Patent ID: 7948865

Claim:
In a unidirectional or broadcasting communication system using OFDM transmission from a base station to subscriber units, means for achieving a bi-directional channel comprising: A. transmitting means in the subscriber units for transmitting signals that are orthogonal to signals transmitted from the base station and are also orthogonal to signals from other subscriber units; B. receiving means in the base station for receiving and processing together signals from a plurality of subscriber units; C. means for allocating to each subscriber unit several carriers that are separated from each other (not adjacent to each other), wherein said base station further includes means for the transmission of Automatic Synchronization Control (ASC) signals to said subscriber units, and wherein said subscriber units further include means for synchronizing transmissions therefrom responsive to said received ASC signals, and wherein the base station further includes means for sending ASC signals so as to bring all the subscriber units in synchronization with the base station, thus maximizing the transmission time and preventing transmission overlap between subscriber units and the base station.