Simple coarse frequency offset estimation schemes for OFDM burst transmission

Simple methods of the estimation of that part of the frequency offset, which is a multiple of the subcarrier spacing in the OFDM (orthogonal frequency division multiplexing) systems have been proposed. Described methods are aimed at burst transmission systems and take use of only one preamble symbol also required for the timing offset estimation. The methods are based on the frequency domain search for the unused subcarriers in the received signal spectrum. The proposed algorithms are immune to a constant phase shift (e.g. caused by timing errors). The estimation range depends on the algorithm but in general can be made as large as desired (but less than a half of the signal bandwidth). Simulation results show that the proposed algorithms estimate an integer part of the frequency offset in the AWGN channel even in the presence of some amount of the intercarrier interference (ICI). Satisfactory performance has been obtained also for OFDM transmission on multipath channels.