Optimal Bit and Power Direct Allocation Algorithm in OFDM Systems Based on the Regularity of Greedy Allocation Result

This paper proposes a new optimal bit and power direct allocation algorithm. Based on the analysis of the regularity of the Greedy allocation result, we propose and prove a necessary and sufficient condition for the Greedy allocation result. According to this condition, a bit and power allocation algorithm aiming to allocate the total bits or total power at a time to all subchannels is proposed. The impact of SNR Gap on the allocation result and the technique to eliminate its impact are analyzed. Though iterations are needed to obtain the ideal allocation result, the computational complexity is lower than that of existing optimal algorithms in the literature, even lower than that of some suboptimal algorithms.