Frequency diversity for OFDM mobile communication via underwater acoustic channels

Abstract

The major constraint on the performance of orthogonal frequency division multiplexing (OFDM) based underwater acoustic (UWA) communication is to keep subcarriers orthogonal. In this paper, Doppler estimation and the respective compensation technique along with various diversity techniques were deliberated for OFDM-based systems best suited for underwater wireless information exchange. In practice, for mobile communication, adjustment and tuning of transducers in order to get spatial diversity is extremely difficult. Considering the relatively low coherence bandwidth in UWA, the frequency diversity design with the Doppler compensation function was elaborated here. The outfield experiments of mobile underwater acoustic communication (UWAC) based on OFDM were carried out with 0.17 bit/(s·Hz) spectral efficiency. The validity and the dependability of the scheme were also analyzed.

Keywords

underwater acoustic channel / orthogonal frequency division multiplexing (OFDM) / underwater acoustic communication / frequency diversity / Doppler estimation / Doppler compensation