11.3.7a Signalling procedures for the user plane

3GPP43.068Release 17Stage 2TSVoice Group Call Service (VGCS)

11.3.7a.1 Group call re-establishment by the BSS

The MSC and BSC negotiate during the setup of a voice group call whether "group call re-establishment by the BSS" is supported by both entities.

If "group call re-establishment by the BSS" is supported by both entities or the network uses a transmission architecture with A-interface link sharing, the following procedures apply:

i) If the BSS needs to release the group call channel in a cell due to an equipment failure or another BSS-generated reason (e.g. preemption), the BSS shall inform the MSC of the failure with either:

– Uplink Release Indication and VGCS Assignment Status message if the group call channel is serving the current talker; or

– VGCS Assignment Status message if the group call channel is not serving the current talker.

The terrestrial resource for the group call channel is not released by the MSC.

ii) When the condition that caused the failure is subsequently removed, the BSS shall re-allocate a radio resource for the group call channel and inform the MSC of the recovery with a VGCS Assignment Status message.

iii) If A-interface link sharing is used, each of the VGCS ASSIGNMENT STATUS messages in item (i) and (ii) shall be sent after expiry of timer Tast.

Otherwise, if "group call re-establishment by the BSS" is not supported by both entities and the network does not use a transmission architecture with A-interface link sharing, the following procedures apply:

i) If the BSS needs to release the group call channel in a cell due to an equipment failure or another BSS-generated reason (e.g. preemption), the BSS shall inform the MSC of the failure with either:

– Uplink Release Indication if the group call channel is serving the current talker; or

– Clear Request if the group call channel is not serving the current talker.

ii) The MSC shall then initiate the clearing of the radio and terrestrial resources for the group call channel. If supported, the MSC may retry the VGCS Assignment procedure for the cell, depending on the reason for release.

Group call re-establishment by the BSS does not apply to the dedicated link of the talker. If the BSS needs to release the dedicated channel of the talker due to an equipment failure or another BSS-generated reason (e.g. preemption), the BSS shall inform the MSC of the failure with an Uplink Release Indication. The MSC shall then initiate the clearing of the radio and terrestrial resources for the dedicated channel.