Digital acoustic communication in multipath underwater channels

A novel transmission scheme based on the Sliding Discrete Fourier Transform (SDFT) is proposed for communicating in multipath acoustic channel and its performance is evaluated by computer simulations. The system described uses constant envelope multifrequency signals and can tolerate large Doppler frequency shifts and strong multipath conditions. Beam diversity is suggested as an additional protection against signal fading caused by acoustic shadow zones. With the availability of VLSI circuits to implement the SDFT algorithm (such as the Recticon Quad Chirped Transversal Filter), the system is particularly attractive in situations where power and space conservation are of prime importance, as in remotely controlled submersibles.