Página 1 dos resultados de 404 itens digitais encontrados em 0.052 segundos

‣ Propostas e analise de estrategias de controle de erros para redes de sensores sem fio; Proposals and analysis of error control strategies for wireless sensor networks

João Henrique Kleinschmidt
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 14/11/2008 Português
Relevância na Pesquisa
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‣ Modelo de sistema de comunicações digital para o mecanismo de importação de proteinas mitocondriais atraves de codigos corretores de erros; Digital communication system model for mitochondrial protein import by use of error-correcting codes

Andrea Santos Leite da Rocha
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/02/2010 Português
Relevância na Pesquisa
100.42464%
Um dos desafios em biologia matemática e mostrar a existência de qualquer forma de códigos corretores de erros na estrutura do DNA. Usando os conceitos da teoria de comunicação, propomos um modelo para o sistema de codificacao e decodificaçao do mecanismo de importaçao de proteínas mitocondriais similar a um sistema de comunicacoes digital. Este modelo consiste de um mapeador responsável por transformar os nucleotídeos (A, C, G, T) no alfabeto (0,1, 2, 3) usado pelo codigo sobre a estrutura de anel; um codificador (cádigo BCH); e um modulador (codigo genetico, tRNA e rRNA). O processo de decodificaçao baseia-se em uma analogia entre o processo de decodificacão do algoritmo Berlekamp-Massey para aneis e o complexo TOM (complexo ancorado na membrana externa da mitocondria responsavel por auxiliar na importacçãao das proteínas precursoras). Neste processo temos um demodulador (proteínas Tom 70 e Tom20), um decodificador (o complexo GIP - poro geral de inserção) e o receptor (subcompartimento mitocondrial). Neste trabalho mostramos que as sequencias de DNA (sequencias de direcionamento) são identificadas como palavras-codigo de um código G-linear sobre a extensão de um anel de Galois. Além disso, essas sequências de DNA e suas fitas complementares estão relacionadas matematicamente através dos polinómios primitivos e seus polinómios recíprocos...

‣ Novos limitantes para a probabilidade de erro de decodificação em canais com apagamento; New bounds on the decoding error probability over erasure channels

Leandro Cruvinel Lemes
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/09/2013 Português
Relevância na Pesquisa
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Considerando canais discretos, sem memória e com apagamento, obtemos limitantes superiores e inferiores para as probabilidades de erro de decodificação e de ocorrências de ambiguidade de códigos corretores de erro lineares. Os limitantes dependem da hierarquia de pesos e dos espectros generalizados e melhoram os limitantes conhecidos. Encontramos expressões exatas para essas probabilidades nos casos em que o código é AMDS ou MDS.; Considering an erasure channel, we improve upper and lower bounds for error decoding and ambiguity probabilities of linear error-correcting codes. The given bounds depend on the generalized weight hierarchy and spectrum of a code. We find explicit formulae in the case of AMDS and MDS codes.

‣ Códigos de subespaço geometricamente uniformes; Geometrically Uniform Subspace Codes

Gabriella Akemi Miyamoto
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/03/2015 Português
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Codificação de rede (do inglês Network coding) é uma área de pesquisa muito ativa e tem como elementos motivadores a transmissão eficiente e confiável da informação em redes tradicionais de comunicações. Além dessas características, codificação de rede tem uma relação muito forte com códigos corretores de erros, porém sob uma nova interpretação, qual seja, "a palavra-código" em um código corretor de erros é substituída por um "subespaço" de um determinado espaço vetorial e o código corretor de erros é substituído por uma união de subespaços de tal forma que estes subespaços formam o código de subespaço. Os códigos de subespaço são os códigos a serem utilizados em codificação de rede para alcançar os objetivos mencionados anteriormente. Dentre as classes de códigos corretores de erros, a classe dos códigos geometricamente uniformes é a mais importante tanto sob o ponto de vista de facilidade de geração e de decodificação quanto para atingir os objetivos mencionados. Neste trabalho, apresenta-se os conceitos de códigos geometricamente uniformes e de códigos de subespaço. Como contribuição, iniciamos uma investigação sobre os Códigos de Subespaço Geometricamente Uniformes, ou seja...

‣ Códigos, reticulados e aplicações em criptografia; Codes, lattices and applications in cryptography

Maiara Francine Bollauf
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/03/2015 Português
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‣ Low-density parity-check codes : construction and implementation.

Malema, Gabofetswe Alafang
Tipo: Tese de Doutorado
Publicado em //2007 Português
Relevância na Pesquisa
90.85022%
Low-density parity-check (LDPC) codes have been shown to have good error correcting performance approaching Shannon’s limit. Good error correcting performance enables efficient and reliable communication. However, a LDPC code decoding algorithm needs to be executed efficiently to meet cost, time, power and bandwidth requirements of target applications. The constructed codes should also meet error rate performance requirements of those applications. Since their rediscovery, there has been much research work on LDPC code construction and implementation. LDPC codes can be designed over a wide space with parameters such as girth, rate and length. There is no unique method of constructing LDPC codes. Existing construction methods are limited in some way in producing good error correcting performing and easily implementable codes for a given rate and length. There is a need to develop methods of constructing codes over a wide range of rates and lengths with good performance and ease of hardware implementability. LDPC code hardware design and implementation depend on the structure of target LDPC code and is also as varied as LDPC matrix designs and constructions. There are several factors to be considered including decoding algorithm computations...

‣ Análise de desgaste de técnicas de correção de erros em phase-change memories; Analysis of wear-out of error correction techniques in phase-change memories

Caio Hoffman
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/07/2013 Português
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‣ Error Correcting Codes on Algebraic Surfaces

Lomont, Chris
Tipo: Artigo de Revista Científica
Publicado em 06/09/2003 Português
Relevância na Pesquisa
90.50979%
Error correcting codes are defined and important parameters for a code are explained. Parameters of new codes constructed on algebraic surfaces are studied. In particular, codes resulting from blowing up points in $\proj^2$ are briefly studied, then codes resulting from ruled surfaces are covered. Codes resulting from ruled surfaces over curves of genus 0 are completely analyzed, and some codes are discovered that are better than direct product Reed Solomon codes of similar length. Ruled surfaces over genus 1 curves are also studied, but not all classes are completely analyzed. However, in this case a family of codes are found that are comparable in performance to the direct product code of a Reed Solomon code and a Goppa code. Some further work is done on surfaces from higher genus curves, but there remains much work to be done in this direction to understand fully the resulting codes. Codes resulting from blowing points on surfaces are also studied, obtaining necessary parameters for constructing infinite families of such codes. Also included is a paper giving explicit formulas for curves with more \field{q}-rational points than were previously known for certain combinations of field size and genus. Some upper bounds are now known to be optimal from these examples.; Comment: This is Chris Lomont's PhD thesis about error correcting codes from algebriac surfaces

‣ The Perfect Binary One-Error-Correcting Codes of Length 15: Part I--Classification

Östergård, Patric R. J.; Pottonen, Olli
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
90.28842%
A complete classification of the perfect binary one-error-correcting codes of length 15 as well as their extensions of length 16 is presented. There are 5983 such inequivalent perfect codes and 2165 extended perfect codes. Efficient generation of these codes relies on the recent classification of Steiner quadruple systems of order 16. Utilizing a result of Blackmore, the optimal binary one-error-correcting codes of length 14 and the (15, 1024, 4) codes are also classified; there are 38408 and 5983 such codes, respectively.; Comment: 6 pages. v3: made the codes available in the source of this paper

‣ On Optimal Binary One-Error-Correcting Codes of Lengths $2^m-4$ and $2^m-3$

Krotov, Denis S.; Östergård, Patric R. J.; Pottonen, Olli
Tipo: Artigo de Revista Científica
Publicado em 20/04/2011 Português
Relevância na Pesquisa
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Best and Brouwer [Discrete Math. 17 (1977), 235-245] proved that triply-shortened and doubly-shortened binary Hamming codes (which have length $2^m-4$ and $2^m-3$, respectively) are optimal. Properties of such codes are here studied, determining among other things parameters of certain subcodes. A utilization of these properties makes a computer-aided classification of the optimal binary one-error-correcting codes of lengths 12 and 13 possible; there are 237610 and 117823 such codes, respectively (with 27375 and 17513 inequivalent extensions). This completes the classification of optimal binary one-error-correcting codes for all lengths up to 15. Some properties of the classified codes are further investigated. Finally, it is proved that for any $m \geq 4$, there are optimal binary one-error-correcting codes of length $2^m-4$ and $2^m-3$ that cannot be lengthened to perfect codes of length $2^m-1$.; Comment: Accepted for publication in IEEE Transactions on Information Theory. Data available at http://www.iki.fi/opottone/codes

‣ Error-Correcting Codes in Projective Spaces via Rank-Metric Codes and Ferrers Diagrams

Etzion, Tuvi; Silberstein, Natalia
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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Coding in the projective space has received recently a lot of attention due to its application in network coding. Reduced row echelon form of the linear subspaces and Ferrers diagram can play a key role for solving coding problems in the projective space. In this paper we propose a method to design error-correcting codes in the projective space. We use a multilevel approach to design our codes. First, we select a constant weight code. Each codeword defines a skeleton of a basis for a subspace in reduced row echelon form. This skeleton contains a Ferrers diagram on which we design a rank-metric code. Each such rank-metric code is lifted to a constant dimension code. The union of these codes is our final constant dimension code. In particular the codes constructed recently by Koetter and Kschischang are a subset of our codes. The rank-metric codes used for this construction form a new class of rank-metric codes. We present a decoding algorithm to the constructed codes in the projective space. The efficiency of the decoding depends on the efficiency of the decoding for the constant weight codes and the rank-metric codes. Finally, we use puncturing on our final constant dimension codes to obtain large codes in the projective space which are not constant dimension.; Comment: Revised for IEEE Transactions on Information Theory

‣ The Perfect Binary One-Error-Correcting Codes of Length 15: Part II--Properties

Östergård, Patric R. J.; Pottonen, Olli; Phelps, Kevin T.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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A complete classification of the perfect binary one-error-correcting codes of length 15 as well as their extensions of length 16 was recently carried out in [P. R. J. \"Osterg{\aa}rd and O. Pottonen, "The perfect binary one-error-correcting codes of length 15: Part I--Classification," IEEE Trans. Inform. Theory vol. 55, pp. 4657--4660, 2009]. In the current accompanying work, the classified codes are studied in great detail, and their main properties are tabulated. The results include the fact that 33 of the 80 Steiner triple systems of order 15 occur in such codes. Further understanding is gained on full-rank codes via switching, as it turns out that all but two full-rank codes can be obtained through a series of such transformations from the Hamming code. Other topics studied include (non)systematic codes, embedded one-error-correcting codes, and defining sets of codes. A classification of certain mixed perfect codes is also obtained.; Comment: v2: fixed two errors (extension of nonsystematic codes, table of coordinates fixed by symmetries of codes), added and extended many other results

‣ Construction algorithm for network error-correcting codes attaining the Singleton bound

Matsumoto, Ryutaroh
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
90.649%
We give a centralized deterministic algorithm for constructing linear network error-correcting codes that attain the Singleton bound of network error-correcting codes. The proposed algorithm is based on the algorithm by Jaggi et al. We give estimates on the time complexity and the required symbol size of the proposed algorithm. We also estimate the probability of a random choice of local encoding vectors by all intermediate nodes giving a network error-correcting codes attaining the Singleton bound. We also clarify the relationship between the robust network coding and the network error-correcting codes with known locations of errors.; Comment: To appear in IEICE Trans. Fundamentals (http://ietfec.oxfordjournals.org/), vol. E90-A, no. 9, Sept. 2007. LaTeX2e, 7 pages, using ieice.cls and pstricks.sty. Version 4 adds randomized construction of network error-correcting codes, comparisons of the proposed methods to the existing methods, additional explanations in the proof

‣ Boolean Functions, Projection Operators and Quantum Error Correcting Codes

Aggarwal, Vaneet; Calderbank, A. Robert
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
90.65135%
This paper describes a fundamental correspondence between Boolean functions and projection operators in Hilbert space. The correspondence is widely applicable, and it is used in this paper to provide a common mathematical framework for the design of both additive and non-additive quantum error correcting codes. The new framework leads to the construction of a variety of codes including an infinite class of codes that extend the original ((5,6,2)) code found by Rains [21]. It also extends to operator quantum error correcting codes.; Comment: Submitted to IEEE Transactions on Information Theory, October 2006, to appear in IEEE Transactions on Information Theory, 2008

‣ A Matroidal Framework for Network-Error Correcting Codes

Prasad, K.; Rajan, B. Sundar
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
91.26644%
We abstract the essential aspects of network-error detecting and correcting codes to arrive at the definitions of matroidal error detecting networks and matroidal error correcting networks. An acyclic network (with arbitrary sink demands) is then shown to possess a scalar linear error detecting (correcting) network code if and only if it is a matroidal error detecting (correcting) network associated with a representable matroid. Therefore, constructing such network-error correcting and detecting codes implies the construction of certain representable matroids that satisfy some special conditions, and vice versa. We then present algorithms which enable the construction of matroidal error detecting and correcting networks with a specified capability of network-error correction. Using these construction algorithms, a large class of hitherto unknown scalar linearly solvable networks with multisource multicast and multiple-unicast network-error correcting codes is made available for theoretical use and practical implementation, with parameters such as number of information symbols, number of sinks, number of coding nodes, error correcting capability, etc. being arbitrary but for computing power (for the execution of the algorithms). The complexity of the construction of these networks is shown to be comparable to the complexity of existing algorithms that design multicast scalar linear network-error correcting codes. Finally we also show that linear network coding is not sufficient for the general network-error detection problem with arbitrary demands. In particular...

‣ Clifford Code Constructions of Operator Quantum Error Correcting Codes

Klappenecker, Andreas; Sarvepalli, Pradeep Kiran
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
90.60165%
Recently, operator quantum error-correcting codes have been proposed to unify and generalize decoherence free subspaces, noiseless subsystems, and quantum error-correcting codes. This note introduces a natural construction of such codes in terms of Clifford codes, an elegant generalization of stabilizer codes due to Knill. Character-theoretic methods are used to derive a simple method to construct operator quantum error-correcting codes from any classical additive code over a finite field.; Comment: 11 pages of character theory; minor changes, theorem 6 added

‣ Dense Error-Correcting Codes in the Lee Metric

Etzion, Tuvi; Vardy, Alexander; Yaakobi, Eitan
Tipo: Artigo de Revista Científica
Publicado em 02/04/2010 Português
Relevância na Pesquisa
90.49786%
Several new applications and a number of new mathematical techniques have increased the research on error-correcting codes in the Lee metric in the last decade. In this work we consider several coding problems and constructions of error-correcting codes in the Lee metric. First, we consider constructions of dense error-correcting codes in relatively small dimensions over small alphabets. The second problem we solve is construction of diametric perfect codes with minimum distance four. We will construct such codes over various lengths and alphabet sizes. The third problem is to transfer an n-dimensional Lee sphere with large radius into a shape, with the same volume, located in a relatively small box. Hadamard matrices play an essential role in the solutions for all three problems. A construction of codes based on Hadamard matrices will start our discussion. These codes approach the sphere packing bound for very high rate range and appear to be the best known codes over some sets of parameters.

‣ Systematic Error-Correcting Codes for Rank Modulation

Zhou, Hongchao; Schwartz, Moshe; Jiang, Anxiao; Bruck, Jehoshua
Tipo: Artigo de Revista Científica
Publicado em 25/10/2013 Português
Relevância na Pesquisa
91.0771%
The rank-modulation scheme has been recently proposed for efficiently storing data in nonvolatile memories. Error-correcting codes are essential for rank modulation, however, existing results have been limited. In this work we explore a new approach, \emph{systematic error-correcting codes for rank modulation}. Systematic codes have the benefits of enabling efficient information retrieval and potentially supporting more efficient encoding and decoding procedures. We study systematic codes for rank modulation under Kendall's $\tau$-metric as well as under the $\ell_\infty$-metric. In Kendall's $\tau$-metric we present $[k+2,k,3]$-systematic codes for correcting one error, which have optimal rates, unless systematic perfect codes exist. We also study the design of multi-error-correcting codes, and provide two explicit constructions, one resulting in $[n+1,k+1,2t+2]$ systematic codes with redundancy at most $2t+1$. We use non-constructive arguments to show the existence of $[n,k,n-k]$-systematic codes for general parameters. Furthermore, we prove that for rank modulation, systematic codes achieve the same capacity as general error-correcting codes. Finally, in the $\ell_\infty$-metric we construct two $[n,k,d]$ systematic multi-error-correcting codes...

‣ An introduction of the theory of nonlinear error-correcting codes

Nenno, Robert B.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
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Nonlinear error-correcting codes are the topic of this thesis. As a class of codes, it has been investigated far less than the class of linear error-correcting codes. While the latter have many practical advantages, it the former that contain the optimal error-correcting codes. In this project the theory (with illustrative examples) of currently known nonlinear codes is presented. Many definitions and theorems (often with their proofs) are presented thus providing the reader with the opportunity to experience the necessary level of mathematical rigor for good understanding of the subject. Also, the examples will give the reader the additional benefit of seeing how the theory can be put to use. An introduction to a technique for finding new codes via computer search is presented.

‣ Soft error propagation in floating-point programs

Li, Sha
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
99.87171%
Li, Xiaoming; As technology scales, VLSI performance has experienced an exponential growth. As feature sizes shrink, however, we will face new challenges such as soft errors (singleevent upsets) to maintain the reliability of circuits. Recent studies have tried to address soft errors with error detection and correction techniques such as error-correcting codes or redundant execution. However, these techniques come at a cost of additional storage or lower performance. We present a different approach to address soft errors. We start from building a quantitative understanding of the error propagation in software and propose a systematic evaluation of the impact of bit flip caused by soft errors on floating-point operations. Furthermore, we introduce a novel model to deal with soft errors. More specifically, we assume soft errors have occurred in memory and try to know how the errors will manifest in the results of programs. Therefore, some soft errors can be tolerated if the error in result is smaller than the intrinsic inaccuracy of floating-point representations or within a predefined range. We focus on analyzing error propagation for floating-point arithmetic operations. Our approach is motivated by interval analysis. We model the rounding effect of floating-point numbers...