The aim of this chapter is to summarize and present recent findings in the field of wireless channel mod-
eling that provide a new method for the reliable calculation of the statistical parameters of large-scale
variations of the average received signal (shadow fading). This algorithm is theoretically based on a
path loss estimation model that incorporates losses due to walls and floors. This has been confirmed
to be the most precise mathematical tool for average signal strength prediction for various frequencies
of interest and propagation environments. The total path loss is estimated as a sum of two independent
attenuation processes: free space loss and losses due to obstacles. This solution allows for a direct and
reliable calculation of the deviation of the fluctuations of the average received signal in an obstacle-
dense environment