Investigation of non-specular scattering by comparing directional channel characteristics from microcell measurement and simulation

Channel characteristics from microcell measurement and simulation are compared. In microcell environment, the dominant propagation mechanisms are not only from reflections and diffractions from buildings but can also come from non-specular scatterings. Propagation prediction tools such as ray-tracing algorithms which calculate only reflections and diffractions are hence not enough to completely predict the channel. To address this issue, an implementation called polygon meshed physical optics (polygon meshed PO) is used. Polygon meshed PO approximates the traditional PO by dividing the scatterer surface into triangular meshes to reduce the surface integral (for calculating the scattering field) into summation of mesh areas. This makes it flexible even for irregularly shaped objects. As PO utilises the whole illuminated scatterer surface to calculate the scattering field, it is not limited to specular directions and can be used to compute the contribution of non-specular scattering. To know the actual propagation channel, wideband measurement was performed inside a university campus. With antenna arrays on both the transmit and receive sides, wideband double-directional channel characteristics such as azimuth-delay power spectrum can be obtained after applying the conventional beamforming. Comparison of measurement and simulation results reveals that small metallic objects cause non-specular scattering and affect the propagation channel. These objects can be predicted by the proposed polygon meshed PO in cooperation with ray tracing.