Synchronization and channel coding in shallow water acoustic communication

GESMA's (Groupe d'Etudes Sous-Marines de l'Atlantique) objective is to develop a sufficiently robust acoustic link allowing the transmission of different information (text, images...). A real-time platform named TRIDENT (TRansmission d'Images et de Donnes EN Temps reel) was designed at TELECOM Bretagne. A blind spatio-temporal equalizer is used to reduce the various perturbations caused by the underwater acoustic channel (UWA). The acoustic link performance was evaluated and its robustness for transmission shown in a strongly disturbed channel. GESMA also wants to increase the link reliability. In order to do so, a channel coding was added to the system. Different kinds of error correcting schemes were tested including Convolutional Codes (CC) and Reed Solomon (RS) block code. Correlation strategies are used to solve both phase ambiguity and frame synchronization before channel decoding.