An overview of channel coding for underwater acoustic communications

The TRIDENT (TRansmission d´Images et de Données EN Temps réeel) project was launched a few years ago by GESMA (Groupe d´Etudes Sous Marine de l´Atlantique). The initial objectives were to develop a multiple-rate underwater acoustic link for images, text and data transmission. Later, the speech option was added, and more recently channel coding options have been introduced to the TRIDENT platform. Convolutional codes (CC) and Reed Solomon (RS) block codes were then checked, but these simple codes were not able to significantly improve the Bit Error Rate (BER) at the channel decoding output. For this reason, GESMA decided to introduce turbo codes options, more specifically the Reed Solomon Block Turbo Codes (RS-BTC), to enhance the channel decoding efficiency. The data transmitted are interleaved and frame recovery is performed in reception. After system validation in static conditions, in the Penfeld river in Brest, France, sea trials were conducted in the Bay of Brest in dynamic conditions. This paper presents various possibilities offered by the platform for images and speech transmissions and the RS-BTC channel coding options.