Propagation Over Parabolic Terrain: Asymptotics and Comparison to Data

Analysis of radio propagation over varying, clutter-covered terrain was carried out aiming at prediction of power received by a terminal immersed in clutter, with the transmitter placed above clutter. The need for such prediction arises, for example, in planning and assessing coverage and interference in radio communications. Following a general formulation of the problem, particular solutions were found when the terrain has constant curvature. Asymptotic evaluation yielded compact expressions both for parabolic valleys and ridges. In both cases, ray-optical term dominated for short ranges, while a single mode dominated at large ranges. Strong focusing was found to occur in valleys, while ridges produced strong blockage beyond the ??horizon??. The resulting procedure for predicting pathloss over varying terrain is therefore to apply the formulae using the terrain curvature extracted from terrain files. In comparison to measured power across a valley, mean errors of less than 1 dB were found, a marked improvement over standard terrain-unaware models that produce a mean error of 30 dB.