Voice Group Call (VGCS)¶

Voice Group Calls are part of the ASCI features introduced primarily for GSM-R. They're basically the bigger brother of Voice_Broadcast_Call (VBS). So if you're unfamiliar with the former, it is suggested to first read up on VBS.

While VBS calls are unidirectional, VGCS calls are bi-directional between multiple parties. There's always one talker and many listeners. The talker can change dynamically over time, basically creating a user experience of a classic two-way radio. There is always only one talker active at any moment.

Like VBS, VGCS works with the concept of groups. Eachs subscriber can be part of up to 50 groups, and calls are made to a specific group. There can be any number of parallel groups active in parallel next to each other. Each group has an area describing a list of cells in which subscribers can participate in the group call.

Arbitration¶

A subscriber who wishes to talk signals this to the network. The right to talk is allocated on a first-come-first-serve basis without queuing.

Specifications¶

• 3GPP TS 42.068 (Stage 1)
• 3GPP TS 43.068 (Stage 2)
• 3GPP TS 44.068 (Stage 3; GCC Layer 3 Protocol)