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In this letter, a low-complexity and low-overhead adaptive bit-loading algorithm for wireless multicarrier schemes is proposed and analyzed. It is based on the diversity gain obtained through the ordering and selection of the more reliable subcarriers. Higher order modulations are used to compensate for the reduced subcarrier utilization. On the contrary to other bit-loading algorithms, it does not require nonuniform bit and power level allocation among subcarriers, thus drastically reducing the modem hardware complexity and making it attractive as a possible extension of existing high-speed wireless local-area network standards. System performance is analyzed in different configurations and conditions, including a realistic 5-GHz propagation scenario. Comparison with optimal adapted and unadapted solutions is also made. Finally, the effect of unideal feedback of the channel state information is analyzed showing the robustness and the low overhead required of the new scheme.
Date of Publication: Sept. 2004