Spatial characterization of urban mobile radio channels

We present statistical evaluations of wideband spatial dual-polarized radio channel measurements. Some 80 different street-level transmitter positions in downtown Helsinki, Finland, were measured. We chose three different receiver array sites below, at, and above the rooftop level of the surrounding urban environment. A super-resolution algorithm allows the determination of the directions of arrival of incident radio waves at a 16/spl times/62 elements base station antenna array. The main conclusion of our investigations is that the incident waves tend to cluster in azimuth, elevation and/or delay, which we justify by detailed statistical evaluations. Clustering is mainly defined by the surroundings of the base station. The cumulative distribution function of the powers of these clusters shows that in 90% of all cases, 75% of the total received power is concentrated in the two strongest clusters. Street guided propagation dominates at all three receiver sites, even if the base station is above the rooftop level.