Sub-optimal power allocation for downlink OFDMA systems

Spectral efficiency is important in designing wireless broadband communication systems. The paper investigates the problem of minimizing overall transmission power while maximizing the spectral efficiency in orthogonal frequency division multiple access (OFDMA) systems. Two adaptive power allocation schemes are presented to allocate transmission power to individual sub-carriers of each user in the downlink frequency-selective fading channels. The proposed algorithms are more computationally efficient than the conventional water-filling algorithm. Performance comparison to the optimal solution shows that the proposed schemes can achieve 99% of the optimum spectral efficiency.