Wireless Communications Systems
Mostrando 13-24 de 29 artigos, teses e dissertações.
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13. MÃtodos estatÃsticos multi-percursos para a identificaÃÃo cega de canais da fonte de aplicaÃÃes Ãs comunicaÃÃes sem fio / High-order statistical methods for blind channel identification and source detection with applications to wireless communications
Les systÃmes de tÃlÃcommunications modernes exigent des dÃbits de transmission trÃs ÃlevÃs. Dans ce cadre, le problÃme dâidentification de canaux est un enjeu majeur. Lâutilisation de techniques aveugles est dâun grand intÃrÃt pour avoir le meilleur compromis entre un taux binaire adÃquat et la qualità de lâinformation rÃcupÃrÃe. En utilis
Publicado em: 2008
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14. Aplicações de antenas adaptativas em sistemas de comunicações móveis / Applications of adaptive antennas in wireless communications systems
The increasing demand for wireless communications services has demanded the development of technologies that allow serving a bigger amount of users without increasing the bandwidth used today. It also has an increasing demand for services that need high transmission rates on mobile terminal, as Internet and video transfer. On the other hand, the user desires
Publicado em: 2007
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15. Análise neurocomputacional de Antenas de microfita multibanda para sistemas de comunicação sem fio
This work presents a study of implementation procedures for multiband microstrip patch antennas characterization, using on wireless communication systems. An artificial neural network multilayer perceptron is used to locate the bands of operational frequencies of the antenna for different geometrics configurations. The antenna is projected, simulated and tes
Publicado em: 2007
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16. EQUALIZAÇÃO DE CANAL EM SISTEMAS COM TRANSMISSÃO EM BLOCOS / CHANNEL EQUALIZATION IN BLOCK TRANSMISSION SYSTEMS
The demand for high rate transmission systems, for example in HDTV, third and fourth generation cellular telephony, DSL and so on, causes the rise of a problem: The multipath communications channel (specially in wireless communications), which leads to intersymbol interference phenomenon (ISI). The present work investigates the performance of single-carrier
Publicado em: 2007
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17. Modelagem tensorial e processamento de sinais por sistemas de comunicaÃÃes de redes / Tensor modeling and signal processing for wireless communication systems
In several signal processing applications for wireless communications, the received signal is multidimensional in nature and may exhibit a multilinear algebraic structure. In this context, the PARAFAC tensor decomposition has been the subject of several works in the past six years. However, generalized tensor decompositions are necessary for covering a wider
Publicado em: 2007
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18. Development of wideband bandpass filter with zeros transmition for ultrawideband communication systems / Desenvolvimento de filtro passa-faixa banda larga com zeros de transmissão para sistemas de comunicação Ultra-Wideband (UWB)
The quick development of wireless communications has introduced new requirements for communications systems being the use of more selective microwave filters. Different filter structures have been developed for applications in UWB systems (Ultra WideBand). It is presented in [1, 2] the highly selective microstrip bandpass filter. In this work, a bandpass fil
Publicado em: 2007
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19. Avaliação de desempenho de radios cognitivos e proposta de estrutura de equalização temporal em sistemas OFDM / Performance assessment of cognitive radio and a proposal for time equalization of OFDM systems
A presente dissertação apresenta um estudo da tecnologia dos rádios cognitivos bem como uma avaliação dos possíveis ganhos desta promissora técnica em relação aos atuais meios de acesso ao espectro eletromagnético. Numa segunda frente de trabalho, tratamos do problema de equalização cega no contexto de canais SIMO, com uma única entrada e múlti
Publicado em: 2007
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20. AD* :algoritmo de roteamento em redes de sensores baseado em inteligência artificial distribuída
The technological innovations introduced by the progress in the micro-electronics systems and the wireless communications provided the Wireless Sensor Networks (WSN), a wide variety of commercial and military applications. Those WSN possess of dozens to thousands of sensor-node subjects the fail with connection wireless and limited resources (e.g. energy, pr
Publicado em: 2007
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21. Methodology for calculation of spectrum requirements estimation for the future development of cell mobile system / Metodologia de cálculo de espectro para suportar a evolução do sistema móvel celular
This work presents a methodology for calculation of spectrum requirement estimation for future development of 3G and beyond-3G systems based on ITU-R recommendations. It presents a systematic approach that incorporates service category definitions, service environments, radio environments, market data analysis and traffic estimation for these categories and
Publicado em: 2007
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22. PLANEJAMENTO DE SISTEMAS FIXOS PARA ACESSO SEM FIO EM FAIXA LARGA OPERANDO EM AMBIENTES ABERTOS EM FREQÜÊNCIAS ENTRE 10 E 66 GHZ / PLANNING OF OUTDOOR BROADBAND FIXED WIRELESS ACCESS SYSTEMS OPERATING AT 10-66 GHZ BAND
The development of outdoor fixed broadband wireless access (BWA) systems operating at 10-66 GHz frequency requires a carefully planning in order to maximizing the use of the bandwidth, maximizing network capacity, assuring minimum requirements of availability and minimizing costs in an environment and in a frequency band where the propagation of electromagne
Publicado em: 2006
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23. Síntese de Filtros de Microondas Compactos com Respostas Elípticas e Pseudoelípticas utilizando a Variável Transformada Z / Synthesis of Compact Microwave Filters with Elliptic and Pseudo-elliptic Response using the Transformed variable Z
This research work develops new analysis techniques and synthesis for the conception of microwaves filters with elliptic or pseudo-elliptic frequency response. The application of these high frequency filters is in the current systems of wireless communications. The fast development of these systems presents challenges, in filters design, such as, considering
Publicado em: 2006
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24. Receptores MIMO baseados em algoritmo de decomposiÃÃo PARAFAC / MIMO receptors based on PARAFAC decomposition algorithm
This work deals with the application of multi-way analysis to the context of signal processing for wireless communications. A tensor decomposition known as PARAFAC (PARAllel FACtors) is considered in the design of multiple-input multiple-output (MIMO) receiver for a wireless communication system with Spread Spectrum codes. We propose two supervised PARAFAC-b
Publicado em: 2005