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Voice Group Call » History » Version 2

laforge, 11/20/2022 06:25 PM

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h1. Voice Group Call (VGCS)
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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.
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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.
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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.
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h2. Arbitration
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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. 
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h2. Specifications
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For more information, see
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* 3GPP TS 42.068 (Stage 1)
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* 3GPP TS 43.068 (Stage 2)
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* 3GPP TS 44.068 (Stage 3; GCC Layer 3 Protocol)
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