Interworking Group

Description

An interworking group is a logical grouping of users that spans both a mission critical (MC) system and a Land Mobile Radio (LMR) system. It is defined in either the MC system or the LMR system and is composed of group members from both systems. This concept is essential for enabling group calls that include participants from both MC and LMR networks. The interworking group is managed by the interworking function (IWF), which ensures that group membership, call setup, and media distribution are coordinated across the two systems. When a group call is initiated for an interworking group, the IWF establishes the call in both systems and bridges the media streams. The group definition includes attributes such as group ID, member list, and associated policies. The interworking group can be defined in the MC system, in which case the MC system is the controlling system, or in the LMR system, in which case the LMR system is the controlling system. The controlling system is responsible for managing the group and its members. The interworking group supports features such as push-to-talk, late entry, and emergency alerts. The 3GPP specifications 23.283, 23.782, and 23.783 define the requirements and procedures for interworking groups. The interworking group is a key enabler for seamless communication between MC and LMR users, allowing them to participate in the same group calls as if they were on the same system. The IWF handles the translation of group call control signaling and media between the two systems. The interworking group may also support interoperability with multiple LMR systems. The management of interworking groups involves provisioning and synchronization of group data between the MC and LMR systems. The interworking group concept is particularly important for public safety agencies that need to communicate across different technologies during joint operations. Overall, the interworking group is a fundamental building block for interworking between MC and LMR systems.

Purpose & Motivation

The interworking group exists to enable group communication across the boundary between mission critical systems and legacy LMR systems. In public safety, group calls are the primary mode of communication, and it is essential that users on different systems can participate in the same group call. Without the interworking group concept, MC users and LMR users would be unable to communicate in groups, severely limiting interoperability. The interworking group solves this by defining a group that spans both systems, with membership from both. It allows agencies to gradually migrate to MC systems while maintaining group communication with LMR users. The 3GPP standardized this concept to provide a clear framework for managing cross-system groups, ensuring that features like group call setup, media distribution, and member management work seamlessly. The interworking group is defined in either the MC or LMR system, providing flexibility in deployment. The motivation is to support coordinated emergency response and day-to-day operations across mixed-technology environments.