An efficient synchronization method for OFDM systems in multipath channels

In this paper an efficient scheme for OFDM data-aided synchronization is presented. It is based on a new single-symbol preamble structure. The preamble symbol comprises two successive equal-duration sub-symbols, the second one of which is a differentially encoded version of the first one, using an adequately designed precoding sequence. We here explore the performance of the method in the case of multipath channels. For timing offset estimation, the performance is presented in terms of correct frame start detection rate and estimation variance. For fractional frequency offset estimation, the performance is evaluated in terms of mean squared error. Compared to some other preamble-based synchronization methods, the obtained results prove enhanced accuracies of the start frame detection and the fractional frequency offset estimation, even at very low SNRs. We show that our time offset estimator has one order of magnitude reduction in time offset standard deviation. The performance is also improved for the fractional frequency offset estimator with a gain of about 25 dB for an MSE target of 10^-4.