The present invention concerns a wireless telecommunication system including at least a base station intended to communicate with terminals over bidirectional communication channels, each channel supporting frames being divided into downlink timeslots and uplink timeslots, each downlink timeslot including a number of symbols intended to be transmitted to at least a terminal, a terminal after having received all the symbols included in a downlink timeslot followed by an uplink timeslot transmits other symbols over said uplink timeslot with a time delay depending on the distance between said terminal and said base station so that the so transmitted symbols are received by said base station at a time separated from the end of the transmission by the base station of the downlink timeslot by a predefined guard period constant whatever said distance, and the base station transmits at least a supplementary downlink symbol during the guard period to terminals that can receive said at least supplementary downlink symbol during the time delays thereof and/or receives during the guard period at least a supplementary uplink symbol from the terminals that can transmit said at least supplementary uplink symbols during the time delays thereof.