A microcellular ray-tracing propagation model and evaluation of its narrow-band and wide-band predictions

Due to the site specific nature of microcellular operational environments, propagation models are required to take into account the exact position, or ientation and electrical properties of individual buildings, and hence, ray tracing techniques have emerged as the dominant methods to predict propaga tion in such environments. A novel hybrid three-dimensional (3-D) ray traci ng algorithm which can evaluate scenarios incorporating many thousands of o bjects by utilising the concept of "illumination zones," is presented in th is paper. In order to evaluate the accuracy of the presented model, comparisons of na rrow-band and wide-band predictions with measurements are performed for a v ariety of scenarios. First, power comparisons show that very accurate predi ctions can be achieved (rms errors less than 3.7 db), Then, wide-band analy sis shows that since the rms delay spread for systems with finite bandwidth is a function of the multipath phase, only average measured and predicted rms delay spread values can be compared and as a result, limited averaging can produce large rms errors. With sufficient averaging the achieved wide-b and accuracy in terms of the predicted rms delay spread, is adequate for mo st planning purposes.