Patent ID: 8068510

Claim:
A demodulation apparatus for receiving signals by an adaptive modulation and coding method, and demodulating the signals, in an OFDMA based packet communication system, comprising: a QAM demapper for performing a QAM (Quadrature Amplitude Modulation) demapping process on the received signals by a modulation method using a maximum modulation ratio, and outputting first data which have a number of bits corresponding to the modulation method using the maximum modulation ratio until modulation methods for each of the sub-channels are analyzed, and performing the QAM demapping process on the received signals by the modulation methods for each of the sub-channels and outputting second data which have a number of bits corresponding to the modulation methods for each of the sub-channels, when the modulation methods for each of the sub-channels are analyzed; a slot buffer for storing the first data and the second data outputted from the QAM demapper for each slot; and a channel decoder for decoding the data stored in the slot buffer, analyzing modulation methods for each of the sub-channels transferring the analyzed modulation methods to the QAM demapper, reading only valid data corresponding to the number of bits for the analyzed modulation methods from among all bits of the first data, demodulating the valid data, once the modulation methods for each of the sub-channels are analyzed by the channel decoder, reading all bits of the second data, demodulating the read bits of the second data, and outputting the demodulated data.