Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 204-215).

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / Cover title. Includes bibliographical references (p. 129-134). Also available online from the MIT website (http://www.mit.edu/).

Thesis (M.Sc. (Geography)) - Rhodes University, 2007.

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 29, 2007) Includes bibliographical references.

Thesis (M.S.)--Air Force Institute of Technology, 2007. / "AFIT/GCS/ENG/07-02." Title from PDF title screen. Includes bibliographical references (p. 104-115). Also available online via the Defense Technical Information Center website (http://www.dtic.mil/).

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 152-162). Available also in a digital version from Dissertation Abstracts.

No description available.

abstract: Global Positioning System (GPS) is a navigation system widely used in civilian and military application, but its accuracy is highly impacted with consequential fading, and possible loss of communication due to multipath propagation and high power interferences. This dissertation proposes alternatives to improve the performance of the GPS receivers to obtain a system that can be reliable in critical situations. The basic performance of the GPS receiver consists of receiving the signal with an antenna array, delaying the signal at each antenna element, weighting the delayed replicas, and finally, combining the weighted replicas to estimate the desired signal. Based on these, three modifications are proposed to improve the performance of the system. The first proposed modification is the use of the Least Mean Squares (LMS) algorithm with two variations to decrease the convergence time of the classic LMS while achieving good system stability. The results obtained by the proposed LMS demonstrate that the algorithm can achieve the same stability as the classic LMS using a small step size, and its convergence rate is better than the classic LMS using a large step size. The second proposed modification is to replace the uniform distribution of the time delays (or taps) by an exponential distribution that decreases the bit-error rate (BER) of the system without impacting the computational efficiency of the uniform taps. The results show that, for a BER of 0.001, the system can operate with a 1 to 2 dB lower signal-to-noise ratio (SNR) when an exponential distribution is used rather than a uniform distribution. Finally, the third modification is implemented in the design of the antenna array. In this case, the gain of each microstrip element is enhanced by embedding ferrite rings in the substrate, creating a hybrid substrate. The ferrite rings generates constructive interference between the incident and reflected fields; consequently, the gain of a single microstrip element is enhanced by up to 4 dB. When hybrid substrates are used in microstrip element arrays, a significant enhancement in angle range is achieved for a given reflection coefficient compared to using a conventional substrate. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

Orientador: Luiz Carlos Kretly / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T21:22:28Z (GMT). No. of bitstreams: 1 VerreJunior_Carlos_M.pdf: 3988779 bytes, checksum: e142d23f246ba59d81a08d0b96595a87 (MD5) Previous issue date: 2011 / Resumo: O uso de dispositivos GPS/GSM em sistemas de monitoramento de veículos, para transmitir informações como posição e direção do veículo para centros de controle através de comunicação sem fio sobre redes GPRS tem se aprimorado rapidamente. Estes dispositivos tem se mostrado bastante eficientes garantindo uma maior segurança ao usuário que pode bloquear e localizar o seu veículo segundos depois de ter seu veículo furtado. Além das informações de posição e direção, também se faz viável a obtenção antecipada de informações de acidentes na rodovia em que o condutor esta trafegando, além de emissões de alertas em casos de acidente acionando assim o serviço de resgate de maneira imediata, passando de maneira precisa a localização correta do veículo. Além dessas vantagens, o condutor também pode contar com o suporte direto das montadoras que transmitem e recebem informações do veículo mantendo assim o usuário atualizado sobre as necessidades de manutenção em seu veículo. Todos os sistemas de segurança do veículo, como por exemplo, o AirBag e o cinto de segurança, são projetados para evitar que após uma colisão os tripulantes do veículo sofram lesões, no entanto não são desenvolvidos para que o acidente seja evitado como é o caso da tecnologia de comunicação R2V. Em busca de solucionar o problema, e antes mesmo que o acidente ocorra o motorista seja avisado, muitas tecnologias estão atualmente à prova pelas montadoras de veículos. Este trabalho apresenta metodologias de projeto e simulações que representam de maneira qualitativa as dificuldades envolvidas em um projeto de rastreamento veicular utilizando as tecnologias de GPS/GSM, estudando o desenvolvimento e otimização de uma antena de GPS (ponto crítico) até a influência sofrida pela antena das partes metálicas do veículo quando a antena é localizada na parte interna do veículo (painel de instrumento), levando como base o teto do veículo (ponto ideal) para a solução e base de comparação da solução / Abstract: The use of GPS / GSM vehicle tracking systems to transmit information such as position and direction of the vehicle to control centers through wireless networks over GPRS has improved rapidly. These devices have been quite effective by ensuring greater security to the user who can block and locate your vehicle seconds after the vehicle has been stolen. Besides the position information and direction, it is also feasible to obtain advance information of accidents on the highway when the driver is traveling, in addition to emissions of alert in case of an accident triggering rescue services in a prompt manner, and allowing for the correct location of the vehicle. Besides these advantages, the driver can also rely on the direct support of the makers that transmit and receive information from the vehicle thus keeping the user updated about the maintenance needs on the vehicle. All current security systems of the vehicle, such as the airbag and seat belts, are designed to keep the passengers of the vehicle from suffering injuries, but are not developed to avoid an accident , as is the case of R2V communication technology. In seeking to solve this problem, by warning the driver even before the accident occurs, many technologies are currently on trial for automakers. This work presents design methodologies and simulations that represent a qualitative way of detecting the difficulties involved in a project vehicle tracking by using the technologies of GPS / GSM, studying the development and optimization of a GPS antenna (critical point) to the effect experienced by the antenna metal parts of the vehicle when the antenna is located inside the vehicle (instrument panel), taking as basis the roof of the vehicle (ideal point) to the solution and the basis for comparison of the solution / Mestrado / Eletrônica / Mestre em Engenharia Automobilistica

The localization of wireless devices, e.g. mobile phones, laptops, and handheld GPS receivers, has gained much interest due to the benefits it provides, including quicker emergency personnel dispatch, location-aided routing, as well as commercial revenue opportunities through location based services.  GPS is the dominant position location system in operation, with 31 operational satellites producing eight line of sight satellites available to users at all times making it very favorable for system implementation in all wireless networks.  Unfortunately when a GPS receiver is in a challenging environment, such as an urban or indoor scenario, the signal quality often degrades causing poor accuracy in the position estimate or failure to localize altogether due to satellite availability. Our goal is to introduce a new solution that has the ability to overcome this limitation by improving the accuracy and availability of a GPS receiver when in a challenging environment.  To test this theory we created a simulated GPS receiver using a MATLAB simulation to mimic a standard GPS receiver with all 31 operational satellites.  Here we are able to alter the environment of the user and examine the errors that occur due to noise and limited satellite availability.  Then we introduce additional user(s) to the GPS solution with the knowledge (or estimate) of the distances between the users.  The new solutions use inter-receiver distances along with pseudoranges to cooperatively determine all receiver location estimates simultaneously, resulting in improvement in both the accuracy of the position estimate and availability. / Master of Science