Enhanced frequency synchronization for OFDM systems using timing error feedback compensation

A strategy of improving the frequency synchronization performance of the conventional maximum-likelihood (ML) algorithm for OFDM systems is proposed. In the conventional ML algorithm, the accuracy of the frequency offset estimation directly depends on the block timing estimation. In the proposed algorithm, the block timing error caused by the ML algorithm is estimated at the post-FFT stage of the OFDM receiver using pilot symbols. An improved frequency offset estimation is obtained from the ML algorithm with timing error feedback compensation. Simulation results show that the proposed algorithm can: (i) eliminate the error floor caused by the ML algorithm and (ii) achieve normalized frequency synchronization errors as low as 1 ppm (< 10^-6) for both AWGN and multipath channels with high SNR.