A NEW APPROACH TO 3-D RAY-TRACING FOR PROPAGATION PREDICTION IN CITIES

A vertical-plane-launch (VPL) technique for approximating a full three dimensional (3-D) site-specific ray trace to predict propagation effe cts in cities for frequencies in the 300-MHz-3-GHz band is described a nd its predictions are compared with measurements for Rosslyn, VA. The VPL technique employs the standard shoot and bounce method in the hor izontal plane while using a deterministic approach to find the vertica l displacement of the unfolded ray paths, This approximation is valid since buildings walls are almost always vertical, The VPL method shows significant improvement compared with the slant-plane/vertical-plane (SP/VP) method for rooftop antennas. For a base station located at str eet level, the VPL method gives better predictions than the two-dimens ional (2-D) method in locations where propagation over buildings is si gnificant.