A frequency offset estimation technique based on frequency error characterization for OFDM communications on multipath fading channels

A novel frequency offset estimation technique based on maximum-likelihood estimation for wireless orthogonal frequency division multiplexing communications on frequency-selective fading channels is proposed. By taking advantage of subcarrier-level differential operation and coherent error characterization, the proposed estimator based on the frequency error characteristics can effectively overcome multipath fading effects. Frequency error characterization is achieved by means of pseudonoise matched filters in the frequency direction; thus, the proposed estimation technique exploits frequency diversity without assistance in the form of accurate timing information. In addition, the proposed technique can combat the rapid time selectivity caused by a wide Doppler spread because it requires channel stationarity for only a short duration due to the exploitation of both a single preamble in its training operation and the following semiblind estimation aided from several pilot subchannels. The proposed technique can easily switch between training mode and semiblind mode by sharing the same system architecture. Extensive simulation results in conjunction with statistical analysis verify the superiority of the proposed technique.