Hybrid Computational Techniques: Electromagnetic Propagation Analysis in Complex Indoor Environments

This study investigates the accuracy with which a simple propagation model based on geometrical optics (GO) and uniform theory of diffraction (UTD) can be used to predict the fading characteristics near a base station. The model uses both standard first order three dimensional GO and UTD to simulate near field propagation at the base station. Simulation results are compared with data from a measurement campaign. The model showed a potential for predictions better than 5 dB accuracy in this type of scenario.

As the wireless communications systems become more and more popular, the subscribers want to use their phone in all the places they live. In these conditions, an indoor planning tool may be very useful for the operators to offer their subscribers the best coverage with the lowest costs. The indoor planning tool that is presented here is a combination of a prediction and an optimization tool. The prediction tool is based on a UTD (Uniform Theory of Diffraction) - Ray Launching. The optimization tool is based on both placement and wiring optimization. This is probably the main originality of this work as the question of the wiring between the BTS and the antennas is rarely studied although it is a very important one.

A design method for an offset-fed, dual reflector antenna (Cassegrain type or Gregorian type) system with an axisymmetric main reflector is presented. Geometrical optics (GO) and the geometrical theory of diffraction (GTD) are used to find the surface-current density on the main reflector. A modified Jacobi-Bessel series (JBS) method is used to find the far-field pattern for the physical optics (PO) integral. In the defocused mode of operation, a new technique is developed to find the reflection point on the subreflector corresponding to the defocused feed and a general field point on the main reflector. Two sample systems are designed.

Two major model sets are used to model a radio wave propagation problem. The first is empirical, based on measurements and statistics. Empirical models are easy to implement and fast. They only consider Tx-Rx separation and thus are not accurate enough as different objects of the environment are not taken into account. The second is deterministic exploiting physical laws to simulate signal propagation. Deterministic propagation prediction models based on a combination of Geometrical Optics (GO) and the Uniform Theory of Diffraction (UTD) represent the unique solution for reliable estimations. The most famous of the second approach is the well-known ray tracing like model, based on the computation of the different paths according to the geometrical optical laws. Concerning the transmitted signal bandwidth (BW), the propagation channel appears differently to Ultra Wideband (UWB) wireless systems than it does to Narrow Band (NB) sine wave systems. The main objective of this paper is to develop a ray tracing Matlab code to estimate the power received as a function of frequency in a given environment. The results were experimentally validated according to time domain corporation specifications where the BW was selected to cover the 3.1-5.3 GHz band with center frequency of 4.3 GHz.

An efficient numerical solution for predicting high frequency radiation patterns of on board antennas is presented. The method is based on geometric optics (GO) and the uniform theory of diffraction (UTD). The body where the antenna is boarded is modeled by plane facets and curved surfaces. For the plane facets the angular Z-Buffer algorithm is used in order to speed up the ray-tracing process. For the curved surfaces the creeping waves phenomenon is included.

The aim of this study is to introduce, for the first time in the literature, a two-way FEMPE algorithm (2W-FEMPE), and to perform calibration tests of both two-way FEMPE and SSPE algorithms against the Image Method and the Geometric Optic (GO) + Uniform Theory of Diffraction (UTD).

Sevgi, Levent (Dogus Author) -- Conference full title: 2010 Mediterranean Microwave Symposium (MMS 2010) Guzelyurt, 25 - 27 August 2010

A fast 3-D ray tracing propagation prediction model based on virtual source tree is presented in this paper, whose theoretical foundations are geometrical optics(GO) and the uniform theory of diffraction(UTD). In terms of typical single room indoor scene, taking the geometrical and electromagnetic information into account, some acceleration techniques are adopted to raise the efficiency of the ray tracing algorithm. The simulation results indicate that the runtime of the ray tracing algorithm will sharply increase when the number of the objects in the single room is large enough. Therefore, GPU acceleration technology is used to solve that problem. As is known to all, GPU is good at calculation operation rather than logical judgment, so that tens of thousands of threads in CUDA programs are able to calculate at the same time, in order to achieve massively parallel acceleration. Finally, a typical single room with several objects is simulated by using the serial ray tracing algorithm and the parallel one respectively. It can be found easily from the results that compared with the serial algorithm, the GPU-based one can achieve greater efficiency.

A model to characterize the radio wave propagation in urban environments is presented. This model is based on asymptotic methods, such as the geometrical optics (GO) and the uniform theory of diffraction (UTD). Because of the complexity of ray tracing techniques, a geometrical modeling of buildings is necessary in order to simplify the process. Simulations are carried out along several routes within a particular urban environment at 900 MHz. Their results provide some conclusions about the influence of the environment in the radio wave propagation.

A MATLAB-based virtual diffraction tool, using analytical exact as well as well-known high-frequency asymptotic (HFA) techniques, is introduced. Electromagnetic wave scattering from a wedge-shaped object with perfect electrical conductor (PEC) boundaries, under both line-source and plane-wave illuminations, can be automatically analyzed. Effects of various parameters on the reflection, refraction, and diffraction can be investigated. Comparisons among Geometrical Optics (GO), Uniform Theory of Diffraction (UTD), Physical Optics (PO), Physical Theory of Diffraction (PTD), and Parabolic Equation (PE) models are possible through many scenarios and illustrations.

Scattering by a conducting circular cylinder is a classical problem solvable by separation of variables. When the radius of the cylinder is very large, computation of the summation becomes very time consuming. Classically, the harmonic series may be converted into an alternative series by Watson's transformation. Practically, high frequency scatterings are approximately solved using optical techniques such an geometric optics, physical optics, or geometric theory of diffraction. Direct numerical solutions of electromagnetic scattering in the optical frequency range have never been attempted because the effort would be too expensive and there is no guarantee that the results will be reliable after an astronomical number of arithmetical operations. The measured equation of invariance (MEI) may have just reversed the situation. The advantage of MEI is its ability to terminate finite difference/element meshes very close to the scatterer surface. We demonstrate that the MEI coefficients at high frequency can be obtained by extrapolation of those at low frequencies. So, using the MEI with its coefficient extrapolation the number of arithmetical operations can be drastically reduced and the direct numerical method becomes feasible in the optical frequency range.

A modified adaptive division beam tracing (MADBT) technique based on the localized kd-tree and the OpenMP–MPI parallel techniques is presented for the simulation of radio propagation in large-scale urban environments. Beams launched from a transmitter are recursively traced by applying the MADBT method and beam trees recorded the propagation path info are generated. By traversing the beam trees, all the valid propagation (transmitted, reflected and diffracted) paths are efficiently determined. Then the receiver power strength can be calculated based on geometrical optics (GO) and uniform theory of diffraction along the arrival paths. By tracing the continuous beams instead of a number of rays, the proposed method performs higher efficiency than the widely used ray tracing method. During the beam tracing procedure, several techniques are adopted to accelerate the calculation. Firstly, a localized kd-tree is built according to the coverage area of the transmitter, which is more efficient than the global kd-tree to do the beam-triangle intersection during the tracing procedure. Secondly, a virtual simulation face is generated to speed up the searching for ray paths. Lastly, the OpenMP and the MPI parallel technique are implemented to further enhance efficiency of the proposed method. As expected, the simulated results for the realistic Malaysia urban environment show good agreement with measured results and performance high efficiency.

Frequency and time domain characteristics of a novel and compact triple band notched ultra wideband (UWB) monopole antenna are investigated. To realize UWB characteristics, the lower edges of a simple rectangular radiating patch are truncated and a new structure including a semi-circle like ring stub is added to the rear side of the antenna. To avoid interferences with coexisting narrow band systems such as WiMAX, WLAN, and X band, two inverse L-shaped slots, a semi-circle like ring slot and two C-shaped resonators are incorporated in the antenna geometry, respectively. The effect of the proposed antenna on a modulated Gaussian pulse as an excitation signal in different scenarios is fully studied. Moreover, the channel impulse response of a simple indoor environment is investigated when a pair of the proposed antennas are applied as transmitting and receiving antennas. Sub-band divided ray tracing method based on the geometrical optics and uniform theory of diffraction is used to simulate the impulse response of the propagation channel. A frequency domain measurement campaign is also employed to measure the channel characteristics. The measured results are compared with those obtained from the simulations to validate the design procedure.

Two-and-one-half dimensional ray tracing models, in combination with the uniform theory of diffraction and geometrical optics, are widely employed for propagation prediction in urban microcellular environments because of their high efficiency and reliable prediction accuracy. In this study, an improved ray tracing algorithm based on the “orientation face set” concept and on the improved 2D polar sweep algorithm is used. The aim of this paper is mainly to analyze the effects of different propagation mechanisms on ray-tracing-based coverage predictions in urban microcellular environments. In addition, the effects associated with the coverage prediction are visually represented.

Interference effects in the light scattering by transparent plates