Decision Hysteresis Reduces Digital Pe

It is shown that the source statistics influence the form of the decision threshold in an optimum receiver. For a first-order Markov source, a simple suboptimum realization is a hysteresis loop. The performance improvement over the single threshold decision rule is modest but in some cases it is possible to cut the Pein half. One case where decision hysteresis performs best is in a modem that uses split phase or data scrambling to ensure that the transmitted signal tends to alternate. As a practical matter, it turns out that hysteresis can do more damage than good if the signal-to-noise ratio is variable.