First time ionospheric refractive index values have been determined at mid latitudes using frequency switched SuperDARN plasma convection velocity estimates. Previous works have found a disparity between high latitude SuperDARN plasma convection velocities and those made by other devices. It was noted that the scattering volume’s refractive index was being neglected when estimating plasma convection velocities, meaning a correction factor was needed in order to more accurately reflect other measurements. Later work proposed a solution which implemented frequency switching in SuperDARN radars and determined a single correction factor based off of many years of data. We present case study driven research which applies the principles of these previous works to mid latitudes in an attempt to determine the refractive effect in mid latitude SuperDARN plasma convection velocity data by examining frequency switched quiet time ionospheric scatter. It was found that the 1/2 hop ionospheric scatter exhibited little to no measurable refractive effect (n ∼ 1), while the 11/2 hop ionospheric scatter tended to exhibit measurable refractive effects (n ∼ 0.7). This is then expanded to a storm-time 1/2 hop ionospheric scatter case study. It was again found that the refractive effects were nearly negligible (n ∼ 1), indicating that the 1/2 hop plasma convection velocities reported by mid latitude SuperDARN radars only require a very small correction factor, if any at all. / Master of Science

GIS are geoprocessing programs that are commonly used to store and perform calculations on terrain data, maps, and other geospatial data. GIS offers the latest terrain and building data as well as tools to process this data. This thesis considers three applications of GIS data and software: a Large Scale Radio Frequency (RF) Model, a Medium Scale RF Model, and Indoor Positioning. The Large Scale RF Model estimates RF propagation using the latest terrain data supplied in GIS for frequencies ranging from 500 MHz to 5 GHz. The Medium Scale RF Model incorporates GIS building data to model WiFi systems at 2.4 GHz for a range of up to 300m. Both Models can be used by city planners and government offcials, who commonly use GIS for other geospatial and geostatistical information, to plan wireless broadband systems using GIS. An Indoor Positioning Experiment is also conducted to see if apriori knowledge of a building size, location, shape, and number of floors can aid in the RF geolocation of a target indoors. The experiment shows that correction of a target to within a building's boundaries reduces the location error of the target, and the vertical error is reduced by nearly half. / Master of Science

Approved for public release; distribution in unlimited. / With the introduction of wireless Local Area Networks (WLANs) in many organizations, it became much easier to intercept confidential files and personal health records. The present study focused on radio frequency propagation in a high-rise building, specifically, the attenuation between floors, and the possibility of intercepting signals through the floors. The current work is based on simulations using the Urbana software tool. It is used to predict the contour of the power levels of signals for a given physical model of the environment using high-frequency ray-tracing methods. The simulation results indicated that the signal levels for a 1 W transmitter could only be detected at the -70 dBm level within two floors (above or below). Even within the two floor range the signal distribution was very nonuniform due to the effects of multipath. The results indicated that closing doors reduced the signal levels, but only slightly for wood doors. Signals escaped the building through the window and were able to travel between floors via this path. The ray tracing accounted for only single diffraction, and therefore rays diffracted two or more times were not included. / Captain, Tunisian Air Force

Indoor use of wireless systems poses one of the biggest design challenges. It is difficult to predict the propagation of a radio frequency wave in an indoor environment. To assist in deploying the above systems, characterization of the indoor radio propagation channel is essential. The contributions of this work are two-folds. First, in order to build a model, extensive field strength measurements are carried out inside two different buildings. Then, path loss exponents from log-distance path loss model and standard deviations from log-normal shadowing, which statistically describe the path loss models for a different transmitter receiver separations and scenarios, are determined. The purpose of this study is to characterize the indoor channel for 802.11 wireless local area networks at 2.4 GHz frequency. This thesis presents a channel model based on measurements conducted in commonly found scenarios in buildings. These scenarios include closed corridor, open corridor, classroom, and computer lab. Path loss equations are determined using log-distance path loss model and log-normal shadowing. The chi-square test statistic values for each access point are calculated to prove that the observed fading is a normal distribution at 5% significance level. Finally, the propagation models from the two buildings are compared to validate the generated equations.

Call number: LD2668 .T4 1978 K57 / Master of Science

ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / In this paper, we propose the exploitation of array beamforming technology in high-speed aeronautical communication applications, e.g., the integrated Network Enhanced Telemetry (iNET) system. By flexible steering of beams and nulls, an array can enhance desired signals whereas the undesired signals such as interference and jammers are suppressed. The proposed adaptive beamforming technology is DSP-based and network-aware, and is designed for the use at aerial vehicle platforms to increase transmission power efficiency, improve receiving signal sensitivity, mitigate interference/multipath effects, and extend the communication range.

The public health emergencies, such as bioterrorist attacks or pandemic outbreaks, have gained serious public and government attentions since the 2001 anthrax attacks and the SARS outbreak in 2003. These events require large-scale and timely dispensing of critical medical countermeasures for protection of the general population. This thesis research focuses on developing mathematical models, real-time algorithms, and computerized decision support systems that enable (1) systematic coordination to tackle multifaceted nature of mass dispensing, (2) fast disease propagation module to allow immediate mitigation response to on-site uncertainties, and (3) user-friendly platform to facilitate modeling-solution integration and cross-domain collaboration. The work translates operations research methodologies into practical decision support tools for public health emergency professionals. Under the framework of modeling and optimizing the public health infrastructure for biological and pandemic emergency responses, the task first determines adequate number of point-of-dispensing sites (POD), by placing them strategically for best possible population coverage. Individual POD layout design and associated staffing can thus be optimized to maximize throughput and/or minimize resource requirement for an input throughput. Mass dispensing creates a large influx of individuals to dispensing facilities, thus raising the risk of high degree of intra-facility infections. Our work characterizes the interaction between POD operations and disease propagation. Specifically, fast genetic algorithm-based heuristics were developed for solving the integer-programming-based facility location instances. The approach has been applied to the metro-Atlanta area with a population of 5.2 million people spreading over 11 districts. Among the 2,904 instances, the state-of-the-art specialized integer programming solver solved all except one instance to optimality within 300,000 CPU seconds and solved all except 5 to optimality within 40,000 CPU seconds. Our fast heuristic algorithm returns good feasible solutions that are within 8 percent to optimality in 15 minutes. This algorithm was embedded within an interactive web-based decision support system, RealOpt-Regional©. The system allows public health users to contour the region of interest and determine the network of PODs for their affected population. Along with the fast optimization engine, the system features geographical, demographical, and spatial visualization that facilitate real-time usage. The client-server architecture facilities front-end user interactive design on Google Maps© while the facility location mathematical instances are generated and solved in the back-end server. In the analysis of disease propagation and mitigation strategies, we first extended the 6-stage ordinary differential equation-based (ODE) compartmental model to accommodate POD operations. This allows us to characterize the intra-facility infections of highly contagious diseases during local outbreak when large dispensing is in process. The disease propagation module was then implemented into the CDC-RealOpt-POD© discrete-event-simulation-optimization. CDC-RealOpt-POD is a widely used emergency response decision support system that includes simulation-optimization for determining optimal staffing and operations. We employed the CDC-RealOpt-POD environment to analyze the interactions between POD operations and disease parameters and identified effective mitigation strategies. The disease propagation module allows us to analyze the efficient frontier between operational efficiencies and intra-POD infections. Emergency response POD planners and epidemiologists can collaborate under the familiar CDC-RealOpt-POD environment, e.g., design the most efficient plan by designing and analyzing both POD operations and disease compartmental model in a unified platform. Corresponding problem instances are formed automatically by combining and transforming graphical inputs and numerical parameters from users. To facilitate the operations of receiving, staging and storage (RSS) of medical countermeasures, we expanded the CDC-RealOpt-POD layout design functions by integrating it with the process flow. The resulting RSS system allows modeling of both system processes along with spatial constraints for optimal operations and process design. In addition, agent-based simulation was incorporated inside where integrated process flow and layout design allow analysis of crowd movement and congestion. We developed the hybrid agent behavior where individual agents make decision through system-defined process flow and autonomous discretion. The system was applied successfully to determine guest movement strategies for the new Georgia Aquarium Dolphin Tales exhibit. The goal was to enhance guest experience while mitigating overall congestion.

International Telemetering Conference Proceedings / October 28-31, 1985 / Riviera Hotel, Las Vegas, Nevada / In many engineering applications, a systems analysis is performed to study the effects of random error propagation throughout a system. Often these errors are not independent, and have joint behavior characterized by arbitrary covariance structure. The multivariate nature of such problems is compounded in complex systems, where overall system performance is described by a q-dimensional random vector. To address this problem, a computer program was developed which generates Taylor series approximations for multivariate system performance in the presence of random component variablilty. A summary of an application of this approach is given in which an analysis was performed to assess simultaneous design margins and to ensure optimal component selection.

This thesis reports the methods, the deployment strategies and the resulting system performance improvement of in-building environmental modification. With the increasing use of mobile computing devices such as PDAs, laptops, and the expansion of wireless local area networks (WLANs), there is growing interest in increasing productivity and efficiency through enhancing received signal power. This thesis proposes the deployment of waveguides consisting of frequency selective surfaces (FSSs) in indoor wireless environments and investigates their effect on radio wave propagation. The received power of the obstructed (OBS) path is attenuated significantly as compared with that of the line of sight (LOS) path, thereby requiring an additional link budget margin as well as increased battery power drain. In this thesis, the use of an innovative model is also presented to selectively enhance radio propagation in indoor areas under OBS conditions by reflecting the channel radio signals into areas of interest in order to avoid significant propagation loss. An FSS is a surface which exhibits reflection and/or transmission properties as a function of frequency. An FSS with a pass band frequency response was applied to an ordinary or modified wall as a wallpaper to transform the wall into a frequency selective (FS) wall (FS-WALL) or frequency selective modified wall (FS-MWALL). Measurements have shown that the innovative model prototype can enhance 2.4GHz (IEEE 802.11b/g/n) transmissions in addition to the unmodified wall, whereas other radio services, such as cellular telephony at 1.8GHz, have other routes to penetrate or escape. The FSS performance has been examined intensely by both equivalent circuit modelling, simulation, and practical measurements. Factors that influence FSS performance such as the FSS element dimensions, element conductivities, dielectric substrates adjacent to the FSS, and signal incident angles, were investigated. By keeping the elements small and densely packed, a largely angle-insensitive FSS was developed as a promising prototype for FSS wallpaper. Accordingly, the resultant can be modelled by cascading the effects of the FSS wallpaper and the ordinary wall (FSWALL) or modified wall (FS-MWALL). Good agreement between the modelled, simulated, and the measured results was observed. Finally, a small-scale indoor environment has been constructed and measured in a half-wave chamber and free space measurements in order to practically verify this approach and through the usage of the deterministic ray tracing technique. An initial investigation showing that the use of an innovative model can increase capacity in MIMO systems. This can be explained by the presence of strong multipath components which give rise to a low correlated Rayleigh Channel. This research work has linked the fields of antenna design, communication systems, and building architecture.

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