In this paper, low-complexity Doppler-shift compensation for orthogonal frequency division multiplexing (OFDM) suitable for underwater acoustic communication (UWAC) is proposed. This algorithm exploits the integer part and the fractional part of the time expansion/compression measured within a fraction of a sample period in each OFDM to jointly estimate the Doppler-shift and the residual carrier frequency offset (CFO). Unlike block-Doppler compensation, the proposed scheme increases the throughput by utilizing single chirp pulse as a preamble. In addition, the Doppler-shift variation within the OFDM symbol is dealt with by adopting a smoothing filter. The proposed scheme was investigated in an experiment, evaluating the system performance over a range of 1 km in the North Sea during the summer of 2009.
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