Underwater acoustic communication using Reed Solomon Block Turbo Codes channel coding to transmit images and speech

In 1997 GESMA (Groupe d´Etudes Sous-Marines de l´Atlantique), in collaboration with TELECOM Bretagne, launched a new project, called TRIDENT. First objectives were to develop a multiple rate underwater acoustic link for images, text and data transmission. This link was designed to provide a wireless communication to AUVs. Since 2006, the platform was extended to low bit rate speech transmission using a MELP coder working at 2400 bps. Such a rate allows to use lower carrier frequencies, able to reach longer ranges in the case of speech transmissions. More recently two channel coding options were added to the TRIDENT platform. Convolutionnal codes (CC) and Reed Solomon (RS) block codes were then checked. These simple codes were not able to improve significantly the Bit Error Rate (BER) at the channel decoding output. That is why, GESMA decided to introduce the turbo codes options and more precisely 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 condition, in Brest Penfeld river (November 2009), sea trials have been recently conducted in Brest bay (March 22 to 26, 2010) in moving condition. This paper presents the different possibilities offered by the platform for images and speech transmissions and the RS BTC channel coding options.