Turbo Codes
Mostrando 1-12 de 17 artigos, teses e dissertações.
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1. Desempenho de codigo turbo quaternario em sistemas de multiplexação por divisão de frequencias ortogonais / Performance of quaternary turbo codes in orthogonal frequency division multiplex systems
This study evaluates the performance of quaternary turbo codes, with generator matrix G = [7, 5] for the constituent convolutional codes and s-random interleaving , in an OFDM transmission system. This performance is measured in terms of bit error rate versus energy per bit to unilateral noise power spectral density ratio. The results obtained are analyzed c
Publicado em: 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. Estimação de canais MIMO variantes no tempo usando filtros de Kalman / Time-varying MIMO channel estimation using Kalman filters
In this work we use Kalman filters to estimate time-varying wireless channels in multiple-input, multiple-output (MIMO) systems. First, we propose an optimal estimator (in the minimum mean squared error sense) to track flat channels in orthogonal space-time block coded systems. Due to the orthogonality inherent to these codes, the Kalman filter equations can
Publicado em: 2009
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4. Evaluation of the spread sequences selection algorithm over frequency selective fading channels with error correcting codes / Avaliação do algoritmo de busca de sequencias de espalhamento em canais com desvanecimento seletivo em frequencia com codigos corretores de erros
The performance of wireless communication systems that use the multiple access code division technique, CDMA, is interference-limited. A sequence selection algorithm allows a reduction in the mean interference of the system. In the standards like CDMA2000 and WCDMA no algorithm is defined for choosing the sequences. For this reason, in this dissertation we e
Publicado em: 2008
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5. Iterative decoding of q-ary turbo-product codes in FFH-CDMA systems / Decodificação iterativa de codigos turbo-produto q-arios em um Canal FFH-CDMA
This work presents a study of q-ary turbo decoding applied to FFH-CDMA systems. To attain the main objective of this dissertation, an algorithm to implement the q-ary soft decoding was designed. Specifically, an adaptation of the Chase decoding method was proposed to comply with q-ary symbols requirements. The proposal of iterative (turbo) decoding makes pos
Publicado em: 2007
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6. Hybrid multilievel turbo codes / Codigos turbo hibridos multiniveis
Neste trabalho apresentamos classes de códigos turbo não binários definidos sobre os campos e anéis de inteiros. Os códigos turbo multiníveis convencionais consistem em dois códigos componentes RSC M-ários, concatenados via um entrelaçador aleatório de N símbolos e com símbolos codificados transmitidos através da modulação M-PSK. Os códigos t
Publicado em: 2007
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7. Analise de desempenho de sistemas de TV digital moveis DVB-H e ISDB-T utilizando concatenação de codigos BCH e turbo codificadores / Performance analysis of mobile digital TV systems DVB-H and ISDB-t by the use of BCH and turbo codes concatenation
The aim of this work is to study the performance of channel encoders with iterative decoder: and also different encoders concatenation schemes to mobile digital television standards ;; DVB-H and ISDB-T. The contribution of this work is a proposal of encoder concatenatic scheme for COFDM systems evaluated through software implementation. The final results I t
Publicado em: 2007
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8. New proposals for optmization of digital TV receivers based on OFDM in regional single frequency network environments / Novas propostas para otimização de receptores de TV digital baseados em OFDM em ambientes de redes de frequencia unica regionais
This thesis deals with the optimization of Digital TV receivers based on OFDM, with performance evaluation in regional single frequency networks (SFN). Such environment facilitates the channel distribution, however its characteristics degrade the receiver operation. Initially, projects of loop canceller filters in relay stations are treated, and they are nec
Publicado em: 2007
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9. ANÁLISE DE DESEMPENHO DE CÓDIGOS TURBO / PERFORMANCE ANALYSIS OF TURBO CODES
Códigos turbo são uma técnica de correção de erro eficiente que vem sendo proposta em diversos padrões de comunicações atuais. Esta técnica apresenta um desempenho que se aproxima dos limites teóricos estabelecidos na Teoria de Codificação. A razão para o excelente desempenho deste tipo de código baseia-se em dois fatores: uma estrutura de codi
Publicado em: 2006
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10. Projeto de EntrelaÃadores para cÃdigos turbo
Interleavers perform a central role in the near channel capacity performance of turbo codes. Besides been introduced as simple random permutations, nowadays there are several classes of interleavers like s-random, DRP, polynomial, and quasi-cyclic that provide a better performance for turbo codes in an AWGN channel and/or are simpler to store. This work has
Publicado em: 2006
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11. Distributed coding turbo codes and second generation wavelets / Codificação distribuida de video digital utilizando codigos turbo e Waveletes de segunda geração
Distributed video coding is a new paradigm for video compression in opposition over the existing video coding standards like MPEG-x and H.26x families. These codecs make use of motion estimation algorithms, the main part of the compression process of the video signal. Hence, the compression process demands a high computational cost and high performance of th
Publicado em: 2006
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12. INFLUÊNCIA DA CODIFICAÇÃO EM MARCAS D ÁGUA DIGITAIS / CODING INFLUENCE ON DIGITAL WATERMARKING
Esta tese pode ser segmentada em duas partes distintas, porém complementares. A primeira parte trata do problema que tange ao desenvolvimento da maioria dos sistemas de marcação d água digital: a necessidade de primeiramente selecionar a técnica de modulação não codificada que fará parte de uma arquitetura codificada. Assim, para proceder adequada s
Publicado em: 2006