Low probability of detection underwater communications using a vector sensor

Abstract

Low probability of detection underwater acoustic communications are required for command and control of mobile underwater platforms performing covert missions. To deal with multipath and increase the signal-to-noise ratio (SNR) at the receiver, this paper presents a study on the low probability of detection communications using a single vector sensor. Compact in size, vector sensors (VS) are suitable for autonomous underwater vehicles, measuring both acoustic pressure and particle velocity, and therefore providing diversity gain. As part of the multidisciplinary EMSO-PT project, an experiment took place off the coast of Algarve/Portugal on Nov 24th, 2021. A single 2D VS was posed on the bottom. Broadband signals were transmitted from several positions, varying both the source-receiver range and the direction of arrival. Recorded noise was added to the signals to reduce the SNR from 0 to -10dB. A superimposed training passive time-reversal approach was employed for equalization. Coherent communication performance was evaluated. Results show that VS multichannel combining may provide an average SNR and mean squared-error gain of up to 9.4 and 3.1 dB, respectively, compared to the pressure channel.