Performance of coherent PSK receivers using adaptive combining, beamforming and equalisation in 50 km underwater acoustic channels

During the first phase of trials, undertaken in the Mediterranean by the MAST2 project “LORACOM”, PSK modulated data was transmitted over a 50 km underwater acoustic channel. The objectives of LORACORM are to achieve reliable underwater acoustic transmission over long ranges for applications such as remote instrumentation and ocean buoy monitoring. The test data were received on both a short vertically aligned transducer array (AV1), and on a number of widely spaced hydrophones in the water column (F1). This paper describes the results of processing this data using a number of digitally implemented coherent receiver structures based on adaptive equalisation, adaptive beamforming, and adaptive multichannel combining