UTD PROPAGATION MODEL IN AN URBAN STREET SCENE FOR MICROCELLULAR COMMUNICATIONS

This paper presents a new three-dimensional propagation model for micr ocellular communications in an urban street scene. The model is based on the Uniform Theory of Diffraction and takes into account multiple r eflections between wall-to-wall, wad-to-ground, and ground-to-wall as well as the diffraction from corners of buildings, and also subsequent reflections from such diffracted signals. The ray geometry is made ex tremely complex by the presence of ground reflections, and the many co mbinations of sequences of reflections or diffractions from walls, edg es, and ground. The major difficulty in this three-dimensional formula tion lies in determining the exact point of reflection at a surface, o r exact point of diffraction at an edge, and the corresponding plane o f incidence. This is necessary to enable us to calculate the polarizat ion components of the reflected or diffracted rays and their subsequen t trajectories. At each reflection or diffraction point, use is made o f the local ray-fixed coordinate system or edge-fixed coordinate syste m together with appropriate dyadic reflection or diffraction coefficie nt matrices. Our theoretical results of the signal path loss along the streets are compared with measurements done in New York and Tokyo for various values of the propagation parameters. The good agreement with these measurements indicates that our UTD formulation is a good model for such urban communication applications.