O. Gutierrez

Efficient ray-tracing techniques for three-dimensional analyses of propagation in mobile communications: application to picocell and microcell scenarios

The application of several ray-tracing techniques, in combination with GTD/UTD (geometrical theory of diffraction/uniform theory of diffraction), for an efficient analysis of propagation in urban scenarios is presented. The frequency of the analysis is in the UHF band, and a three-dimensional model of the geometry, using flat facets, is considered. After a review of the most commonly used ray-tracing techniques, a new method, called the angular z-buffer (AZB) technique, is presented. As is shown and validated with results, the AZB appears to be extremely efficient for GTD/UTD applications.

THE APPLICATION OF RAY-TRACING TO MOBILE LOCALIZATION USING THE DIRECTION OF ARRIVAL AND RECEIVED SIGNAL STRENGTH IN MULTIPATH INDOOR ENVIRONMENTS

This work presents a new indoor localization method based on the fingerprinting technique. The proposed method uses a ray-tracing model that provides information about multipath effects. This information is stored in a dataset during the first stage of the fingerprinting method. The direction of arrival (DOA) and received signal strength (RSS) are used in the fingerprinting technique as a hybrid system. The localization estimation is calculated while taking into account the Euclidian distance between the DOA and the RSS from each unknown position and the information of the fingerprints. Numerical calculations were performed to show the mean and the standard deviation of the estimated error.

FASANT: past computer tool for the analysis of on-board antennas

FASANT is a computer tool for the analysis of antennas on-board satellites, ships, aircraft, and other complex bodies. The structure under analysis, which can be metallic or dielectric (with and/or without losses), must be modeled by plane and/or curved surfaces. The geometrical input files are in DXF format, and can be generated by the most commonly used computer-aided geometrical-design (CAGD) tools. The code can also be applied to the analysis of arrays and arbitrarily shaped reflectors. The kernel of the code is based on the uniform theory of diffraction (UTD). Special algorithms have been developed to speed up the ray-tracing computation for both flat and curved surfaces. FASANT can obtain far-field patterns, field levels at points near the structure, can calculate the mutual coupling between antennas or between array elements, and can show each ray-tracing mechanism.

Localization Approach Based on Ray-Tracing Including the Effect of Human Shadowing

This work presents an accurate and realistic positioning approach for indoor environments based on fingerprinting and raytracing techniques. Fading caused by multipath seriously degrades the performance of communication systems operating inside buildings. For this reason, the proposed localization method considers multipath effects due to reflections and diffraction from walls, roof and floor. However, fading in indoor environments can also be caused by the movement of people or the presence of furniture. Because people are the primary absorption agents in indoor channels, their influence on the radio propagation channel must be considered. The proposed localization method takes into account the effects of human body shadowing to provide a realistic estimation of the mobile station position. Numerical calculations in real indoor scenarios show reasonable results.

Application of multilevel fast multipole method to the analysis of the scattering of complex bodies modeled by NURBS surfaces

An application of the MLFMA to the electromagnetic analysis of realistic bodies modeled by NURBS surfaces is presented. The discretization of the geometry is carried out using also NURBS surfaces that permit an exact representation of the body under analysis. The basis and test functions are also conformed to the geometry to take advantage of the exact representation. A dual mesh is used to improve the convergence of the method and to allow the analysis of non conducting bodies

Fast Ray-Tracing for Computing N-Bounces Between Flat Surfaces at Indoor/Outdoor Propagation

A new ray-tracing method has been developed to compute the propagation at indoor/outdoor environments considering n-bounces. The Angular Z-Buffer algorithm (AZB) together with the A* heuristic search method are considered. The approach is very efficient allowing the analysis of high-order bounces in reasonable CPU-time utilizing an affordable computer.

Calculation of the RCS from the double reflection between planar facets and curved surfaces

A method to obtain the contribution to the monostatic radar cross section (RCS) due to double reflections between plane facets and curved surfaces is presented. This method is applied to arbitrary targets modeled by NURBS (non-uniform rational B-spline) surfaces. The method developed is a combination of geometrical optics (GO) and the stationary phase method (SPM).

Iterative PO method based on currents modes and angular Z-buffer technique

An efficient scheme based on physical optics (PO), the angular Z-buffer (AZB) technique and the volumetric space partitioning (SVP) algorithms for computing the RCS of large and complex bodies is presented. An iterative process to calculate multiple interactions between patches has been considered. Ray-tracing acceleration techniques, like the angular Z-buffer has been applied to reduce the CPU-time

A Comparative Study of Localization Methods in Indoor Environments

A comparative study, based on three different measurements (direction of ray arrival, time difference of arrival and received signal strength), to compute the unknown position of mobile stations in indoor environments is presented in this paper. The comparison is carried out considering the results of analyses in a real building in Madrid. To overcome the problems that arise in indoor areas due to the presence of non line of sight conditions, the fingerprinting technique is applied in each of the cases. Data for computations are provided by a simulation tool based on the uniform theory of diffraction and ray-tracing techniques. This information is stored in the fingerprinting database and contains information related to every mobile station, every reference node and every access point located inside the environment under analysis. Experimental results compare the mean error when localizing several mobile stations by using the three different approaches. The goal is to obtain high precision in the localization by means of alternative methods to the received signal strength classical measurement. These techniques will be useful in critical environments where high operational security requirement are demanded.

Efficient Time-Domain Ray-Tracing Technique for the Analysis of Ultra-Wideband Indoor Environments including Lossy Materials and Multiple Effects

This paper presents an efficient application of the Time-Domain Uniform Theory of Diffraction (TD-UTD) for the analysis of Ultra-Wideband (UWB) mobile communications for indoor environments. The classical TD-UTD formulation is modified to include the contribution of lossy materials and multiple-ray interactions with the environment. The electromagnetic analysis is combined with a ray-tracing acceleration technique to treat realistic and complex environments. The validity of this method is tested with measurements performed inside the Polytechnic building of the University of Alcala and shows good performance of the model for the analysis of UWB propagation.