An efficient reduced-complexity two-stage differential sliding correlation approach for OFDM synchronization in the multipath channel

In this paper we propose a reduced-complexity two-stage time and frequency synchronization approach for OFDM systems, operating in multipath channels. The proposed approach exploits a single-symbol preamble with a repetitive structure, composed of two identical m-sequences. The first coarse stage, based on a sliding correlation, finds out the reduced uncertainty interval over which the second fine stage, based on a differential correlation, is performed. The combined use of the sliding correlation, characterized by its low complexity, and the differential correlation, which is much more complex, carried for a limited number of times results in an overall reduced complexity approach. For the time synchronization, the performance is evaluated in terms of correct detection rate of the frame start and the estimation variance. For the frequency synchronization, we focus on the fractional part of the frequency offset which is evaluated in terms of mean squared error. The simulation results prove that, compared to the considered benchmarks, the accuracy of the frame start detection and the fractional frequency offset estimation are greatly enhanced, even at very low SNRs. The proposed two-stage reduced-complexity approach is also compared to the single-stage brute-force approach, where differential correlation is exclusively used, to assess the performance degradation occasioned by the complexity reduction.