Approximate Solutions to the Distribution of the Fading Intervals of Lognormal Processes

In this paper, we derive two approximate solutions for the probability density function (PDF) of lognormal shadow fading intervals at deep fading levels. The first approximate solution is based on the Rice probability function, while the second one is deduced from the asymptotic behavior analysis of lognormal processes. Based on the latter approximate solution, expressions for the average as well as the variance of fading intervals are also provided. The validity of the analytical solutions is verified by computer simulations obtained for different propagation environments.