WO2024149512A1

WO2024149512A1 - Methods and apparatuses for enabling control of event exposure for a wireless device

Info

Publication number: WO2024149512A1
Application number: PCT/EP2023/083530
Authority: WO
Inventors: Emiliano Merino Vazquez; Maria Cruz Bartolome Rodrigo
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-01-11
Filing date: 2023-11-29
Publication date: 2024-07-18
Anticipated expiration: 2025-07-11
Also published as: EP4649701A1

Abstract

Embodiments described herein relate to methods and apparatuses for enabling control of event exposure for a wireless device, in particular where the wireless device is roaming in a visitor network. A method in a first network function in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network, comprises: receiving a first subscription request for exposure of a first event type for the wireless device from a second NF, wherein the first subscription request comprises one or more service level agreement identifier, SLA-Ids; obtaining SLA information associated with the one or more SLA-Ids, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device; and responsive to the SLA information indicating that the exposure of the first event type is permitted in the first visitor network for the wireless device, forwarding the first subscription request to a third NF in the first visitor network.

Description

METHODS AND APPARATUSES FOR ENABLING CONTROL OF EVENT EXPOSURE FOR A WIRELESS DEVICE

Technical Field

Embodiments described herein relate to methods and apparatuses for enabling control of event exposure for a wireless device, in particular where the wireless device is roaming in a visitor network.

Background

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

Figure 1 illustrates an example of event exposure for a consumer NF in relation to a wireless device that is not currently roaming in a visitor network.

In this example, a consumer NF may transmit a subscription request to a Unified Data Management function (UDM). The subscription request may then be passed to either the Session Management Function (AMF) or the Access and Mobility management function (AMF) depending on the type of event that is being subscribed to. The SMF or the AMF may respond accordingly. These event exposures may be allowed within a home network of the wireless device. However, when a UDM receives a subscription request for an Event Exposure (EE) for a UE, the UDM does not take into account whether the UE is roaming or not to proceed the request. In EPC/4G networks, the responsibility to allow EE in a visitor network (e.g. visitor public land mobile network (vPLMN)) may lie with the serving node, e.g. see TS 23.682 v 17.3.0 which states that:

“the Mobility Management Entity (MME)/ Serving General Packet Radio Service support node (SGSN) verifies the request, e.g. if the Monitoring Type is covered by a roaming agreement when the request is from another PLMN”.

It may be then assumed that, in 5^th Generation (5G) Core networking (5GC), that the responsibility is for the Access and Mobility Management Function (AMF) in the vPLMN to allow exposure requests for inbound roamers based on Service Level Agreements (SLAs), that may be specific for an event exposure or based on whether the vPLMN supports exposure in the first place.

However, this is not clearly stated in 3GPP, where only is mentioned that a roaming agreement is required, see clause 4.15.3.1 in 3GPP TS 23.502 version 17.56.0: Procedures for the 5G System: “To support monitoring features in roaming scenarios, a roaming agreement needs to be made between the HPLMN and the VPLMN. ”

Figure 2 illustrates an example of forwarding a subscription request from a home network (e.g. a home PLMN (hPLMN)) to a visitor network (e.g. a vPLMN) for a roaming user equipment UE1.

In this example, in step 201 , the application function, AF, transmits a subscription request to a Network Exposure function, NEF. The subscription request comprises an event type that the AF is subscribing to for UE1. The subscription request also comprises an identification for the AF, AF Id, and an identification for the Mobile Telecommunications (MTC) provider.

In step 202 the NEF forwards the subscription request to the Unified Data Management (UDM) function, adding in an address for the NEF.

In step 203, the UDM retrieves subscription data for UE1 from the UDR.

In in step 204, the UDM authorized the event exposure for the UE1 in the home network. This check is performed independently of whether or not the UE1 is roaming. In step 205, the UDM, responsive to determined that the MTC provider and the AF are allowed to monitor the UE1 , and that the event exposure (EE) is permitted in the home network, stores the Event subscription information in the UDR.

In step 206, the UDM determines the current Access and Mobility Management Function (AMF) for the UE1 , for example, based on the UE subscription data obtained in step 203.

In step 207, without any further checks, the UDM forwards the subscription request comprising the UE1 identification, the event type and the address for the NEF, to the current AMF.

In this example, it is determined the event subscription is also allowed in the visitor AMF. However, it is not currently standardized how the EE roaming agreements will be checked at the AMF.

As the EE is allowed in the visitor network, the AMF stores the subscription information in step 208, and an acknowledgement of success is passed back to the AF in steps 209 to 211.

Summary

In contrast to the example illustrated in Figure 2, in some examples, the EE will not be allowed in the visitor network.

Figure 3 illustrates an example in which the EE is not allowed in the visitor network. In Figure 3 it is assumed that the EE support is checked by the AMF, mimicking 4G behavior.

Steps 301 to 307are the same as steps 201 to 207 described with reference to Figure In step 308, the serving AMF in the visitor network checks configured roaming agreement. In this example, the EE e.g. for this particular Event and from the particular home network (e.g. hPLMN) is not allowed. This can be very common for some Events, even events that may occur very frequently, e.g. change of location, because the support of EE in the visitor network requires the visitor network resources, to offer a value to another operator AF (to an AF in another PLMN). Therefore, operators usually only support EE from another network based on roaming agreements (as indicated by 3GPP).

For example, resources in the visitor network that may be required by a subscription to Event Monitoring from a home network may comprise one or more of the following:

Storage in the AMF Detection of ethe vent Signalling from visitor network to the home network.

In step 309, the EE subscription is responded with to an error.

In step 310, it would be expected for the NEF to receive a successful response because the subscription is properly processed by UDM, however, this case (in which the EE is not allowed in the visitor network), is not clearly described in 3GPP.

The rejection in the visitor network (e.g. vPLMN) of a subscription from a home network (e.g. hPLMN) may have one or more of the following disadvantages:

• The configuration of the Service Level Agreements (SLAs) is per AMF. Therefore, when an EE is deployed, configuration will be required in all AMFs in the world.

If the configuration of one or more SLAs is changed in the AMFs, this will be unknown to a UDM and it may then not be possible to consider the new SLAs in the network. That is, the former SLAs will keep being applied until the Events are newly updated/created.

• The subscription request reaches the visitor network and only then is the visitor network is able to reject it.

This results in excess signalling from the UDM (via ecurity edge protection proxies (SEPPs), and even Service Communication Proxies (SCPs) with Indirect Communication) to the AMF to finally provide a rejection. - Either the AF stores the visitor network rejections, or the subscription for EE may need to be sent again in the future, for different events. Therefore, again there will be excess signalling to the visitor network in order to provide rejection of the subscription requests.

• Roaming agreements in the visitor AMF may need to be checked for each Subscription request. This may create overhead as therefore may be many UEs for whom the subscriptions will need checking.

Another problem with current methods is that the support of synchronization of event exposure information in the (description in AMF procedures (e.g. in the description of the ESSYNC feature) is incomplete (See 3GPP TS 29.518 version 187.08.0: Access and Mobility Management Services). Furthermore, the scenario in which the AMF does support ESSYNC, but UDM does not support ESSYNC is not currently covered discussed. The usage of “noEeSubscriptionlnd” flag in Nudm_UECM_Register by AMF, to request the UDM to send subscribed EE subscriptions for a certain UE, is not clear.

According to some embodiments there is therefore provided a method in a first network function in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network. The method comprises receiving a first subscription request for exposure of a first event type for the wireless device from a second NF, wherein the first subscription request comprises a service level agreement identifier, SLA-ld; obtaining SLA information associated with the SLA-ld, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device; and responsive to the SLA information indicating that the exposure of the first event type is permitted in the first visitor network for the wireless device, forwarding the first subscription request to a third NF in the first visitor network.

According to some embodiments there is provided a method in a fifth network function in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network. The method comprises storing service level agreement information associated with an SLA-ld, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device.

According to some embodiments there is provided a method in a second network function in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network. The method comprises receiving a subscription request to subscribe to exposure of a first event type for the wireless device from an application function, inserting one or more SLA-lds that is associated with the MTC provider or application function into the subscription request, and forwarding the subscription request to a first network function.

According to some embodiments there is provided a method in a fourth network function in a first visitor network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in a home network and the wireless device is roaming in the first visitor network. The method comprises obtaining event exposure subscription information for the wireless device, responsive to the first NF and/or the fourth NF not supporting synchronization of event exposure information: removing the event exposure subscription information from context information; and transmitting a second registration request for the wireless device to the first NF, wherein the second registration request comprises an indication that the fourth NF has no access to event exposure subscription information for the wireless device.

According to some embodiments there is provided a first network function, NF, in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network. The first NF comprises processing circuitry configured to cause the first NF to: receive a first subscription request for exposure of a first event type for the wireless device from a second NF, wherein the first subscription request comprises one or more service level agreement identifiers, SLA-ld; obtain SLA information associated with the SLA-ld, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device; and responsive to the SLA information indicating that the exposure of the first event type is permitted in the first visitor network for the wireless device, forward the first subscription request to a third NF in the first visitor network. According to some embodiments there is provided a fifth network function, NF, in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network. The fifth NF comprises processing circuitry configured to cause the fifth NF to: store service level agreement information associated with an SLA-ld, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device.

According to some embodiments there is provided a second network function, NF, in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network. The second NF comprises processing circuitry configured to cause the second NF to: receive a subscription request to subscribe to exposure of a first event type for the wireless device from an application function, insert one or more Service Level Agreement identifiers (SLA-IDs) that are associated with the MTC provider or application function into the subscription request, and forward the subscription request to a first network function.

According to some embodiments there is provided a fourth network function, NF in a first visitor network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in a home network and the wireless device is roaming in the first visitor network. The fourth NF comprises processing circuitry configured to cause the fourth NF to: obtain event exposure subscription information for the wireless device; and responsive to the first NF and/or the fourth NF not supporting synchronization of event exposure information: remove the event exposure subscription information from context information; and transmit a second registration request for the wireless device to the first NF, wherein the second registration request comprises an indication that the fourth NF has no access to event exposure subscription information for the wireless device.

Brief Description of the Drawings

For a better understanding of the embodiments of the present disclosure, and to show how it may be put into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: Figure 1 illustrates an example of event exposure for a consumer NF in relation to a wireless device that is not currently roaming in a visitor network;

Figure 2 illustrates an example of forwarding a subscription request from a home network (e.g. a home PLMN (hPLMN)) to a visitor network (e.g. a vPLMN) for a roaming user equipment UE1 ;

Figure 3 illustrates an example in which the EE is not allowed in the visitor network;

Figure 4 illustrates a method in a first network function in a home network for controlling event exposure for a wireless device;

Figure 5 illustrates a method in a fifth network function in a home network;

Figure 6 illustrates a method in a second network function in a home network for controlling event exposure for a wireless device;

Figure 7 illustrates an example implementation of the methods of Figures 4 to 6;

Figure 8 illustrates a method in a fourth network function in a visitor network for controlling event exposure for a wireless device;

Figure 9 illustrates an example implementation of the method of Figure 8;

Figure 10 illustrates an example implementation of the method of Figure 8;

Figure 11 illustrates an example implementation of the method of Figure 8;

Figure 12 illustrates an example implementation of Figure 8;

Figure 13 illustrates an example implementation of Figure 8;

Figure 14 illustrates a variant of the implementation of Figure 13;

Figure 15 illustrates a network function 1500 comprising processing circuitry; Figure 16 is a block diagram illustrating a first NF 1600 according to some embodiments;

Figure 17 is a block diagram illustrating a fifth NF 1700 according to some embodiments;

Figure 18 is a block diagram illustrating a second NF 1800 according to some embodiments;

Figure 19 is a block diagram illustrating a fourth NF 1900 according to some embodiments.

Description

The following sets forth specific details, such as particular embodiments or examples for purposes of explanation and not limitation. It will be appreciated by one skilled in the art that other examples may be employed apart from these specific details. In some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted so as not obscure the description with unnecessary detail. Those skilled in the art will appreciate that the functions described may be implemented in one or more nodes using hardware circuitry (e.g., analog and/or discrete logic gates interconnected to perform a specialized function, ASICs, PLAs, etc.) and/or using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. Nodes that communicate using the air interface also have suitable radio communications circuitry. Moreover, where appropriate the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.

Hardware implementation may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analogue) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions. In order to address the problems mentioned above, embodiments described herein store service level agreement information relating to roaming in the home network UDR. For example, this information may be stored as part of the Application Data Set and may be accessible by using an identifier for the SLA, SLAId.

Herein a home network may be referred to as a home public land mobile network (hPLMN) and a visitor network may be referred to as a visitor public land mobile network (vPLMN).

In some examples, the MTC Provider/App onboarding to NEF requires this SLA information to be stored in UDR, as well as configuring the NEF with an SLA Id for the MTC Provider/App.

For example, SLA information associated with a first SLA-ld may indicate one or more vPLMNs and one or more allowed event types. Different events have different resource/signaling demands in the vPLMN. Taking into account the traffic demands (and then resource usage) in the vPLMN is very different between different events, this means that for an operator there may be interest to support some Events with low frequency (e.g. Communication failure), but not Events that may be very frequent (e.g. Location reporting). Location Reporting may be a frequent event, but the frequency and the resource demands in the vPLMN depends a lot on the accuracy level of the Event:

Location Reporting with Cell-Id accuracy: demands AMF subscribes to the gNB to receive Cell-Id changes, what increases signalling in RAN, as well as interaction from vPLMN to hPLMN. Location Reporting with gNB accuracy: it does not demand extra RAN signalling since when the UE moves from gNB already the RAN informs AMF. Therefore, a Location Reporting with accuracy level up to gNB may be accepted (based on roaming agreements), but not with lower accuracy level.

In some examples, therefore the SLA information may comprise may indicate one or more vPLMNs, one or more allowed event types, and one or more characteristics (e.g. accuracy as described above) of the one or more allowed event types. .

Roaming agreements at Event level (even with extra information like accuracy) may be expected. As indicated, a Roaming-EE-SLA may be expected per vPLMN + Event Type (e.g. an event type comprising extra information like accuracy). Therefore, the SLA information may comprise a list of allowed Event types (e.g. Boolean array) for each allowed vPLMN.

In order to minimize storage needs, and to improve reusability of SLA-info, two SLAs may be defined as follows:

Roaming-EE-AllowedvPLMNs-SLA info: allowed vPLMNs

Roaming-EE-AllowedEvents-SLA info: allowed Events

When the Network Exposure Function (NEF) receives an EE Subscription request, the NEF provides the SLAId to the UDM in the EE Subscription request. The UDM may then be able to fetch SLA information from UDR using the SLAId, and based on that, performs the corresponding checks to decide whether the EE subscription request can be proceeded to the vPLMN (if the vPLMN allows this EE) or on the contrary it will be rejected, and the AF may be informed.

If the UE moves from one AMF to another AMF, a registration request may be received by UDM The UDM may then check whether the current serving AMF needs to receive all or updated EE subscriptions. This may depend on whether or not the new AMF has access to event exposure subscription information.

Apart from that, the UDM may subscribe to receive indications of updates to SLA information, and may inform serving AMFs of updates to SLA information.

Embodiments described herein therefore provide mechanisms to allow a UDM to be able to check whether an EE subscription should be sent to an AMF based on the vPLMN SLAs for EE with roaming.

Figure 4 illustrates a method in a first network function in a home network for controlling event exposure for a wireless device. In this example, a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network.

The method 400 may be performed by a network function, which may comprise a physical or virtual network node, and may be implemented in a computing device or server apparatus and/or in a virtualized environment, for example in a cloud, edge cloud or fog deployment. In some examples, the first network function comprises a UDM network function. In step 401 , the method comprises receiving a first subscription request for exposure of a first event type for the wireless device from a second NF, wherein the first subscription request comprises one or more service level agreement identifiers, SLA- Id. For example, the second NF may comprise a Network Exposure Function. The first subscription request may therefore have been received at the NEF from an AF, and the NEF may be forwarding the first subscription request on to the first NF.

In step 402, the method comprises obtaining service level agreement (SLA) information associated with the SLA-ld, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device. In some example, the SLA information may be obtained from a fifth NF (e.g. a UDR), as will be described in more detail with reference to Figure 5. However, in some examples it will be appreciated that the SLA information may be cached in the first NF.

In some examples, the SLA information indicates whether exposure of one or more event types with particularly characteristics is permitted in the first visitor network for the wireless device. For example, the SLA information may indicate that Location Reporting with the characteristic Cell-Id accuracy is permitted, whereas Location Reporting with the characteristic of gNB accuracy is not permitted.

In step 403, the method may comprise determining whether the SLA information indicates that the exposure of the first event type is permitted in the first visitor network for the wireless device.

If in step 403 it is determined that the SLA information indicates that the exposure of the first event type is permitted in the first visitor network for the wireless device, the method passes to step 404 in which the first subscription request is forwarded to a third NF in the first visitor network.

If in step 403 it is determined that the SLA information indicates that the exposure of the first event type is not permitted in the visitor network for the wireless device, the method passes to step 405 in which the first NF refrains from transmitting the first subscription request to the third NF in the visitor network. In other words, by only forwarding the subscription request to the third NF (e.g. an AMF) in the visitor network when the stored SLA information for that visitor network indicates that the EE will be permitted, the method of Figure 4 avoids the excess signalling between the home and visitor networks when rejection of the subscription request will occur.

In some examples, the method of Figure 4 further comprises storing subscription information associated with the wireless device based on the subscription request. For example, the subscription information may indicate that the wireless device has subscribed to exposure of the first event type. The subscription information may further comprise the SLA-ld.

In some examples, the first NF may receive an indication that the wireless device has moved from the third NF to a fourth NF in a second visitor network. This indication may comprise a registration request for the wireless device received at the first NF from the fourth NF.

In these examples, the method of Figure 4 may further comprise obtaining subscription information and SLA information associated with the wireless device, responsive to at least one of the following conditions being met: the indication comprises an indication that the fourth NF does not have access to event exposure subscription information for the wireless device (this indication may be sent when the fourth NF does not support synchronisation of event exposure information, and so does not keep the EE subscription information (which may be received in the wireless device context information or previously cached); or if the fourth NF does support synchronization of event exposure information but the first NF does not support synchronization of event exposure information, in that case, the fourth NF does not keep the EE subscription information); and the second visitor network is not the same as the first visitor network.

It will be appreciated that an AMF may be considered to have access to event exposure subscription information, for example, if is holds or has created the event exposure subscription information. The AMF may be considered not to have access to the event exposure subscription information if, for example, has received the event exposure subscription information but decided to remove it as the AMF does not support synchronization of event exposure information.

In other words, when one of these conditions is met, the first NF may determine that it is required that the UE subscription information be in some way updated at the fourth NF.

In this example, once the subscription information and SLA information has been obtained, responsive to one or more event type subscriptions in the subscription information being allowed in the second visitor network (e.g. according to the SLA information), the method may further comprise transmitting a second subscription request to the fourth NF for the one or more event type subscriptions.

In some examples, however, all of the following conditions may be met: the indication comprises an indication that the fourth NF has access to event exposure subscription information for the wireless device; and the second visitor network is the same as the first visitor network.

In these examples, the first NF may then refrain from transmitting a second subscription request to the fourth NF in the visitor network. In other words, in this example, the first NF may determine that there is no need to update the subscription information for the wireless device at the fourth NF.

In some examples, the first NF and the fourth NF may both support synchronization of event exposure information, but the first visitor network is not the same as the second visitor network. In these example, the method may comprise determining, from the subscription information, a change in permitted event type subscriptions based on event type subscriptions permitted in the second visitor network compared to event type subscriptions that were permitted in the first visitor network. The method of Figure 4 may then further comprise transmitting a subscribe or unsubscribe request to the fourth NF indicating the change in permitted event type subscriptions.

The subscribe or unsubscribe request may be transmitted per wireless device. It will be appreciated that whether or not a change in permitted event type subscriptions has occurred may be determined on a per wireless device basis. In some examples, there may be a modification to the SLA information associated with a particular visitor network. In this examples, the method of Figure 4 may comprise receiving an indication that the SLA information has been modified to updated SLA information. The method of Figure 4 may then further comprise obtaining subscription information for one or more wireless devices associated with the updated SLA information, and for each of the one or more wireless devices: determining, from the subscription information, a change in permitted event type subscriptions for the first visitor network based on event type subscriptions permitted in the updated SLA information compared to event type subscriptions that were permitted in the SLA information; and transmitting a subscribe or unsubscribe request to the fourth or third NF indicating the change in permitted event type subscriptions.

Figure 5 illustrates a method in a fifth network function in a home network for in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network.

The method 500 may be performed by a fifth network function, which may comprise a physical or virtual network node, and may be implemented in a computing device or server apparatus and/or in a virtualized environment, for example in a cloud, edge cloud or fog deployment. In some examples, the fifth network function comprises a UDR network function.

In step 501, the method comprises storing service level agreement information associated with an SLA-ld, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device.

In some examples, in step 502 the method further comprises receiving a request for SLA information comprising the SLA-ld from a first NF, and, in step 503, transmitting the SLA information to the first NF. For example, a first NF performing the method of Figure 4 may request the SLA information from the fifth NF performing the method of Figure 5.

In some examples, the fifth NF is also used to store subscription information for the wireless device. The subscription information may indicate that the wireless device has subscribed to exposure of the first event type. The subscription information may further comprise the SLA-ld.

In some examples, the method of Figure 5 further comprises receiving a request for subscription information for the wireless device from a first NF, and transmitting the subscription information to the first NF with the SLA-ld.

Figure 6 illustrates a method in a second network function in a home network for controlling event exposure for a wireless device. A subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network.

The method 600 may be performed by a second network function, which may comprise a physical or virtual network node, and may be implemented in a computing device or server apparatus and/or in a virtualized environment, for example in a cloud, edge cloud or fog deployment. In some examples, the second network function comprises a NEF.

In step 601 the method comprises receiving a subscription request to subscribe to exposure of a first event type for the wireless device from an application function.

In step 602, the method comprises inserting one or more SLA-ld(s) that are associated with the mobile telecommunications provider or application function into the subscription request.

In step 603, the method comprises forwarding the subscription request to a first network function. Step 603 may correspond to step 401 of Figure 4.

Figure 7 illustrates an example implementation of the methods of Figures 4 to 6.

In step 701a the method comprises storing SLA information in the UDR indexed by multiple SLA-lds. For example, SLA information may be stored in UDR indexed by one or multiple SLA-ld(s). Step 701a comprises an example implementation of step 401 of Figure 4. The SLA information may be stored as part of the Application Data Set, under a new Event Exposure field, or under an SLA with an SLA identifier.

In step 701b, for initial onboarding of an MTC provider/Application into the network, the NEF may be configured with the SLA-ld or Ids that will apply for each MTC Provider/Application.

In step 702, the AF transmits to the NEF a first subscription request for exposure of a first event type (Event Type) for the wireless device (identified by UE Id). Step 702 comprises an example implementation of step 401 of Figure 4. It will be appreciated that the first subscription request may comprise more than one event type and more than one wireless device identifier.

In step 703, the NEF inserts the SLA-ld(s) that are applicable to the first subscription request (i.e. MTC Provider/App) and forwards the subscription request to the UDM. For example, the NEF may look up the MTC provider ID to find one or more SLA-lds that are associated with that provider (e.g. based on the onboarding in step 701b). Step 703 comprises an example implementation of steps 602 and 603 of Figure 6. Step 703 may also comprise an example implementation of step 401 of Figure 4.

In step 704, the UDM obtains information related to the UE from the UDR.

In step 705, the UDM performs Event Exposure authorization checks per UE ID, based on UE information for the UE IDs obtained from UDR. This authorization check authorizes the event exposure in the home network for the MTC provider/MTC application.

The authorization in step 705 check one or more of the following for the home network:

- That MTC provider/MTC application is allowed to monitor the UE

- That the Event type is allowed to be monitored

- That the AF identification (which may be included in the subscription request in step 703 and refers to the AF server instance) is allowed to be monitored. It will be appreciated that this particular check may not be used, because the checks may be required to avoid being linked to specific instances. In step 706 the UDM stores subscription information in UDR. For example, the subscription information may comprise the wireless devices (e.g. UEld) and the event types (Event Type) in the subscription request, also with the SLA-ld(s).

In step 707, the UDM checks the current PLMN for each UEld. In this example, it is assumed that there is only one UE identified in the subscription request. In this example, it is determined that the UE is roaming in a first visitor network.

In step 708, the UDM obtains the SLA information associated with the SLA-ld(s) in the subscription request received in step 703.

In step example, the SLA information has not previously been cached, and so the UDM retrieves the SLA information from the UDR, in step 708, using the provided SLA-ld(s) in step 703. In some examples, the SLA information may then be cached locally in step 709. Step 708 comprises an example implementation of steps 502 and 503 of Figure 5.

Based on the SLA information, in step 710, the UDM is able to determine whether the EE subscription for affected first event type (indicated in step 703) is allowed for the first visitor network.

In step 711 , the method comprises, responsive to the exposure of the first event type being permitted in the first visitor network for the wireless device, forwarding the first subscription request to an AMF in the first visitor network. In other words, the EE subscription is allowed by the vPLMN, then the UDM sends the EE subscription to the serving AMF. At this point, the AMF does not need to perform any SLA checks, in contrast to the legacy systems described in the background above. Step 711 comprises an example implementation of Step 404 of Figure 4.

In step 712, a subscription response is transmitted to the UDM by the AMF, and then forwarded on to the NEF and the AF in steps 713 and 714.

In step 715, the method comprises, responsive to the exposure of the first event type not being permitted in the first visitor network for the wireless device, refraining from refraining from transmitting the subscription request to the third NF in the visitor network. Step 715 may therefore be considered to comprise an example implementation of step 405 of Figure 4. Instead, in step 715 a response may be transmitted to the NEF to indicate that the subscription has been successfully processed by the UDM and stored in the UDR, but that if the UE is roaming, then the UE will not be monitored for the time being.

In addition, a new error code may be used to inform the NEF about this situation, that is, indicating that the subscription was not allowed in the vPLMN the UE is roaming in. In some examples, the vPLMN Id may also be included in step 715, so that the AF may identify the vPLMN that does not accept the event exposure subscription. This inclusion of the vPLMN Id allows the AF to understand why event exposure is not performed for that UE, and the AF may then consider requesting different agreements with other vPLMNs.

Once the UE roams into its hPLMN, the UDM will check the EE subscription information and will send the EE subscription to the serving AMF.

For a simple Roaming SLA where for all vPLMNs all EEs are not allowed if the UE is roaming a “Default-SLA” may be used. In this case, the default-SLA may be configured in the UDM (e.g. in all the UDM instances), and it may not be required to store the default-SLA in the UDR. In this example, when MTC providers/Applications start requiring specific SLAs (for e.g. some Events, or some vPLMNs), then the SLA- Ids may be defined and stored in the UDR.

Figure 8 illustrates a method in a fourth network function in a first visitor network for controlling event exposure for a wireless device. A subscriber profile of the wireless device is held in a home network and the wireless device is roaming in the first visitor network.

The method 800 may be performed by a fourth network function, which may comprise a physical or virtual network node, and may be implemented in a computing device or server apparatus and/or in a virtualized environment, for example in a cloud, edge cloud or fog deployment. In some examples, the fourth network function comprises an AMF.

In step 801, the method comprises obtaining event exposure subscription information for the wireless device. The event exposure subscription information may be received in context information for the wireless device, or may be cached at the fourth NF. The event subscription information may comprise subscription information as described above.

In step 802, the method comprises responsive to the first NF and/or the fourth NF not supporting synchronization of event exposure information: removing the event exposure subscription information from context information; and transmitting a second registration request for the wireless device to the first NF, wherein the second registration request comprises an indication that the fourth NF has no access to event exposure subscription information for the wireless device. For example, the fourth NF may transmit a “noeesubscription” flag set to “true” in the second registration request which indicates to the first NF that the fourth NF has no access to the event exposure subscription information, regardless of the fact that the event exposure information may have been obtained in step 801.

In some examples, however, step 802 may comprise transmitting a first registration request for the wireless device to the first NF, wherein, responsive to a first NF and the fourth NF supporting synchronization of event exposure information, the first registration request comprises an indication that the fourth NF has access to the event exposure subscription information for the wireless device. For example, the fourth NF may transmit a “noeesubscription” flag set to “false” in the first registration request which indicates that the fourth NF has access to the event exposure subscription information. It will be appreciated that there may be other factors involved in determining whether or not to set the “noeesubscription” flag set to “false”.

The method of Figure 8 may then further comprise responsive to transmitting the first registration request, receiving a subscribe or unsubscribe request from the first NF indicating a change in permitted event type subscriptions for the wireless device.

In some examples, the method of Figure 8 may further comprise the AMF determining whether first NF supports synchronization of event exposure information.

It will also be appreciated that the “noeesubscription” may be set to true when the EE subscription information for the wireless device is not available to the AMF.

Figure 9 illustrates an example implementation of the method of Figure 8. In this example, a wireless device moves to another AMF (e.g. in a visitor network). The AMF then registers this wireless device in the UDM of the home network. In the example of Figure 9 the AMF does not support synchronization of event exposure information. For example, the ESSYNC feature is not supported.

Step 900 indicates the precondition that the AMF does not support the ESSYNC feature.

In step 901 , as the AMF does not support ESSYNC feature, then if EE subscription information is received in the UE context from another AMF (e.g. with UE mobility), then the AMF removes the event exposure subscription information from context information. Step 1 of Figure 9 therefore comprises an example implementation of step 802 of Figure 8.

In step 902, the AMF sends a registration request for the UE in the v-PLMN to the UDM in the hPLMN. This registration request may be considered to comprise an indication to the UDM that the wireless device has moved to the AMF from a different AMF. In this example, the registration request comprises an indication to the UDM that it does not keep EE subscription information. For example, the registration request comprises an indication that the fourth NF has no access to event exposure subscription information for the wireless device, e.g. by including the “noEeSubscription” flag set to TRUE).

In step 903, the UDM obtains UE data from the UDR. In step 904, the UDM checks if registration of UEs is allowed form the current PLMN (e.g the vPLMN), based on UE data read from UDR.

In step 905, the UDM checks whether the registration in step 901 comprises the flag “noeeesubscription” set to TRUE. If so the condition that the AMF does not have access to event exposure subscription information for the UE is met, and therefore the UDM obtains subscription information and SLA information assocaited with the wireless device. For example, the UDM may in step 906, obtain EE subscription information from the UDR. The EE subscription information may comprise a SLA-ld(s) that had previously been stored.

In step 907, the UDM determines which event types are included in the obtained EE subscription information. In step 0908, the UDM obtains the SLA information. It will be appreciated that the SLA information may comprise an indication of previous event types that the wireless device has subscribed to. In step 908, the UDM may checks if the SLA info is currently cached at the UDM, and, if not, may retrieve the SLA information from the UDR utilizing the SLA-ld received in step 906.

In step 909, the UDM checks if the current vPLMN allows the event exposures subscribed to in the SLA information for the UE.

In step 910, if the vPLMN allows for the required event exposures then the UDM transmits an EE subscription for the wireless device to the AMF. The EE subscription may comprise a list of the event exposures subscribed to in the SLA information for the UE.

In step 911 , the AMF responds to the EE subscription received in step 910.

In step 912, if the vPLMN does not allow for the EE subscribed to in the SLA information, then the UDM refrains from sending the EE subscription to the AMF.

Figure 10 illustrates an example implementation of the method of Figure 8. In this example, a wireless device moves to the AMF from another AMF. The AMF then registers this wireless device in UDM of the home network. In the example of Figure 10, then AMF supports synchronization of event exposure information (e.g. the ESSYNC feature) but the UDM does not support synchronization of event exposure information (e.g. the ESSYNC feature).

Step 1000a indicates the precondition that the AMF supports the ESSYNC feature.

Step 1000b indicates the precondition that the AMF receives EE subscription information in the UE context and/or the EE subscription information may be cached at the AMF.

Step 1000c indicates the precondition that the UDM does not support synchronization of event exposure information (e.g. the ESSYNC feature).

It may be defined that the event exposures subscribed to from UDM (with Nudm_EE_Subscribe) may comprise a flag (e.g. eventSyndnd) that identifies the UDM supports ESSYNC, and this flag is included in the EE subs information sent in the UE context from one AMF to another. In step 1001 , in this example, the AMF does not have EE subscription information received from UDM, so the AMF does not know whether the UDM supports synchronization of event exposure information or not. In this example, therefore the AMF behaves as if UDM does not support synchronization of event exposure information.

In step 1002, based on step 1001 , when UDM does not support synchronization of event exposure information, the AMF may remove any indication of received or obtained EE subscriptions for the UDM. This step is required to avoid the AMF keeping duplicated EE subscription (after UDM sends EE subscriptions in a later step).

In step 1003, the AMF sends a registration request for the UE in the v-PLMN to the UDM in the hPLMN. This registration request may be considered to comprise an indication to the UDM that the wireless device has moved to the AMF from a different AMF. In this example, the registration request comprises an indication to the UDM that it does not keep EE subscription information. For example, the registration request comprises an indication that the fourth NF has no access to event exposure subscription information for the wireless device (e.g. by including the “noEeSubscription” flag set to TRUE). Step 1003 may be considered to comprise an example implementation of step 802 of Figure 8.

The remaining procedure may then follow steps 903 to 912 of Figure 9.

Figure 11 illustrates an example implementation of Figure 8. In this example, a wireless device moves to the AMF from another AMF. The AMF then registers this wireless device in UDM of the home network. In the example of Figure 11 , the AMF does not require UDM to send EE subscription information after the UE moves to the AMF. This may be determined because both the UDM and the AMF support synchronization of event exposure information, and the vPLMN is not changed in the move to the AMF. It will be appreciated that there may be other factors involved in determining whether or not to set the “noEeSubscription” flag set to FALSE. In step 1101 , the AMF transmits a registration request for the wireless device to the UDM. This registration request may be considered to indicate that the wireless device has moved from a previous AMF to the AMF. In this example, the registration request comprises an indication that the AMF has access to event exposure subscription information for the wireless device (e.g. by including the “noEeSubscription” flag set to FALSE). Step 1101 may be considered to comprise an example implementation of step 802 of Figure 8.

Steps 1102, 1103 and 1104 of Figure 11 are similar to steps 903, 904 and 905 of Figure 9.

In step 1105, the UDM checks if a change in vPLMN has occurred on the wireless device moving to the AMF. In this example, there has been no change in vPLMN.

In step 1106 therefore, the UDM refrains from transmitting a second subscription request to the AMF as all of the following conditions are met:

- the registration request indicates that the AMF has access to event exposure subscription information for the wireless device; and

- the second visitor network (i.e. the current visitor network) is the same as the first visitor network (the network of the previous AMF).

In some examples, the as following condition may also be required in order to refrain from sending a subscription request in step 1106:

- the EE subscriptions are still valid within the current vPLMN (e.g. the same Roaming SLAs apply for the vPLMN).

Figure 12 illustrates an example implementation of Figure 8. In this example, a wireless device moves to the AMF from another AMF. The AMF then registers this wireless device in UDM of the home network. In the example of Figure 11 , the AMF does not require UDM to send all EE subscription information after the UE moves to the AMF. This may be determined because both the UDM and the AMF support synchronization of event exposure information. However, the vPLMN has changed, so the EE subscription information may need to be updated at the AMF. It will be appreciated that there may be other factors involved in determining whether or not to set the “noEeSubscription” flag set to FALSE. In steps 1200A, 1200B, 1200C of figure 12, when after UE mobility, the AMF creates a new EE subscription resource, it may need to update this information to allow UDM to manage the existing subscriptions (with the new created subscription Id). This new EE subscription Id is updated by UDM in UDR.

It will be appreciated that the “Namf_EE_Unsubscribe_req” (transmitted later in step 1214 of Figure 12) may require the Universal Resource Indicator (URI) of the subscription resource to be unsubscribed from. The steps 1200A, 1200B and 1200C in Figure 12 allow the UDM access to the URI.

It may be required that the steps A and B are executed before the UECM_Register in step 1201 of Figure 12 is sent. However, in some examples, instead of ensuring this proposed order of execution, the UECM_Register may be enhanced to include the information in the notification, i.e. the newly created Subscription Ids. In this way, UDM may receive the required information with the UECM_Register.

For example, step 1200B may comprise transmitting, to the first NF, an indication of one or more resource identifiers associated with one or more subscription resources in the event exposure subscription information for the wireless device. In this example, the step of transmitting, to the first NF, the indication of the one or more resource identifiers is performed prior to transmitting a second registration request. However, it will be appreciated that the indication of the one or more resource identifiers may be transmitted as part of the second registration request.

Steps 1201 to 1205 are similar to steps 1101 to 1105 of Figure 11. However, in this example in step 1205 the UDM determines that there has been a change in vPLMN upon the wireless device moving to the AMF.

Steps 1206 to 1209 of Figure 12 are similar to steps 906 to 909 of Figure 9.

In this example, in step 1210 the UDM checks whether the EE subscriptions in the EE subscription information were permitted for the previous vPLMN. In step 1211 , the UDM may then compare the event exposures allowed in the current vPLMN with the event exposures allowed in the previous vPLMN and determines if any change in permitted event exposures has occurred. In other words, step 1211 may comprise determining, from the EE subscription information, a change in permitted event type subscriptions based on event type subscriptions permitted in the current vPLMN compared to event type subscriptions that were permitted in the previous vPLMN. It will be appreciated that some event exposures may be newly allowed in the current vPLMN, and some event exposures may be newly disallowed in the current vPLMN.

In step 1212, the UDM transmits a subscription request to the AMF indicating any newly allowed event exposures determined in step 1211. The AMF responds to this subscription request in step 1213.

In step 1214, the UDM transmits an unsubscribe request to the AMF indicating any newly disallowed event exposures determined in step 1211. The AMF responds to this subscription request in step 1215.

Figure 13 illustrates an example implementation of the method of Figure 8. In this example,

The following figure covers the SLA information for a particular vPLMN has been updated to updated SLA information.

Step 1300 indicates the precondition that the AMF is aligned with EE subscriptions according to the original SLA information associated with SLA-ld1 before it is modified.

In step 1301 , the UDM is notified of the change to the SLA information. In order to receive this notification, the UDM may transmit a subscription request subscribing to receive updates to the SLA information every time it receives an SLA-ld. However, since the SLA information is not expected to be changed that frequently, an alternative may be for the UDM to register in NRF in the UDM profile a new default notification endpoint to receive notifications from UDR when the SLA info is modified.

In step 1302, the SLA information associated with SLA-ld 1 is modified in UDR.

In step 1303, the UDR notifies the UDM of the changes to the SLA information associated with SLA-ld1. In step 1304 the UDM updates its SLA-ld1 SLA information cache.

In step 1305 the UDM gets the EE subscription information that comprise the SLA- Id1. For this, SLA-ld is required as a key to access relevant EE subscription information in the UDR. With this, the UDM retrieves the UEs that are affected by the SLA information change.

In step 1306 the UDM retries UE data for the affected UEs. In step 1307, the UDM determines the current PLMNs of the affected UEs from the retrieved UE data.

In steps 1308 and 1309, for the identified current PLMNs (of the affected UEs), the UDM compares the SLA before and after the modifications, to identify newly allowed or newly disallowed EE subscriptions.

In step 1310, based on the identification of the newly allowed EE subscriptions, for each affected PLMN and UE, the UDM transmits an EE subscription request to the AMF. In step 1311 the AMF responds to this EE subscription request.

In steps 1312, based on the identification of newly disallowed EE subscriptions, for each affected PLMN and UE, the UDM transmits an unsubscribe request to the AMF. The AMF may then respond to the unsubscribe request in step 1313.

Figure 14 illustrates a variant of the implementation of Figure 13. In this example, the EE subscription is required not for a single UE, but for anyUE (e.g. all the UEs in the network) or for a Group of UEs, in the figure “anyUE” is used, but it will be appreciated that the methods may be equally applied to a defined group of UEs.

Step 1401 to 1406 are similar to steps 701 to 706, with the difference that the subscription request applies to a group of UEs or anyUE, not to a single UE.

Step 1407 to 1409 of Figure 14 similar to steps 708 to 710 of Figure 7.

In step 1410, the UDM obtains a list of AMFs (with EE services) for the relevant PLMNs (the one that allows required EEs for “anyUE”).

Steps 1411 and 1412 are similar to steps 711 and 712 of Figure 7, but considering “anyUE”. Steps 1413 and 1414 are similar to steps 713 and 714 in figure 7, but in this example the indication to the NEF/AF is not per vPLMN, since the “anyllE” will affect a plurality/all PLMNs. The indication may therefore include that the request is not allowed for a list of PLMNIds.

Figure 15 illustrates a network function 1500 comprising processing circuitry (or logic) 1501. The processing circuitry 1501 controls the operation of the network function 1500 and can implement the method described herein in relation to an network function 1500. The processing circuitry 1501 can comprise one or more processors, processing units, multi-core processors or modules that are configured or programmed to control the network function 1500 in the manner described herein. In particular implementations, the processing circuitry 1501 can comprise a plurality of software and/or hardware modules that are each configured to perform, or are for performing, individual or multiple steps of the method described herein in relation to the network function 1500. It will be appreciated that the network function 1500 may comprise one or more virtual machines running different software and/or processes. The network function 1500 may therefore comprise, or be implemented in or as one or more servers, switches and/or storage devices and/or may comprise cloud computing infrastructure that runs the software and/or processes.

Briefly, the processing circuitry 1501 of the network function 1500 is configured to perform the method as described with reference to any of the first to fifth network functions herein.

In some embodiments, the network function 1500 may optionally comprise a communications interface 1502. The communications interface 1502 of the network function 1500 can be for use in communicating with other nodes, such as other virtual nodes. For example, the communications interface 1502 of the network function 1500 can be configured to transmit to and/or receive from other nodes requests, resources, information, data, signals, or similar. The processing circuitry 1501 of network function 1500 may be configured to control the communications interface 1502 of the network function 1500 to transmit to and/or receive from other nodes requests, resources, information, data, signals, or similar. The communications interface 1502 can use any suitable communication technology. Optionally, the network function 1500 may comprise a memory 1503. In some embodiments, the memory 1503 of the network function 1500 can be configured to store program code that can be executed by the processing circuitry 1501 of the network function 1500 to perform the method described herein in relation to the network function 1500. Alternatively or in addition, the memory 1503 of the network function 1500, can be configured to store any requests, resources, information, data, signals, or similar that are described herein. The processing circuitry 1501 of the network function 1500 may be configured to control the memory 1503 of the network function 1500 to store any requests, resources, information, data, signals, or similar that are described herein. The network function 1500 may be configured operate in the manner described herein in respect of an network function.

Figure 16 is a block diagram illustrating a first NF 1600 according to some embodiments. The first NF 1600 comprises a receiving module 1602 configured to receive a first subscription request for exposure of a first event type for the wireless device from a second NF, wherein the first subscription request comprises one or more service level agreement identifiers, SLA-ld. The first NF 1600 comprises an obtaining module 1604 configured to obtain SLA information associated with the one or more SLA-lds, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device. The first NF further comprises a forwarding module 1606 configured to responsive to the SLA information indicating that the exposure of the first event type is permitted in the first visitor network for the wireless device, forward the first subscription request to a third NF in the first visitor network. The first NF 1600 may operate in the manner described herein in respect of a first NF.

Figure 17 is a block diagram illustrating a fifth NF 1700 according to some embodiments. The fifth NF 1700 comprises a storing module 1702 configured to store service level agreement information associated with an SLA-ld, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device. The fifth NF 1700 may operate in the manner described herein in respect of a fifth NF.

Figure 18 is a block diagram illustrating a second NF 1800 according to some embodiments. The second NF 1800 comprises a receiving module 1802 configured receive a subscription request to subscribe to exposure of a first event type for the wireless device from an application function. The second NF 1800 further comprises an inserting module 1804 configured to insert one or more Service Level Agreement identifiers (SLA-IDs) that are associated with the MTC provider or application function into the subscription request. The second NF further comprises a forwarding module 1806 configured to forward the subscription request to a first network function. The second NF 1800 may operate in the manner described herein in respect of a second NF.

Figure 19 is a block diagram illustrating a fourth NF 1900 according to some embodiments. The fourth NF 1900 comprises an obtaining module 1902 configured to obtain event exposure subscription information for the wireless device. The fourth NF further comprises a removing module 1904 configured to: responsive to the first NF and/or the fourth NF not supporting synchronization of event exposure information, remove the event exposure subscription information from context information. The fourth NF further comprises a transmitting module 1906 configured to transmit a second registration request for the wireless device to the first NF, wherein the second registration request comprises an indication that the fourth NF has no access to event exposure subscription information for the wireless device. The fourth NF 1900 may operate in the manner described herein in respect of a fourth NF.

There is also provided a computer program comprising instructions which, when executed by processing circuitry (such as the processing circuitry 1501 of the network function 1500 described earlier), cause the processing circuitry to perform at least part of the method described herein. There is provided a computer program product, embodied on a non-transitory machine-readable medium, comprising instructions which are executable by processing circuitry to cause the processing circuitry to perform at least part of the method described herein. There is provided a computer program product comprising a carrier containing instructions for causing processing circuitry to perform at least part of the method described herein. In some embodiments, the carrier can be any one of an electronic signal, an optical signal, an electromagnetic signal, an electrical signal, a radio signal, a microwave signal, or a computer-readable storage medium.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims. Any reference signs in the claims shall not be construed so as to limit their scope.

Claims

1. A method in a first network function in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network, the method comprising: receiving a first subscription request for exposure of a first event type for the wireless device from a second NF, wherein the first subscription request comprises one or more service level agreement identifier, SLA-lds; obtaining SLA information associated with the one or more SLA-lds, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device; and responsive to the SLA information indicating that the exposure of the first event type is permitted in the first visitor network for the wireless device, forwarding the first subscription request to a third NF in the first visitor network.

2. The method as claimed in claim 1 wherein the SLA information indicates whether exposure of one or more event types associated with one or more particular characteristics are permitted in the first visitor network for the wireless device

3. The method as claimed in any one of claims 1 or 2 further comprising: responsive to the SLA information indicating that the exposure of the first event type is not permitted in the visitor network for the wireless device, refraining from transmitting the first subscription request to the third NF in the visitor network.

4. The method as claimed in claim 1 or 3 further comprising: storing subscription information associated with the wireless device based on the subscription request, wherein the subscription information comprises the one or more SLA-lds.

5. The method as claimed in claim 1 to 4 further comprising receiving an indication that the wireless device has moved from the third NF to a fourth NF in a second visitor network.

6. The method as claimed in claim 5 further comprising: obtaining subscription information and SLA information associated with the wireless device, responsive to at least one of the following conditions being met: the indication comprises an indication that the fourth NF does not have access to event exposure subscription information for the wireless device; and the second visitor network is not the same as the first visitor network.

7. The method as claimed in claim 6 further comprising: responsive to one or more event type subscriptions in the subscription information being allowed in the second visitor network, transmitting a second subscription request to the fourth NF for the one or more event type subscriptions.

8. The method as claimed in claim 5 further comprising, refraining from transmitting a second subscription request to the fourth NF in the visitor network responsive to all of the following conditions being met: the indication comprises an indication that the fourth NF has access to event exposure subscription information for the wireless device; and the second visitor network is the same as the first visitor network.

9. The method as claimed in claim 6 wherein the first visitor network is not the same as the second visitor network, further comprising: determining, from the subscription information, a change in permitted event type subscriptions based on event type subscriptions permitted in the second visitor network compared to event type subscriptions that were permitted in the first visitor network; and transmitting a subscribe or unsubscribe request to the fourth NF indicating the change in permitted event type subscriptions.

10. The method as claimed in any preceding claim further comprising: receiving an indication that the SLA information has been modified to updated SLA information; obtaining subscription information for one or more wireless devices associated with the updated SLA information; and for each of the one or more wireless devices: determining, from the subscription information, a change in permitted event type subscriptions for the first visitor network based on event type subscriptions permitted in the updated SLA information compared to event type subscriptions that were permitted in the SLA information; and transmitting a subscribe or unsubscribe request to the fourth or third NF indicating the change in permitted event type subscriptions.

11. The method as claimed in any preceding claim wherein first network function comprises a UDM.

12. The method as claimed in any preceding claim wherein the second network function comprises a network exposure function in a home network of the wireless device.

13. The method as claimed in any preceding claim wherein the third NF comprises an AMF.

14. A method in a fifth network function in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network, the method comprising: storing service level agreement information associated with one or more SLA-lds, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device.

15. The method as claimed in claim 14 further comprising: receiving a request for SLA information comprising the one or more SLA-lds from a first NF, and transmitting the SLA information to the first NF.

16. The method as claimed in claim 14 and 15 further comprising: receiving a request for subscription information for the wireless device from a first NF; and transmitting the subscription information to the first NF with the one or more SLA-lds.

17. A method in a second network function in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network, the method comprising: receiving a subscription request to subscribe to exposure of a first event type for the wireless device from an application function, inserting one or more SLA-lds that is associated with the MTC provider or application function into the subscription request, and forwarding the subscription request to a first network function.

18. A method in a fourth network function in a first visitor network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in a home network and the wireless device is roaming in the first visitor network, the method comprising: obtaining event exposure subscription information for the wireless device, responsive to the first NF and/or the fourth NF not supporting synchronization of event exposure information: removing the event exposure subscription information from context information; and transmitting a second registration request for the wireless device to the first NF, wherein the second registration request comprises an indication that the fourth NF has no access to event exposure subscription information for the wireless device.

19. The method as claimed in claim 18 further comprising: responsive to transmitting the first registration request, receiving a subscribe or unsubscribe request from the first NF for event type subscriptions for the wireless device.

20. The method as claimed in claim 18 or 19 further comprising: transmitting a first registration request for the wireless device to a first NF, wherein, responsive to the first NF and the fourth NF supporting synchronization of event exposure information, the first registration request comprises an indication that the fourth NF has access to the event exposure subscription information for the wireless device...

21. The method as claimed in any one of claims 18 to 20 further comprising: transmitting, to the first NF, an indication of one or more resource identifiers associated with one or more subscription resources in the event exposure subscription information for the wireless device.

22. The method as claimed in claim 21 wherein the step of transmitting, to the first NF, the indication of the one or more resource identifiers is performed prior to transmitting a second registration request.

23. The method as claimed in claim 21 wherein the indication of the one or more resource identifiers is transmitted as part of the second registration request.

24. A first network function, NF, in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network, the first NF comprising processing circuitry configured to cause the first NF to: receive a first subscription request for exposure of a first event type for the wireless device from a second NF, wherein the first subscription request comprises one or more service level agreement identifiers, SLA-ld; obtain SLA information associated with the one or more SLA-lds, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device; and responsive to the SLA information indicating that the exposure of the first event type is permitted in the first visitor network for the wireless device, forward the first subscription request to a third NF in the first visitor network.

25. The first NF as claimed in claim 24 wherein the processing circuitry is further configured to cause the first NF to perform the method as claimed in any one of claims 2 to 13.

26. A fifth network function, NF, in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network, the fifth NF comprising processing circuitry configured to cause the fifth NF to: store service level agreement information associated with an SLA-ld, wherein the SLA information indicates whether exposure of one or more event types is permitted in the first visitor network for the wireless device.

27. The fifth NF as claimed in claim 26 wherein the processing circuitry is further configured to cause the first NF to perform the method as claimed in any one of claims 15 to 16.

28. A second network function, NF, in a home network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in the home network and the wireless device is roaming in a first visitor network, the second NF comprising processing circuitry configured to cause the second NF to: receive a subscription request to subscribe to exposure of a first event type for the wireless device from an application function, insert one or more Service Level Agreement identifiers (SLA-IDs) that are associated with the MTC provider or application function into the subscription request, and forward the subscription request to a first network function.

29. A fourth network function, NF in a first visitor network for controlling event exposure for a wireless device, wherein a subscriber profile of the wireless device is held in a home network and the wireless device is roaming in the first visitor network, the fourth NF comprising processing circuitry configured to cause the fourth NF to: obtain event exposure subscription information for the wireless device; and responsive to the first NF and/or the fourth NF not supporting synchronization of event exposure information: remove the event exposure subscription information from context information; and transmit a second registration request for the wireless device to the first NF, wherein the second registration request comprises an indication that the fourth NF has no access to event exposure subscription information for the wireless device.

30. The fourth NF as claimed in claim 29 wherein the processing circuitry is further configured to cause the first NF to perform the method as claimed in any one of claims 19 to 23.

31. A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out a method according to any of claims 1 to 23.

32. A computer program product comprising non transitory computer readable media having stored thereon a computer program according to claim 31.