SSFB: Signal-Space-Frequency Beamforming for Underwater Acoustic Video Transmission

Transmitting large amounts of data such as videos underwater is an important yet challenging problem in the harsh underwater environment in which radio-frequency waves are absorbed for distances above a few tens of meters, optical waves require narrow laser beams and suffer from scattering and ocean wave motion, and acoustic waves—while being able to propagate up to several tens of kilometers—lead to a communication channel that is very dynamic, prone to fading, spectrum limited with passband bandwidths of only a few tens of kHz, and affected by non-Gaussian noise. Notwithstanding these challenges, a hybrid solution that is capable of transmitting at high data rates underwater via acoustic waves at short/medium distances is proposed. The solution introduces a novel signaling method, called Signal-Space-Frequency Beamforming (SSFB), for a multiple antenna where each antenna consists of Uniform Circular Array (UCA) hydrophones mounted on an underwater vehicle to steer the beam in both azimuth and elevation planes; then, an array of Acoustic Vector Sensors (AVS)—hydrophones that are able to capture the acoustic particle velocity/direction of arrival in addition to measuring regular scalar pressure—are mounted on the surface buoy. Detection is performed based on the beam spatial separation and direction of arrival angles' estimation. Simulation results confirm that this solution outperforms stateof-the-art underwater acoustic transmission techniques, whose data rates are limited only to few tens of kbps.