Adaptive tone diversity for OFDMA in broadband wireless communications

The paper considers an OFDMA system using M-ary QAM signaling for broadband wireless communications. The bit error probability of the system over equal-power multipath Rayleigh fading channels is derived. The throughput performance in quasi-synchronous multipath frequency-selective fading channels is discussed. It is shown that with tone diversity, OFDMA can outperform a time-domain single-user RAKE receiver. Simulation results also show that this system has a better performance than MC-CDMA and random access FH-OFDMA. In addition, a group-optimal adaptive-tone-diversity (GO-ATD) technique is proposed, and the resulting throughput degradation is shown to be negligible as compared to the optimal scheme, while the computational complexity is much less.