5 High level requirements

22.1533GPPMultimedia priority serviceRelease 19TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.1 General

The system shall provide preferential treatment based on the subscription for MPS for:

– An authorized Service User using a UE with an MPS subscription,

NOTE 1: In this case of an UE with an MPS subscription, subscription related information stored in the UE is used, e.g., membership in a special access class as per TS 22.011 [6] is used for E-UTRAN access to the EPC and membership in Access Identity 1 as per TS 22.261 [7] is used for 5GS (NR and E-UTRA access to the 5GC).

– An authorized Service User using a UE that does not have an MPS subscription, and

NOTE 2: In this case, the Service User is not identified by the subscription related information stored in the UE (e.g., the Service User borrows a UE that does not have an MPS subscription). In this case, radio interface priority may not be provided for the initial request for invocation of MPS. It is provided only after MPS is established for the MPS Voice, Video or Data session.

– An authorized IoT device with an MPS subscription.

NOTE 3: In this case of an IoT device with an MPS subscription, subscription related information stored in the IoT device is used to allow invocation/revocation of MPS through machine interactions that may not directly involve a human MPS Service User.

Upon invocation of MPS, the system shall provide preferential treatment for access and core network resources associated with the session (i.e., signalling and media bearer related resources within a domain and across domains), including, when applicable, priority treatment towards an enterprise network supporting MPS.

NOTE 4: ‘enterprise network’ (mentioned above, and in other following sections) may be a 3GPP or non-3GPP network.

A Service User is assigned a priority level by a regional/national authority i.e., agency authorised to issue priority levels. Upon MPS invocation the calling Service User’s priority level is used to identify the priority to be used for the session being established.

Pre-emption of active sessions shall be subject to regional/national regulatory requirements.

Subject to regional/national regulatory policy, a PLMN should have the capability to retain public access as a fundamental function. Therefore, MPS traffic volumes should be limited (e.g. not to exceed a regional/national specified percentage of any concentrated network resource, such as eNodeB capacity), so as not to compromise this function.

5.2 Priority session treatment in originating network

When an MPS session is originated by a Service User, the session shall receive priority treatment (priority access to signalling and media bearer resources for voice, video, data, and messaging service) in the originating PLMN based on the originating Service User priority information (i.e., priority indication and priority level).

When an MPS session is requested by a Service User and the originating network supporting session establishment cannot assign the necessary resources to the MPS session, the MPS session request shall be:

– Queued,

– Processed for the next available resource in accordance with the calling Service User’s priority level and session initiation time.

The network shall support the capability to inform the calling Service User about the status of the MPS session (e.g., tones or signalling messages can be used to indicate that the session request has been queued).

If the queued MPS session times out, then normal session processing applies.

5.3 Priority session progression

For an MPS session, a Service User shall receive priority session treatment/progression through the PLMN(s). In case the MPS session traverses or terminates in other networks (e.g., the PSTN), the network providing priority session treatment/progression shall support the capability to indicate to the other network that this is an MPS session.

NOTE: If there is no agreement on priority handling between networks, the priority does not carry across network boundaries.

5.4 Priority session treatment in terminating network

When a terminating network receives an incoming MPS session establishment attempt, the MPS session shall receive priority treatment (priority access to signalling and media bearer resources for voice, video, data, and messaging service) in the terminating PLMN, based on the originating Service User priority information. When requested, this includes MPS treatment towards an enterprise network supporting MPS.

As an operator option, the terminating network may invoke priority treatment for an incoming session from a non-MPS subscriber to an MPS subscriber (see clause 4).

When the terminating network supporting session establishment cannot assign the necessary resources to the MPS session, the MPS session request shall be:

– Queued,

– Processed for the next available resource in accordance with the Service User’s priority level and session arrival time.

If the queued MPS session times out, then normal session processing applies.

5.4a Priority Data Bearer Service

The Priority Data Bearer Service provides MPS priority for data and video services not under IMS control.

When a Service User invokes Priority Data Bearer Service for transport of any data packets to and from that Service User, the network should give priority in admission/upgrade of the Priority Data Bearer(s) and in packet data scheduling in the event of congestion (for new sessions and upgrade to existing sessions), subject to regional/national regulatory policy. Specifically:

– A Priority Data Bearer service session shall be given priority for admission/upgrade over non-Priority Data Bearer sessions during times of congestion;

– Data packets belonging to a Priority Data Bearer service shall not be dropped before data packets belonging to a non-Priority Data Bearer service session, when the network is experiencing congestion, subject to the limitation imposed by public access. Priority Data Bearer session QoS, as required for the type of service invoked (e.g., packet delay), should be maintained throughout the activity of the data session.

MPS for Data Transport Service (DTS) is a generic priority packet transport service that applies independently of the specific data application being used. In the case of EPS, MPS for DTS enables the prioritization of all traffic on the default bearer upon request. It may also apply to other bearers based on operator policy and regulatory rules. In the case of 5GS, MPS for DTS enables the prioritization of all traffic on the QoS Flow associated with the default QoS rule upon request. It may also apply to other QoS flows based on operator policy and regulatory rules. MPS for DTS is a specific example of Priority Data Bearer Service. MPS for DTS service specific requirements are described in clause 9.3.

NOTE: MPS for streaming video can be provided as an Over The Top (OTT) service using the MPS for DTS service.

5.5 Priority levels

The Service User shall be assigned one of "n" user priority levels. The priority levels are defined with 1 being the highest priority level and "n" being the lowest priority level.

The 3GPP network shall be able to support at least 5 user priority levels.

Assignment of priority levels is a matter of regional/national and operator policy.

In case of interconnecting networks that have different priority levels, mappings between priority levels should be established.

5.6 Invocation on demand

MPS priority shall be invoked only when requested by the Service User. However, certain priority treatments are provided prior to invocation as specified in Section 5.13.

MPS is applied when idle resources required for an origination session request are not available.

If idle resources are available when MPS is requested, the request shall be allowed to proceed as normal, but marked as an MPS request.

An indication of an MPS session should be propagated towards the terminating network regardless of the availability of resources in the originating network.

5.7 Multimedia priority service code/identifier

MPS shall be requested by including an MPS code/identifier in the session origination request, or optionally, by using an MPS input string (e.g., an MPS public user identity).

5.8 Roaming

MPS shall be supported when the Service User is roaming and the visited network and home network support MPS, and roaming agreements are in place for MPS.

5.8.1 Roaming within the home country

The system shall support MPS when a UE with an MPS subscription is roaming within the home country and the visited and home network support MPS, and roaming agreements are in place for MPS.

NOTE 1: Roaming within a home country is subject to national/regional rules and operator policy.

NOTE 2: The subscription related information stored in the UE is used for roaming within the home country. Membership in a special access class as per TS 22.011 [6] is used for EUTRAN access to the EPC and membership in Access Identity 1 as per TS 22.261 [7] clause 6.22.2.2 is used for 5G (NR and E-UTRAN access to the 5GC).

5.8.2 Roaming outside the home country

The system shall support MPS when a UE with an MPS subscription is roaming outside of the home country and the visited and home network support MPS, and roaming agreements are in place for MPS.

NOTE 1: Roaming outside a home country is subject to national/regional rules and operator policy.

NOTE 2: The UE subscription in the home PLMN is configured for MPS with the visited PLMN outside the home country as specified in TS 22.261 [7] clause 6.22.2.2, for 5GS (E-UTRA and NR access to the 5GC).

NOTE 3: The home PLMN can configure the UE to discover and select a network supporting MPS when roaming outside of the home country (e.g., the UE is configured to select a specific MPS capable visited PLMN when roaming in a country that may have multiple PLMNs where some are MPS capable and some are not MPS capable).

5.9 Handover

MPS shall be supported during and after the handover (i.e., sessions shall continue to get priority treatment in the network during and after the handover). Resource allocation for the session during handover shall receive priority treatment (priority access to signalling and media bearer resources for voice, video, and data) in the target cell based on the Service User priority information (i.e., priority indication and priority level).

For handover of an MPS voice call to CS, only the active, or if all calls are on hold, only the most recently active voice call shall be transferred and receive the priority treatment in CS. Any remaining non-MPS voice sessions in PS may be released. Any remaining MPS sessions, e.g., MPS data, in PS shall not be released.

5.10 Interworking with CS domain

5.10.1 Mobile origination in the CS domain -> MPS mobile termination

For a Priority Service voice call, as described in [2] and as specified in [3, 4, 5], originated by a Service User in the CS Domain, MPS shall support priority Mobile Termination of the session in the IMS. The priority information received from the CS domain shall be mapped and used in the IMS accordingly.

5.10.2 MPS mobile origination -> mobile termination to the CS domain

For an MPS voice session originated by a Service User in the IMS, MPS shall support priority delivery of the voice session to the serving CS Domain. The calling Service User priority level shall be sent to the CS Domain.

5.10.3 CS Fallback from LTE

Circuit Switched (CS) fallback from LTE needs to be given priority in the LTE system to support MPS voice in cells where voice is not supported in the PS domain. Priority treatment applies to both mobile originated calls and mobile terminated calls.

When an MPS Service User in LTE originates a voice call intended to be supported in the CS domain, and when configured by the operator, the LTE system shall provide priority treatment in the signalling and resource allocations needed to support priority CS fallback.

When a terminating LTE network receives indication of an incoming call to the CS domain, the LTE system shall provide priority treatment in the signalling and resource allocations needed to support priority CS fallback.

5.10a Fallback in 5GS

MPS voice calls need to be provided priority treatment following a voice fallback in 5GS when configured by the operator to fallback to another RAN type and/or core network type to support voice. The priority treatment applies to both mobile originated calls and mobile terminated calls. Non-voice PDU sessions that have priority in the 5GS prior to a voice fallback need to be given priority after the voice fallback. The priority treatment applies when the MPS non-voice PDU sessions move with the MPS voice PDU session and when MPS non-voice PDU sessions do not move with the MPS voice PDU session.

When an MPS Service User in a 5GS originates an MPS voice call and when configured by the operator for voice fallback to another RAN type and/or core network type, the system shall provide priority treatment in the signalling and resource allocations to support the priority voice fallback.

When a 5GS receives indication of a terminating MPS voice call and when configured by the operator for voice fallback to another RAN type and/or core network type, the system shall provide priority treatment in the signalling and resource allocations to support the priority voice fallback.

When the 5GS initiates a voice fallback for an MPS call, the system shall provide priority treatment in the signalling and resource allocations needed to support non-voice priority PDU sessions, if any exist at the time of the voice fallback. The priority treatment shall apply whether the MPS non-voice PDU session moves with the MPS voice PDU session or not.

5.11 Network Management Functions

Based on regional/national requirements and network operator policy, an MPS session shall be exempted from network management controls up to the point where further exemption would cause network instability. Congestion controls, overload controls, load balancing, and load re-balancing shall not adversely impact MPS.

5.12 Policy Control

The 3GPP network shall be able to make and enforce policy decisions regarding relative treatment of MPS application services (Voice, Video, Data, and Messaging) for admission control subject to regional/national regulatory requirements and operator policy.

The 3GPP network shall be able to make and enforce policy decisions regarding relative treatment of MPS application services traffic depending on the media type subject to regional/national regulatory requirements and operator policy (e.g., based on operator policy or regulation, Voice may have higher priority than Video or Data).

5.13 Priority before service invocation

5.13.1 Overview of priority before service invocation

Providing priority treatment to MPS-subscribed UEs during attachment/registration for radio access and network connectivity before the MPS application service session invocation requests improves the probability of an MPS session request being successful. This involves providing priority treatment for the signalling during the UE attachment for radio access and network connectivity based on a subscription profile. Prior to accessing subscription related information in the network, subscription related information stored in the UE is used, e.g., membership in the special access class required to be reserved for MPS use as per 3GPP TS 22.011 [6], or the special Access Identity used for MPS as per 3GPP TS 22.261 [7]. Without such priority treatment, a Service User’s UE might fail to gain radio access network and CN connectivity which in turn means that there is no access to the MPS application services (Voice, Video, and Data). Priority treatment before MPS session request increases the probability of successful MPS session establishment and any associated process for the Service User authorization (e.g., credential collection).

5.13.2 Requirement for priority before service invocation

The 3GPP network shall be able to provide priority treatment to an MPS-subscribed UE before the MPS application service invocation (e.g., priority treatment for the default and IMS signalling bearers establishment based on a subscription profile).

The 3GPP network shall be able to provide priority requests for access and attachment to the 3GPP network from an MPS-subscribed UE, including those procedures applied prior to and during the access of subscription related information (e.g., based on the UE membership in a special access class for MPS, or when allowed to operate with Access Identity 1 as per 3GPP TS 22.261 [7]).

5.14 Recovery/Restoration

The 3GPP system shall allow operational measures to expedite service recovery and restoration (i.e., service restoration after failure/unavailability). Should a disruption occur, MPS shall be re-provisioned, repaired, or restored to required service levels on a priority basis subject to regional/national regulatory requirements and operator policy.

5.15 Quality of Service (QoS)

In certain cases, the QoS characteristics (e.g., packet delay and packet loss) for an MPS session may be the same as the underlying communication service (e.g., voice, video, data or messaging) used to support the MPS session, with the MPS session being provided priority treatment subject to regional/national regulatory and operator policies. In other cases, there may be a need to request specific QoS characteristics for the MPS session (e.g., specific data communications as described in clause 5.4a, 9.3).

The 3GPP network shall allow selection and/or configuration of QoS rule(s) appropriate for MPS Voice, Video, Data and Messaging.

The 3GPP network shall allow enforcement of QoS rule(s) for MPS Voice, Video, Data, and Messaging.

The system shall support means to retain MPS sessions invoked for Voice, Video, Data and Messaging during transient network degradation conditions and recovery (e.g., during short radio link interruption), and re-verify any recovered MPS session afterwards.

5.16 Inter-network aspects

The system shall allow MPS priorities to be signalled across interconnected networks.

NOTE 1: Support of MPS services across networks is based on policy and agreements between the network operators.

NOTE 2: Intermediate 3GPP networks not supporting MPS (e.g., transit networks between an originating network and terminating network) should allow MPS priorities to be signalled transparently, based on operator policy and agreements for MPS.

The system shall support means to identify that an incoming voice, video, data or messaging service session from another network is an MPS session and to handle it with priority.

The system shall support measures to verify policy and admit an incoming MPS session for Voice, Video, Data, or Messaging service received from another network with priority.

5.17 Interactions with supplementary services

Interactions with a supplementary service might occur during set-up or after establishment of an MPS call or session. A supplementary service is a service which modifies or supplements a basic telecommunication service (see definition in 3GPP TR 21.905 [1]).

The system shall provide MPS priority for a supplementary service associated with an MPS call or session in progress when the supplementary service is associated with the Service User authorized for MPS.

When a supplementary service (e.g., Communication Diversion) results in an established authorized MPS call or session being redirected or extended, MPS priority shall be provided for the redirected or extended call or session.

When a supplementary service (e.g., Conference/Three-Party) is used to join an MPS priority call or session (e.g., to add parties to the established MPS call/session), MPS priority shall be retained on that leg when joined to the supplementary service.