11.3.5 Cell change

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

11.3.5.1 Listening subscriber

In all cases change of cell shall be initiated and performed by the service subscriber’s mobile station. In order for the service subscribers changing from one cell to another within the group call area a cell list for the neighbouring cells belonging to this group call area is periodically broadcast on the downlink SACCH of the voice group call. In this case, mobile stations entering a new cell shall perform cell change according to the algorithm C2, see 3GPP TS 45.008 and 3GPP TS 43.022.

Mobile stations which want to enter a cell shall listen to the BCCH and to the NCH to determine which channel they shall retune to so that they can continue with the voice group call if available in that cell.

NOTE: Mobile stations may require an additional receiver to read the BCCH and NCH of the neighbour cells in order to ensure a higher probability of receiving the relevant messages without degradation of the received speech quality. The additional receiver may be the same as used in subclause 11.3.1.3.

Mobile stations entering a new location area shall perform location updating as normal.

11.3.5.2 Talking subscriber

Standard mobile station assisted handover shall be used for the cell change of the talking service subscriber as defined in 3GPP TS 45.008.

If the "talker channel parameter" indicates that the network shall always establish and maintain a dedicated channel for the talking service subscriber, the channel allocated by the network in the target cell shall always be a dedicated channel.

If the network supports uplink access option (i) as defined in subclause 7.2, collision cases between a handover of the talking service subscriber to a voice group call channel and an uplink access message on the same group call channel uplink shall be treated in the following way:

– when the BSS allocates the handover resources for the talking service subscriber, the BSS shall send an updated UPLINK BUSY message in the target cell and no longer accept uplink access messages on this group call channel uplink ;

– when the BSS already granted the uplink to another subscriber , the BSS shall delay the resource allocation for the handover of the current talker to the same cell. If the MSC accepts the uplink request for the new talker , the BSS shall cancel the handover resource allocation . Additionally, if the current talker is served by the BSS, the BSS shall release the current talker. Otherwise, if the MSC does not accept the uplink request for the new talker, the BSS shall release the new talker and proceed with the handover of the current talker.

If the talking subscriber leaves the group call area or enters a BSC area not belonging to the service area, the uplink shall not be maintained by the network.

If the BSS does not know if one or more of the target cells are outside the group call area, the BSS shall use the MSC controlled handover procedure. The MSC shall reject the handover in the case that all target cells are outside the GCA and as an option release the uplink.

In a RANflex configuration with or without group call redundancy, if the target cell belongs to a location area for which the group call serving MSC is not the old cell’s serving MSC, an inter MSC handover shall be performed.

11.3.5.3 Dispatcher

Dispatchers which are mobile subscribers shall change the cell by standard handover procedures.