Patent ID: 8059574

Claim:
A method for communication among a plurality of sites in a land mobile radio (LMR) system, the plurality of sites being interconnected by a data network, the method comprising: configuring the sites to dynamically operate as control points on the data network by periodically broadcasting talk group participation information to one another over the data network and maintaining the talk group participation information at each site, including: (a) transmitting by the sites a respective first message, the respective first message including the identity of the transmitting site and a list of one or more sites from which each of the sites will accept messages; and (b) receiving at the sites the transmitted first messages, wherein each site having a list of a group of sites including from whom each member of the group will accept messages; causing a site initiating a call request to operate as the control point for setting up a call within one of the talk groups and thereby negotiate among participants of the talk group an assignment of multicasting source role for the call within the talk group to the site initiating the call request, including: (a) transmitting a call request message by an initiating site that intends to communicate with one or more sites in the system, the call request message being multicast over the data network to the participants of the talk group; and (b) receiving, by the initiating site, an acknowledgement message from the other sites that are participants in the talk group confirming their willingness to communicate with the initiating site, the acknowledgement message being unicast over the data network; and conducting the call within the talk group, wherein the site initiating the call request and receiving the acknowledgement message assumes the multicasting source role for the call, including: (a) transmitting, by the initiating site, a voice message, the voice message being multicast over the data network to the participants of the talk group; and (b) receiving the multicast voice message at the other sites.