Small Submersible Acoustic Communications System Design

A design is presented for a system providing highly reliable command and control acoustic communications between a mother ship and a number of small, fast submersibles. The small submersibles may be employed for underwater mining, exploration, bottom mapping, or military surveillance. Modulation and coding design is presented; the techniques discussed provide multiple protection against multipath and fading, high reliability, acceptable transmitted signal total time duration, simplicity, and economy. The required decision point signal-to-noise ratio (SNR) for Rayleigh fading conditions is derived for the modulation and coding design. Particular attention is paid in the receive signal processing to the initial doppler and message doppler variation problems inherent in a scenario with mobile end points. A Figure-of-Merit calculation is provided for typical geometrical and environmental parameters. It is shown for a realistic source level that the required SNR can be achieved at long range with extreme end point motion.