Apparatus and method for signal constitution for downlink of ofdma-based cellular system

The present invention adjusts the number of transmission antennas fluidly by demand of a user's movement speed, a channel situation, or a user by the link for the bottoms of the cellular system of an OFDMA base, and presents the adaptation pilot symbol arrangement system which arranges a suitable pilot symbol. Moreover, an ultra high-speed move user's traffic volume by assumption of almost small-coming out compared with all the traffic, The subcarrier allocation formula for the high-speed movable body which assigns the partial subcarrier of all the subcarriers, arranges the suitable pilot symbol for an ultra high-speed move user, remains in other users, assigns a subcarrier, and arranges a suitable pilot symbol is shown. According to the present invention, the transmission electricity usage and the overhead by a pilot can be reduced, and the total rate of data communications can be raised.