Compensation of multipath fading in underwater spread-spectrum communication systems

Techniques for achieving reliable communications over underwater acoustic channels are investigated in this work. We consider implementation of an underwater spread-spectrum communication system. To compensate the multipath fading and Doppler effects in the underwater acoustic channel, a transform-domain approximate RLS (TARLS) blind equalizer is incorporated in the receiver. The computational complexity of the TARLS blind equalizer is in the same order as that of conventional LMS blind equalizers. Nevertheless, the TARLS blind equalizer significantly outperforms conventional LMS blind equalizers in the convergence and tracking ability. The TARLS blind equalizer is also shown to have good numerical stability in a finite-precision environment and thus is ready for digital implementation. The goodness of the proposed equalizer is demonstrated by applying it to a simulated multipath fading channel often encountered in underwater acoustic communications.