Polarisation Behaviour of Discrete Multipath and Diffuse Scattering in Urban Environments at 4.5GHz

In this paper, the polarisation behaviour of the mobile MIMO radio channel is analysed from polarimetric double directional channel measurements, which were performed in a macro-cell rural environment in Tokyo. The recorded data comprise non line of sight, obstructed line of sight and line of sight conditions. The gradient based Maximum-Likelihood estimation framework RIMAX was used to estimate both specular and dense multipath components. Joint angular-delay results are gained only for the specular components. The dense multipath components, which may be attributed to diffuse scattering, can be characterized only in delay domain. Different characteristics describing the polarisation behaviour and power-weighted crossand co-polarisation ratios for both types of components are introduced. Statistical analysis of long measurement track segments indicate global trends whereas local analysis emphasizes specific behaviour such as polarisation dependency on angle of incidence in streets and under shadowing conditions. The results also underline the importance of modelling changing and transient propagation scenarios which is currently not common in available MIMO channel models.