A propagation model for urban microcellular systems at the UHF band

This paper presents a new propagation model for urban environments, which t akes into account propagation over buildings and inside streets. The formul ation for multiple diffraction loss over rooftops results from a combinatio n of Vogler's and Xia and Bertoni's models, which enables its application t o profiles of buildings with nonuniform heights and spacings, keeping the c alculation time low, A ray-tracing tool based on the image method and on th e Uniform Theory of Diffraction (UTD) has been developed to estimate the at tenuation inside streets; loss introduced by vegetation is also accounted f or. The results obtained with the application of the model to two areas of Lisb on show the importance of rays conducted by transversal streets and diffrac ted by vertical edges when predicting the signal near crossroads. Average v alues of 3.5 dB, -0.07 dB, and 2.6 dB were obtained for the mean absolute a nd relative errors and for the standard deviation error, respectively.