Time-Frequency Characterization and Receiver Waveform Design for Shallow Water Environments

Papier accepté en IEEE Transactions on Signal Processing en Novembre 2008International audienceThe shallow water environment can be considered as a time-dispersive system whose time-varying impulse response can be expressed as a superposition of time-frequency components with dispersive characteristics. In this paper, we propose a frequency-domain characterization of the shallow water system based on the normal-mode model that treats the system as an acoustic medium. After studying the dispersive characteristics of this system, a blind time-frequency processing technique is employed to separate the normal-mode components without knowledge of the relevant environment parameters. This technique is based on first approximating the time-frequency structure of the received signal and then designing time-frequency separation filters based on warping techniques. Following this method, two types of receivers are developed to exploit the diversity of the shallow water channel and to improve underwater communications performance. Simulation results demonstrate the dispersive characterization of this system and the improved processing performance of the receiver schemes