The office of Naval Research and the Naval Research Laboratory experimentation in underwater acoustic communications research: U.S. Navy and Air Force reservists integrated seamlessly in at-sea experiments in the past year on board NRL research vessels

CHIPS, Jan-March, 2006 by Michael T. McCord

Naval Reserve Chief Fire Control Technician Jan Caban was eager to participate in the NRL experiment. "I saw the opportunity as tremendously exciting--a chance to go to sea again, which 1 truly love... "

Naval Reserve Cryptologic Technician (maintenance) 1st Class Catherine Christian said the experience exceeded her expectations." ... The team atmosphere of the NRL research staff particularly impressed me. The other reservists onboard and the vessel's crew all became equally enthusiastic about the goals of the project. I'm sure it was this our-of-the-box approach that led the entire team to overcome multiple technical and weather challenges..."

The Excitement Begins

Typical at-sea experiments begin with a week of system preparations. University of Delaware-owned Research Vessel Cape Henlopen at 120-feet and 197 gross tonnage was not the usual ride for Navy officers and Sailors. The ride was rough because the Henlopen is a small vessel. But the mission was important, and it wasn't long before reservists got their "sea legs."

Equipment was installed in racks to facilitate system integration months before the experiment. This provided excellent protection for shipment and allowed quick set-up on board. Almost all the equipment used was purchased off-the-shelf and has proven to be dependable.

The Surface Acoustic Communications Data Storage unit contains the wireless LAN electronics and is loosely tethered to the subsurface unit. Fiber optic lines within the tether provide a 100Base-T network link to the subsurface unit.

Located near the edge of the continental shelf, operations areas are selected in the more challenging acoustic regions to better understand the effects of multipath, reverberation and Doppler. Among the challenges our team faced in the September 2003 experiment was rough weather in the Atlantic Ocean caused by the approach of Hurricane Isabel.

Conditions were so choppy that by the time we arrived on station, we had quite a challenge to deploy the Acoustic Communications Data Storage units. The difficulty was in standing still while the ship was rocking and having our hands free to conduct the experiment.

Results

During this experiment, data from point to point transmissions were evaluated for high data rate (voice and video rate) acoustic telemetry. Data between moored and towed systems were evaluated for acoustic communication networking. Some analysis was conducted at sea, but the bulk of the work is done in the lab. NRL has developed system performance modeling and prediction capability that incorporates site-dependent signal propagation characteristics.

Improved algorithms have been developed to mitigate environmental and platform motion effects on communications data rate and bit-error rate. Applications include reliable communications for submarines operating at tactical speeds and depths and robust networking capabilities between unmanned underwater vehicles.

We gratefully acknowledge the research funding provided by the Office of Naval Research. Results from the research is delivered to our ONR sponsor and published in science journals.