New innovative multimodulation acoustic communication system

In most applications, underwater acoustic transmissions have to be adapted to the environmental conditions (vertical, horizontal or slant link, multipaths, noise...). The multimodulation acoustic transmission system is a newly designed equipment which acts as a modem whose modulation schemes and baud rates are remotely controlled by the operator. Three types of modulation are implemented in the same system: phase shift keying (PSK) for vertical transmission, chirp and frequency hopping modulations for horizontal communication. The user can select in real time the two main parameters (modulation and baud rate), test the reliability of the transmission and finally decide to use the modulation scheme and the baud rate which will insure the best quality. The underwater unit is then remotely programmed by the acoustic link. The system is described in detail with emphasis on the types of modulation results obtained during campaigns at sea are presented