Introduction
This paper proposes an extension of a ray-tracing based model for radiowave propagation in the presence of vegetation, to account for the wind-induced channel dynamics in vegetated environments. The original propagation model uses various point scatterers with specific re-radiation and it has been proven to be suitable for a wide range of scenarios. However, the swaying motion of the tree branches and leaves, as an effect of the wind, creates a constantly changing environment that influences the propagating radio signals in both amplitude and phase, resulting in signal level fluctuations.
Methods
A large measurement campaign intending to record and characterize the effect of wind-induced dynamics in vegetated environments, was conducted in a controlled environment, inside an anechoic chamber. Experiments included various wind directions and at varying speeds: stationary (0 m/s), low (1.9 m/s) and high (4.7 m/s). The dynamic re-radiation pattern of trees present in the radio path were recorded at 20 and 62.4 GHz signal frequencies. The available experimental data was then used to develop a statistical model which is sought to characterize wind-induced dynamics of the point scatterers’ re-radiation function. Finally, the performance of the proposed dynamic model while predicting the received signal level fluctuations inside a tree formation scenario, was assessed against dynamic directional spectra measurements conducted in a controlled environment, for four different artificially generated wind incidences and two wind speeds, low (1.9 m/s) and high (4.7 m/s).
Results and Discussion
This experiment proved that the proposed elementary model could be an asset on the characterization of the time-varying effects found in vegetation areas under wind influence.