Convolutional Codes
Mostrando 1-12 de 16 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. Uma proposta de um sistema criptografico de chave publica utilizando codigos convolucionais classicos e quanticos / A proposal of a cryptographic system of public key using classical and quantum convolutional codes
The proposal of a cryptographic system of public key that uses classical and quantum convolutional codes of unit-memory presented in this work, is based on the use of trapdoors functions which when applied to submatrices reduce the capacity of correction of errors of the code. This process gives us an increase in the degree of privacy of information being se
Publicado em: 2008
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3. 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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4. Quantum block codes with unequal error protection / CÃdigos de bloco quÃnticos com proteÃÃo desigual de erros
Quantum error correction codes have been developed to enhance the reliability of the quantum hardware. The majority of the known quantum codes belong to the class of block codes, while quantum convolutional codes have been recently proposed. The class of unequal error protection (UEP) codes, well known in the theory of classical codes, has not been studied i
Publicado em: 2008
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5. m estudo sobre o uso da codificação de canal para otimização do consumo de energia em redes de sensores
Wireless Sensor Networks (WSN) are a set of tiny electronic devices, which monitor physical phenomena over a specific region and send this data to a sink node. The sensor nodes connect to the other ones in the range of the transmitted signal, establishing a collaborative network operation. The collected data are forwarded to other nodes until the sink is rea
Publicado em: 2007
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6. Codificadores bit-geometricamente uniformes para sistemas com concatenação serial / Bit-geometrically uniform encoders for serially concatenated systems
This thesis approaches the problem of building bit-geometrically uniform (BGU) encoders to be used as inner encoders in systems with serially concatenated codes. By using this type of encoders, certain parameters that are used to analyze the system s performance are easily determined. There is a great control over these parameters when building encoders usin
Publicado em: 2006
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7. CodificaÃÃo iterativa para o canal adtivo com dois usuÃrios binÃrios
This thesis is concerned with an investigation of iterative coding schemes for the two-user binary adder channel (2-BAC). A coding scheme is introduced for the 2-BAC using a single convolutional code which permits efficient decoding. The constructed two-user trellis codes have a significant practical advantage because iterative decoding techniques used in th
Publicado em: 2005
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8. Codigos convolucionais quanticos concatenados
Decoherence is one of the major challenges facing the field of quantum computation. The field of quantum error correction has developed to meet this challenge. A group-theoretical structure and associated class of quantum codes, the stabilizer codes, has proved particularly fruitful in producing codes and in understanding the structure of both specified code
Publicado em: 2004
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9. OPTIMUM GROUP MULTIUSER DETECTION IN DS/CDMA M-PSK SYSTEMS WITH CONVOLUTIONAL CODING / DETECÇÃO MULTIUSUÁRIO ÓTIMA POR GRUPOS EM SISTEMAS DS/CDMA M-PSK COM CODIFICAÇÃO CONVOLUCIONAL
Este trabalho propõe um receptor multiusuário híbrido para utilização em um sistema DS/CDMA com modulação M-PSK e codificação convolucional. O receptor proposto é composto por um receptor decorrelator ao final do qual é realizada uma decodificação convolucional por grupos. Resultados de desempenho obtidos por simulações para grupos de dois usu
Publicado em: 2004
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10. EVUATION OF TCP PERFORMANCE IN SATELLITE TRANSMISSION IN PRESENCE OF BURST ERRORS IN THE CHANNEL / AVALIAÇÃO DE DESEMPENHO DO PROTOCOLO TCP NA TRANSMISSÃO VIA SATÉLITE EM PRESENÇA DE ERROS NO CANAL
Este trabalho é um estudo sobre o desempenho das principais versões do protocolo TCP e de sua variação denominada STP na transmissão via satélite. Devido à grande distância da terra aos satélites geoestacionários, a transmissão via satélite se caracteriza por um grande atraso de propagação e maior ocorrência de erros em comparação com a tran
Publicado em: 2003
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11. Estudo da viabilidade da utilização de codigo de Reed Solomon na codificação de canal movel TDMA
This study aims to investigate the use of Reed-Solomon codes in the channel coding of the TDMA IS-136 system. Block codes seem to be more suitable to the time slot structure of the TDMA frame. Moreover, the choice of a Reed-Solomon code was based on the best capability and the minimization of the redundant bits introduced by the actual convolutional encoding
Publicado em: 2002
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12. Codigos de linha a partir de codigos corretores de erro concatenados
This work deals with the construction of line codes based on concatenated binary error control codes, which are a combination of outer Reed-Solomon codes with inner codes that possess good properties of line coding. The inner codes were obtained by modification of known error correcting codes (block and convolutional) in which the number of consecutive like-
Publicado em: 2001