Support for priority for SMS over IMS

Abstract

Systems and methods are disclosed for supporting Multimedia Priority Service (MPS) for messaging over Internet Protocol (IP) Multimedia Subsystem (IMS). In one embodiment, a method performed by a Proxy Call Session Control Function (P-CSCF) for on-demand MPS for messaging comprises receiving, from a Serving Call Session Control Function (S-CSCF), a notification that indicates that MPS messaging is activated for a User Equipment (UE) or subscriber. The method further comprises receiving a Session Initiation Protocol (SIP) message from the UE and inserting a resource-priority header into the SIP message, the resource-priority header being such that the SIP message is handled in accordance with MPS messaging being activated for the UE or subscriber. In this manner, support for MPS message over IMS is provided.

Description

SUPPORT FOR PRIORITY FOR SMS OVER IMSRelated Applications

[0001] This application claims the benefit of provisional patent application serial number 63 / 556,110, filed February 21, 2024, the disclosure of which is hereby incorporated herein by reference in its entirety.Technical Field

[0002] The present disclosure relates to Multimedia Priority Service (MPS) over Internet Protocol (IP) Multimedia Subsystem (IMS) and, more specifically, to MPS for messaging over IMS.Background

[0003] Multimedia Priority Service (MPS) is an existing feature that enables subscribers who have the feature to be able to get priority when initiating an Internet Protocol (IP) Multimedia Subsystem (IMS) session. Subscribers who do not have this feature can also initiate a regular IMS session preceded with a certain feature code that enables a third party to authorize these subscribers for priority service for the IMS session. The existing feature ensures that a subscriber authorized for a priority IMS session shall have the signaling bearer and the user plane bearer provisioned with the proper Quality of Service (QoS) and Allocation and Retention Policy (ARP) so they are exempt from pre-emption in case of congestion. The 3rd Generation Partnership Project (3GPP) Technical Specifications (TSs) 23.501 (see up to V18.4.0), 23.502 (see up to V18.4.0), 23.503 (see up to V18.4.0), 23.401 (see up to V18.4.0), and 23.203 (see up to V17.2.0) already specify how 4th Generation (4G) and 5th Generation (5G) systems support MPS.Summary

[0004] Systems and methods are disclosed for supporting Multimedia Priority Service (MPS) for messaging over Internet Protocol (IP) Multimedia Subsystem (IMS). In one embodiment, a method performed by a Proxy Call Session Control Function (P-CSCF) for on-demand MPS for messaging comprises receiving, from a Serving Call Session Control Function (S-CSCF), a notification that indicates that MPS messaging is activated for aUser Equipment (UE) or subscriber. The method further comprises receiving a Session Initiation Protocol (SIP) message from the UE and inserting a resource-priority header into the SIP message, the resource-priority header being such that the SIP message is handled in accordance with MPS messaging being activated for the UE or subscriber. In this manner, support for MPS message over IMS is provided.

[0005] In one embodiment, the method further comprises sending the SIP message including the resource-priority header to a next hop in a delivery path of the SIP message.

[0006] In one embodiment, the resource-priority header ensures that the SIP message is transported with priority over other non-MPS traffic.

[0007] In one embodiment, the method further comprises subscribing to receive, from the S-CSCF, the notification that indicates MPS messaging is activated for the UE or subscriber. In one embodiment, subscribing to receive the notification comprises subscribing for notifications of changes in the registration of the UE or subscriber during an IMS registration procedure of the UE.

[0008] Corresponding embodiments of a P-CSCF and an IMS node for implementing a P-CSCF are also disclosed.

[0009] Embodiments of a method performed by a Home Subscriber Server, HSS, of an IMS are also disclosed. In one embodiment, a method performed by an HSS of an IMS for on-demand MP for messaging comprises updating a UE profile of a UE to activate MPS messaging for the UE or subscriber and sending, to a P-CSCF, a notification that indicates that MPS messaging is activated for the UE or subscriber.

[0010] In one embodiment, updating the UE profile is responsive to a request received at the HSS or at an associated Unified Data Management (UDM) to activate MPS messaging for the UE or subscriber.

[0011] Corresponding embodiments of an HSS and an IMS node for implementing an HSS are also disclosed.

[0012] Embodiments of a method performed in a core network of a cellular communications system are also disclosed. In one embodiment, a method performed in a core network of a cellular communications system comprises, at a Network Exposure Function (NEF), receiving a request from an Application Function (AF) to activate MPS messaging for a UE or subscriber and sending a request to a Unified Data Management (UDM) of the core network to activate MPS messaging for the UE or subscriber. Themethod further comprises, at the UDM, receiving the request from the NEF to activate MPS messaging for the UE or subscriber and updating a UE profile of the UE or subscriber to activate MPS messaging for the UE or subscriber.

[0013] In one embodiment, the method further comprises, at the UDM or at associated Unified Data Repository (UDR), sending a notification to a Policy and Control Function (PCF) that indicates that MPS messaging is activated for the UE or subscriber. In one embodiment, the method further comprises, at the UDM or the associated UDR, starting a timer associated to the activation MPS messaging for the UE or subscriber, wherein MPS messaging for the UE or subscriber is deactivated upon expiry of the timer. In one embodiment, the method further comprises, at the PCF, receiving the notification that indicates that MPS messaging is activated for the UE or subscriber and sending, to a Session Management Function (SMF), a request to update Policy and Charging Control (PCC) rules wherein the update ensures that a default signaling bearer of the UE or subscriber is updated to a Quality of Service (QoS) that prioritizes MPS messaging traffic over other traffic. In one embodiment, the PCF subscribes to the UDR to be notified when there are changes to MPS messaging.

[0014] In one embodiment, the method further comprises, at the NEF), sending an update message to the UDR that indicates that MPS messaging is activated for the UE or subscriber.

[0015] In one embodiment, the method further comprises, at the UDM, sending a request to an Access and Mobility Management Function (AMF) to activate MPS messaging for the UE or subscriber. In one embodiment, the method further comprises, at the AMF, receiving the request to activate MPS messaging for the UE or subscriber and sending, to an SMF, an update request that indicates that MPS messaging is activated for a corresponding PDU session of the UE. The method further comprises, at the SMF, receiving the update request that indicates that MPS messaging is activated for the corresponding PDU session of the UE and sending, to a PCF, a request that informs the PCF that MPS messaging is activated for the corresponding PDU session of the UE. The method further comprises, at the PCF, receiving the request from the SMF and initiating a procedure to update PCC rules of the UE, wherein the update ensures that a default signaling bearer of the UE or subscriber is updated to a QoS that prioritizes MPS messaging traffic over other traffic.

[0016] Embodiments of a method performed by an NEF are also disclosed. In one embodiment, a method performed in NEF in a core network of a cellular communications system comprises receiving a request from an AF to activate MPS messaging for a UE or subscriber and sending a request to activate MPS messaging for the UE or subscriber to a UDM of the core network.

[0017] In one embodiment, the method further comprises sending an update message to a UDR that indicates that MPS messaging is activated for the UE or subscriber.

[0018] Corresponding embodiments of an NEF and a network node for implementing an NEF are also disclosed.Brief of the

[0019] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0020] Figure 1 illustrates one example of a wireless communication system in which a User Equipment (UE) has the capability to utilize a cellular access network, which is shown as a 3rdGeneration Partnership Project (3GPP) (Radio) Access Network ((R)AN).

[0021] Figure 2 illustrates a specific example of the wireless communication system of Figure 1 in which the 3GPP core network is a 5thGeneration Core (5GC).

[0022] Figure 3 is a call flow that illustrates an embodiment of the present disclosure in accordance with a first option described herein.

[0023] Figure 4 is a call flow that illustrates an embodiment of the present disclosure in accordance with a second option described herein.

[0024] Figure 5 is a call flow that illustrates an embodiment of the present disclosure in accordance with a third option described herein.

[0025] Figures 6 and 7 are schematic block diagrams of exemplary embodiments of an Internet Protocol (IP) Multi-media Subsystem (IMS) node.

[0026] Figures 8 and 9 are schematic block diagrams of exemplary embodiments of a network node.Detailed Description

[0027] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0028] Radio Node: As used herein, a "radio node" is either a radio access node or a User Equipment (UE).

[0029] Radio Access Node: As used herein, a "radio access node" or "radio network node" or "radio access network node" is any node in a Radio Access Network (RAN) of a cellular communications network that operates to wirelessly transmit and / or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a base station (e.g., a network node that implements a gNB Central Unit (gNB-CU) or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node.

[0030] Core Network Node: As used herein, a "core network node" is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Home Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing an Access and Mobility Management Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like.

[0031] User Equipment (UE): As used herein, a UE is a wireless communication device, which may be any type of wireless device that has access to (i.e., is served by) a wireless communication network (e.g., a cellular communication network). Some examples of a UE include, but are not limited to: a 3GPP UE (i.e., a UE in a 3GPP network), a Machine Type Communication (MTC) device, and an Internet of Things (loT) device. Such UEs may be, or may be integrated into, a mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or PC. The UE may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and / or data via a wireless connection.

[0032] Network Node: As used herein, a "network node" may be any node that is either part of the RAN or the core network of a cellular communications network / system. Other types of network nodes may be network node that are external to the RAN and core network of a cellular communications network such as, e.g., a network node hosting a non-trusted Application Function (AF) that accesses the 5GC via a Network Exposure Function (NEF).

[0033] IMS Node: As used herein, an "IMS node" is a node that implements all or part of the functionality of an Internet Protocol (IP) Multimedia Subsystem (IMS) entity such as, e.g., Proxy Call Session Control Function (P-CSCF), an Interrogating Call Session Control Function (I-CSCF), a Serving Call Session Control Function (S-CSCF), an Access Transfer Control Function (ATCF), an Access Gateway (AGW), or the like.

[0034] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system.

[0035] There currently exist certain challenge(s). Multimedia Priority Service (MPS) is an existing feature that enables subscribers who have the feature to be able to get priority when initiating an Internet Protocol (IP) Multimedia Subsystem (IMS) session. Subscribers who do not have this feature can also initiate a regular IMS session preceded with certain feature code that enables a third party to authorize these subscribers for priority service for the IMS session. The existing feature ensures that a subscriber authorized for a priority IMS session shall have the signaling bearer and theuser plane bearer provisioned with the proper Quality of Service (QoS) and Allocation and Retention Policy (ARP) so they are exempt from pre-emption in case of congestion. 3GPP TSs 23.501, 23.502, 23.503, 23.401 and 23.203 already specify how 4thGeneration (4G) and 5thGeneration (5G) systems support MPS.

[0036] There is a new requirement to support priority for messaging (i.e., MPS Messaging) on demand for subscribers as well. This implies that subscribers authorized for MPS Messaging will have priority for their messages over other traffic. This feature can be orthogonal to the original MPS feature. However, there is no solution currently specified for this requirement in the 3GPP specifications.

[0037] Certain aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges. Three options are presented below (i.e., "Option 1", "Option 2", and "Option 3").

[0038] In regard to Option 1, embodiments of the disclosed solution rely on an external Application Function (AF) setting the MPS subscription in Unified Data Management (UDM) / Unified Data Repository (UDR) when the AF wants to grant an MPS Messaging subscription for a subscriber. The subscription is temporary in nature. In one embodiment, the subscription is enabled for a configured time in the UDM and is removed (i.e., disabled) once the timer expires.

[0039] In IMS, when an MPS Messaging subscription is granted, the UDM informs Home Subscriber Server (HSS) so it updates the IMS subscription for the subscriber to activate MPS Messaging. The HSS informs the Serving Call Session Control Function (S- CSCF) of the activation of MPS Messaging, and the S-CSCF informs the Proxy Call Session Control Function (P-CSCF) through a NOTIFY associated with the Registration event package. This enables the P-CSCF to insert the Resource-Priority-Header (RPH) when a Session Initiation Protocol (SIP) MESSAGE is received from a subscriber having MPS Messaging active.

[0040] In the 5G System (5GS), the UDM / UDR informs the Policy and Control Function (PCF) through a NOTIFY of a change to the MPS Messaging subscription. The PCF subscribes to the UDR to be notified of changes to MPS messaging when the IMS Protocol Data Unit (PDU) session is established. The PCF in turn updates the Session Management Function (SMF) with new Policy and Charging Control (PCC) rules to update the User Plane Function (UPF) associated with the signaling bearer for the PDU session with the proper QoS and ARP corresponding to MPS Messaging.

[0041] When timer in the UDM expires, same steps above are repeated to remove MPS Messaging to ensure that normal treatment of SMS over IMS resume.

[0042] The timer applies to all options.

[0043] In general, when MPS messaging shows in a call flow, it is a trigger for new behavior. This is in addition to the timer in UDM.

[0044] Certain embodiments may provide one or more of the following technical advantage(s). Embodiments of the present disclosure provide solutions reusing existing principles for MPS.

[0045] In this regard, Figure 1 illustrates one example of a wireless communication system 100 in which a UE 102 has the capability to utilize a cellular access network, which is shown as a 3GPP (Radio) Access Network ((R)AN) 104. The 3GPP (R)AN 104 may be a Fourth Generation (4G) RAN (e.g., an LTE or LTE-Advanced RAN, including a number of base stations which are referred to as eNBs) or a 5G RAN (e.g., a NR RAN (also referred to as a NG-RAN), including a number of base stations which are referred to as gNBs). The 3GPP (R)AN 104 is connected to a core network, which is shown as a 3GPP core network 106 (e.g., an Evolved Packet Core (EPC) or 5G Core (5GC)). The 3GPP core network 106 is connected to an Internet Protocol (IP) Multimedia Subsystem (IMS) 108, as will be appreciated by one of skill in the art.

[0046] Figure 2 illustrates a specific example of the wireless communication system 100 of Figure 1 in which the 3GPP core network 106 is a 5GC 200. As will be appreciated by one of skill in the art, the 5GC 200 includes a number of Network Functions (NFs) connected by service-based interfaces in the control plane. An NF may be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., a cloud infrastructure. As illustrated, the 5GC 200 includes a UPF 202, an SMF 204, an AMF 206, an AUSF 208, a NSSF 210, a NEF 212, a NRF 214, a PCF 216, a UDM 218, and an Application Function (AF) 220. Note that, while in Figure 2, the AF 220 is shown as part of the 5GC 200, the AF 220 may alternatively be external to the 5GC 200 (e.g., a non-trusted or 3rdpart AF).

[0047] Note that while Figure 2 illustrates the 5GC 200 as a service-based architecture, a reference point representation may alternatively be used. Reference point representations of the 5G network architecture are used to develop detailed call flows in the normative standardization. Each NF interacts with another NF directly. It ispossible to use intermediate functions to route messages from one NF to another NF. In the control plane, a set of interactions between two NFs is defined as a service so that its reuse is possible. This service enables support for modularity. The user plane supports interactions such as forwarding operations between different UPFs 202.

[0048] The service(s) that an NF provides to other authorized NFs can be exposed to the authorized NFs through the service-based interface. In Figure 2, the service-based interfaces are indicated by the letter "N" followed by the name of the NF (e.g., Namf for the service based interface of the AMF 206 and Nsmf for the service based interface of the SMF 204, etc.).

[0049] As will be understood by those of skill in the art, the IMS 112 includes various IMS entities such as, for example, a Proxy Call Session Control Function (P-CSCF) 222, an Interrogating Call Session Control Function (I-CSCF) 224, a Serving Call Session Control Function (S-CSCF) 226, an Access Transfer Control Function (ATCF) 228, and an Access Gateway (AGW) 230. The operational details of the P-CSCF 222, the I-CSCF 224, the S-CSCF 226, the ATCF 228, and the AGW 230 are well known to those of skill in the art and are therefore not described here.

[0050] Now, a more detailed description of embodiments of the present disclosure will be provided. These details include a description of three options, denoted herein as "Option 1", "Option 2", and "Option 3".

[0051] Option 1 is aligned with the above description.

[0052] Figure 3 is a call flow that illustrates an embodiment of the present disclosure in accordance with Option 1. Note that the procedure does not include the update of RAN Resources to reflect the new ARP, triggered by the SMF 204 via the AMF 206 for brevity.

[0053] The steps in the call flow are as follows:• Step 0: The UE 102 performs IMS registration (i.e., the UE 102 IMS registers) after initiating an IMS PDU session based on existing procedures in 3GPP TS 23.228. In this procedure, the P-CSCF 222 subscribes to the S-CSCF 226 for the Registrations event package to be notified of any changes in registration. In an alternative embodiment, in conjunction with an IMS registration, the P-CSCF 222 subscribes to the PCF 216 (over N5) for MPS for Messaging (MPS4MSG) policy changes. I.e., when the PCF 216 gets Notified by UDR (N36) about MP4MSG activation, the PCF 216 makes an MPS notify to P-CSCF 222 over N5, whereby P-CSCF 222 stores a trigger to add an RPH header to forthcoming Mobile Originating (MO) SIP MESSAGES.• Step 0.1: The PCF 216 subscribes to UDR for changes in the MPS Messaging subscription. This is an extension of the existing procedure to include MPS Messaging.• Step 1: An external / internal AF needing to authorize a specific subscriber for the MPS Messaging feature issues a request to the NEF 212 via the Nnef_ParameterProvision_Update Request (Activate MPS Messaging, ...) Request to activate MPS Messaging for the subscriber. This is an extension of the existing request to support MPS Messaging.• Step 2: The NEF 212 issues a request to UDM via the Request Nudm_SDM_ModifySubscription Request (MPS Messaging, ...) to activate the MPS messaging subscription. This existing Request is extended to support this new feature. In one embodiment, the UDM associates a configured timer with the MPS Messaging activation. In one embodiment, the value of the timer may be proposed by the AF. When the timer expires, the UDM automatically removes the MPS Messaging subscription for the subscriber. In one embodiment, the UDM starts the timer when it successfully responds to the NEF 212.• Step 3: The UDM informs HSS of the update to the MPS subscription for the subscriber IMS subscription.• Step 4: The HSS notifies the S-CSCF 226 that the subscriber now has MPS Messaging (i.e., that MPS Messaging is enabled for the subscriber).• Step 4.5: The S-CSCF 226 notifies the P-CSCF 222 that the subscriber now has MPS Messaging (i.e., the MPS Messaging is enabled for the subscriber). o Note that, in the example above of steps 4 and 4.5, the P-CSCF 222 is notified of the activation of MPS Message for the subscriber (or associated UE 102) by receiving the notification from the S-CSCF 226, which was notified by the HSS. However, any mechanism for notifying the P-CSCF 222 of the activation of MPS messaging for the subscriber (or associated UE 102) can be used. Examples include the following:■ Example 1: The P-CSCF 222 receives the notification from Registration event package.■ Example 2: The P-CSCF 222 subscribes to the PCF 216 (or PCRF) for a new event for MPS messaging and, when the PCF / PCRF is notified of the activation of MPS messaging for the subscriber (or associated UE 102), the PCF / PCRF then notifies the P-CSCF 222.■ Example 3: The P-CSCF 222 issues a request to the S-CSCF 226. The S-CSCF 226 is updated from the HSS about MPS messaging activation for the subscriber (or associated UE 102), and the S- CSCF 226, based on this update, can then notify the P-CSCF 222.• Step 5: The UDM / UDR issues a Nudr_Notify Request (MPS Messaging set) to notify the PCF 216 that the Subscriber has MPS Messaging set.• Step 6: The PCF 216 issues a Npcf_SMPolicyControl_Update service Request (New PCC rules including upgrade of signalling bearer) to the SMF 204 to download new PCC rules to ensure that the default signaling bearer is upgraded to the proper QoS and allocated ARP has the proper value as well. The QoS and ARP are a QoS and ARP are set to values suitable for MPS Messaging.• Step 7: The SMF 204 issues an N4 Session Establishment / Modification Request to the UPF 202 to download the new policies and PCC rules.• Step 8: The SMF 204 returns to the PCF 216 an Npcf_SMPolicyControl_Update service Response.• Step 9: The subscriber sends a SIP MESSAGE to the P-CSCF 222.• Step 10: The P-CSCF 222 checks the UE context and, based on MPS Messaging being set and active, inserts the proper resource-priority header to ensure that the SIP MESSAGE gets the proper treatment before proxying it to the next hop. Alternatively, the S-CSCF 226 receives the SIP message from the P-CSCF 222 and, based on MPS Messaging being set and active, inserts the proper resourcepriority header to ensure that the SIP message gets the proper treatment before proxying it to the next hop.

[0054] Subsequently the SIP MESSAGE is delivered to the SMS_C. All nodes on the path ensure that transport of such a Message gets high priority over other traffic.

[0055] In embodiments in which the timer is started in the UDM in step 2 expires, the same steps are undertaken to ensure that the default signaling bearer is restored to its original status and the P-CSCF 222 is informed that the MPS Messaging is removed.No call flow is shown as these are essentially the same steps, removing the MPS Messaging and updating the UPF with corresponding new PCC rules.

[0056] Figure 4 is a call flow that illustrates an embodiment of the present disclosure in accordance with Option 2. Compared to option 1, in Option 2, the PCF 216 subscribes to the UDR to be notified when there are changes to MPS Messaging (step 0.1).Additionally, when the AF activates the MPS Messaging for the subscriber in step 1, the NEF 212 updates the UDR (step lb). This in turn triggers a notification to the PCF 216 in step 5.

[0057] In the call flow of Figure 4, Steps 0.1 and 5 are different, and step lb is extra compared to Option 1 (shown in Figure 3).

[0058] Given that the additional and different steps are explained above, all other steps are identical to option 1 and are not repeated.

[0059] In Option 3, the AMF 206 is informed when the AF activates the MPS priority via the NEF 212 as in Option 1 and Option 2. The UDM is updated as in Option 1 and Option 2.

[0060] The following is new for Option 3 as compared to Option 1 and Option 2. The AMF 206 is notified about MPS Messaging change in subscription. The AMF 206 then issues a PDU Session update to the SMF 204 to inform the SMF 204 of the activation of MPS Messaging for this PDU Session. The SMF 204 in turn issues to the PCF 216 a policy authorization update request to fetch new PCC rules. Following that, and this is the same as in Option 1 and Option 2, the PCF 216 updates the SMF 204 with the new PCC rules which are downloaded to the UPF 202.

[0061] Figure 5 is a call flow that illustrates an embodiment of the present disclosure in accordance with Option 3. The call flow illustrates the above procedure. The steps in the call flow of Figure 5 are as follows:• Steps 0, 1, 3, 4, and 4.5 are the same as the corresponding steps 0, 1, 3, 4, and 4.5 of Option 1 and Option 2.• In Step 4b, the AMF 206 is notified of the changes in MPS Messaging subscription.• In step 5b, the AMF 206 initiates an Nsmf_PDUSession_updateSMContext Request to inform the SMF 204 that the MPS Messaging is activated for this PDU session.• In step 5c, the SMF 204 initiates an Npcf_PolicyAuthorization_Update Request to inform the PCF 216 so it provides the SMF 204 with new PCC rules to upgrade the QoS and ARP to appropriate values.• Steps 6-11 are the same as the corresponding steps of Option 1 and Option 2.

[0062] Some exemplary Technical Specification (TS) impacts for an exemplary embodiment of the present disclosure are as follows:• P-CSCF: 3GPP TS 23.228. o P-CSCF subscribes to S-CSCF to be notified of an MPS messaging activation / deactivation to insert the proper resource-priority-header (RPH) based on received SIP MESSAGE when conditions apply. o All options• HSS: 3GPP TS 23.228. o HSS notifies S-CSCF of an MPS messaging activation / deactivation. The S- CSCF notifies the P-CSCF of the MPS messaging activation / deactivation upon notification from HSS. o All Options• UDM / UDR: 3GPP TS 23.502 / 23.501. o UDM enables provisioning of MPS Messaging (all options) o (optional) Starts and stops the timer associated with MPS for messaging (all options) o Notifies the PCF due to a subscription change in MPS Messaging in option 1 o Notifies the AMF due to a subscription change in MPS Messaging in option 3.• PCF: 3GPP TS 23.502 / 23.501. o Handles Notifications from UDM - option lr elated to MPS Messaging. o Informs SMF of new PCC rules associated with MPS Messaging when conditions apply - all options o Subscribes to be informed of change in subscription data related to MPS Messaging - Option 1.• NEF: 3GPP TS 23.502 / 23.501. o Supports request to UDM for provisioning of MPS Messaging in all options o Updates UDR in option 2• AMF: 3GPP TS 23.502 / 23.501 - Option 3 o AMF to initiate modification of SMF when notified that MPS Messaging is activated.

[0063] In Options 1, 2, and 3 above, the P-CSCF 222 is notified of the activation MPS messaging for the subscriber (or associated UE 102), and, based on this notification, the P-CSCF 222 inserts the priority header into the SIP message(s) for originating SMS received from the UE 102. However, in another variation that is applicable to Option 1, 2, and 3, the P-CSCF 222 may not be notified of the activation of MPS messaging for the subscriber (or associated UE 102). Instead, the S-CSCF 226 is notified of the activation of MPS messaging for the subscriber (or associated UE 102), and the S-CSCF 226 inserts the priority header in the SIP message(s) from the UE 102 that the S-CSCF 226 receives from the P-CSCF 222.

[0064] Figure 6 is a schematic block diagram of an IMS node 600 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The IMS node 600 may be, for example, a node that implements all or part of the functionality of an IMS entity (e.g., the P-CSCF 222, HSS, or the like) as described herein. As illustrated, the IMS node 600 includes one or more processors 604 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and / or the like), memory 404, and a network interface 608. The one or more processors 604 are also referred to herein as processing circuitry. The one or more processors 604 operate to provide one or more functions of the IMS node 600 as described herein. In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 606 and executed by the one or more processors 604.

[0065] Figure 7 is a schematic block diagram that illustrates a virtualized embodiment of the IMS node 600 according to some embodiments of the present disclosure. As used herein, a "virtualized" IMS node is an implementation of the IMS node 600 in which at least a portion of the functionality of the IMS node 600 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, the IMS node 600 includes one or more processing nodes 700 coupled to or included as part of a network(s) 702. Each processing node 700 includes one or more processors 704 (e.g., CPUs, ASICs, FPGAs, and / or the like), memory 706, and a network interface 708.

[0066] In this example, functions 710 of the IMS node 600 described herein are implemented at the one or more processing nodes 700 or distributed across two or more of the processing nodes 700 in any desired manner. In some particular embodiments, some or all of the functions 710 of the IMS node 600 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environ ment(s) hosted by the processing node(s) 700.

[0067] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the IMS node 600 or a node (e.g., a processing node 700) implementing one or more of the functions 710 of the IMS node 600 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0068] Figure 8 is a schematic block diagram of a network node 800 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The network node 800 may be, for example, a network node that implements all or part of the functionality of NF in a core network as described herein (e.g., one or more functions of the AMF 206, UPF 202, SMF 204, PCF 216, UDM, UDR, or the like, as described herein). As illustrated, the network node 800 includes one or more processors 804 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and / or the like), memory 806, and a network interface 808. The one or more processors 804 are also referred to herein as processing circuitry. The one or more processors 804 operate to provide one or more functions of the network node 800 as described herein (e.g., one or more functions of the AMF 206, UPF 202, SMF 204, PCF 216, UDM, UDR, or the like, as described herein). In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 806 and executed by the one or more processors 804.

[0069] Figure 9 is a schematic block diagram that illustrates a virtualized embodiment of the network node 800 according to some embodiments of the present disclosure. Again, optional features are represented by dashed boxes. As used herein,a "virtualized" network node is an implementation of the network node 800 in which at least a portion of the functionality of the network node 800 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, the network node 800 includes one or more processing nodes 900 coupled to or included as part of a network(s) 902. Each processing node 900 includes one or more processors 904 (e.g., CPUs, ASICs, FPGAs, and / or the like), memory 906, and a network interface 908.

[0070] In this example, functions 910 of the network node 800 described herein (e.g., one or more functions of the AMF 206, UPF 202, SMF 204, PCF 216, UDM, UDR, or the like, as described herein) are implemented at the one or more processing nodes 900 or distributed across two or more of the processing nodes 900 in any desired manner. In some particular embodiments, some or all of the functions 910 of the network node 800 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 900.

[0071] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the network node 800 or a node (e.g., a processing node 900) implementing one or more of the functions 910 of the network node 800 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0072] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory,flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according to one or more embodiments of the present disclosure.

[0073] While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

[0074] Some exemplary embodiments of the present disclosure are as follows:

[0075] Embodiment 1: A method performed by a Proxy Call Session Control Function, P-CSCF, (222), for on-demand multimedia priority service, MPS, the method comprising any one or more of the following: subscribing (Fig. 3, step 0; Fig. 4, step 0; Fig. 5, step 0) for notifications of changes in registration of a User Equipment, UE, (102) (or subscriber); receiving (Fig. 3, step 4.5; Fig. 4, step 4.5; Fig. 5, step 4.5) a notification that indicates that MPS messaging is activated for the UE (102) (or subscriber); receiving (Fig. 3, step 9; Fig. 4, step 9; Fig. 5, step 10) a Session Initiation Protocol, SIP, message from the UE (102); and inserting (Fig. 3, step 10; Fig. 4, step 10; Fig. 5, step 11) a resource-priority header into the SIP message, the resource-priority header such that the SIP message gets handled in accordance with MPS messaging being activated for the UE (102).

[0076] Embodiment 2: The method of embodiment 1, further comprising sending the SIP message including the resource-priority header to a next hop in a delivery path of the SIP message.

[0077] Embodiment 3: The method of embodiment 2, wherein the delivery path of the SIP message is via a cellular communications system, and the resource-priority header ensures that the SUP message is transported through the cellular communications system in accordance with a certain Quality of Service, QoS, and / or Allocation and Retention Policy, ARP, for MPS traffic.

[0078] Embodiment 4: The method of embodiment 1 or 2, wherein the resourcepriority header ensures that the SUP message is transported with priority over other non-MPS traffic.

[0079] Embodiment 5: The method of any of embodiments 1 to 4, wherein subscribing for the notifications comprises subscribing to a Home Subscriber Server, HSS, for the notifications of changes in the registration of the UE (102) (or subscriber), and receiving the notification comprises receiving the notification that indicates MPS messaging is activated for the UE (102) (or subscriber) from the HSS.

[0080] Embodiment 6: The method of any of embodiments 1 to 5, wherein subscribing for notifications of changes in the registration of the UE (102) (or subscriber) is performed during an IMS registration procedure of the UE (102) after an IMS PDU session has been established for the UE (102).

[0081] Embodiment 7: A Proxy Call Session Control Function, P-CSCF, (222) adapted to perform the method of any of embodiments 1 to 6.

[0082] Embodiment 8: An Internet Protocol, IP, Multimedia Subsystem, IMS, node for implementing a Proxy Call Session Control Function, P-CSCF, (222), the IMS node comprising: a communication interface; and processing circuitry associated with the communication interface, the processing circuitry configured to cause the IMS node to perform the method of any of embodiments 1 to 6.

[0083] Embodiment 9: A method performed by a Serving Call Session Control Function, S-CSCF, (226), for on-demand multimedia priority service, MPS, the method comprising any one or more of the following: receiving (Fig. 3, step 4; Fig. 4, step 4; Fig. 5, step 4) a notification that indicates that MPS messaging is activated for a UE (102) (or subscriber); receiving, from a Proxy Call Session Control Function, P-CSCF, (222), a Session Initiation Protocol, SIP, message originating from the UE (102); and inserting a resource-priority header into the SIP message, the resource-priority header such that the SIP message gets handled in accordance with MPS messaging being activated for the UE (102).

[0084] Embodiment 10: The method of embodiment 9, further comprising sending the SIP message including the resource-priority header to a next hop in a delivery path of the SIP message.

[0085] Embodiment 11: The method of embodiment 10, wherein the delivery path of the SIP message is via a cellular communications system, and the resource-priorityheader ensures that the SUP message is transported through the cellular communications system in accordance with a certain Quality of Service, QoS, and / or Allocation and Retention Policy, ARP, for MPS traffic.

[0086] Embodiment 12: The method of embodiment 9 or 10, wherein the resourcepriority header ensures that the SUP message is transported with priority over other non-MPS traffic.

[0087] Embodiment 13: A Serving Call Session Control Function, S-CSCF, (226) adapted to perform the method of any of embodiments 9 to 12.

[0088] Embodiment 14: An Internet Protocol, IP, Multimedia Subsystem, IMS, node for implementing a Serving Call Session Control Function, S-CSCF, (226), the IMS node comprising: a communication interface; and processing circuitry associated with the communication interface, the processing circuitry configured to cause the IMS node to perform the method of any of embodiments 9 to 12.

[0089] Embodiment 15: A method performed by a Serving Call Session Control Function, S-CSCF, (226) of an Internet Protocol, IP, Multimedia Subsystem, IMS, for on- demand multimedia priority service, MPS, the method comprising any one or more of the following: receiving (Fig. 3, step 0; Fig. 4, step 0; Fig. 5, step 0), from a Proxy Call Session Control Function, P-CSCF, (222) of the IMS, a subscription request for notifications of changes in registration of a User Equipment, UE, (102) (or subscriber); receiving (Fig. 3, step 4; Fig. 4, step 4; Fig. 5, step 4) a notification (e.g., from HSS) that MPS messaging is activated for the UE (102) (or subscriber); and sending (Fig. 3, step 4.5; Fig. 4, step 4.5; Fig. 5, step 4.5), to the P-CSCF (222), a notification that indicates that MPS messaging is activated for the UE (102) (or subscriber).

[0090] Embodiment 16: The method of embodiment 15, wherein receiving the notification that MPS messaging is activated for the UE (102) (or subscriber) is responsive to a request, received at the HSS or at an associated UDM, to activate MPS messaging for the UE (102) (or subscriber).

[0091] Embodiment 17: The method of embodiment 15 or 16, wherein receiving the subscription request comprises receiving the subscription request from the P-CSCF (222) during an IMS registration procedure of the UE (102) after an IMS PDU session has been established for the UE (102).

[0092] Embodiment 18: A Serving Call Session Control Function, S-CSCF, (226) of an Internet Protocol, IP, Multimedia Subsystem, IMS, the HSS adapted to perform the method of any of embodiments 15 to 17.

[0093] Embodiment 19: An Internet Protocol, IP, Multimedia Subsystem, IMS, node for implementing a Serving Call Session Control Function, S-CSCF, (226), the IMS node comprising: a communication interface; and processing circuitry associated with the communication interface, the processing circuitry configured to cause the IMS node to perform the method of any of embodiments 15 to 17.

[0094] Embodiment 20: A method performed by a Home Subscriber Server, HSS, of an Internet Protocol, IP, Multimedia Subsystem, IMS, for on-demand multimedia priority service, MPS, the method comprising any one or more of the following: updating (Fig. 3, step 3; Fig. 4, step 3; Fig. 5, step 3) a UE profile of a UE (102) to activate MPS messaging for the UE (102) (or subscriber); and sending (Fig. 3, step 4.5; Fig. 4, step 4.5; Fig. 5, step 4.5), to a P-CSCF (222), a notification that indicates that MPS messaging is activated for the UE (102) (or subscriber).

[0095] Embodiment 21: The method of embodiment 20, wherein updating the UE profile is responsive to a request, received at the HSS or at an associated UDM, to activate MPS messaging for the UE (102) (or subscriber).

[0096] Embodiment 22: A Home Subscriber Server, HSS, of an Internet Protocol, IP, Multimedia Subsystem, IMS, the HSS adapted to perform the method of any of embodiments 20 to 21.

[0097] Embodiment 23: An Internet Protocol, IP, Multimedia Subsystem, IMS, node for implementing a Home Subscriber Server, HSS, the IMS node comprising: a communication interface; and processing circuitry associated with the communication interface, the processing circuitry configured to cause the IMS node to perform the method of any of embodiments 20 to 21.

[0098] Embodiment 24: A method performed in a core network (106, 200) of a cellular communications system (100), the method comprising:• at a Network Exposure Function, NEF, (212): o receiving (Fig. 3, step 1; Fig. 4, step 1) a request from an Application Function, AF, to activate multimedia priority service, MPS, messaging for a User Equipment, UE, (102) (or subscriber);o sending (Fig. 3, step 2; Fig. 4, step 2) a request to a Unified Data Management, UDM, of the core network (106, 200) to activate MPS messaging for the UE (102) (or subscriber);• at the UDM: o receiving (Fig. 3, step 2; Fig. 4, step 2) the request from the NEF (212) to activate MPS messaging for the UE (102) (or subscriber); o update (Fig. 3, step 3; Fig. 4, step 2) a UE profile of the UE (102) (or subscriber) to activate MPS messaging for the UE (102) (or subscriber).

[0099] Embodiment 25: The method of embodiment 24, further comprising at the UDM or at associated UDR, sending (Fig. 3, step 5; Fig. 4, step 5) a notification to a Policy and Control Function, PCF, (216) that indicates that MPS messaging is activated for the UE (102) (or subscriber).

[0100] Embodiment 26: The method of embodiment 25, further comprising at the UDM or the associated UDR, starting a timer associated to the activation MPS messaging for the UE (102) (or subscriber), wherein MPS messaging for the UE (102) (or subscriber) is deactivated upon expiry of the timer.

[0101] Embodiment 27: The method of embodiment 25 or 26, further comprising:• at the PCF (216): o receiving (Fig. 3, step 5; Fig. 4, step 5) the notification that indicates that MPS messaging is activated for the UE (102) (or subscriber); and o sending (Fig. 3, step 6; Fig. 4, step 6), to a Session Management Function, SMF, (204), a request to update Policy and Charging Control, PCC, rules (e.g., to ensure that a default signaling bearer of the UE (102) (or subscriber) is updated to a Quality of Service, QoS, that prioritizes MPS messaging traffic over other traffic).

[0102] Embodiment 28: The method of embodiment 27, wherein the PCF (216) subscribes to the UDR to be notified when there are changes to MPS messaging.

[0103] Embodiment 29: The method of any of embodiments 24 to 28, further comprising, at the NEF (212), sending (Fig. 4, step lb) an update message to the UDR that indicates that MPS messaging is activated for the UE (102) (or subscriber).

[0104] Embodiment 30: The method of embodiment 24, further comprising at the UDM, sending (Fig. 5, step 4b) a request to an Access and Mobility Management Function, AMF, (206) to activate MPS messaging for the UE (102) (or subscriber).

[0105] Embodiment 31: The method of embodiment 30, further comprising:• at the AMF (206): o receiving (Fig. 5, step 4b) the request to activate MPS messaging for the UE (102) (or subscriber); o sending (Fig. 5, step 5b), to a Session Management Function, SMF, (204), an update request that indicates that MPS messaging is activated for a corresponding PDU session of the UE (102); and• at the SMF (204): o receiving (Fig. 5, step 5b) the update request that indicates that MPS messaging is activated for the corresponding PDU session of the UE (102); and o sending (Fig. 5, step 5c), to a Policy and Control Function, PCF, (216), a request that informs the PCF (216) that MPS messaging is activated for the corresponding PDU session of the UE (102); and• at the PCF (216): o receiving (Fig. 5, step 5c) the request from the SMF (204); and o initiating (Fig. 5, step 6) a procedure to update Policy and Charging Control, PCC, rules of the UE (102) (e.g., to ensure that a default signaling bearer of the UE (102) (or subscriber) is updated to a Quality of Service, QoS, that prioritizes MPS messaging traffic over other traffic).

Claims

Claims1. A method performed by a Proxy Call Session Control Function, P-CSCF, (222), for on-demand multimedia priority service, MPS, the method comprising: receiving (Fig. 3, step 4.5; Fig. 4, step 4.5; Fig. 5, step 4.5), from a Serving Call Session Control Function, S-CSCF, (226), a notification that indicates that MPS messaging is activated for a User Equipment, UE, (102) or subscriber; receiving (Fig. 3, step 9; Fig. 4, step 9; Fig. 5, step 10) a Session Initiation Protocol, SIP, message from the UE (102); and inserting (Fig. 3, step 10; Fig. 4, step 10; Fig. 5, step 11) a resource-priority header into the SIP message, the resource-priority header being such that the SIP message is handled in accordance with MPS messaging being activated for the UE (102) or subscriber.

2. The method of claim 1, further comprising sending the SIP message including the resource-priority header to a next hop in a delivery path of the SIP message.

3. The method of claim 1 or 2, wherein the resource-priority header ensures that the SIP message is transported with priority over other non-MPS traffic.

4. The method of any of claims 1 to 3, further comprising subscribing to receive, from the S-CSCF (226), the notification that indicates MPS messaging is activated for the UE (102) or subscriber.

5. The method of claim 4, wherein subscribing to receive the notification comprises subscribing for notifications of changes in the registration of the UE (102) or subscriber during an IMS registration procedure of the UE (102).

6. A Proxy Call Session Control Function, P-CSCF, (222) adapted to perform the method of any of claims 1 to 5.

7. An Internet Protocol, IP, Multimedia Subsystem, IMS, node for implementing a Proxy Call Session Control Function, P-CSCF, (222), the IMS node comprising: a communication interface; andprocessing circuitry associated with the communication interface, the processing circuitry configured to cause the IMS node to perform the method of any of claims 1 to 5.

8. A method performed by a Home Subscriber Server, HSS, of an Internet Protocol, IP, Multimedia Subsystem, IMS, for on-demand multimedia priority service, MPS, the method comprising: updating (Fig. 3, step 3; Fig. 4, step 3; Fig. 5, step 3) a User Equipment, UE, profile of a UE (102) to activate MPS messaging for the UE (102) or subscriber; and sending (Fig. 3, step 4.5; Fig. 4, step 4.5; Fig. 5, step 4.5), to a Proxy Call Session Control Function, P-CSCF, (222), a notification that indicates that MPS messaging is activated for the UE (102) or subscriber.

9. The method of claim 8, wherein updating the UE profile is responsive to a request received at the HSS or at an associated Unified Data Management, UDM, to activate MPS messaging for the UE (102) or subscriber.

10. A Home Subscriber Server, HSS, of an Internet Protocol, IP, Multimedia Subsystem, IMS, the HSS adapted to perform the method of any of claims 8 to 9.

11. An Internet Protocol, IP, Multimedia Subsystem, IMS, node for implementing a Home Subscriber Server, HSS, the IMS node comprising: a communication interface; and processing circuitry associated with the communication interface, the processing circuitry configured to cause the IMS node to perform the method of any of claims 8 to 9.

12. A method performed in a core network (106, 200) of a cellular communications system (100), the method comprising:• at a Network Exposure Function, NEF, (212): o receiving (Fig. 3, step 1; Fig. 4, step 1) a request from an Application Function, AF, to activate multimedia priority service, MPS, messaging for a User Equipment, UE, (102) or subscriber;o sending (Fig. 3, step 2; Fig. 4, step 2) a request to a Unified Data Management, UDM, of the core network (106, 200) to activate MPS messaging for the UE (102) or subscriber;• at the UDM: o receiving (Fig. 3, step 2; Fig. 4, step 2) the request from the NEF (212) to activate MPS messaging for the UE (102) or subscriber; and o updating (Fig. 3, step 3; Fig. 4, step 2) a UE profile of the UE (102) or subscriber to activate MPS messaging for the UE (102) or subscriber.

13. The method of claim 12, further comprising at the UDM or at associated Unified Data Repository, UDR, sending (Fig. 3, step 5; Fig. 4, step 5) a notification to a Policy and Control Function, PCF, (216) that indicates that MPS messaging is activated for the UE (102) or subscriber.

14. The method of claim 13, further comprising at the UDM or the associated UDR, starting a timer associated to the activation MPS messaging for the UE (102) or subscriber, wherein MPS messaging for the UE (102) or subscriber is deactivated upon expiry of the timer.

15. The method of claim 13 or 14, further comprising:• at the PCF (216): o receiving (Fig. 3, step 5; Fig. 4, step 5) the notification that indicates that MPS messaging is activated for the UE (102) or subscriber; and o sending (Fig. 3, step 6; Fig. 4, step 6), to a Session Management Function, SMF, (204), a request to update Policy and Charging Control, PCC, rules wherein the update ensures that a default signaling bearer of the UE (102) or subscriber is updated to a Quality of Service, QoS, that prioritizes MPS messaging traffic over other traffic.

16. The method of claim 15, wherein the PCF (216) subscribes to the UDR to be notified when there are changes to MPS messaging.

17. The method of any of claims 12 to 16, further comprising, at the NEF (212), sending (Fig. 4, step lb) an update message to the UDR that indicates that MPS messaging is activated for the UE (102) or subscriber.

18. The method of claim 12, further comprising at the UDM, sending (Fig. 5, step 4b) a request to an Access and Mobility Management Function, AMF, (206) to activate MPS messaging for the UE (102) or subscriber.

19. The method of claim 18, further comprising:• at the AMF (206): o receiving (Fig. 5, step 4b) the request to activate MPS messaging for the UE (102) or subscriber; o sending (Fig. 5, step 5b), to a Session Management Function, SMF, (204), an update request that indicates that MPS messaging is activated for a corresponding PDU session of the UE (102); and• at the SMF (204): o receiving (Fig. 5, step 5b) the update request that indicates that MPS messaging is activated for the corresponding PDU session of the UE (102); and o sending (Fig. 5, step 5c), to a Policy and Control Function, PCF, (216), a request that informs the PCF (216) that MPS messaging is activated for the corresponding PDU session of the UE (102); and• at the PCF (216): o receiving (Fig. 5, step 5c) the request from the SMF (204); and o initiating (Fig. 5, step 6) a procedure to update Policy and Charging Control, PCC, rules of the UE (102) wherein the update ensures that a default signaling bearer of the UE (102) or subscriber is updated to a Quality of Service, QoS, that prioritizes MPS messaging traffic over other traffic.

20. A method performed in a Network Exposure Function, NEF, (212) in a core network (106, 200) of a cellular communications system (100), the method comprising:receiving (Fig. 3, step 1; Fig. 4, step 1) a request from an Application Function, AF, to activate multimedia priority service, MPS, messaging for a User Equipment, UE, (102) or subscriber; and sending (Fig. 3, step 2; Fig. 4, step 2) a request to activate MPS messaging for the UE (102) or subscriber to a Unified Data Management, UDM, of the core network (106, 200).

21. The method of claim 20, further comprising sending (Fig. 4, step lb) an update message to a Unified Data Repository, UDR, that indicates that MPS messaging is activated for the UE (102) or subscriber.

22. A Network Exposure Function, NEF, (212) for a core network (106, 200) of a cellular communications system (100), the NEF (212) adapted to perform the method of any of claims 20 to 21.

23. A network node for implementing a Network Exposure Function, NEF, (212) for a core network (106, 200) of a cellular communications system (100), the network node comprising: a communication interface; and processing circuitry associated with the communication interface, the processing circuitry configured to cause the network node to perform the method of any of claims 20 to 21.

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