On the Diffusion of Electromagnetic Waves and Applicability of Diffusion Equation to Multipath Random Media

Abstract

The diffusion behavior of electromagnetic (EM) waves in two dimensional (2-D) multipath media is studied through integral equation based full wave Monte Carlo simulations. The influences of some physical factors are explored, among which the area density of the embedded obstacles manifests itself to be the most important one in determining wave diffusion. A lossy system starts to behave diffusively when the area density approximately exceeds 5%, and the diffusion equations are generally applicable for predicting power decay. At low densities, the power-distance relation of the waves appears to follow power laws. The sizes and shapes of the obstacles have a secondary effect on the diffusion of waves. Whenever a system contains small objects or objects with reflecting sides, the waves therein are more diffusive and the diffusion equation approximates the reality more accurately. Absorption loss decreases wave diffusion in general, but our results show that the diffusion equation for a system with very lossy but small obstacles can work very well for predicting power decay.

Hybrid Computational Techniques: Electromagnetic Propagation Analysis in Complex Indoor Environments

“…It can be seen that the mean error and standard deviation for the fully GO/UTD/DE approach and the novel technique GO/DE increase significantly in this third scenario. Thus, it is shown that DE approach does not work in this scenario, with planes with obstacles densities smaller than 10%, as it is shown in [43]. It can be concluded that it is highly important to achieve a tradeoff between precision of the results and simulation computational time, when these hybrid approaches are employed.…”

“…Following the approach described in [11,25,43], it has been developed a new module to be implemented in the 3D RL tool. This new module is based on DE and considers absorption and scattering losses caused by obstacles.…”

“…The GO/DE approach has been presented in [25]. The new technique is based on the statement that if the obstacles area density is higher than 10%, then diffusion approaches can be applied to indoor scenarios [43]. The principle is that the whole 3D environment is divided in terms of horizontal and vertical 2D planes.…”

“…Because of that, it has been treated also with DE to show that in this case the mean error is larger when DE is applied to those planes with a density smaller than 10%. Thus, only those planes with a larger obstacle density than 10% must be treated with the DE approach [43]. Firstly, simulations have been done in the office environment scenario, where the impact of furniture has been assessed.…”