Modal Expansion Approach for Electromagnetic Propagation in Street Canyons

We present a simple and efficient model to compute electromagnetic (EM) propagation in urban street canyons, when transmitting and receiving antennas are located below the rooftop level. A parallel-plate dielectric hollow waveguide model of the street canyon is proposed, and propagation is analyzed by using the modal expansion approach. Obtained results for the case of line-of-sight (LoS) propagation are substantially equivalent to those obtained with the ray-optics method, but, with respect to the latter, our method presents important advantages: it is more efficient from a computational viewpoint, it allows deriving a very simple and reasonably accurate formulation of the average received signal strength, and it provides a fairly simple way to compute coupling at cross-junctions, exploited to obtain an analogous formulation for the non-LoS case. Obtained results are compared with simulations of a ray-tracing-based EM solver and with experimental measurements available in the literature.