ICI mitigation and diversity gain for OFDM systems in time-varying multipath fading channels

In orthogonal frequency division multiplexing (OFDM) systems, channels' rapid variations cause intercarrier interference (ICI), resulting in performance degradation. Although ICI caused by channels' variations makes the reliable signal detection difficult, it also introduces Doppler diversity, which can be exploited to improve the system performance. In this paper, an ICI mitigation and Doppler-multipath diversity technique based on fractionally sampling at the receiver is proposed for OFDM systems over time-varying multipath fading channels. To reduce the computation burden of minimum mean-square error (MMSE) equaliser with successive detection (SD), an efficient algorithm is presented by using the property of matrix decomposition. The algorithm avoids direct or recursive computation of matrix inversion, thereby reducing the computation complexity and ensuring numerical stability. Simulations show that the proposed techniques can collect both Doppler and multipath diversity gains with moderate complexities. Copyright (C) 2010 John Wiley & Sons, Ltd.