Performance of Fractioned and Nonfractioned Equalizers with High-Level QAM

This paper presents a comparative study of 16-QAM, 32QAM, 64-QAM, and 128-QAM 140 Mbit/s digital radio in the presence of multipath fading. Conventional
T
-spaced and fractional tapspaced equalizers have been considered to compensate for the ISI-induced symbols. The performance measure used is the bit error ratio (BER); thus, upper and lower bounds on BER have been developed. Based on this calculation procedure, results showing the net fade margin versus the gross fade margin have been obtained in a variety of cases that include the presence of both nonlinear and linear equalizer structures.