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This paper describes two important improvements to a 3-D shooting-and-bouncing-polygon (SBP) ray tracer for radio propagation modeling. It introduces a way to trace diffracted–reflected (D–R) rays in the SBP framework and improves SBP accuracy when the D–R rays play an important role. It also introduces a better space partitioning scheme for the use with SBP and improves the SBP’s computation efficiency by more than $10\times $ in some applications. The numerical results are compared against published measurements and 3-D full-wave solutions. They show that the improved SBP ray tracer is a good multipurpose 3-D ray tracer which can be used to simulate urban street canyon (without double over-rooftop diffraction), indoor, and tunnel propagation environments. [ABSTRACT FROM AUTHOR]

Abstract: Radio wave propagation through wireless channels is characterized by 4 main physical phenomena: reflection, diffraction, scattering, and absorption. Considerable efforts have been devoted to develop precise mathematical description of signal fluctuations which is very helpful in designing and evaluating the performance of wireless communication systems. A space diversity reception technique presents effective method for increasing channel capacity and upgrading transmission reliability at relatively low cost. In this paper, wireless communication system with maximal‐ratio combining (MRC) microdiversity and selection combining (SC) macrodiversity reception operating over correlated gamma shadowed Nakagami‐m fading channels is studied. Average bit error probability (ABEP), outage probability and average channel capacity, being significant and generally adopted performance measures, are employed to investigate how system performance is affected by the number of base stations and the number of antennas per base station. [ABSTRACT FROM AUTHOR]

Based on the generalized Rayleigh-Sommerfeld diffraction integral, the equations of nonparaxial propagation, far field propagation and paraxial propagation of a partially coherent four-petal Gaussian beam in free space are obtained. The results show that the far field propagation and paraxial propagation can be regarded as special cases of nonparaxial propagation. The normalized intensity and degree of coherence of a nonparaxial partially coherent four-petal Gaussian beam are illustrated and analyzed using numerical example. [ABSTRACT FROM AUTHOR]

A hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation for the analysis of multiple-diffraction of spherical waves by a series of rectangular plateaux is compared with measurements performed at 62 GHz. The comparison shows a solid agreement between predicted and measured results. Therefore, since the array of plateaux under investigation can be considered as a scaled-model of an urban environment, the results support the validity of the proposed UTD-PO formulation in the analysis of urban radiowave propagation. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents a simulation model of the origin and propagation of speckle field within the Fresnel approximation and verification of the model through a speckle correlation method for determination of in-plane object''s translation. There is used a convolution form of the Fresnel–Kirchhoff diffraction integral in the simulation model instead of often used Fast Fourier Transform approach. A possible way of simulation of the light scattering by object''s surface and in-plane translation of the illuminated surface is mentioned, whereas two types of illumination (plane wave and Gaussian beam) are used. Finally, results of numerical correlation of generated displaced speckle fields are shown and compared with the results obtained by theoretical relations. [Copyright &y& Elsevier]

Abstract: Ray tracing is a technique based on the numerical simulation of geometrical optics and the uniform theory of diffraction, two well-known approximate methods for estimating a high-frequency electromagnetic field, based on the ray theory of field propagation. Radio-wave propagation prediction models based on ray tracing play an important role in wireless network planning, as they take into account diverse physical phenomena such as reflection, diffraction and foliage attenuation and are considered critical for the analysis of long term evolution (LTE) systems, which requires a detailed description of the wireless channel. A major practical drawback of these models is that they can easily become very computationally expensive, as the required level of accuracy and the corresponding areas of study increase. In this paper, a parallel ray tracing algorithm for radio-wave propagation prediction based on the electromagnetic theory of images is presented. The implementation of the algorithm is based on the message passing interface (MPI). The decomposition of the problem is conducted by partitioning the image tree, while dynamic load balancing techniques are employed by means of the master–worker and the work–pool patterns. The performance of the parallel implementation is studied for different problems and task assignment schemes, showing that high speedups can be achieved. [ABSTRACT FROM AUTHOR]

In this paper, we consider UHF radio wave propagation in vegetated residential environments. The attenuating effects of trees as well as those due to diffraction over the buildings are investigated. A new radio wave propagation prediction model based on the combined method of ray tracing and diffraction (CMRTD) is proposed. A row of trees is modeled as a two-dimensional (2-D) cylinder. It is then represented by an equivalent phase object (EPO); a row of buildings is replaced by an absorbing screen. The position and size of the EPO as well as the amplitude and phase distributions of the input field at the EPO are determined by ray tracing. Next the scattered field is computed by the Kirchhoff diffraction theory. Among the numerical results are those of the scattering from a row of trees with circular or elliptic canopies and the scattering from a row of trees/buildings configuration. The calculations treat both plane- and cylindrical-incident waves. By comparing the results with those obtained from the exact eigenfunction expansion method, we show that the CMRTD is an accurate and efficient method to calculate the scattering from a 2-D cylinder. Moreover, the range of the validity of using the CMRTD to model the scattering from one row of trees is determined. [ABSTRACT FROM AUTHOR]

A time domain (TD) solution for the analysis of multiple diffraction of spherical waves after an array of nonperfectly conducting wedges with different interior angles is presented.The proposed TD solution is based on the representation of the inverse Laplace transform of the corresponding frequency domain solution in closed form, as it is given by a hybrid of the uniform theory of diffraction (UTD)-physic optics (PO) solution. The new formulation, validated with the results from technical literature, does not need to incorporate the TD version of the higher-order diffraction coefficients and allows for the calculation of large number of wedges. It has the major advantage in terms of the mathematical complexity and computation efficiency when compared with other TD solutions. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1006–1008, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25094 [ABSTRACT FROM AUTHOR]

Propagation characteristics while entering tunnels are analyzed by using a ray-launching technique and the uniform theory of diffraction (UTD). RMS angular spread is studied and related to the “excitation zone.” This paper presents interesting differences in the behavior of this parameter and the RMS delay spread. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 196–198, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10866 [ABSTRACT FROM AUTHOR]

This letter presents a characterization of the vertical plane propagation in terms of the satellite elevation angle for different mechanisms of propagation. The effect of blockage by buildings on the received signal level versus the satellite elevation angle at L-band for urban environments is performed using the uniform theory of diffraction (UTD). © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 336–338, 2000. [ABSTRACT FROM AUTHOR]