A Practical Bit and Power Allocation Algorithm for MIMO-OFDM System in Time Varying Wireless Channels

In this paper, we propose a computationally efficient bit allocation algorithm for adaptive modulation in MIMO-OFDM systems. In adaptive modulation, QAMs are often employed. However, square QAMs are more power efficient than rectangular QAMs. Based on this fact and the characteristic of MIMO-OFDM channels, the algorithm is developed. The complexity of the proposed algorithm is very low and nearly independent to the total transmission rate. This is applauded especially by systems operate with a high signal-lo-noise ratio (SNR). Simulation results demonstrate that the algorithm only requires almost the same power as the optimal Hughes-Hartogs algorithm.