A Discrete RET Model for Millimeter-Wave Propagation in Isolated Tree Formations

In this paper, a method based on the Radiative Energy Transfer theory (RET) to estimate the scattered radio signals from isolated groups of trees is presented. The proposed method consists of measuring the re-radiation function of each tree in the group, parameterising the function and subsequently using these in a discrete algorithm to estimate the overall attenuation at any location within the forest scenario. The discrete algorithm (dRET) presented here has some major improvements over previously published ones, offering substantially enhanced applicability. These improvements allow the use of larger vegetation cells, the enhancement of angular resolution of predicted results and the consideration of the receiving antenna radiation pattern. The estimated received signals using the re-radiation function, on the one hand, and its parameterised counterpart, on the other hand, are compared with measurements performed inside an anechoic chamber on Ficus Benjamina indoor plants at 20 and 62.4 GHz. The overall model performance was assessed in terms of RMS error between measured and predicted results.