High-speed acoustic communication in shallow water using multiple coherent path beamformer technique

Abstract

A multiple coherent space-time processing method is used for acoustic communication at high data rate in very shallow water, between 16 and 32 kHz. The multiple coherent path beamformer (MCPB) method for processing the signals uses an adaptive processor that forms beams in the direction of a collection of coherent signals representing the strongest path. The source is the FAU Utility Acoustic Modem used for acoustic networking during AUV operations. The system encodes data using coherent modulation schemes with coded rates varying between 4000 and 48<th>000 bps. The receiver system is composed of a 64-channel Mills–Cross array attached to an FAU embedded 64-channel acquisition system. Results already obtained show that the MCPB can decode data reliably at 3200 m for rates up to 32<th>000 bps, with a platform speed of 2–3 knots and a sea-state of 1–2. For a source level of 186 dB, BPSK encoding and 62.5&♯61549;s symbols (16<th>000 bps), the MCPB achieves a bit error rate of 0.2% without any Forward Error Coding. These results demonstrate the long-range and high-data rate transmission ability of the system, and make possible real-time transmission of side-scan data and other low-resolution video images.