Maximum-Likelihood Symbol Timing Estimation Algorithm for OFDM Systems Based on a Repeated Preamble

An efficient synchronization scheme based on a repetitive preamble structure for orthogonal frequency division multiplexing systems was proposed by Schmidl and Cox. However, standard autocorrelation based estimation algorithms result in a plateau in the timing metric due to the cyclic prefix (CP), resulting in a region of uncertainty. Several modifications, either to the preamble structure itself or the estimation algorithm, have been proposed to remedy this problem. In this paper, we present a maximum-likelihood (ML) symbol timing estimation algorithm taking into account the presence of the CP. The performance of its practical modification is evaluated via computer simulations