Group communication system for the transmission of multimedia data

A communication system for the transmission of group multimedia data to a set of multimedia clients, each multimedia client being affiliated to at least one communication group, said communication system comprising:

• at least one control entity;
• at least one signalling participating entity;
• at least one participating entity, which is a unicast entity, supporting a unicast distribution service;
• at least one participating entity, which is a broadcast entity, supporting a broadcast distribution service;
• media sessions for one or more multimedia group communications being established between the at least one control entity and the at least one participating entity, the at least one signalling participating entity and the at least one unicast entity each serving at least one sub-set of multimedia clients of the set of multimedia clients, independently of the geographic location of said multimedia clients;
• the at least one broadcast entity serving local multimedia clients of the set of multimedia clients in a given geographic zone, independently of the signalling participating entity serving said local multimedia clients;
• said communication system further comprising a software bus linking the different participating entities to convey information messages exchanged between the different participating entities, said information messages comprising update data for:
• enabling each unicast entity to
• maintain up to date a first list containing for each communication group to which has become affiliated at least one multimedia client served by said unicast entity the multimedia clients affiliated to said group and served by said unicast entity;
• maintain up to date a second list containing for each geographic zone in which is situated at least one multimedia client served by said unicast entity the multimedia clients situated in said geographic zone and served by said unicast entity;
• enabling each broadcast entity to maintain up to date a third list containing for each communication group to which has become affiliated at least one multimedia client present in the geographic zone served by said broadcast entity, among said set of multimedia clients, the multimedia clients that are affiliated to said communication group and that are present in said geographic zone.