivity, the event is detected when the mobile reachability timer expires.

For UE reachability, the event is detected when the UE changes to connected mode or when the UE will become reachable for paging.

Fig. 12 is a block diagram of a network node 1900 according to an embodiment of the present disclosure.

The network node 1200 includes a communication interface 1210, a processor 1220 and a memory 1230. The memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an NEF, perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 2. Particularly, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an NEF: transmit, to a UDM, a first request to modify a subscription for an event associated with a group of UEs. The first request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

In an embodiment, the memory 1230 may further contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing the NEF: receive, from the UDM, a first response containing a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained; and update a total remaining number of reports for the group based on the total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained.

In an embodiment, the memory 1230 may further contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing the NEF: receive, from the UDM or an AMF, a notification message containing a remaining number of reports for one of the one or more UEs for which the event is to be terminated; and update a total remaining number of reports for the group based on the remaining number of reports for the one UE.

In an embodiment, the notification message may be an Nudm_EventExposure_Notify message or an Namf_EventExposure_Notify message. In an embodiment, the memory 1230 may further contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing the NEF: receive, from an AF, a second request to modify the subscription for the event associated with the group of UEs, the second request indicating the one or more UEs in the group for which the event is to be terminated or the one or more UEs in the group for which the event is to be maintained. The first request may be transmitted in response to receiving the second request.

Alternatively, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing a UDM, perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 3. Particularly, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing a UDM: receive, from an NEF, a first request to modify a subscription for an event associated with a group of UEs. The first request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

In an embodiment, the memory 1230 may further contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing the UDM: transmit, to the NEF, a first response containing a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained.

In an embodiment, the memory 1230 may further contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing the UDM: transmit, to each of one or more AMFs, a third request to modify the subscription for the event associated with the group of UEs, the third request indicating the one or more UEs in the group for which the event is to be terminated or the one or more UEs in the group for which the event is to be maintained.

In an embodiment, the memory 1230 may further contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing the UDM: receive, from each of the one or more AMFs, a third response containing a total remaining number of reports for at least one UE served by the AMF in the group for which the event is to be terminated or at least one UE served by the AMF in the group for which the event is to be maintained; determine a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained, based on the total remaining number of reports received from each of the one or more AMFs; and transmit, to the NEF, a first response containing the total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained.

In an embodiment, the memory 1230 may further contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing the UDM: transmit, to the NEF, a notification message containing a remaining number of reports for one of the one or more UEs for which the event is to be terminated.

In an embodiment, the notification message may be an Nudm_EventExposure_Notify message. Alternatively, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an AMF, perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 4. Particularly, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an AMF: receive, from a UDM, a third request to modify a subscription for an event associated with a group of UEs. The third request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

In an embodiment, the memory 1230 may further contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing the AMF: transmit, to the UDM, a third response containing a total remaining number of reports for at least one UE served by the AMF in the group for which the event is to be terminated or at least one UE served by the AMF in the group for which the event is to be maintained.

In an embodiment, the memory 1230 may further contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing the AMF: transmit, to an NEF, a notification message containing a remaining number of reports for one UE served by the AMF, out of the one or more UEs, for which the event is to be terminated.

Alternatively, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an AF, perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 6. Particularly, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an AF: transmit, to an NEF, a second request to modify a subscription for an event associated with a group of UEs. The second request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

Alternatively, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing a UDM, perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 8. Particularly, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing a UDM: transmit, to an AMF, a request to modify a subscription for an event associated with a group of UEs, the request indicating one UE served by the AMF in the group for which the event is to be terminated; and transmit, to an NEF, a notification message containing a remaining number of reports for the one UE for which an event associated with the group event is to be terminated.

Alternatively, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an AMF, perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 9. Particularly, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an AMF: receive, from a UDM, a request to modify a subscription for an event associated with a group of UEs, the request indicating one UE served by the AMF in the group for which the event is to be terminated; and transmit, to an NEF, a notification message containing a remaining number of reports for the one UE. In an embodiment, the request may be an Nudm_SDM_Notification request or an Nudm_UECM_DeregistrationNotification request, and/or the notification message may be an Namf_EventExposure_Notify message.

Alternatively, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an NEF, perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 10. Particularly, the memory 1230 may contain instructions executable by the processor 1220 whereby the network node 1200 is operative to, when implementing an NEF: receive, from a UDM or an AMF, a notification message containing a remaining number of reports for a UE, in a group of UEs, for which an event associated with the group is to be terminated; and update a total remaining number of reports for the group based on the remaining number of reports for the UE.

The present disclosure also provides at least one computer program product in the form of a non-volatile or volatile memory, e.g., a non-transitory computer readable storage medium, an Electrically Erasable Programmable Read-Only Memory (EEPROM), a flash memory and a hard drive. The computer program product includes a computer program. The computer program includes: code/computer readable instructions, which when executed by the processor 1220 causes the network node 1200 to perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 2, 3, 4, 6, 8, 9, or 10.

The computer program product may be configured as a computer program code structured in computer program modules. The computer program modules could essentially perform the actions of the flow illustrated in Fig. 2, 3, 4, 6, 8, 9, or 10.

The processor may be a single CPU (Central Processing Unit), but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuits (ASICs). The processor may also comprise board memory for caching purposes. The computer program may be carried in a computer program product connected to the processor. The computer program product may comprise a non-transitory computer readable storage medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random Access Memory (RAM), a Read-Only Memory (ROM), or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories.

The disclosure has been described above with reference to embodiments thereof. It should be understood that various modifications, alternations and additions can be made by those skilled in the art without departing from the spirits and scope of the disclosure. Therefore, the scope of the disclosure is not limited to the above particular embodiments but only defined by the claims as attached.

The present disclosure further provides the following embodiments based on the 3GPP TS 23.502, V17.0.0. 5.2.2.3.2 Namf_EventExposure_Subscribe service operation

Service operation name: Namf EventExposure Subscribe.

Description: The consumer NF uses this service operation to subscribe to or modify event reporting for one UE, a group of UE(s) or any UE.

Input, Required: NF ID, Target of Event Reporting: UE(s) ID (SUPI or Internal Group Identifier or indication that any UE is targeted), ((set of) Event ID(s) defined in clause 5.2.2.3.1, Notification Target Address (+ Notification Correlation ID))s, Event Reporting Information defined in Table 4.15.1-1.

Input, Optional: (Event Filter (s) associated with each Event ID; Event Filter (s) are defined in clause 5.2.2.3.1, Subscription Correlation ID (in the case of modification of the event subscription), Expiry time. Information of UEs that are removed from the group event. Output, Required: When the subscription is accepted: Subscription Correlation ID (required for management of this subscription), Expiry time (required if the subscription can be expired based on the operator's policy).

Output, Optional: First corresponding event report is included, if available (see clause 4.15.1), Remaing number of reports of impacted UE. The NF consumer subscribes to the event notification by invoking Namf EventExposure to the AMF. The AMF allocates an Subscription Correlation ID for the subscription and responds to the consumer NF with the Subscription Correlation ID. UE ID identifies the UE, SUPI and/or GPSI. Event ID (see clause 4.15.1) identifies the events that the NF consumer is interested in. The Subscription Correlation ID is unique within the AMF Set. The ((set of) Event ID(s), Notification Target Address (+ Notification Correlation ID)) helps the Event Receiving NF to co-relate a notification against a corresponding event subscription for the indicated Event ID.

In the case that the NF consumer subscribes to the AMF on behalf of other NF, the NF consumer include the Notification Target Address(+Notification Correlation ID) of other NF for the Event ID which is to be notified to other NF directly, and the Notification Target Address(+Notification Correlation ID) of itself for the Subscription Correlation ID change event. Each Notification Target Address(+ Notification Correlation ID) is associated with the related (set of) Event ID(s).When the Subscription Correlation ID change due to the AMF reallocation, the notification is sent to NF consumer which triggers this subscription.

Event filter may include "AN type(s)" as part of the list of parameter values to match, and it indicates to subscribe the event per Access Type.

Event receiving NF ID identifies the NF that shall receive the event reporting.

When the consumer NF needs to modify an existing subscription previously created by itself in the AMF, it invokes Namf EventExposure Subscribe service operation which contains the Subscription Correlation ID and the new Event Filters with Event ID to the AMF.

5.2.2.3.3 Namf_EventExposure_UnSubscribe service operation

Service operation name: Namf EventExposure UnSubscribe.

Description: The NF consumer uses this service operation to unsubscribe for a specific event for one UE, group of UE(s), any UE.

Input, Required: Subscription Correlation ID.

Input, Optional: None.

Output, Required: Operation execution result indication Output, Optional: None.

The NF consumer unsubscribes the event notification by invoking Namf EventExposure Unsubscribe (Subscription Correlation ID) to the AMF.

5.2.2.3.4 Namf_EventExposure_Notify service operation

Service operation name: Namf EventExposure Notify.

Service operation description: Provides the previously subscribed event information to the NF Consumer which has subscribed to that event before.

Input, Required: AMF ID (GUAMI), Notification Correlation Information, Event ID, corresponding UE(s) (SUPI(s) and if available GPSI(s)), time stamp.

Input, Optional: Event specific parameter list, Remaing number of reports of impacted UE.

Output, Required: None.

Output, Optional: None.

When the AMF detects a UE access and mobility event corresponding to a Subscription, it invokes Namf EventExposure Notify service operation to the NF consumed» which has subscribed to the UE mobility event before. The event is notified towards the consumers for which the Event filters (which may include "AN type(s)") match. The Notification Target Address (+ Notification Correlation ID) indicates to the Event Receiving NF the specific event notification subscription. The event specific parameter indicates the type of mobility event and related information, e.g. Registration Area Update/new Registration Area.

The optional event specific parameter list provides the values that matched for generating the event notification. The parameter values to match are specified during the event subscription (see clause 5.2.2.3.2). For example if the event type reported is "AN change", the event specific parameter list contains the value of the new AN. 5.2.3.5 Nudm_EventExposure service

5.2.3.5.1 General

See clause 4.15.3.1.

5.2.3.5.2 Nudm_EventExposure_Subscribe service operation

Service operation name: Nudm EventExposure Subscribe

Description: The NF consumer subscribes to receive an event, or if the subscription is already defined in UDM, then the subscription is updated.

NF Consumers: NEF.

Inputs, Required: Target of Event Reporting: UE(s) ID (SUPI or GPSI, Internal Group Identifier or External Group Identifier, or indication that any UE is targeted), Event filter containing the Event Id(s) (see clause 4.15.3.1) and Event Reporting Information defined in Table 4.15.1-1.

Inputs, Optional: Expiry time, DNN, S-NSSAI, traffic descriptor identifying the somce of the downlink IP or Ethernet traffic (for Availability after DDN Failure and downlink data delivery status events). Information of UEs that are removed from the group event.

For configuration of monitoring events applicable to both EPC and 5GC, a combined SCEF+NEF indicates that the monitoring event is also applicable to EPC (i.e. the event must be reported both by 5GC and EPC) and may include a SCEF address (i.e. if the event needs to be configured in a serving node in the EPC and the corresponding notification needs to be sent directly to the SCEF).

Outputs, Required: Operation execution result indication When the subscription is accepted: Subscription Correlation ID, Expiry time (required if the subscription can be expired based on the operator's policy).

Outputs, Optional: First corresponding event report is included, if corresponding information is available (see clause 4.15.1), Number of UE if the External Group Identifier and Maximum Number of Reports are included in the inputs, Remaing number of reports of impacted UE.

Number of UEs indicates the number of UEs within the group identified by the External Group Identifier. The NEF uses this value to determine whether the monitoring event has been reported for all group member UEs.

5.2.3.5.3 Nudm_EventExposure_Unsubscribe service operation

Service operation name: Nudm EventExposure Unsubscribe

Description: the consumer deletes the subscription of an event if already defined in UDM.

Inputs, Required: Subscription Correlation ID.

Outputs, Required: Operation execution result indication

5.2.3.5.4 Nudm_EventExposure_Notify service operation

Service operation name: Nudm EventExposure Notify

Description: UDM reports the event to the consumer that has previously subscribed.

Inputs, Required: Event ID, Notification Correlation Information, time stamp.

Inputs, Optional: Event specific parameters list, Remaing number of reports of impacted UE.

Outputs, Required: None. 5.2.6.2 Nnef_EventExposure service

5.2.6.2.1 General

See clause 4.15.3.1 and clause 4.15.2a.

In order to support the NWDAF to collect data from the AF via the NEF, the Event IDs associated with available data to be collected from the AF are defined in clause 5.2.19.2.1, which can be subscribed by the NWDAF. The Event filters for the specific Event IDs as defined in clause 5.2.19.2.1 can also be used for collecting data from the AF via the NEF.

5.2.6.2.2 Nnef_EventExposure_Subscribe operation

Service operation name: Nnef EventExposure Subscribe

Description: the consumer subscribes to receive an event, or if the event is already defined in NEF, then the subscription is updated.

Inputs, Required: (Set of) Event ID(s) as specified in clause 4.15.3.1 orNpcf Policy Authorization Notify and Naf EventExposure Subscribe service operation, Target of Event Reporting (GPSI, SUPI, External Group Identifier, or Internal Group Identifier), Event Reporting Information defined in Table 4.15.1-1, Notification Target Address (+ Notification Correlation ID).

Inputs, Optional: Event Filter, (set of) Application Identifier(s), Subscription Correlation ID (in the case of modification of the event subscription), Expiry time. Information of UEs that are removed from the group event.

Outputs, Required: When the subscription is accepted: Subscription Correlation ID, Expiry time (required if the subscription can be expired based on the operator's policy).

Outputs, Optional: First corresponding event report is included, if available (see clause 4.15.1).

5.2.6.2.3 Nnef_EventExposure_Unsubscribe service operation

Service operation name: Nnef EventExposure Unsubscribe

Description: the NF consumer deletes an event if already defined in NEF.

Inputs, Required: Subscription Correlation ID.

Outputs, Required: Operation execution result indication

5.2.6.2.4 Nnef_EventExposure_Notify service operation

Service operation name: Nnef EventExposure Notify

Description: NEF reports the event to the consumer that has previously subscribed.

Inputs, Required: Event ID, Notification Correlation Information, time stamp.

Inputs, Optional: Event information (defined on a per Event ID basis).

Outputs, Required: Operation execution result indication The present disclosure further provides the following embodiments based on the 3GPP TS 29.503, V17.2.0.

5.5.2.2.2 Subscription to Notification of event occurrence

Figure 5.5.2.2.2-1 (see Fig. 13) shows a scenario where the NF service consumer sends a request to the UDM to subscribe to notifications of event occurrence (see also 3GPP TS 23.502 figure 4.15.3.2.2-1 step 1 and 3GPP TS 23.502 Figure 4.15.3.2.3b-l step 1). The request contains a callback URI, the type of event that is monitored and additional information e.g. event filters and reporting options.

1. The NF service consumer sends a POST request to the parent resource (collection of subscriptions) (.../{ueldentity }/ee-subscriptions), to create a subscription as present in message body. The values ueldentity shall take are specified in Table 6.4.3.2.2-1. The request may contain an expiry time, suggested by the NF Service Consumer, representing the time upto which the subscription is desired to be kept active and the time after which the subscribed event(s) shall stop generating notifications, the indication on whether the subscription applies also to EPC.

If MTC Provider information and/or AF ID are received in the request, the UDM shall check whether the MTC Provider and/or the AF is allowed to perform this operation for the UE; otherwise, the UDM shall skip the MTC provider and/or AF authorization check.

If the subscription is targeting a group and certain UE(s) within the group are not to be monitored, the NF consumer shall indicate the excluded UEs in the request body.

2a. On success, the UDM responds with "201 Created" with the message body containing a representation of the created subscription. The Location HTTP header shall contain the URI of the created subscription. If the event subscription was for a group of UEs:

- The "maxNumOfReports" in the "reportingOptions" IE shall be applicable to each UE in the group;

- The UDM shall return the number of UEs in that group in the "numberOfUes" IE.

The NF service consumer shall keep track of the maximum number of reports reported for each UE in the event report and when "maxNumOfReports*numberOfUes" limit is reached, the NF service consumer shall initiate the unsubscription of the notification towards the UDM (see clause 5.5.2.3.2).

If the event subscription was for a list events, the "maxNumOfReports" in the "reportingOptions" IE shall be applicable to each event. The NF service consumer shall keep track of the maximum number of reports reported for each event in the event report and when "maxNumOfReports*number of events" limit is reached, the NF service consumer shall initiate the unsubscription of the notification towards the UDM (see clause 5.5.2.3.2).

The response, based on operator policy, may contain the expiry time, as determined by the UDM, after which the subscription becomes invalid. Before the subscription is going toexpire, if the NF Service Consumer wants to keep receiving notifications, it shall modify the subscription in the UDM with a new expiry time. The NF Service Producer shall not provide the same expiry time for many subscriptions in order to avoid all of them expiring and recreating the subscription at the same time. If the expiry time is not included in the response, the NF Service Consumer shall not associate an expiry time for the subscription.

If the indication on whether the subscription applies also to EPC is included in the request, the response shall include the indication on whether the subscription was also successful in EPC domain.

2b. If the user does not exist, HTTP status code "404 Not Found" shall be returned including additional error information in the response body (in the "ProblemDetails" element).

2c. If there is no valid subscription data for the UE, i.e. based on the UE's subscription information monitoring of the requested EventType is not allowed, or the requested EventType is not supported, or when MTC Provider or AF are not allowed to perform this operation for the UE, HTTP status code "403 Forbidden" shall be returned including additional error information in the response body (in the "ProblemDetails" element).

On failure, the appropriate HTTP status code indicating the error shall be returned and appropriate additional error information should be returned in the POST response body. 5.5.2.5.2 Modification of a subscription

The service operation is invoked by a NF Service Consumer, e.g. NEF, towards the UDM, when it needs to modify an existing subscription previously created by itself at the UDM.

The NF Service Consumer shall modify the subscription by using HTTP method PATCH with the UR1 of the individual subscription resource (see clause 6.4.3.3) to be modified. Referring to Fig. 5.5.2.5.2-1 (see Fig. 14):

1. The NF service consumer (e.g. NEF) shall send a PATCH request to the resource representing a subscription. The modification may be for the events subscribed or for updating the event report options. If certain UE(s) within the group are no longer to be monitored, the NF consumer shall indicate the excluded UEs in the request body.

2a. On success, the request is accepted, the UDM shall respond with "204 No Content".

2b. If the resource does not exist e.g. the subscriptionld cannot be found, HTTP status code "404 Not Found" should be returned including additional error information in the response body (in the "ProblemDetails" element).

2c. If the modification can't be accepted, HTTP status code "403 Forbidden" should be returned including additional error information in the response body (in the "ProblemDetails" element).

On failure, the appropriate HTTP status code indicating the error shall be returned and appropriate additional error information should be returned in the PATCH response body.

6.4.6.2.2 Type: EeSubscription

Table 6.4.6.2.2-1: Definition of type EeSubscription

e

5.5.2.4.x Event Subscription Termination for Individual UE in Group Subscription

When UDM detects that an ongoing group subscription is no longer applicable for a UE, e.g. the subscription of the UE is deleted or the UE is removed from the group or the NF consumer is no longer authorized to monitor the UE or the UE is excluded from the group monitoring, and the group subscription is configured with maximum number of reports, the UDM shall send a notification to the NF consumer to indicate the termination of the group event subscription for the UE.

The requirement in clause 5.3.2.4.1 applies, with following modifications: 1. Same as step 1 of 5.3.2.4.1-1, the request body shall include the following:

- the "terminatelnd" IE with value "true" in monitroing report; and

- the remainReports IE indicates the remaining number of reports not generated for the event.

NOTE: When the NF consumer (e.g. NEF) received the notification indicating the termination of the group event subscription for the UE, the NF consumer deduct the remaining number of reports for the UE from the total expected number of reports for the group subscription.

6.4.6.2.4 Type: MonitoringReport

Table 6.4.6.2.4-1 : Definition of type MonitoringReport

The present disclosure further provides the following embodiments based on the 3GPP TS 29.518, V17.1.0.

5.3.2.2.2 Creation of a subscription

The Subscribe service operation is invoked by a NF Service Consumer, e.g. NEF, towards the AMF, when it needs to create a subscription to monitor at least one event relevant to the AMF. The NF Service Consumer may subscribe to multiple events in a subscription. A subscription may be associated with one UE, a group ofUEs or any UE.

The NF Service Consumer shall request to create a new subscription by using HTTP method POST with URI of the subscriptions collection, see clause 6.2.3.2.

The NF Service Consumer shall include the following information in the HTTP message body:

- NF ID, indicates the identity of the network function instance initiating the subscription;

- Subscription Target, indicates the target(s) to be monitored, as one of the following types:

- A specific UE, identified with a SUPI, a PEI or a GPSI;

- A group of UEs, identified with a group identity. Optionally with a list of UE to be excluded;

- Any UE, identified by the "anyUE" flag.

- Notification URI, indicates the address to deliver the event notifications generated by the subscription;

- Notification Correlation ID, indicates the correlation identity to be carried in the event notifications generated by the subscription;

- List of events to be subscribed;

- Event Types per event, as specified in clause 5.3.1.

The NF Service Consumer may include the following information in the HTTP message body:

- Immediate Report Flag per event, indicates an immediate report to be generated with current event status;

- Event Trigger, indicates how the events shall be reported (One-time Reporting or Continuously Reporting).

- Maximum Number of Reports, defines the maximum number of reports after which the event subscription ceases to exist;

- Expiry, defines maximum duration after which the event subscription ceases to exist;

- Sampling ratio, defines the random subset of UEs among target UEs, and AMF only report the event(s) related to the selected subset ofUEs;

- Periodic Report Flag per event, indicates the report to be generated periodically;

- Repetition Period, defines the period for periodic reporting;

- Event Filter per applicable event, defines further options on how the event shall be reported.

- Reference Id per event, indicates the value of the Reference Id associated with the event to be monitored. If provided, the Reference Id shall be included in the reports triggered by the event.

Referring to Figure 5.3.2.2.2-1 (see Fig. 15): 1. The NF Service Consumer shall send a POST request to create a subscription resource in the AMF. The payload body of the POST request shall contain a representation of the individual subscription resource to be created. The request may contain an expiry time, suggested by the NF Service Consumer as a hint, representing the time upto which the subscription is desired to be kept active and the time after which the subscribed event/ s) shall stop generating report.

2a. On success, the request is accepted, the AMF shall include a HTTP Location header to provide the location of a newly created resource (subscription) together with the status code 201 indicating the requested resource is created in the response message. If the NF Service Consumer has included more than one events in the event subscription and some of the events are failed to be subscribed, the AMF shall accept the message and provide the successfully subscribed event(s) in AmfEventSubscription. If the NF Service Consumer has included the immediateFlag with value as "true" in the event subscription, the AMF shall include the current status of the events subscribed, if available (e.g. last known location information is included if the subscribed event is LOCATION REPORT). If the events with immediateFlag set to "true" are subscribed by an NF service consumer on behalf of a third NF and the notification will be sent to the third NF directly, i.e. subsChangeNotifyUri is included in the event subscription, the current status of the events subscribed shall not be included in response. The AMF shall subsequently send a notification to the third NF including the current status of the events subscribed.

If the NF Service Consumer has set the event reporting option as ONE TIME and if the AMF has included the current status of the events subscribed in the response, then the AMF shall not do any subsequent event notification for the events given in the AmfCreateEventSubscription parameter. If the NF Service Consumer has set the event reporting option as ONE TIME, the subscribed event as LOCATION REPORT and the immediateFlag is set to false or absent, the AMF shall send an event notification to notify the current location of the UE after the subscription.

The response, based on operator policy and taking into account the expiry time included in the request, may contain the expiry time, as determined by the AMF, after which the subscription becomes invalid. Once the subscription expires, if the NF Service Consumer wants to keep receiving notifications, it shall create a new subscription in the AMF. The AMF shall not provide the same expiry time for many subscriptions in order to avoid all of them expiring and recreating the subscription at the same time. If the expiry time is not included in the response, the NF Service Consumer shall consider the subscription to be valid without an expiry time.

If the sampling ratio ("sampRatio") attribute is included in the subscription, the AMF shall select a random subset of UEs among target UEs according to the sampling ratio and only report the event(s) related to the selected subset of UEs.

2b. On failure or redirection, one of the HTTP status code listed in Table 6.2.3.2.3.1-3 shall be returned. For a 4xx/5xx response, the message body shall contain a ProblemDetails structure with the "cause" attribute set to one of the application error listed in Table 6.2.3.2.3.1-3.

6.2.6.2.2 Type: AmfEventSubscription

Table 6.2.6.2.2-1 : Definition of type AmfEventSubscription

_ _

6.2.6.2.14 Type: AmfUpdateEventSubscriptionltem

Table 6.2.6.2.14-1: Definition of type AmfUpdateEventSubscriptionltem

5.3.2.4.x Event Subscription Termination for Individual UE in Group Subscription

When AMF detects that an ongoing group subscription is no longer applicable for a UE, e.g. the subscription of the UE is deleted in UDM or the UE is removed from the group, and the group subscription is configured with maximum number of reports, the AMF shall send a notification to the NF consumer to indicate the termination of the group event subscription for the UE.

The requirement in clause 5.3.2.4.1 applies, with following modifications:

1. Same as step 1 of 5.3.2.4.1-1, the request body shall include the following:

- the "active" flag with value "FALSE" in eventState IE in the event report; and - the remainReports IE indicates the remaining number of reports not generated for the event.

6.2.6.2.5 Type: AmfEventReport

Table 6.2.6.2.5-1 : Definition of type AmfEventReport

6.2.6.27 Type: AmfEventState

Table 6.2.6.2.7-1 : Definition of type AmfEventState

Claims

1. A method (200) performed by a Network Exposure Function, NEF, comprising: transmitting (210), to a Unified Data Management, UDM, a first request to modify a subscription for an event associated with a group of User Equipments, UEs, wherein the first request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

2. The method (200) of claim 1 , wherein the first request is an Nudm_EventExposure_Subscribe request.

3. The method (200) of claim 1 or 2, further comprising: receiving, from the UDM, a first response containing a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained; and updating a total remaining number of reports for the group based on a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained.

4. The method (200) of claim 3, wherein the first response is an Nudm_EventExposure_Subscribe response.

5. The method (200) of any of claims 1-4, further comprising: receiving, from an Application Function, AF, a second request to modify the subscription for the event associated with the group of UEs, the second request indicating the one or more UEs in the group for which the event is to be terminated or the one or more UEs in the group for which the event is to be maintained, wherein the first request is transmitted in response to receiving the second request.

6. The method (200) of claim 5, wherein the second request is an

Nnef_EventExposure_Subscribe request.

7. The method (200) of any of claims 1-6, further comprising: receiving, from the UDM or an Access and Mobility Management Function, AMF, a notification message containing a remaining number of reports for one of the one or more UEs for which the event is to be terminated; and updating a total remaining number of reports for the group based on the remaining number of reports for the one UE.

8. The method (200) of claim 7, wherein the notification message is an Nudm_EventExposure_Notify message or an Namf_EventExposure_Notify message.

9. A method (300) performed by a Unified Data Management, UDM, comprising: receiving (310), from a Network Exposure Function, NEF, a first request to modify a subscription for an event associated with a group of User Equipments, UEs, wherein the first request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

10. The method (300) of claim 9, wherein the first request is an Nudm_EventExposure_Subscribe request.

11. The method (300) of claim 9 or 10, further comprising: transmitting, to the NEF, a first response containing a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained.

12. The method (300) of claim 9 or 10, further comprising: transmitting, to each of one or more Access and Mobility Management

Functions, AMFs, a third request to modify the subscription for the event associated with the group of UEs, the third request indicating the one or more UEs in the group for which the event is to be terminated or the one or more UEs in the group for which the event is to be maintained.

13. The method (300) of claim 12, further comprising: receiving, from each of the one or more AMFs, a third response containing a total remaining number of reports for at least one UE served by the AMF in the group for which the event is to be terminated or at least one UE served by the AMF in the group for which the event is to be maintained; determining a total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained, based on the total remaining number of reports received from each of the one or more AMFs; and transmitting, to the NEF, a first response containing the total remaining number of reports for the one or more UEs for which the event is to be terminated or the one or more UEs for which the event is to be maintained.

14. The method (300) of claim 11 or 13, wherein the first response is an Nudm_EventExposure_Subscribe response.

15. The method (300) of claim 12, wherein the third request is an Namf_EventExposure_Subscribe request.

16. The method (300) of claim 13, wherein the third response is an Namf_EventExposure_Subscribe response.

17. The method (300) of claim 9 or 10, further comprising: transmitting, to the NEF, a notification message containing a remaining number of reports for one of the one or more UEs for which the event is to be terminated.

18. The method (300) of claim 17, wherein the notification message is an Nudm_EventExposure_Notify message.

19. A method (400) performed by an Access and Mobility Management Function,

AMF, comprising: receiving (410), from a Unified Data Management, UDM, a third request to modify a subscription for an event associated with a group of User Equipments, UEs, wherein the third request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

20. The method (400) of claim 19, wherein the third request is an Namf_EventExposure_Subscribe request.

21. The method (400) of claim 19 or 20, further comprising: transmitting, to the UDM, a third response containing a total remaining number of reports for at least one UE served by the AMF in the group for which the event is to be terminated or at least one UE served by the AMF in the group for which the event is to be maintained.

22. The method (400) of claim 21 , wherein the third response is an Namf_EventExposure_Subscribe response.

23. The method (400) of claim 19 or 20, further comprising: transmitting, to a Network Exposure Function, NEF, a notification message containing a remaining number of reports for one UE served by the AMF, out of the one or more UEs, for which the event is to be terminated.

24. The method (400) of claim 23, wherein the notification message is an Namf_EventExposure_Notify message.

25. A method (600) performed by an Application Function, AF, comprising: transmitting (610), to a Network Exposure Function, NEF, a second request to modify a subscription for an event associated with a group of User Equipments, UEs, wherein the second request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

26. The method (600) of claim 25, wherein the second request is an Nnef_EventExposure_Subscribe request.

27. A Network Exposure Function, NEF, (1200), comprising: a communication interface (1210), a processor (1220) and a memory (1230), the memory (1230) comprising instructions, which when executed by the processor (1220), cause the NEF (1200) to: transmit, to a Unified Data Management, UDM, a first request to modify a subscription for an event associated with a group of User Equipments, UEs, wherein the first request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

28. The NEF (1200) of claim 27, wherein the instructions, when executed by the processor (1220), further cause the NEF (1200) to perform any of the methods of claims 2 to 8.

29. A Unified Data Management, UDM, (1200), comprising: a communication interface (1210), a processor (1220) and a memory (1230), the memory (1230) comprising instructions, which when executed by the processor (1220), cause the UDM (1200) to: receive, from a Network Exposure Function, NEF, a first request to modify a subscription for an event associated with a group of User Equipments, UEs, wherein the first request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

30. The UDM (1200) of claim 29, wherein the instructions, when executed by the processor (1220), further cause the UDM (1200) to perform any of the methods of claims 10 to 18.

31. An Access and Mobility Management Function, AMF, (1200), comprising: a communication interface (1210), a processor (1220) and a memory (1230), the memory (1230) comprising instructions, which when executed by the processor (1220), cause the AMF (1200) to: receive, from a Unified Data Management, UDM, a third request to modify a subscription for an event associated with a group of User Equipments, UEs, wherein the third request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

32. The AMF (1200) of claim 31 , wherein the instructions, when executed by the processor (1220), further cause the AMF (1200) to perform any of the methods of claims 20 to 24.

33. An Application Function, AF, (1200), comprising: a communication interface (1210), a processor (1220) and a memory (1230), the memory (1230) comprising instructions, which when executed by the processor (1220), cause the AF (1200) to: transmit, to a Network Exposure Function, NEF, a second request to modify a subscription for an event associated with a group of User Equipments, UEs, wherein the second request indicates one or more UEs in the group for which the event is to be terminated or one or more UEs in the group for which the event is to be maintained.

34. TheAF (1200) of claim 33, wherein the second request is an Nnef_EventExposure_Subscribe request.

35. A computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions, when executed by a processor of a network node, configure the network node to, when implementing a Network Exposure Function, NEF, perform the method according to any of claims 1-8, or when implementing a Unified Data Management, UDM, perform the method according to any of claims 9-18, or when implementing an Access and Mobility Management Function, AMF, perform the method according to any of claims 19-24, or when implementing an Application Function, AF, perform the method according to claim 25 or 26.