Abstract
Underwater acoustic (UWA) channels are characterized by spreading of received signals in space (angle of arrival) and delay. The spread is often limited to a small number of clusters. For combining signals spread in delay, equalizers are used. To separate space clusters, antenna arrays are used. In this paper, a receiver is investigated that exploits space-time clustering in UWA channels. The investigated receiver is designed for a communication system using guard-free orthogonal frequency division multiplexing (OFDM) signals with superimposed pilot symbols and a vertical linear array of hydrophones. We investigate and compare performance of several space-time processing techniques and show that the space-time cluster combining demonstrates the best performance. The comparison has been done using signals recorded on a 14-element vertical antenna array in sea trials at a distance of 105 km transmitted by a fast moving transducer. In these conditions, with the receiver, exploiting the cluster combining, error free transmission is achieved at a data rate of 0.33 bits/s/Hz. We also show that the cluster combining approach allows reduction in the complexity of the receiver.
Published Version
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