The Design of Radio Maps in Tokyo City Based on Stochastic Multi-Parametric and Deterministic Ray-Tracing Approaches [Wireless Corner]

This study is related to the investigation of two popular planning tools based on different approaches. The first is a stochastic model as a combination of a statistical description of features of rough built-up terrain (with arrays of buildings inside it), and the stochastic description of radio propagation above such a terrain, accounting for multiple reflection, scattering, and diffraction. The second is a deterministic ray-tracing model using direct computations of numerous rays arriving at the receiver from each point of the obstructions placed in the terrain. Both models are used to explain the propagation phenomena occurring inside urban communication links, and to design radio maps of areas of service in the space domain, for various elevations of the base-station antenna with respect to the buildings' overlay profiles. A comparison of two such theoretical predictors is done for an experimental site in Tokyo. It is shown that both proposed predictors are in good agreement with each other. At the same time, simple engineering formulas obtained from the stochastic model, taking into account shadowing effects caused by diffraction from buildings having non-regular overlay profiles with respect to the base-station antenna's elevation, have a vivid physical and mathematical form, usually converted into the “straight line” equations obtained from the proposed stochastic model. The general trend is predicted by this stochastic model, and the deterministic ray tracing provides us with fine structures superimposed on such a trend.