Date Added: Aug 2012
UnderWater Acoustic (UWA) communications have to deal with channels that exhibit widely time-spreading multipath responses, together with Doppler spreading and limited bandwidth. These features seriously limit data throughput, even for sophisticated modulation schemes. Focusing on the large time-spreading characteristics, the authors analyze in this paper an OFDM UWA system such that the channel is longer than the Cyclic Prefix (CP) used. Under this condition, and considering an array of hydrophones at the receiver, they propose in this paper a Minimum Mean Square Error (MMSE) beamformer that makes use of two partial FFTs of half the original number of subcarriers to demodulate the OFDM signal.