Pilot Identity

Description

The Pilot Identity is a concept defined in 3GPP TS 21.905 that represents a service-specific public address used for initial contact. It is associated with a group of publicly addressable identities, such as E.164 telephone numbers or SIP URIs. This identity serves as a single point of contact for a service, allowing users or network entities to initiate communication without needing to know the individual addresses of all members in the group. The Pilot Identity is particularly relevant in the context of IMS (IP Multimedia Subsystem) and other service platforms where group communication, service discovery, and routing are essential.

In practice, the Pilot Identity acts as a virtual address that maps to multiple underlying identities. When a request is sent to the Pilot Identity, the network resolves it to the appropriate group members or service instances. This mechanism is used in various services, such as group calls, push-to-talk, and emergency services, where a single address can represent a team, a department, or a set of users. The Pilot Identity is not a physical identifier but a logical one, enabling flexible service provisioning and management.

The architecture supporting the Pilot Identity involves several network elements. In IMS, the Pilot Identity may be stored in the HSS (Home Subscriber Server) as part of the service profile, and the S-CSCF (Serving Call Session Control Function) uses it during registration and session establishment. The identity is also used by application servers to route requests to the correct group. The mapping between the Pilot Identity and the group members is typically managed by the service provider and can be dynamic, allowing for changes in group composition without affecting the public address.

Key components include the Pilot Identity itself, the group of publicly addressable identities, and the resolution mechanism. The resolution can be based on static configuration or dynamic queries to a database. The Pilot Identity is designed to be globally unique within the service context, ensuring that requests are correctly routed. It also supports security and privacy, as the individual identities of group members are not exposed to the requester.

The Pilot Identity plays a crucial role in enabling scalable and efficient service delivery. By decoupling the service address from individual user addresses, it simplifies service creation and reduces the need for multiple addresses. It also facilitates load balancing and redundancy, as the Pilot Identity can point to different sets of users based on availability or location. Overall, the Pilot Identity is a fundamental building block for group-oriented services in 3GPP networks.

Purpose & Motivation

The Pilot Identity was introduced to address the need for a single, service-specific contact point that can represent a group of users or resources. In traditional telecommunication systems, each user or device had a unique address, making group communication cumbersome and inefficient. The Pilot Identity solves this by providing a virtual address that maps to multiple underlying identities, enabling services like group calls, push-to-talk, and emergency dispatch to be initiated with a single address.

Historically, before the introduction of the Pilot Identity, group services required either a dedicated server to manage group membership or the use of distribution lists that were not standardized. This led to interoperability issues and limited scalability. The Pilot Identity, standardized in 3GPP TS 21.905, provides a common framework for group addressing across different services and networks. It allows service providers to offer group-based features without exposing individual user addresses, enhancing privacy and security.

The Pilot Identity also supports the evolution towards all-IP networks, where SIP URIs and E.164 numbers are used interchangeably. By associating a Pilot Identity with a group of such identities, it enables seamless integration of circuit-switched and packet-switched services. This is particularly important for operators transitioning to IMS and VoLTE, where group communication is a key differentiator.