An enhanced millimeter-wave foliage propagation model

In this paper, the behavior of wave propagation through coniferous forest stands at millimeter-wave frequencies is characterized both theoretically and experimentally. A coherent wave propagation model is used to simulate the propagation through foliage. The coherent model is composed of two components: a forest stand generator that makes use of a stochastic fractal model, and an electromagnetic model that makes use of Foldy's approximation and single scattering. An outdoor measurement system is designed and used for characterizing the channel behavior for a pine tree stand at Ka-band (35 GHz). In this experiment, 84 independent spatial samples of transmitted signal through the pine stand were collected to obtain the path-loss statistics. The comparison between measurement and simulation results showed that single scattering theory overestimates the wave attenuation through foliage. To improve the accuracy of the coherent model, partial multiple scattering occurred among the needles of highly dense leaf clusters must be included for the estimation of the coherent attenuation. Distorted Born approximation is used to macromodel the scattering pattern from needle clusters. This technique has comparable accuracy and requires much less computational resources than a full-wave solution, such as method of moment. By including multiple scattering effects of needle clusters in the simulation model, much better agreement is obtained for both mean and standard deviation of the path-loss.