Voice Broadcast Call » History » Revision 3
Revision 2 (laforge, 11/20/2022 05:01 PM) → Revision 3/5 (laforge, 11/20/2022 05:03 PM)
h1. 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. Subscribers can activate/deactivate their group membership; that information is stored on the SIM card. h2. Security 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. Before Release 6, VBS calls were always in cleartext. Release 6 introduced the optional ciphering of VBS. The Subscribers can activate/deactivate their group specific key material are membership; that information is stored on the USIM (e.g. via OTA). SIM card. h2. 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)
