Interconnection group

Description

An Interconnection group is a specialized type of Mission Critical (MC) service group defined within the 3GPP Mission Critical Services (MCS) framework. Its primary characteristic is that it is explicitly configured to permit the inclusion of members who are users of a partner MC system, i.e., a separate MC system operated by another organization or administrative domain. This allows users from different MC systems to communicate as part of the same group, which is essential for inter-agency or cross-border operations.

The concept was introduced in Release 14 as part of the initial MCPTT (Mission Critical Push To Talk) specifications, where it was termed an 'MCPTT group' configured for partner system users. With the expansion of MC services beyond MCPTT to include MCVideo and MCData, the term was generalized in Release 15 to 'MC service group' to cover all mission-critical service types. The group is defined and managed within the group management (GM) framework, typically via the Group Management Server (GMS) or the MC service server.

Technically, an Interconnection group is identified by a globally unique identifier and is associated with a set of policies that govern membership, including which partner MC systems are allowed to include their users. When a user from a partner system attempts to join the group, the local MC system verifies the user's credentials and the interconnection agreement with the partner system. The group communication is then facilitated through inter-system interfaces, such as the MC interworking function (IWF) or the inter-system reference point (e.g., MCPTT-5 for MCPTT).

The group's configuration includes parameters such as the maximum number of members, the priority level, and the allowed media types. It also defines the security and authentication mechanisms for partner users, ensuring that only authorized users can participate. The Interconnection group is a key enabler for interoperability between different MC systems, which is crucial for public safety and disaster relief scenarios where multiple agencies need to collaborate.

In summary, the Interconnection group is a fundamental building block for cross-system MC communication, allowing users from different MC systems to join a common group and communicate seamlessly. Its definition has evolved from a purely MCPTT-specific concept to a generic MC service group, reflecting the broadening scope of mission-critical services in 3GPP.

Purpose & Motivation

The Interconnection group exists to solve the problem of cross-system communication in mission-critical scenarios. In public safety, different agencies (e.g., police, fire, ambulance) often operate their own MC systems, and during joint operations, they need to communicate as a single team. Without a standardized way to include users from partner systems in a group, each agency would have to manually bridge communications or use proprietary solutions, leading to delays and interoperability issues. The Interconnection group provides a standardized, policy-driven mechanism to allow users from partner MC systems to be members of a group, ensuring seamless and secure communication.

Historically, before Release 14, mission-critical communication was limited to within a single system, and cross-system communication was not standardized. The introduction of the Interconnection group in Release 14 addressed this gap by defining a group type that could include external users. This was initially focused on MCPTT but was later expanded to all MC services in Release 15, reflecting the growing need for integrated voice, video, and data services across agencies. The concept continues to be refined in subsequent releases to support more complex interconnection scenarios, such as multiple partner systems and dynamic membership.