Voice Group Call Service
The Voice Group Call Service ( VGCS ., English for group call service ) is a service in GSM - mobile network , which enables participants to communicate with several other persons simultaneously.
description
The service allows voice-based communication of a predefined group of participants in half-duplex mode, which means that only one participant in a group call can speak at a time. Only certain group members are authorized to set up VGCS calls. Special cell phones that support the VGCS are required. The VGCS works fundamentally different to Push-to-Talk over Cellular and should not be confused with it.
This service was first used in the networks of European rail network operators.
function
Each call group has a unique identifier. In the SIM, the terminals keep a list of the call groups in which the subscriber is a member, as well as a list with the identifiers of the group calls that are to be accepted. This list can be edited in the terminal.
A special channel, the Notification Channel ( NCH ), is required to inform the end devices about a group call .
The MSC maintains a list of subscribers who are authorized to participate in a special group call. In addition, the MSC decides in which cells a specific group call is to be sent. The MSC continues to decide on the allocation of the uplink on a first-come-first-served basis.
The network can handle a group call in a very resource-saving manner, since only one participant in the group call can speak at a time. Therefore, regardless of the number of call participants, only one uplink and one downlink channel is required per radio cell .
In addition to the mobile subscribers, a limited number of subscribers in the fixed network can be defined for each call group.
As soon as a terminal is in a cell in which a group call is being transmitted, the terminal checks the identifier of the group call. If this identifier is included in the list of group calls to be accepted, the terminal sets up a connection and starts playing the voice data transmitted in the downlink. The active group call is signaled to the user.
If the user is currently on a call, the presence of a group call is signaled. If eMLPP is implemented in the mobile network, the current call can be suppressed, depending on the configuration.
See also
Individual evidence
- ↑ 3GPP TS 42.068: Voice Group Call Service (VGCS) Stage 1 ( English , ZIP / DOC; 58 KB) March 25, 2008. Accessed December 29, 2009.
- ↑ 3GPP TS 43.068: Voice Group Call Service (VGCS) Stage 2 ( English , ZIP / DOC; 1.2 MB) December 15, 2009. Accessed December 29, 2009.