A broadcast group call is a special group call where the initiating user expects no response from the receiving users so that when the transmission is complete, so is the call. The initiating user can be an MCPTT user or can be an LMR user.
The group-broadcast group is defined as a set of groups, not a set of users. The user that originates the group-broadcast group call is the only one transmitting media during this call.
The group-broadcast group is defined with a hierarchy. For example, groups A and B may be subordinate to a group-broadcast group. All subordinate groups belonging to a group-broadcast group are defined either in the MCPTT system or the LMR system.
Subclause 10.6.2.5.2.1 of TS 23.379 describes the procedure for a group-broadcast group call within a single MCPTT system. The present procedure describes a group-broadcast group call that includes the IWF.
In this procedure, the MCPTT server is initiating the broadcast and is the owner of the group-broadcast group.
The procedure shows the case where the call is initiated by a MCPTT user. However, if the override feature is enabled, then the call originator may be overridden.
Figure 10.3.4.2-1 illustrates the procedure for group-broadcast group call establishment (the group-broadcast group is defined in the MCPTT system).
Pre-conditions:
The group (e.g. A) to which MCPTT client 2 and the IWF are members is a subordinate group of the group-broadcast group (i.e., the group-broadcast group was defined with group A as a subordinate group).
The group (e.g. A) currently has an on-going MCPTT group call that is not an MCPTT emergency group call.
The call initiator of the group-broadcast group is a member of another group (e.g., X, not group A) which is also a subordinate group of the group-broadcast group (i.e., the group-broadcast group was defined with group X as a subordinate group).
The group-broadcast group and its subordinate groups are defined in the same group management server and served by the same MCPTT server.
The MCPTT server needs to resolve the group-broadcast group ID into its subordinate groups in order to contact the affiliated MCPTT users of those subordinate groups.
The MCPTT server then needs to consider any on-going group calls on those subordinate groups because this may affect the behaviour for what happens next. In this case a group call exists on a subordinate group. Thus, the MCPTT users involved in the group call on this subordinate group.
A group-broadcast group call request is sent to MCPTT client 2 and an IWF group-broadcast group call request to the IWF. If the IWF has affiliated to this group on behalf of the group's LMR users, only one IWF group-broadcast group call request is sent to the IWF. If the MCPTT server has received individual affiliations from the group's LMR users, an individual IWF group-broadcast group call request is sent (to the IWF) for each affiliated LMR user.
MCPTT client 2 and the IWF respond to the IWF group-broadcast group call request by sending an IWF group-broadcast group call response. If the IWF has affiliated to this group on behalf of the group's LMR users, only one IWF group-broadcast group call response is sent to the MCPTT server. If the MCPTT server has received individual affiliations from the group's LMR users, an individual IWF group-broadcast group call response is sent (to the MCPTT server) for each affiliated LMR user.
The MCPTT server responds to MCPTT client 1 (the call initiator) that the group-broadcast group call has been established by sending a group-broadcast group call response.
Subclause 10.6.2.5.2.1 of TS 23.379 describes the procedure for a group-broadcast group call within a single MCPTT system. The present procedure describes a group-broadcast group call that includes the IWF.
In this procedure, the IWF is the owner of the group-broadcast group and is initiating the group-broadcast group call.
The procedure only shows the case where the call is initiated by a MCPTT user. However, if the override feature is enabled, then the call originator may be overridden.
Figure 10.3.4.3-1 illustrates the procedure for group-broadcast group call establishment (the group-broadcast group is defined in the LMR system).
Pre-conditions:
The group (e.g. A) to which MCPTT client 2 is a member is a subordinate group of the group-broadcast group (i.e., the group-broadcast group was defined with group A as a subordinate group).
The group (e.g. A) currently has an on-going MCPTT group call that is not an MCPTT emergency group call.
The call initiator, MCPTT client 1, of the group-broadcast group is a member of another group (e.g., X, not group A) which is also a subordinate group of the group-broadcast group (i.e., the group-broadcast group was defined with group X as a subordinate group).
The group-broadcast group and its subordinate groups are defined in the IWF.
The MCPTT server responds to MCPTT client 1 (the call initiator) that the group-broadcast group call has been established by sending a group-broadcast group call response.