Suppression of effects of the synchronization error with adaptive down-conversion for underwater acoustic communication

Abstract

In underwater acoustic communication, inaccurate synchronization can cause an incorrect estimation of the uniform Doppler shift, thereby degrading demodulation performance. In this paper, the effect of inaccurate synchronization on demodulation is mathematically described, theoretically demonstrating that adaptive down-conversion, which has been proposed to suppress the effects of nonuniform Doppler shift, reduces the degradation of demodulation performance caused by inaccurate synchronization. The improvement in demodulation performance by adaptive down-conversion was evaluated using experimental data. The demodulation results including the intended synchronization errors clearly show that adaptive down-conversion reduces the effects of the synchronization errors and improves demodulation performance in cases with inaccurate synchronization.