Beaujean P., Blue P., Kriel D.

Homeland defense, anti-terrorism and force protection organizations need to efficiently inspect ship hulls and piers for foreign objects. Existing diver teams are time and manpower intensive, and ordnance searches are particularly hazardous to divers. The use of Unmanned Underwater Vehicles in the field of hull survey and port security greatly reduces the risk to divers. Some UUVs are now capable of hovering around a target or the hull of a ship and record high-definition sonar images, while keeping key personnel at a safe distance from a potentially dangerous device, typically a hundred meters away from the point of deployment. Having human-in-the-loop capability is essential to efficiently execute this type of operation, and requires the transmission of images to a remote user. Today, this high-bandwidth information is transmitted by cable, which severely limits the UUV maneuverability and prevents the UUV from operating in confined areas. A one-way high-speed high-frequency acoustic modem (HS-HFAM) operating between 240 kHz and 380 kHz has been developed to replace such cable. High high-data rates are made possible using a high-resolution decision feedback equalizer with a parallel algorithm tracking and compensating large Doppler, developed at Florida Atlantic University (FAU). Current tests, using experimental hardware developed at FAU and EdgeTech, achieved reliable acoustic communications at a coded rate of up to 150000 bits-per-second at a range of 50 m, in ports and very shallow waters. The maximum range is currently limited to 100 m, with the peak relative velocity between source and receiver not exceeding 1.5 meters-per-second. These results were obtained using a very compact source with output power of 0.63 W, which shows that the HS-HFAM is remarkably power efficient and ideal for small UUVs and divers, as it achieves 130,692 bits-per-Joule at 150,000 coded bits-per-second.