Wave Propagation Characterization in Complex Urban Areas using EM Terrano

摘要

The trend in propagation prediction in recent years has been toward the development of physics-based propagation models [1], [2], which represent various features in the physical environment and tend to be more accurate than heuristic or simplified analytic models. These models are site-specific, and the intent is to allow for the simulation of any environment for which the physical scenario is know. Recently, the trend in physics-based propagation prediction for urban areas has been toward the so called quasi-3D methods, such as the vertical plane launch method (VPL) [3]. Their application is based on the premise that the computational time required for full 3-D ray-tracing (covering 4π steradians) in a highly scattering environment is prohibitive. Based on this premise, methods such as VPL, confine the ray coverage area to the 2-D, horizontal plane, and extend the rays to the 3-D plane, by calculating the difference between transmitter and receiver heights. Ground reflection is accounted for by applying image theory. These methods however, apply only 2-D reflection and diffraction coefficients, which, at each ray intersection point, can accumulate significant error in the received ray strength. It is expected that this error will be especially significant for situations in which the transmitter and receiver are at a substantial height difference. In addition, for indoor scenarios, a full 3D ray tracer is essential to account for both floor and ceilings. Because of these limitations in the quasi-3D approaches, an investigation has begun into methods for improving the computational efficiency of full 3D ray tracing, so as to make it of practical use in propagation prediction. With this in mind, a full 3D ray tracing algorithm [4] has been incorporated into the propagation simulation tool. EM Terrano, developed at EMAG Technologies, Ann Arbor, Michigan. By the application of "intelligent ray tracing," preliminary results are shown in this paper, which testify as to the practicality of using a full 3D ray tracing engine in a propagation simulation tool such as EM Terrano.