Method and apparatus for a talkgroup call in a wireless communication system

In a wireless communication system comprising a plurality of subscriber units in wireless communication with a fixed infrastructure, a method for the fixed infrastructure to establish a talkgroup call, the method comprising steps of:

• receiving, from a first subscriber unit of the plurality of subscriber units, a request for the talkgroup call, the request comprising an identity of the first subscriber unit and an identity of a talkgroup;
• identifying, based on the identity of the talkgroup, a talkgroup of subscriber units comprising at least two subscriber units of the plurality of subscriber units;
• identifying, based on the identity of the first subscriber unit, a sub-talkgroup of subscriber units of the talkgroup;
• assigning an outbound time slot in a frequency channel to subscribers in the sub-listengroup;
• assigning a plurality of outbound time slots in the frequency channel in a one-to-one manner to subscribers in the sub-talkgroup if there is more than one talker;
• and
• assigning, in a one-to-one manner, at least one inbound time slot in the frequency channel to the sub-talkgroup.