A Low Bit-Rate Speech Underwater Acoustic Phone using Channel Coding for Quality Improvement

Abstract

GESMA's (Groupe d'Etudes Sous-Marines de l'Atlantique) objective is to develop a sufficiently robust acoustic link allowing the transmission of different data (text, images, etc.). Implementation of the acoustic link has led the ENST Bretagne to develop a real-time platform called TRIDENT (TRansmission d'Images et de Données EN Temps réel). To reduce the various perturbations caused by the underwater acoustic channel (UWA), a blind spatio-temporal equalizer is used. The acoustic link performance was evaluated and has shown its robustness for transmission over a strongly disturbed channel. GESMA also wants to increase the link reliability and provide a strongly protected low bit rate speech (MELP, 2400 bit/s) transmission. In order to do so, channel coding will be added to the system. Different kinds of error correcting schemes will be tested including convolutional codes (CC) and Reed Solomon (RS) block codes.

Design of an Acoustic Communication System Based on FHMA for Multiple Underwater Vehicles

“…However, the complex environment in the ocean makes it rather difficult to communicate normally, such as the problems of high noise, multipath effect and large delay. So far, many researches have been made to ensure the communication reliability underwater, including the simulation and measure of the channel [1]; research on the use and algorithm of signal processor in the receiver [2]; diversity reception technique [3] and coding technique (compression coding and error correction coding) [4]. As the tasks that we require underwater vehicles to undertake grow more and more complicated, precise and various, only an underwater vehicle can hardly satisfy all the requirements.…”