Voice Broadcast Call (VBCS)¶

Voice Broadcast Calls are part of the ASCI features introduced primarily for GSM-R.

They allow the distribution of speech (or other signals which can be transmitted via the speech codec), generated by a service subscriber, into a predefined geographical area to all or a group of service subscribers located in this area.

VBS is an uni-directional service.

Voice can originate from any subscriber (with related privileges).

VBS contains the notion of a VBS group. Subscribers are either part of a group or not. Each subscriber can be part of up to 50 groups. Every group is identified by a Group ID. Every group is realted to a Group Call Area (a group of cells in).

Only subscribers that are members of the Group ID which are currently within the Group Call Area will receive the voice information. If they leave the area, they loose the call.

Normal GSM authentication is only performed for the calling subscriber, but not for the called (receiving) subscribers; those have uni-directional downlink signals only with no return channel.

Subscribers can activate/deactivate their group membership; that information is stored on the SIM card.

Specifications¶

For more information, see

• 3GPP TS 42.069 (Stage 1)
• 3GPP TS 43.069 (Stage 2)
• 3GPP TS 44.069 (Stage 3; BCC Layer 3 Protocol)