Josefa Gómez

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.

Prospective study of epidemiology and prognostic factors in community-acquired pneumonia.

Of 342 patients with community-acquired pneumonia, 100 were diagnosed etiologically. In these patients, disease epidemiology, prognostic factors, and influence of antibiotic treatment were analyzed prospectively. Fifty-two patients were treated with a broad-spectrum antibiotic (ceftriaxone), and 48 received a medium-spectrum antibiotic (cefuroxime); some patients in each group also received erythromycin.Streptococcus pneumoniae was the most frequently isolated microorganism (43%), followed byChlamydia pneumoniae (21%),Haemophilus influenzae (19%), andMycoplasma pneumoniae (11%). Factors significantly associated with increased mortality were initially critical or poor clinical condition, involvement of two or more lobules, and complications. Prior administration of antibiotics was predictive of penicillin and erythromycin resistance inStreptococcus pneumoniae, but had no effect on the course of the disease. Eight patients died, 89 were cured, and three had recurrences; there was no significant difference in outcome between treatment groups, regardless of whether patients also received erythromycin. Increased knowledge of epidemiological, predictive, and prognostic factors can significantly improve early diagnosis of community-acquired pneumonia and facilitate the choice of appropriate antibiotic treatment, thereby helping to reduce morbidity and mortality.

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.

Optimization of a Dual-Band Helical Antenna for TTC Applications at S Band

A compact dual-band equatorial helical antenna for TTC (telemetry, tracking, and control) applications in satellites is presented. The network feeding system of the antenna was also designed, analyzed, and measured to achieve circular polarization. A Moment Method code was used to evaluate the performance of both the helical antenna and the feed-circuit network. The whole system was optimized to fulfill rather strict specifications, while maintaining quite small size and weight. A prototype of the helical antenna was fabricated and measured. The design process of the geometrical model, and comparisons between the predicted and measured values, are presented. The results led to the conclusion that it is a very suitable antenna for operating at S band.

Fast Analysis of a Dual-Band Reflectarray Using Two Different Numerical Approaches Based on the Moment Method

This communication presents two efficient approaches for the electromagnetic field analysis of complex 3D bodies. The first method can provide a fast and accurate analysis of arbitrary metallic and dielectric/magnetic structures and combines the moment method (MM), the multilevel fast multipole algorithm (MLFMA), physics optics (PO) and the characteristic basis function method (CBFM) to solve very large scattering problems. The second technique is based on a domain decomposition approach that divides the geometry into several parts to minimize the vast computational resources required when applying the MM. A parallelization process was carried out by using the message passing interface (MPI) algorithm to minimize the memory and time requirements for each simulation. A dual-band reflectarray was successfully analyzed to compare the performance of both codes.

Design and Optimization of an EBG Antenna with an Efficient Electromagnetic Solver

A novel electromagnetic bandgap (EBG) antenna has been designed, optimized, and analyzed using an efficient electromagnetic solver based on the moment method. Very good agreement between simulations and measurements in anechoic chamber has been obtained. Comparisons of the antenna with and without the EBG structure have been conducted to study its influence in terms of gain. This new EBG antenna is an excellent candidate for several applications due to its high gain and good polarization purity.

Application of EBG Structures to the Design of a Multibeam Reflector Feed

This work deals with the design, analysis, and measurement of a novel multibeam reflector feed at X band. The whole system is composed of a five-horn array and two layers of electromagnetic bandgap (EBG) material. The goal of this antenna is to obtain high gain over a wide bandwidth, while maintaining a compact size. An efficient optimization process was carried out to find the optimum dimensions of the feed antenna. The final design was built and measured. High illumination performance was achieved. The feed antenna provided 5.5% of 3 dB gain bandwidth and 3.1% of 1.5 dB gain bandwidth, which is higher compared to designs previously reported in the literature.

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.

Numerical approach for the fast analysis of radiation patterns of antennas in complex environments

A numerical technique for the analysis of the radiation pattern of antennas which interact with complex structures is presented in this work. Different parts of the geometry are isolated and the primary currents are obtained. In the next steps, we compute the interactions between different parts of the geometry and update the total currents. This method is especially well suited for problems that lie beyond the scope of both rigorous and high-frequency conventional techniques, due to computational and/or accuracy requirements.

Influence of the feed location on the performance of a conformed Fresnel zone reflector

This letter investigates the effect of varying the feed position along the focal axis on the performance of a conformed Fresnel zone reflector. Bandwidth and aperture efficiency are analyzed by illuminating the proposed reflector antenna with a pyramidal horn at Ku band. The antenna under study is a new type of Fresnel zone plate antenna that, compared to the conventional parabolic reflectors, has the benefits of flat profile and small weight. In comparison to reflectarrays, conformed Fresnel zone reflectors present lower losses and are easier to fabricate. An offset-fed square reflector of 40 × 40 cm2 was designed and analyzed, providing 26% of 1.5-dB gain-bandwidth and 55% of aperture efficiency. Numerical results show that modifying the feed position leads to a remarkable shift in operating frequency band. Therefore, the proposed design offers the possibility of changing the operating band by moving the feed without redesigning the entire antenna. Also, a notable increase in gain is observed when the feed is moved away from the center of the antenna.