Member Identifier

Description

The Member ID is a key identifier in 3GPP Proximity Services (ProSe) and Vehicle-to-Everything (V2X) communications, as defined in specifications such as TS 23.287 and TS 23.304. It uniquely identifies a member within an Application Layer managed group, and its management is delegated to the ProSe application layer. This identifier is essential for group communication scenarios where multiple users or devices participate in a shared session, such as Mission Critical Push-to-Talk (MCPTT), public safety group calls, or platooning in V2X.

In the ProSe architecture, an Application Layer managed group is a group of UEs that are managed by a ProSe application (e.g., a group communication service). The Member ID is assigned by the ProSe application layer, which resides outside the 3GPP core network, and is used within the group for identifying each member. The 3GPP network (e.g., the 5G Core) may not be aware of the Member ID itself; instead, it uses other identifiers like the ProSe UE ID or the Source/Destination Layer-2 IDs for routing. However, the Member ID is crucial for the application layer to manage group membership, permissions, and communication policies.

How it works: When a UE joins a ProSe group, the ProSe application layer (e.g., a group management server) assigns a Member ID to that UE. This ID is then used in application-layer signaling and may be included in the user data packets to identify the sender. For example, in a group call, each participant's media packets carry their Member ID so that receiving applications can display the speaker's identity. The Member ID is also used for access control, ensuring that only authorized members can send or receive data in the group. The 3GPP network provides the underlying connectivity (e.g., via PC5 sidelink or Uu interface) but does not interpret the Member ID.

The Member ID is distinct from other identifiers in the 3GPP system. For instance, the ProSe UE ID is a link-layer identifier used for direct communication, while the Member ID is an application-layer identifier. The Application Layer managed group may have its own Group ID, and the Member ID is unique within that group. The management of Member IDs includes creation, update, and deletion, typically performed by the ProSe application server. The 3GPP specifications define the requirements for how the ProSe application layer interacts with the 3GPP network to ensure that Member IDs are correctly mapped to network-level identifiers when necessary.

Key components involved in Member ID management include the ProSe Application Server (which manages groups and assigns Member IDs), the ProSe Function (which provides network-related ProSe services), and the UE (which stores and uses the Member ID). The Member ID may be used in various interfaces, such as PC5 (sidelink) for direct communication or Uu (cellular) for network-mediated communication. In V2X, the Member ID can identify vehicles in a platoon or a group of vehicles traveling together, enabling coordinated maneuvers.

The Member ID plays a vital role in enabling secure and efficient group communications. It allows the application layer to implement fine-grained access control and personalized services. For example, in a mission-critical push-to-talk system, the Member ID can be used to determine the priority of a speaker or to route the media to specific recipients. Without a standardized Member ID, group communications would rely on proprietary identifiers, hindering interoperability. The 3GPP definition ensures that different ProSe applications can interoperate by adhering to common rules for Member ID management.

As 5G evolves, the Member ID concept is being extended to support new use cases like network slicing for group communications and integration with edge computing. The identifier remains application-layer managed, but its mapping to network resources may become more dynamic to support QoS and policy enforcement.

Purpose & Motivation

The Member ID was introduced to provide a standardized way to identify members within Application Layer managed groups in ProSe and V2X communications. Before its definition, group communication systems often used proprietary identifiers, which made interoperability between different vendors and applications difficult. The lack of a common identifier also hindered the ability to apply consistent security and policy controls across different group services.

The motivation for Member ID stems from the need for efficient group management in scenarios like public safety, where first responders need to communicate in groups with clear identification of each member. In V2X, vehicles in a platoon need to identify each other to coordinate maneuvers. The Member ID allows the application layer to manage group membership independently of the underlying 3GPP network, which simplifies network operations and gives flexibility to service providers.

By delegating Member ID management to the ProSe application layer, 3GPP ensures that the network does not need to be aware of application-specific group structures. This separation of concerns allows the network to focus on connectivity and QoS, while the application layer handles group semantics. The Member ID is thus a key enabler for scalable and interoperable group communications over 3GPP networks.