Millimeter wave propagation through foliage: Comparison of models

Foliage attenuation is one of the key impairments in millimeter wave propagation. Existing literature shows that the foliage attenuation is a function of a multitude of parameters, including frequency, foliage depth, tree types, foliage thickness, leaf density, leaf size, branches, trunks, humidity, wind speed, height of the tree relative to the antenna heights, path length through foliage, etc. This paper surveys the current development in the foliage attenuation study in millimeter wave bands and reviews the established propagation models. Numerical simulations are presented to assess and compare the existing empirical models. The results show that the Weissberger model provides the most optimistic estimate (the lowest attenuation) while the FITU-R model delivers the most pessimistic estimate (the highest attenuation). The results also reveal that the ITU-R model has the highest rate of increase in foliage attenuation as a function of foliage depth.