Acoustic vector sensor underwater communications in the Makai Experiment

Abstract

The performance of a vector sensor array (VSA) receiving communication signals in the Makai experiment is quantified. The VSA composed of 4 vector sensors (VS) was tied to a drifting research vessel in shallow water. A bottom-moored source was used to transmit signals from 8k to 14kHz. In the present study, pressure and particle velocity channels are weighted-combined leading to a directional gain (VS beam steering). The communication chain for coherent modulation is composed of noise normalization, VS beam steering, synchronization, Doppler tracking, and a single Decision Feedback Equalizer.The noise normalization step (denoising) is used since the noise power is not uniformly distributed among the pressure and velocity channels. This normalization emphasizes the vertical particle velocity, which benefit communication performance. Bit error rate(BER) performance is estimated for the pressure-only array, a single VS, and the VSA. It is shown that a single VS may provide similar communication performance to four pressure sensors. The BER for the shorter range (230m) varies from 0 to 5%, depending on the number of sensors used. It is noticed that in a multipath environment, steering to the Direction of Arrival (DoA) elevation may not lead to the lowest error for communications.