A Tracking and Telemetry System for Severe Multipath Acoustic Channels

Underwater telemetry systems require special design when they are to be used in severe multipath acoustic channels. This paper describes a modulation/signal processing method, called Spaced-Frequency-Shift Keying (SFSK), that effectively penetrates such channels. SFSK includes features for reliable message validation, message identification, transfer of binary telemetry, and operation over Doppler ranges commensurate with maximum-speed underwater vehicles. Although SFSK was developed for the specific purpose of underwater vehicle tracking, it is easily adaptable to a wide range of underwater communications applications.