MPSK underwater acoustic communication modem

The underwater acoustic communication is important for AW. We developed a prototype MPSK underwater acoustic communication modem, which consists of transmitter unit and receiver unit. The receiver adopts space diversity (SD), decision feedback equalizer (DFE), fast self-optimized LMS phase estimator (FOLMSPE) techniques jointly. The fast self-optimized LMS (FOLMS) algorithm is implemented in DFE. This algorithm was also compared with others. A short vertical hydrophone array is suspended on the receiver vessel for signal reception. The separation between each hydrophone is far larger than the wavelength. A shallow water experiment was performed in November 1997 in a lake in North China. Our acoustic modem was successfully operated at ranges over 100 -4000m (constrained by the test area). The results show that the bit error rate (BER) for QPSK with symbol rate 5.0 ks/s is between 10(-4) and 10(-5). Further work for real-time communication is under way.