Mitigation of Intercarrier Interference in Ofdm Systems over Underwater Acoustic Channels

Transmission schemes based on orthogonal frequency division multiplexing (OFDM) are promising for underwater acoustic (UWA) communications, thanks to their robustness to large multipath spreads. On the other hand, due to the significant time variations in the UWA channels, the effectiveness of the standard OFDM receivers is impaired by intercarrier interference (ICI). In this paper, we propose two novel ICI-mitigation techniques. In the first scheme, the ICI coefficients are explicitly estimated, and minimum mean square error (MMSE) equalization based on such estimates is performed. In the second approach, no explicit ICI estimation is performed, and detection is based on an adaptive decision-feedback equalizer (DFE) applied in the frequency domain across different subcarriers. We report simulation results showing the effectiveness of the proposed schemes, compared to the performance of a standard OFDM receiver neglecting ICI, and results obtained by processing real data recorded in the recent KAM08 experiment.