Experimental results on MMSE turbo equalization in underwater acoustic communication using high order modulation

This paper presents some results on MMSE turbo equalization applied to real sea water trials in the Atlantic ocean. High order modulations (8-PSK, 16-QAM and 32-QAM) have been tested. The channel data rate on the underwater acoustic channel is up to 20 kbps. The receiver includes timing recovery, equalization, interleaving and channel coding. The results which are evaluated in term of bit error rate (BER) and mean square error (MSE) show that turbo equalization improves the performance of the receiver and allows reliable high order transmissions when the signal to noise ratio is sufficient.