Mean Doppler Compensation for SIMO Turbo Equalization in Underwater Acoustic Communications

Abstract

Underwater acoustic (UWA) communication is a major tool for underwater wireless data transmission. UWA communications with multiple receivers, as vertical receive arrays could utilize space diversity to improve system reliability. For equalization, direct-adaptive turbo equalization (DA-TEQ) uses the exchange of extrinsic information between equalizer and decoder to improve system performance. However, due to the distance between adjacent receive array, each hydrophone of the whole receive array may have different Doppler spreads, which need to be carefully processed. In this paper, a mean Doppler compensation strategy for multi-array UWA communications is proposed for UWA communication signal equalization. The Doppler spread is estimated for each hydrophone separately, and mean Doppler spread is calculated prior to compensate the Doppler spread for the received signal to correct the carrier phase distortion for each receiving hydrophone. Afterwards, time-reversal is performed for multichannel combination, and directive-adaptive turbo equalization (DA-TEQ) is applied for symbol recovery. The proposed mean Doppler compensation strategy is verified by lake experiment results.