We measure the capacity of multiple-input multiple-output radio systems in microcellular environments. We use a new data evaluation method that allows to evaluate the cumulative distribution function of the capacity from a single measurement. This method is based on an extraction of the parameters of the multipath components and, thereafter, a synthetic variation of their phases. In the analyzed environments, we find capacities to be about 30% smaller than would be anticipated from an idealized model. In addition, the frequency selectivity of the channel makes the cdf of the capacity steeper and, thus, increases the outage capacity, compared with the frequency-flat case, but the influence on the mean capacity is small.Index Terms-Multipath channels, multiple-input multiple-output, radio propagation. 0733-8716/02$17.00 © 2002 IEEE Martin Steinbauer(S'99-A'01) was born in Vienna, Austria, in 1973. In 1996, he received the Dipl.-Ing. degree from Technische Universität Wien, Vienna, Australia, with distinction.After studies on GSM1800 behavior at high vehicular speeds, he joined the Institut für Nachrichtentechnik und Hochfrequenztechnik at TU-Wien, Vienna, Austria, as a Research Engineer. During his three year participation in the EU-project META-MORP, he specialized in radio channel measurement and characterization. As Chairman of a subgroup on directional channel modeling within the European research initiative COST259, he promoted harmonization among different channel modeling approaches toward a common setting for directional channel simulations. His main interests are now on the propagation side of MIMO systems including appropriate measurement techniques, data evaluation and signal processing.Mr. Steinbauer is a member of the Austrian Electrical Engineering Society.

We present a statistical analysis of wideband three-dimensional channel measurements at base station locations in an urban environment. Plots of the received energy over azimuth, elevation, and delay planes suggest that the incident waves group to clusters in most measured transmitter positions. A super-resolution algorithm (Unitary ESPRIT) allows to resolve individual multipath components in such clusters and hence enables a detailed statistical analysis of the propagation properties. The origins of clusters-sometimes even individual multipath components-such as street apertures, large buildings, roof edges, or building corners can be localized on the city map. Street guided propagation dominates most of the scenarios (78%-97% of the total received power), while quasi-line-of-sight over-the-rooftop components are weak (3%-13% of the total received power). For this measurement campaign, in 90% of the cases, 75% of the total received power is concentrated in the two strongest clusters, but only 55% in the strongest one. Our analysis yields an exponential decay of power with 8.9 dB/ s, and a standard deviation of the log-normally distributed deviations from the exponential of 9.0 dB. The power of cross-polarized components is 8 dB below copolarized ones on average (vertical transmission). Index Terms-Multipath channels, radio propagation, mobile radio channel, spatial channel modeling, smart antennas, clusters. I. INTRODUCTION A DAPTIVE antennas (AA) will be a major factor for the successful introduction of third-generation wireless systems like Universal Mobile Telecommunication System