Multimedia Priority Service Subscribed User Equipment

Description

An MPS-subscribed UE is a User Equipment (UE) that is authorized to receive Multimedia Priority Service (MPS) based on its subscription. Specifically, the UE has a Universal Subscriber Identity Module (USIM) with the MPS indication set, and it has an MPS subscription in its Home Public Land Mobile Network (HPLMN). This means that the user's subscription profile includes the MPS service, and the USIM is configured to indicate this capability to the network. When such a UE requests a session, the network can recognize it as an MPS-subscribed UE and apply priority treatment to its sessions, as defined for MPS sessions.

The MPS subscription is stored in the HPLMN's subscriber database, such as the Home Subscriber Server (HSS) or Unified Data Management (UDM) in 5G. The subscription includes information that authorizes the user for MPS, which may include priority levels, allowed services, and other parameters. The USIM contains an MPS indication, which is a flag or parameter that the UE can read and use to determine that it is MPS-subscribed. This indication may be used by the UE to request priority treatment when initiating sessions, and it may also be used by the network to verify the UE's authorization.

The process of identifying an MPS-subscribed UE involves both the UE and the network. When the UE attaches to the network, it may provide an indication of its MPS subscription, or the network may retrieve the subscription information from the HSS/UDM. During session establishment, the UE may include an MPS session indication in its request, and the network checks the subscription to ensure that the UE is indeed authorized for MPS. If authorized, the network applies priority treatment to the session. The MPS-subscribed UE concept ensures that only authorized users receive priority, preventing abuse of the priority service.

The MPS-subscribed UE is defined in 3GPP specifications such as TS 22.153 (Multimedia priority service), TS 23.228 (IP Multimedia Subsystem (IMS)), TS 23.501 (System architecture for the 5G System), and TS 23.854 (Enhancements for Multimedia Priority Service). These specifications outline the requirements for MPS subscription, the role of the USIM, and the procedures for authorization and priority treatment. The concept has evolved over releases, with the definition being refined to clarify the requirements for the USIM and the HPLMN subscription.

In summary, an MPS-subscribed UE is a UE that has the necessary subscription and USIM configuration to access MPS. It is a key enabler for priority communications, ensuring that critical users can obtain priority treatment when needed. The network uses the MPS subscription information to authorize and enforce priority, while the UE uses the USIM indication to request priority. This combination provides a secure and reliable way to deliver MPS to authorized users.

Purpose & Motivation

The MPS-subscribed UE concept exists to identify and authorize users who are entitled to Multimedia Priority Service. Without a clear definition of which UEs are allowed to receive priority, the network could not enforce priority treatment effectively, and the service could be abused. By defining an MPS-subscribed UE as one with a USIM MPS indication and an MPS subscription in the HPLMN, 3GPP provides a standardized way for networks to recognize authorized users and grant them priority.

Before this concept, priority services might have been implemented in proprietary ways, lacking interoperability and consistent authorization. The MPS-subscribed UE ensures that priority is based on subscription, which is managed by the home network, and that the UE can signal its capability using the USIM. This allows roaming scenarios where the visited network can trust the home network's authorization. It also enables the UE to know that it is MPS-subscribed and to request priority accordingly.

The evolution of the definition, particularly the clarification in Rel-19 that the UE must have both the USIM MPS indication set and an MPS subscription in the HPLMN, reflects the need for precise authorization criteria. This prevents UEs with only a USIM indication but no valid subscription from receiving priority, and vice versa. The MPS-subscribed UE is thus a fundamental building block for secure and reliable priority communications in 3GPP networks.