Real-time high data rate acoustic link based on spatio-temporal blind equalization: the TRIDENT acoustic system

Abstract

There is no doubt about the growing interest for the underwater acoustic communications. Among all existing applications, the objective of the Groupe d'Etudes Sous-Marines de I'Atlantique (GESMA) is to develop a sufficiently robust high data rate acoustic link, named TRIDENT. For that purpose, different kinds of information (texts, images ...) could be periodically transmitted through the acoustic channel. A realtime receiver, based on the spatio-temporal blind adaptive decisiun feedback equalizer, developed and patented by ENST Bretagne [I], was designed to cope with all perturbations induced by such harsh channels. Some sea trials have been carried out in June 2002. The first results are clearly convincing since most of the 48 sequences of 5 minutes are successfully detected by the DSP-based real-time receiver. This acoustic system allows transmission at data rates ranging from 8 to 25 kbps in horizontal configuration.

Variable observation window length blind equalization detector for underwater acoustic communication

“…Constant modulus algorithm (CMA) and multimodulus algorithm (MMA) are the two most approved blind equalization algorithms. In [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], the CMA and the improved CMA are applied to underwater acoustic communication. To implement phase recovery in the constellation, the rotator needs to be added to the output of the CMA blind equalizer, and thus, the complexity of the receiver is increased.…”

Check and validate Reed Solomon Block Turbo Codes in shallow underwater acoustic communication

“…The TRIDENT system [1] can use four carrier frequencies (11.2, 17.5, 20.0 and 34 kHz). The bit rate under consideration range from 2.8 to 23.3 kbps with a QPSK modulation (Quadrature Phase Shift Keying).…”

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

“…The TRIDENT system (Fig. 1) [1] can use four carrier frequencies (11.2, 17.5, 20.0 and 34 kHz) with a QPSK modulation (Quadrature Phase Shift Keying) and different bit rates, ranging from 2.8 to 23.3 kbps. Multipath propagation, Doppler effect and noise bring a lot of perturbation on underwater acoustic communication, such as time dispersion and a variability to the received signal.…”