ADAPTIVE EQUALIZATION OF DIGITAL LINE-OF-SIGHT RADIO SYSTEMS

This paper gives a state-of-the-art review of adaptive channel equalization in digital line-of-sight radio systems employing bandwidth-efficient modulation techniques. A particular emphasis is placed on decision-feedback equalizer (DFE) implementation and performance in the presence of nonminimum-phase fading. Stability problems of fractionally-spaced equalizers (FSE's) are discussed, and a newly developed adaptation technique is outlined. We also discuss the blind adaptation algorithms that are used to reduce outage by preventing the equalizer coefficients to diverge during severe fade events and carrier synchronism loss. Finally, we discuss further issues related to asymmetric equalizers and to the interaction of the equalizer adaptation algorithm with the carrier recovery loop.