Ray tracing based prediction of impulse responses in urban microcells

An important situation in microcells is when a mobile user turns around a corner from line-of-sight (LOS) to non-LOS. In this case, the radio channel needs to be characterized as it may change abruptly. This characterization is useful, both for the analysis of system performance, and to gain insights into the propagation phenomena involved. Software based on image theory and ray tracing is used to analyze two simple cases of street intersection. The results include predictions of the radio channel impulse response and comparisons with measurements undertaken in a city (Fribourg, Switzerland). It is shown that specular reflections can explain some measured results. However, reflection and diffraction cannot explain adequately all situations, especially if only building walls are considered. Thus, scattering effects need to be further investigated