Spectral properties of signal fading and Doppler spectra distribution in urban mobile communication links

Abstract

In this work, we continue the analysis of a probabilistic approach and the corresponding stochastic multiparametric model of wave propagation, in built-up areas with randomly distributed buildings. We have concentrated on the spectral properties of signal strength spatial variations and on Doppler spread spectrum distribution of signal power. The analysis is based on a unified stochastic approach of radio wave propagation above the built-up terrain with applications to mobile communications. We analyze the signal power spectrum of spatial frequencies and the signal power distribution in the Doppler domain for moving vehicles, taking into account a Doppler shift proportional to the vehicle antenna speed relative to the base station. The comparison between the theoretical prediction and experimental data was motivated by the proposed stochastic model and other existing statistical models to verify the signal power distribution in the Doppler domain for various urban environments and terminal heights with respect to building rooftops. New effects of terrain features on signal spectrum are obtained, examined and compared with existing models.

Spectral properties of signal fading and doppler spectra distribution in urban mobile communication links

“…Here Γ is the absolute value of the reflection coefficient from the wall. As in [1,2], the average value of the reflection coefficients is zero, i.e., Fig. 2).…”

“…2, where 1s r is the location of the transmitting antenna 5150 0-7803-8521-7/04/$20.00 © 2004 IEEE at the height z 1 , 2 s r is the location of receiving antenna at the height z 2 . We consider, according to [1,2], that each building as a non-transparent phase-amplitude screen. The reflection properties of the screen described by the complex reflection coefficient, Γ( , ) ϕ s s r , by the phase that is uniformly distributed over the range [0,2 ] π and the correlation function which is presented in general form as…”

“…In [1,2], an array of randomly distributed buildings and other natural and man-made obstacles placed on the rough ground surface was considered as urban built-up area, where the plane 0 = z is the ground surface, and the polynomial function ) , ( y x Z with exponent n describes the non-regular rough ground surface relief ) , ( y x Z z = (see Fig. 1).…”

“…2). In [1,2], the law of distribution of the obstacles was assumed to be Poisson, that is, we have assumed that the number of rays N which arrive at the receiver during time t after scattering by randomly distributed buildings can be described by the Poisson distribution law of such scatterers. Such mathematical description of an array of buildings randomly distributed on the rough terrain allows, according to [1,2], to determine a probability of direct visibility between antennas that depends on the following parameter 0 γ , the onedimension buildings' density (in km -1 ),…”

“…Below we consider the spectral characteristics of the received (or transmitted) signals in order to describe the Doppler spectrum for moving terminals in various built-up areas and for different antenna elevations with respect to building profile height. We propose, as in [1,2], the stochastic multiparametric model of the channel, according to which the builtup environment can be modeled by the array of randomly distributed buildings or natural obstacles placed on rough terrain according to Poisson law of their distribution. Using the proposed model of wave propagation in such an urban channel, the field intensity attenuation, angle-of-arrival, time delay distribution and other signal characteristics [1,2] can be examined and the single and multiple scattering effects can be estimated, depending on the different positions of the receiver and the transmitter with respect to buildings surrounding them.…”