On the Probability Density of Intersymbol Interference

The paper presents a simple and rapid algorithm for numerically evaluating the probability density function (pdf) of intersymbol interference (ISI) in digital transmission systems. The results coincide with the analytical solutions available for very few cases only. The biterror rate calculated from the pdf's of ISI and of Gaussian noise agree with upper and lower bounds as published by many authors. Examples of the pdf of ISI in some cases of practical interest are given for various QAM-modulation schemes.