Due to the enormous performance gains associated with the use of antenna arrays in wireless networks, it is inevitable that these technologies will become an integral part of future systems. This report focuses on signal propagation modeling for antenna array systems and on its relationship to the performance of these systems. Accurate simulation and analytical models are prerequisite to the characterization of antenna array system performance. Finally, an understanding of the performance of these systems in various environments is needed for effective overall network design. This report begins with an overview of the fundamentals of antenna array systems. A survey of vector channel models is presented. Angle of arrival and time of arrival statistics for the circular and elliptical (Liberti's Model) models are derived. A generalized optimum output SINR analysis is derived for space-time processing structures in frequency selective fading channels. The hardware and software of the MPRG Antenna Array Testbed (MAAT) is described. A literature review of previous antenna array propagation measurements is given. Antenna array measurement results obtained with the MAAT are used to compare the properties of the received signal vector in the various environmental conditions. The influence of channel parameters on the ability of antenna arrays to separate the signals of two users on the reverse link is studied using simulation. Finally, forward link beamforming techniques are reviewed. / Ph. D.

Maps of chosen areas in Chicago, San José, London and Shibuya, areimported from Open Street Map into matlab in order to run LTE networksimulations for various scenarios. Firstly, two path loss models arecompared, the empirically based WINNER model and a set of sitespecificmodel. Secondly, low load network simulations are runseparately at two different carrier frequencies, 700MHz and 2GHz, forcity specific base station deployments. Simulation results show thatuser performance is quite unique for each city and that deploymentstrategies and city environments are strongly influencing path gain,SINR and throughput. In general, user performance in UL issignificantly worse at 2GHz than at 700MHz, whereas DL performance isnot as affected by the change in carrier frequency.

Radio Tomographic imaging (RTI) is an exciting new field that utilizes a sensor network of a large number of relatively simple radio nodes for inverse imaging, utilizing similar mathematical algorithms to those used in medical imaging. Previous work in this field has almost exclusively focused on device-free object location and tracking. In this thesis, the application of RTI to propagation problems will be studied-- specifically using RTI to measure the strength and location of attenuating objects in an area of interest, then using this knowledge of the shadowing present in an area for radio coverage prediction. In addition to radio coverage prediction, RTI can be used to improve the quality of RSS-based position location estimates. Because the traditional failing of RSS-based multilateration is ranging error due to attenuating objects, RTI has great potential for improving the accuracy of these estimates if shadowing objects are accounted for. In this thesis, these two problems will primarily be studied. A comparison with other inverse imaging, remote sensing, and propagation modeling techniques of interest will be given, as well as a description of the mathematical theory used for tomographic image reconstruction. Proof-of-concept of the efficacy of applying RTI to position location will be given by computer simulation, and then physical experiments with an RTI network consisting of 28 Zigbee radio sensors will be used to verify the validity of these assertions. It will be shown in this thesis that RTI does provide noticeable improvement in RSS-based position location accuracy in cluttered environments, and it produces much more accurate RSS estimates than a standard exponential path-loss model is able to provide. / Master of Science

No description available.

The detection and localization of important acoustic events in a complex urban environment, such as gunfire and explosions, is critical to providing effective surveillance of military and civilian areas and installations. In a complex environment, obstacles such as terrain or buildings introduce multipath propagations, reflections, and diffractions which make source localization challenging. This dissertation focuses on the problem of source localization in three-dimensional (3D) realistic urban environments. Two different localization techniques are developed to solve this problem: a) Beamforming using a few microphone phased arrays in conjunction with a high fidelity model and b) Fingerprinting using many dispersed microphones in conjunction with a low fidelity model of the environment. For an effective source localization technique using microphone phased arrays, several candidate beamformers are investigated using 2D and corresponding 3D numerical models. Among them, the most promising beamformers are chosen for further investigation using 3D large models. For realistic validation, localization error of the beamformers is analyzed for different levels of uncorrelated noise in the environment. Multiple-array processing is also considered to improve the overall localization performance. The sensitivity of the beamformers to uncertainties that cannot be easily accounted for (e.g. temperature gradient and unmodeled object) is then investigated. It is observed that evaluation in 3D models is critical to assess correctly the potential of the localization technique. The enhanced minimum variance distortionless response (EMVDR) is identified to be the only beamformer that has super-directivity property (i.e. accurate localization capability) and still robust to uncorrelated noise in the environment. It is also demonstrated that the detrimental effect of uncertainties in the modeling of the environment can be alleviated by incoherent multiple arrays. For efficient source localization technique using dispersed microphones in the environment, acoustic fingerprinting in conjunction with a diffused-based energy model is developed as an alternative to the beamforming technique. This approach is much simpler requiring only microphones rather than arrays. Moreover, it does not require an accurate modeling of the acoustic environment. The approach is validated using the 3D large models. The relationship between the localization accuracy and the number of dispersed microphones is investigated. The effect of the accuracy of the model is also addressed. The results show a progressive improvement in the source localization capabilities as the number of microphones increases. Moreover, it is shown that the fingerprints do not need to be very accurate for successful localization if enough microphones are dispersed in the environment. / Ph. D.

In June 2003, the Littoral Acoustic Demonstration Center conducted an acoustic characterization experiment for a standard seismic exploration array. Two moorings with Environmental Acoustic Recording Systems (EARS) were deployed in the northern part of the Gulf of Mexico to measure ambient noise and collect shot information. A 21-element seismic airgun array was towed along five parallel linear tracks with horizontal closest approach points to the EARS buoy position of 63, 500, 1000, 2000, and 5000 m. Calibrated acoustic pressure measurements collected during the experiment were analyzed to obtain zero-to-peak sound pressures, sound exposure levels, and pressure levels in 1/3-octave frequency bands. In addition, the experimental data were modeled by using a modified underwater acoustic propagation model to fill in missing data measurements. The resulting modeling procedure showed good agreement between measured and modeled data in absolute pressure amplitudes and frequency interference patterns for frequencies up to 1000 Hz. The analysis is important for investigating the potential impact on marine mammals and fish and predicting the exposure levels for newly planned seismic surveys in other geographic areas. Based on results of the experiment conducted and data analysis performed, a new experimental design was proposed to maximize the amount of collected data using the available equipment while minimizing the time needed for the source ship. The design used three patches, one with 3º angular spacing between the lines at a reference depth. Embedded is a smaller patch with 1º spacing and within that a still smaller patch with one half degree spacing. This arrangement gives a reasonably uniform distribution of shots versus solid angle with a large variety of emission and azimuthal angles for different ranges. Due to the uncertainty of positioning systems, the angular space is divided into solid angle bins. Simulations predicted more than 200 shots per bin for emission angles greater than 13 degrees. Statistical analysis of collected data will be performed on the proposed bin basis. An experiment based on the proposed design was conducted in Fall 2007. The data measurements collected during the experiment are currently being analyzed and will be reported in the near future.

LOW ALTITUDE RADAR WAVE PROPAGATION MODELLING In this PhD thesis, propagation aspects of low altitude radar performance have been modeled using geometrical optics. Both the path propagation factor and the radar clutter have been modeled. Such models already exist at various complexity levels, such as round earth specular reflection combined with knife edge hill diffraction [SEKE:IEEE,Ap- 34,No:8,1980] and round earth and slant plateau reflection combined with hill diffraction [RADCAL: 1988-2000,EE,METU]. In the proposed model we have considered an extension to RADCAL&rsquo / s model to include convex and concave slant plateaus between hills and depressions (troughs). This propagation model uses a reflection model based on the Geometrical Theory of Reflection for the convex and concave surfaces. Also, back scattering from surface (clutter) is formulated for the new model of the terrain profile. The effects of the features of the terrain profile on the path propagation factor have been investigated. A real terrain data have been smoothed on the basis of the above study. In order to verify the formulation, the Divergence and Convergence Factors associated with the convex and concave plateaus, respectively are inserted into the RADCAL program. The chosen terrains have convex or concave plateaus in the model. The output of the RADCAL is compared with measured values and other propagation algorithms such as Forward-Backward Spectrally Accelerated (FBSA) [FBSA:IEEE Vol.53, No:9,2005] and Parabolic Equation Method [TPEM:IEEE Vol.42,No:1,1994]. Moreover, as the RADCAL Propagation model is based on the ray optics, the results are also compared with another ray optics based propagation model. For this purpose the results of SEKE [Lincoln Lab.] propagation model are used. SEKE model has been used to compute path loss for different types of terrain as a function of receiving antenna height at a fixed distance between transmit and receive antennas. For Beiseker W35 Terrain profile, the results of RADCAL, SEKE and measurements are compared. All results are in good agreement with those of RADCAL.

The interconnection of molecular machines with different functionalities to form molecular communication systems can increase the number of design possibilities and overcome the limited reliability of the individual molecular machines. Artificial information exchange using molecular signals would also expand the capabilities of single engineered cell populations by providing them a way to cooperate across heterogeneous cell populations for the applications of synthetic biology and lab-on-a-chip systems. The realization of molecular communication systems necessitates analysis and design of the communication channel, where the information carrying molecular signal is transported from the transmitter to the receiver. In this thesis, significant progress towards the use of microfluidic channels to interconnect molecular transmitter and receiver pairs is presented. System-theoretic analysis of the microfluidic channels are performed, and a finite-impulse response filter is designed using microfluidic channels. The spectral density of the propagation noise is studied and the additive white Gaussian noise channel model is developed. Memory due to inter-diffusion of the transmitted molecular signals is also modeled. Furthermore, the interference modeling is performed for multiple transmitters and its impact on the communication capacity is shown. Finally, the efficient sampling of the signal transduction by engineered bacterial receivers connected to a microfluidic channel is investigated for the detection of the pulse-amplitude modulated molecular signals. This work lays the foundation for molecular communication over microfluidic channels that will enable interconnection of engineered molecular machines.

[pt] Sintetizadores de séries temporais de atenuação por chuva constituem um importante recurso para o projeto, teste e otimização de Técnicas de Mitigação de Desvanecimento. Como dados experimentais de propagação não estão disponíveis para todas as configurações possíveis de enlaces Terra-espaço, a síntese de séries temporais de atenuação por chuva torna-se uma solução interessante, permitindo a reprodução das características dinâmicas de longa duração da atenuação pela chuva. Nesta tese de doutorado, modelos de canal capazes de sintetizar períodos curtos e longos de atenuação por chuva são analisados, testados e validados para os climas tropical e equatorial brasileiros. Aspectos críticos que determinam o correto comportamento destes geradores de séries temporais são analisados e sua faixa de validade é apresentada. Em regiões de clima tropical e equatorial, o desenvolvimento insuficiente da estrutura de telecomunicações terrestre e, por vezes, a necessidade de vencer distâncias continentais, amplificam a necessidade de implementação de sistemas de comunicação por satélite no médio prazo. Tais sistemas apresentam a vantagem de servir grandes áreas com curto tempo de implantação e a possibilidade de atingir mercado considerável. Para as novas aplicações, fortemente focadas em conteúdo multimídia para consumidores corporativos e residenciais, a banda C não é atraente porque o desenvolvimento de novos sistemas com pequenos terminais, como desejado, é incompatível com as grandes antenas necessárias para a proteção dos sistemas existentes nesta banda. Para o fornecimento de serviços multimídia a altas taxas é previsto o uso da banda Ka. Problemas de propagação são severos nestas altas faixas de frequência de forma que figuras de mérito padrão para desempenho e disponibilidade são difíceis de ser obtidas em regiões climáticas tropicais e equatoriais. Por esta razão, metodologias tradicionais de cálculo de enlaces, que levam ao uso de altas margens fixas não são as mais indicadas. Lança-se mão de Técnicas de Mitigação de Desvanecimento (Fade Mitigation Techniques, FMT). No projeto e otimização de FMTs, o conhecimento do comportamento dinâmico do canal de radiopropagação é necessário. Objetivando preencher este requisito, são usadas séries temporais de atenuação por chuva nas simulações de sistema. Porém, séries temporais experimentais não estão disponíveis em nível global em todas as frequências e inclinações de enlace desejadas, para que se projete e teste FMTs. Portanto, a alternativa ao uso de séries experimentais é a geração (sintetização) de séries temporais de atenuação por chuva fazendo uso de características climatológicas bem como de parâmetros geométricos e de propagação relativos ao enlace. Neste trabalho, modelos de canal baseados na abordagem original de Maseng e Bakken são testados com dados de beacon em 11,5 GHz (banda Ku), medidos em quatro localidades Brasileiras, representativas de climas tropical, subtropical e equatorial. Ainda, um modelo misto usando cadeias de Markov e um modelo, já existente, gerador de eventos de atenuação por chuva sob demanda é proposto e analisado. Validação é realizada por meio de variáveis de teste propostas pela ITU-R e também pela análise da fidelidade que características específicas dos eventos sintetizados possuem em relação às características de eventos reais medidos. / [en] Rain attenuation time series synthesizers constitute an important resource to the design, test and optimization of Fade Mitigation Techniques (FMTs). In the absence of experimental propagation data for every possible Earth-Space configuration, the synthesis of rain attenuation time series becomes an interesting solution to allow for the reproduction of the long-term dynamic characteristics of rain attenuation. In this thesis, channel models able to synthesize long- and shortterm rain attenuation periods are discussed, tested and validated for the Brazilian tropical and equatorial climates. Critical issues determining the correct behavior of such time series generators are analyzed and their range of validity is presented.

The localization of the sensor nodes is a fundamental issue in the area of wireless sensor networks (WSNs). An attractive way for estimating the location of mobile or static wireless objects is by using the received signal strength (RSS) attenuation with the distance, which does not require any additional hardware. This is possible due to the fact that in most sensor nodes radios the received signal strength indicator (RSSI) is a standard feature and can be obtained automatically by the received messages. On the other hand the RSS is known for being noisy, unstable, variable and difficult to use in practice. For achieving a better understanding of the nature of these difficulties and limitations, and for identifying the range of applicability of the RSS in localization and tracking scenarios, a thorough study about the RSS and its dependence on the various factors and environmental conditions is essential. The present doctoral dissertation investigates the feasibility of sensor node localization and target tracking with the resources of the WSN technology, when using only the RSS of the exchanged messages. Moreover, it offers experimental support to the hypothesis that proper modeling of the RSS behavior and appropriate selection of the topology parameters are essential for the applicability of WSN in real world conditions. In brief, the present doctoral dissertation concerns with: (i) identifying the main factors that influence the accuracy, the variability and the reliability of the obtained RSS, (ii) modeling the RF signal propagation in the context of WSNs, and (iii)defining the basic deployment constraints and evaluation of the topology parameters that can guarantee successful localization and tracking. For assessing the practical value of various RF-models, experiments using Tmote Sky and TelosB sensor nodes in real-field outdoor environment were carried out. The impact of a number of factors, such as the operating frequency of the radio, the transmitter–receiver distance, the variation of transceivers hardware due to manufacturing tolerances, the antenna orientation, and the environmental conditions, on the RSS was investigated. The influence of the various factors that affect the RF signal propagation and some constraints imposed by the WSN nature was accounted in order to design practical models, suitable for outdoor unobstructed and outdoor tree-obstructed environments. A pre-deployment simulation framework has been introduced and in its context a RF signal propagation-based connectivity strategy (RFCS) has been developed to fulfill three deployment provisions: (i) discovering the most appropriate height from the ground and distances for the sensor nodes, (ii) reducing the transmission power, and (iii) minimizing the interference from non-neighbor nodes. The RFCS uses a RF signal propagation model to predict the RSS in order to identify the most appropriate communication-based deployment parameters, i.e. T-R distance, height from the ground and transmission power. The localization and tracking considerations, by means of localization and tracking techniques, topology parameters and factors influencing the localization and tracking accuracy, are combined in illustrative simulation examples to evaluate their significance concerning the performance of the localization and tracking task. Furthermore, the propagation model and the topology parameters being identified were validated in real outdoor sensor node localization and target tracking tests. / -