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.