Iterative reconstruction of oversampled OFDM signals over deep fading channels

Abstract

Conventional OFDM symbol detection at the receiver becomes difficult if multipath fading channels have spectral nulls. In this paper, we consider an oversampled OFDM system which is a special case of the precoded OFDM systems. We show that the system performance is significantly improved if the deep faded symbols on the subcarriers of each oversampled OFDM signal are discarded and then reconstructed from the remaining ones. In fact, dropping the weak symbols at the receive side results in a nonuniform sampled version of the oversampled OFDM signal and as the nonuniform sampling theorem guarantees, as long as the average symbol rate of the symbols on the remaining subcarriers stays above the Nyquist rate, the perfect OFDM signal recovery is possible. For reconstructing the symbols on the weak subcarriers from the symbols on the remaining subcarriers at the receiver, we consider an iterative receiver for its fast convergence rate and its simple implementation. Simulation results reveal the oversampled OFDM system performance valuable merits as compared to that of the conventional detector for the OFDM system.