Acoustic communications system for the AMMT program

The acoustic modem developed for the Autonomous Minehunting and Mapping Technology (AMMT) program is based on state of the art coherent communication methods which are in the transition from basic research to field applications. The AMMT program was the first operational demonstration of this new class of undersea communication capability. The acoustic modem provided regular status updates and data upload from the UUV to a surface vessel, as well as downlink to the vehicle from the support ship. It is based on an extensible software and hardware system that allows operation over a wide range of date rates and carrier frequencies. The raw burst data rate of the uplink was up to 10 000 bits per second though the system was operated primarily at 5 000 bits per second. The raw burst rate of the downlink was 2 500 bps. The receiver incorporates algorithms for Doppler estimation and compensation, equalization and error correction coding. In addition, it handles compression and transmission of laser linescan and camera images including retransmission of bad packets. The modem was successfully operated at ranges over 2000 m and vehicle depths up to 300 m.