s harq retransmission is carried out at a predetermined time with respect to initial transmission synchronous means synchronization in time in contrast the time interval between initial transmission and retransmission is not set in as harq the present invention is described in the context of s harq that allows for easy implementation and simple operation s harq is further branched into pure s harq that allows retransmission without a change in resources and resource adaptive s harq ras harq that may change resources for retransmission hereinafter a pure s harq system is simply referred to as an s harq in the s harq scheme a retransmission time and resources are preset if persistent resource allocation is adopted for the s harq scheme even an initial transmission time can be fixed the ras harq scheme differs from the s harq scheme in that when control information is delivered for retransmission resources can be changed for a retransmission packet for persistent resource allocation an initial transmission time can be fixed also in the ras harq in an application of the two harq schemes to the ofdma system where data can be sent simultaneously on a plurality of channels in one time slot a retransmission channel is fixed in the s.