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An adaptive transmission scheme using QAM and LDPC code is proposed for an OFDMA cellular system employing FDD. Also, adaptive algorithms for active user selection, subchannel transmission power allocation, and modulation and coding set selection are proposed. The performance of the proposed scheme is obtained from computer simulation and is compared with that of the conventional scheme using mean SNR only. It is shown that the proposed scheme can provide up to 5.1 dB gain over the conventional scheme at the expense of only 3 more bits in feedback information.