Patent ID: 7826543

Claim:
A mobile station of an orthogonal frequency division multiplexing access (OFDMA) system having a variable number of subchannels according to communication environments, the mobile station comprising: a modulator for modulating transmit data according to the number of allocated subchannels and outputting the transmit data; a variable gain amplifier for amplifying the transmit data outputted by the modulator and transmitting the amplified transmit data to a base station through an antenna; a gain controller for controlling a gain of the transmit data inputted to the variable gain amplifier from the modulator according to a subchannel gain value corresponding to the number of subchannels (the subchannel gain value being predetermined according to the number of subchannels so as to maintain an output value inputted to the variable gain amplifier from the modulator to be constant); and a power controller for generating a power control gain for controlling power of the transmit data except the subchannel gain value with reference to the signal received from the base station through the antenna, and outputting the power control gain to the variable gain amplifier.