Incorporating the Fresnel Zone Theory in Ray Tracing for Propagation Modelling of Fixed Wireless Access Channels

A propagation model which combines the Fresnel zone theory and the ray tracing techniques is presented in this paper. The aim of this novel approach is a more accurate representation of the fixed wireless access channel. Deterministic models do not consider power loss when the radio waves propagate close to roof tops. However, according to the theory of the Fresnel zones, even when there is line-of-sight (LOS), the loss can be as much as 6 dB due to a single obstacle just below the LOS. In the model presented here, the path of each ray is found by a three-dimensional (3D) ray tracing algorithm and the electromagnetic field of each ray is calculated according to geometric optics (GO) and the uniform theory of diffraction (UTD). The first Fresnel zone of each ray is also found and examined and the losses due to its partial blockage are taken into account. Simulation results show significant differences in the power predictions when the blockage of the Fresnel zones is considered.