Two-dimensional pilot-symbol-aided frequency offset tracking in orthogonal multicarrier wireless systems

Pilot-Symbol Assisted-Modulation (PSAM) is employed in coherent OFDM for channel estimation and it is based on inserting known symbols in the time-frequency grid. We show how this two-dimensional embedded signalling can be used for frequency offset tracking. The ML estimator has been derived, but though optimal, may not be practical due to its complexity. Hence, a frequency-domain low-complex estimator has been proposed, based on only the samples at pilot positions. Also, the stability of the generated estimate is improved significantly by averaging over a few number of OFDM symbols. This estimator is efficient against AWGN and also suitable for use in time dispersive channels.