Coded Modulation
Mostrando 1-12 de 20 artigos, teses e dissertações.
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1. Sistema e processo para geração, sincronização remota e comparação de sinais temporais precisos / System and process for the generation, remote synchronization and comparison of precise time signals
This thesis present new proposals for time dissemination systems, which were analyzed and implemented as complete solutions providing high resolution in radio links focusing in the requirements of the new geolocation system known as GEOLOCAL. The solutions found are useful for other applications equiring time synchronization. The work has been developed in d
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 05/07/2010
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2. Enumeração de espectro de distâncias de esquemas de modulação codificada em treliça empregando codificação turbo
In this work, a performance analysis of transmission schemes employing turbo trellis coded modulation. In general, the performance analysis of such schemes is guided by evaluating the error probability of these schemes. The exact evaluation of this probability is very complex and inefficient from the computational point of view, a widely used alternative is
Publicado em: 2010
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3. Modulação quantizada para sistemas com codificação wavelet sujeitos ao desvanecimento rayleigh
Wavelet coding is an efficient technique to overcome the multipath fading effects, which are characterized by fluctuations in the intensity of the transmitted signals over wireless channels. Since the wavelet symbols are non-equiprobable, modulation schemes play a significant role in the overall performance of wavelet systems. Thus the development of an effi
Publicado em: 2009
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4. Contributions to the search methods of optimum trellis codes on new lattices partitioning / Contribuições aos metodos de procura dos codigos de treliça otimos sobre novas partições de reticulados
This thesis presents some contributions to the coded modulation schemes for the trellis codes based on lattices partitioning. One of the main contributions is the construction of the trellis codes based on novel lattices partitioning and also on chains partitioning. In order to optimize the search for the optimum trellis codes, a search algorithm was propose
Publicado em: 2008
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5. In vitro modulation of alkaline phosphatase activity of Saccharomyces cerevisiae grown in low or high phosphate medium
Our objective was to characterize the modulation of the activity of Saccharomyces cerevisiae alkaline phosphatases (ALPs) by classic inhibitors of ALP activity, cholesterol and steroid hormones, in order to identify catalytic similarities between yeast and mammalian ALPs. S. cerevisiae expresses two ALPs, coded for by the PHO8 and PHO13 genes. The product of
Brazilian Journal of Medical and Biological Research. Publicado em: 17/12/2007
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6. Modulação Codificada por Blocos de Baixa Complexidade com Códigos de Comprimentos Diferentes / Low complexity block coded modulation with different length codes
O objetivo desta dissertação é apresentar esquemas de modulação codificada por blocos onde são empregados códigos corretores de erros com comprimentos diferentes para diferentes níveis de codificação. Este proposta é uma solução de compromisso para a obtenção de bons ganhos de codificação sem que a taxa de codificação implique em expansão
Publicado em: 2006
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7. ESQUEMAS DE MODULAÇÃO PARA DISTRIBUIÇÃO QUÂNTICA DE CHAVES COM CODIFICAÇÃO DE FREQÜÊNCIA / MODULATION SCHEMES FOR FREQUENCY CODED QUANTUM KEY DISTRIBUTION
Quantum cryptography has been proposed as a solution to the cryptographic key distribution problem with absolute security guaranteed by the principles of quantum mechanics. Through this scheme it is possible to find out whether a spy tried to eavesdrop on the transmission, which was impossible to discover using classical transmission techniques. In this work
Publicado em: 2005
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8. Modulação Multiportadora M-QAM Não-Quadrada Codificada por Blocos para Canais com Modelo de Rummler
Um dos principais fatores que provocam a degradação da qualidade dos sistemas digitais de longo alcance em linha de visada com taxas de transmissão na ordem de algumas dezenas de Mb/s, são os desvanecimentos seletivos em freqüência. Uma das alternativas para diminuir o efeito provocado pelos desvanecimentos seletivos em freqüência é a utilização d
Publicado em: 2004
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9. Modulação multiportadora codificada por bloco para radioenlaces digitais em microondas com linha de visada
The availability of line-of-sight (LOS) microwave digital systems which work at high transmission rates such as 155 Mb/s, may be strongly limited by frequency-selective fading effects. The main countermeasure techniques against the fading are equalizations, diversity and error control coding. Under adverse geoclimatic conditions, the path length and/or the t
Publicado em: 2002
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10. Utilização conjunta de equalização adaptativa e codigos corretores de erro em processamento espacial e temporal
This work deals with the joint use of adaptive equalization and forward error correction codes. Firstly, we show some representative techniques of joint adaptive equalization and error correction codes. Secondly, we analyze through simulations and error surfaces the blind convergence of a linear transversal filter adapted by the least mean square (LMS) algor
Publicado em: 2001
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11. Codigos treliça baseados em partições de reticulados : propriedades estruturais e determinação de codigos otimos
Inserted in the mathematical theory of the error correcting codes and, in particular, for coded modulation schemes using trellis codes based on lattices partitions, this thesis introduces the new concepts of special subsets and the norm-matrix GN, with the objective of proposing an efficient algorithm for the exhaustive search, and determination, of new opti
Publicado em: 1999
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12. Decodificação multiestagio de esquemas de modulação multidimensional codificada
In this dissertation, the decoding of block coded modulation schemes is considered. Multidimensional signal constellations are studied instead of traditional schemes that use two-dimensional signal constellations. This investigation is restricted to the use of PSK based schemes, because this kind of schemes are more appropriate for certain communication chan
Publicado em: 1998