An adaptive modulation and power-allocation algorithm in OFDM system

Orthogonal frequency division multiplexing (OFDM) modulation scheme is adopted by more and more wireless communication systems to help achieve reliable and high-rate data transmission. Wideband wireless systems based on OFDM are limited in their performance by the dips in the frequency spectrum of the multipath fading channel. The performance of an OFDM-based system can be augmented by the adaptive loading and power-allocation of the subcarriers. Several algorithms have been developed, most of them based on high-complexity iteration. We develop a low-complexity and fast converging algorithm that guarantees integer bit rate. Simulation shows that the proposed adaptive algorithm improves the system performance considerably, more than 5 dB for BER under 10^-2.