The invention relates to a frequency division communication system. An orthogonal frequency division communication system enables the distribution ratio of uplink and downlink to be changed more flexibly, while maintains advantages which are similar to those of TDD (Time Division Duplex), comprises a base station and a plurality of mobile stations connected by uplinks and downlinks, and a plurality of mutually orthogonal frequencies are allocated on the frequency axis and the time axis to the uplinks and downlinks and to a plurality of mobile stations.