A modified model for the fading signal at a mobile radio channel (original) (raw)
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A theoretical model of UHF propagation in urban environments
IEEE Transactions on Antennas and Propagation, 2000
Urban communications systems in the UHF band, such as cellular mobile radio, depend on propagation between an elevated antenna and antennas located at street level. While extensive measurements of path loss have been reported, no theoretical model has been developed that explains the effect of buildings on the propagation. The development of such a model is given in which the rows or blocks of buildings are viewed as diffracting cylinders lying on the earth. Representing the buildings as absorbing screens, the propagation process reduces to multiple forward diffraction past a series of screens. Numerical computation of the diffraction effect yields a power law dependence for the field that is within the measured range. Accounting for diffraction down to street level from the rooftops gives an overall path loss whose absolute value is in good agreement with average measured path loss.
A three-dimensional scattering model for fading channels in land mobile environment
IEEE Transactions on Vehicular Technology, 1999
Clarke's scattering model, one of the most widely accepted channel models for the land mobile environment, is a two-dimensional (2-D) model because of the assumption of horizontal traveling plane waves. By introducing a nonzero elevation angle of the arriving wave, a three-dimensional (3-D) model is more general and accurate, especially for the urban environment. Though the concept of the 3-D model has been proposed already, there is still a lack of satisfying results regarding the distribution of the elevation angle, from both theoretical analysis and field measurement, and the power spectral density (PSD) of the received signal. In this paper, a family of functions with two parameters, fm; ng, where m and n are positive integers, for both the symmetrical and asymmetrical probability density function (PDF) of the elevation angle (EA), is proposed. Among these functions, those with odd m and n lead to analytical solutions of the PSD of the received signal in addition to satisfying other requirements for a PDF of the EA previously proposed in literature. The PSD's in closed form associated with m and n equal to one and three are derived in particular, and the autocorrelation functions are obtained numerically. Since a family of functions rather than a single function is proposed for the PDF of the EA, it provides certain flexibility in application and covers a wide range of environments. Another contribution of this paper is a new expression which directly relates the PDF of the EA in the 3-D model to the PSD of the received signal.
IEEE Transactions on Vehicular Technology, 2002
__ One of the main assumptions in the Clarke's classic channel model is isotropic scattering, i.e. uniform distribution for the angle of arrival of multipath components at the mobile station. However, in many mobile radio channels we encounter non-isotropic scattering, which strongly affects the correlation function and power spectrum of the complex envelope at the mobile receiver. In this contribution, we propose the use of the versatile von Mises angular distribution, which includes and/or closely approximates important distributions like uniform, impulse, cardioid, Gaussian, and wrapped Gaussian, for modeling the non-uniform angle of arrivals at the mobile. Based on this distribution, associated correlation function and power spectrum of the complex envelope at the mobile receiver are derived. The utility of the new results is demonstrated by comparison with the correlation function estimates of measured data.
Characterization of temporal fading in urban fixed wireless links
IEEE Communications Letters, 2006
We study the temporal fluctuations of a fixed wireless link in an urban environment by characterizing the Ricean K-factor as a function of the positioning of the customer premises antenna. Our main observation is that temporal fluctuation of received power is due mainly to vehicular traffic close to the remote antenna. Furthermore, a strong correlation between average envelope power and K-factor is observed when placing the remote antenna at similar distances to traffic. Therefore, optimizing antenna placement based on received power reduces fade depth at the same time.
A Propagation Model of Cellular Mobile Radio Communication in Urban Areas
A numerical modeling of the propagation path loss using Uniform Theory of Diffraction (UTD) has been presented here. Computed results at 835 MHZ have been presented for various parameters of interest. The results at 2.154GHz have been obtained and compared with that of Walfish and Bertoni [1]. These are found to be in excellent agreement thereby establishing the validity of the code. Method is simple, efficient and reliable. Both shadow zone and line of sight zone have been considered.
Modelling the mobile-radio channel
1990
permit direct confirmation of an essential aspect of the model, viz. that the reflections encountered by the transmitted signal may be treated as ideal (i.e., non-distorting) reflections, an extension of the Wiener filter theory was carried out that permits estimation of the received signal at an artificially increased sampling rate. The measurement data, processed by this interpolating Wiener filter, is used to validate the ideal reflection hypothesis of the model.
A Statistical Model for Urban Radio Propagation
A statistical model, based on extensive experimental data, statistical model behind. Then, a modified Poisson process was was established to characterize the urban radio propagation medium in presented to model the path arrival time since the simple various urban environments. Describing the medium by a linear filter, the peaks of the multipath response were analyzed statistically concem-Poisson model in [ 5 ] failed to fit some experimental data. ing the distribution of the path the path time. The Though the Simflar models appear in [l 1 -I1 3i , there statistical properties of these quantities depend on the modulation to be no previous work on the statistical model of the Path delay time. The resulting model can be used for simulation,experi-arrival time except [ 51 .
Physics-Based Modeling of Experimental Data Encountered in Cellular Wireless Communication
IEEE Transactions on Antennas and Propagation, 2018
This paper presents a physics based macro model that can predict with a high degree of accuracy the various experimental data available for the propagation path loss of radio waves in a cellular wireless environment. A theoretical macro model based on the classical Sommerfeld formulation can duplicate the various experimental data including that of Y. Okumura and his coworkers carried out in 1968. It is important to point out that there are also many statistical models but they do not conform to the results of the available experimental data. Specifically, there are separate path loss propagation models available in the literature for waves travelling in urban, suburban, rural environments and the like. However no such distinction is made in the results obtained from the theoretical analysis and measured experimental data. And based on the analysis using the macro model developed after Sommerfeld's classic century old analytical formulation, one can also explain the origin of slow fading which is due to the interference between the direct wave from the base station antenna and the ground wave emanating from the reflections of the direct wave and occurs only in the near field of the transmitting antenna. The so called height gain occurs in the far field of a base station antenna deployment which falls generally outside the cell of interest while in the near field, within the cell, there is a height loss of the field strength for observation points near the ground. A physical realization of the propagation mechanism is illustrated through Vander Pol's exact transformation of the Sommerfeld integrals for the potential to a spatial semi-infinite volume integral and thus illustrates why buildings, trees and the like have little effects on the propagation mechanism.
A Vectorial Analysis of UHF Propagation in Urban and Rural Environments
2005
In this work we present a vectorial analysis of the two-ray model, as well as a vectorial analysis of the whole street waveguide model in the UHF band. For both, an ideal dipole is assumed to be the transmitting aerial. For the analysis of the two-ray model, parallel polarization is investigated and a comparison between the approximated analysis (only algebraic sum of the fields) and non-approximated analysis (considering dipole's gain and vectorial analysis) is provided as well as an analysis of the error versus r distance. A comparison between vertical and horizontal components of the electric field is also carried out. Regarding the street model, the street is modeled as a multislit waveguide, and horizontal and vertical polarizations are investigated. As in the tworay model, a comparison between the approximated and non-approximated analysis is provided as well as a comparison between the total field and the field due to lateral reflections only. Still for the street model, slits are inserted and comparisons and analyses are made. Comparisons provided show that a vectorial and gain analysis can be a very useful tool toward increasing theoretical analysis in spite of empirical analysis in the field of prediction.