A Very High Bit Rate Broadband Acoustic Modem for Short-to-Medium Range Data Transmission in Ports and Shallow Water using Spread-Spectrum Modulation

This proposal presents the development, testing and commercialization of two very high bit rate broadband acoustic modem prototypes, capable of achieving true data rates of up to 100 kbps at a maximum range of 300 meters, for a maximum rate-range of 30 kbps-km. The frequency band of operation is 240 kHz to 360 kHz approximately. The technology is based on an improved algorithm for estimating the time-varying impulse response of the ocean in rapidly fluctuating environments, and exploitation of the temporal diversity of acoustic channels. It uses direct-sequence spread-spectrum modulation techniques, combined with high-resolution decision feedback equalizing with parallel tracking of large Doppler. This methodology was developed by Prof. Beaujean at Florida Atlantic University. The proposed broadband acoustic modem will provide a hovering AUV the capability to uplink high-resolution images in compressed format using acoustic transmissions in real-time or near real-time, while performing its mission without the risk of entanglement. Option A will provide a low bit rate command/control acoustic downlink to an AUV. Option B will add a two-way acoustic voice channel between a diver and a topside operator.