A group regroup may be achieved by regrouping MCPTT groups into a new MCPTT regroup group which uses the configuration of a separate preconfigured MCPTT group. The MCPTT regroup group configuration needs to be provided to the relevant MCPTT group members of the MCPTT groups that will be regrouped in advance of the regrouping operation.
The preconfigured MCPTT group that provides the configuration is not used as the MCPTT regroup group itself, it only provides configuration for one or more MCPTT regroup groups. The MCPTT group ID of the regroup group is provided by the authorized user when the preconfigured regrouping is carried out.
The MCPTT regroup group can be specified to be a broadcast or non-broadcast type according to the configuration of the MCPTT group whose configuration is specified by the regroup request. The broadcast type of regroup is used for one-way communication where only an authorized MCX user is allowed to transmit and all other regroup members are only allowed to receive the communication (e.g. a call from a dispatcher to all regroup members). The non-broadcast type is used for two-way communication where all regroup members can transmit and receive (i.e, the regroup group call behaves like a normal non-broadcast group call).
These procedures provide a regrouping service for MCPTT only and are independent of group regrouping procedures specified in TS 23.280. If the MCPTT server has been notified by the group management server that one of the MCPTT groups that has been requested for regrouping by means of this procedure has already been regrouped by the group regrouping procedure specified in TS 23.280, the MCPTT server shall reject the request for regrouping described in the following procedure.
Figure 10.6.2.9.2.1-1 illustrates the procedure to initiate a group regroup procedure using a preconfigured MCPTT group. The procedure takes place prior to the establishment of a group call to the regroup group.
MCPTT client 2 is an affiliated member of MCPTT group 1 and MCPTT client 3 is an affiliated member of MCPTT group 2.
The MCPTT group identity and group configuration for the regroup MCPTT group have been preconfigured in MCPTT clients 2 and 3, and MCPTT clients 2 and 3 have received the relevant security related information to allow them to communicate in the regroup MCPTT group.
MCPTT client 1 is authorized to initiated a preconfigured regroup procedure.
MCPTT client 1 is aware of a suitable preconfigured regroup group whose configuration has been preconfigured in the MCPTT UEs of the group members who will be regrouped.
In order to be aware whether the group is regrouped, the MCPTT server is subscribed to the group configuration in GMS.
The authorized user of MCPTT client 1 initiates the regroup procedure, specifying the list of MCPTT groups to be regrouped (MCPTT groups 1 and 2), the MCPTT group ID of the regroup group (if available) and the MCPTT group ID of the group from which configuration information for the regroup group is to be taken.
The MCPTT server checks that MCPTT client 1 is authorized to initiate a preconfigured regroup procedure, and resolves the group identities of the MCPTT groups requested in step 1. The MCPTT server also checks which group members are affiliated to MCPTT groups 1 and 2. The MCPTT server may retrieve the configuration for the regroup group from the GMS if that configuration information is not already known to the MCPTT server. The MCPTT server also checks that none of the MCPTT groups that are requested for regrouping are already regrouped by any mechanism. If the preconfigured regroup request is authorized, the MCPTT server assigns a MCPTT group ID for this regroup group call if:
If the MCPTT server determines that any of the groups requested for regrouping, including the regroup group, have been regrouped by other group regrouping procedures, the MCPTT server then sends a preconfigured regroup reject back to MCPTT client 1 with a reject reason indicating that one of the groups has already been regrouped, and this procedure terminates.
MCPTT clients 2 and 3 may send the preconfigured regroup response to the MCPTT server to acknowledge the regrouping action. These acknowledgements are not sent in response to a multicast transmission of the preconfigured regroup request.
The MCPTT server sends a preconfigured regroup response to MCPTT client 1.
After the group regrouping procedure, the regrouping remains in effect until explicitly cancelled by the procedure in clause 10.6.2.9.2.2.
MCPTT client participation in the ongoing regroup persists until the MCPTT client is no longer affiliated to any of the regrouped groups (group 1 or 2 in this procedure).
MCPTT client affiliation to the regroup group may cease when the UE's MCPTT service ceases, e.g. when the UE is powered down, or by performing a log-off operation.
MCPTT clients 2 and 3 may send the preconfigured regroup cancel response to the MCPTT server to acknowledge the cancellation of the regrouping function. These acknowledgements are not sent in response to a multicast transmission of the preconfigured regroup cancel request.