Statistical characterization of urban spatial radio channels

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 one 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/μs, 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)     

A Rule‐Based Algorithm for Common Pilot Channel and Antenna Tilt Optimization in UMTS FDD Networks

In this paper we address the problem of capacity optimization in a Universal Mobile Telecommunication System (UMTS) radio network. We present an optimization algorithm for finding the best settings of the antenna tilt and common pilot channel power of the base stations. This algorithm is a parametric method, based on a set of rules. We evaluated our optimization technique on a virtual network scenario with 75 cells. For this scenario we show an increase in capacity compared to the initial settings of about 60 percent.     

3-D double-directional radio channel characterization for urban macrocellular applications

We measured the spatial properties of the three-dimensional (3D) double-directional radio channel in urban macrocell environments separately at both ends of the link. In this paper, we study propagation conditions pertaining to reception and transmission at the mobile terminal, measured using a wideband channel sounder and a dual-polarized spherical antenna array. We were able to refine the results of the measurements conducted at the base station, and extend the study to full double-directional 3D channels. Individual propagation paths could be identified precisely, in some cases even considerable scattering from lampposts was observed. Our results show that over-rooftop-dominated propagation often occurs via building roofs with LOS to the base station antenna, acting as strong secondary signal sources. Based on measurements along continuous routes we demonstrate that the dominant propagation mechanisms can vary considerably when the mobile moves in the environment. We also present typical directional properties of the 3D radio channel at the mobile terminal in urban macrocell environments characterized by street canyons, showing how the angular distribution of energy is correlated with the excess delay.     

UMTS radio network planning — maximizing return on investment

This article describes, based on the fundamentals of GSM radio network planning, the process of planning and optimizing UMTS networks. It highlights the key differences to existing 2G technologies and explains why UMTS radio network optimization is so complex that it cannot be done manually any more. This article gives some examples of cost efficient UMTS radio network enhancements in order to maximize future network capacities. It explains how UMTS return on investment is influenced by using advanced methods for radio network planning and optimization.     

Azimuth, elevation, and time-delay distributions in wireless communication channels

We investigate the wave-propagation characteristics in urban environments as functions of the angle-of-arrival distribution, both in the azimuth and elevation planes. We also take into consideration the time delays for various base-station antenna elevations. We combine a statistical multi-parametric model, describing randomly distributed buildings, and a waveguide model, describing a grid of crossing streets with buildings lining the sides to create a new stochastic model. The joint probability of signal distributions in the azimuth-elevation, azimuth-time delay, and elevation-time delay planes are obtained and compared with high-resolution three-dimensional experiments carried out in urban areas in Helsinki, Finland. A good agreement between experimental and theoretical results is obtained.     

Wideband 3D characterization of mobile radio channels in urbanenvironment

This paper describes three-dimensional (3D) radio channel measurements at the base station site in an urban environment. We introduce a measurement concept which combines an RF switched receiver array and a synthetic aperture technique and allows full 3D characterization of the channel. Additionally, dual-polarized patch antennas as array elements enable full determination of the polarization properties of the impinging signals. We describe measurements at over 70 different transmitter positions and three receiver array sites with different sectors and antenna heights. Our results show that the received energy is concentrated within identifiable clusters in the azimuth-elevation-delay domain. We demonstrate that the observed propagation mechanisms are mainly determined by the environment close to the base station. Street canyon propagation dominates also when the receiver array is at or even above rooftop level with the studied measurement distances. Thus, the azimuth spectrum at the BS site is fairly independent of the location of the mobile. Signal components propagating over the rooftop are often related to reflections from high-rise buildings in the surroundings     

Capacity of MIMO systems based on measured wireless channels

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