A bidirectional communication system is provided. In one embodiment, a system comprises a host unit and a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit using orthogonal frequency division multiplexing (OFDM). The host unit repeatedly performs...http://www.google.de/patents/US7420914?utm_source=gb-gplus-sharePatent US7420914 - Synchronization techniques in multipoint-to-point communication using orthogonal frequency division multiplexing
