Ofdm transmission system and method for effective allocating frequency supports hsdpa

The present invention is to provide an apparatus and method for transmitting high-speed forward packet data to the base station the mobility of a user terminal in a mobile communication system supporting the OFDM / HSDPA. After this the present invention provides an orthogonal frequency division multiplexing mobile communication system, the base station receives to distinguish the plurality of user terminals into two groups according to the speed information indicating a plurality of speed change from the user terminal in the same cell from each other and in that it comprises that transmits packet data using different frequency allocation schemes. Thus, with the high speed downlink packet data to a plurality of user terminals of different moving speed of receiving it has the maximum receiving guaranteed effect the quality of service. Multicarrier acclimatized prefix number (Cyclic Prefix), Doppler value, frequency hopping scheme, a frequency scheduling method, time-frequency mapping method, Costas sequence