Página 1 dos resultados de 6310 itens digitais encontrados em 0.039 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
Relevância na Pesquisa
57.138516%

## Avaliação de desempenho de esquemas de modulação e codificação na presença de interferência de co-canal; Performance evaluation of modulation and coding schemes in the presence of co-channel interference

Carlos Daniel Altamirano Carrillo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
47.03443%
Este trabalho avalia os efeitos da interferência de co-canal na taxa de erro de bits (BER) de sistemas de transmissão digitais sem fio. O ambiente do sistema considera canais com ruído gaussiano (AWGN) e canais com desvanecimento Rayleigh na presença de um interferente de co-canal dominante, onde os usuários empregam esquemas de modulação BPSK e M-QAM e também códigos corretores de erros. Os códigos corretores de erros utilizados em sistemas com expansão de banda são os códigos convolucional e turbo, e em sistemas sem expansão de banda são a modulação-codificada por treliça (TCM) e a modulação-codificada turbo (TTCM). Os efeitos da interferência de co-canal na taxa de erro de bit serão avaliados derivando-se expressões teóricas e mediante a simulação de Monte Carlo, variando o tipo de canal e os esquemas de modulação e codificação. Este trabalho mostra que a interferência de co-canal introduz patamares na taxa de erro de bit, que os sistemas sem expansão de banda são mais susceptíveis à interferência e que os códigos corretores de erro são uma boa ferramenta para mitigar os efeitos da interferência de co-canal; This work evaluates the effects of co-channel interference on the bit error rate (BER) of digital transmission systems. The transmission system considers gaussian noise channels (AWGN) and Rayleigh fading channels in the presence of a dominant co-channel interferer...

## Error control variability in pathway-based microarray analysis

Gold, David L.; Miecznikowski, Jeffrey C.; Liu, Song
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.904243%
Motivation: The decision to commit some or many false positives in practice rests with the investigator. Unfortunately, not all error control procedures perform the same. Our problem is to choose an error control procedure to determine a P-value threshold for identifying differentially expressed pathways in high-throughput gene expression studies. Pathway analysis involves fewer tests than differential gene expression analysis, on the order of a few hundred. We discuss and compare methods for error control for pathway analysis with gene expression data.

## Straight to the Source: Detecting Aggregate Objects in Astronomical Images with Proper Error Control

Friedenberg, David A.; Genovese, Christopher R.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.938994%
The next generation of telescopes, coming on-line in the next decade, will acquire terabytes of image data each night. Collectively, these large images will contain billions of interesting objects, which astronomers call sources. One critical task for astronomers is to construct from the image data a detailed source catalog that gives the sky coordinates and other properties of all detected sources. The source catalog is the primary data product produced by most telescopes and serves as an important input for studies that build and test new astrophysical theories. To construct an accurate catalog, the sources must first be detected in the image. A variety of effective source detection algorithms exist in the astronomical literature, but few if any provide rigorous statistical control of error rates. A variety of multiple testing procedures exist in the statistical literature that can provide rigorous error control over pixelwise errors, but these do not provide control over errors at the level of sources, which is what astronomers need. In this paper, we propose a technique that is effective at source detection while providing rigorous control on source-wise error rates. We demonstrate our approach with data from the Chandra X-ray Observatory Satellite. Our method is competitive with existing astronomical methods...

## Crosstalk-aware multiple error control for reliable on-chip interconnects

Fu, Bo (1978 - ); Ampadu, Paul
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xix, 195 leaves
Português
Relevância na Pesquisa
67.069175%
Thesis (Ph. D.)--University of Rochester. Dept. of Electrical and Computer Engineering, 2010.; To achieve high speed, energy efficient and reliable on-chip communication, solutions that can simultaneously address multiple logic errors and crosstalk-induced delay uncertainty are needed. In this dissertation, we propose a method for combining Hamming product codes and type-II hybrid automatic repeat request (HARQ) with skewed transitions to address this critical issue. As technology scales, interconnects are becoming susceptible to multiple random and burst errors, requiring more powerful error control coding (ECC) techniques than those previously used. We propose the combination of Hamming product codes with type-II HARQ to provide a strong yet energy-efficient error control approach for onchip interconnects. We analyze the performance of the proposed method in terms of the required number of wires, codec delay and residual flit error rate. The proposed method is shown to achieve several orders of magnitude reduction in residual flit error rate compared to previous solutions when multiple random and burst errors are considered. Two design scenarios are investigated. For implementation with low link swing voltages, the combination of Hamming product codes with type-II HARQ are shown to meet the same reliability requirements as previous solutions while using a lower link swing voltage...

## Transient and permanent error management for networks-on-chip

Yu, Qiaoyan (1979 - ); Ampadu, Paul
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xviii, 251 leaves; Illustrations:ill. (some col.)
Português
Relevância na Pesquisa
57.37811%
Thesis (Ph. D.)--University of Rochester. Dept. of Electrical and Computer Engineering, 2011.; Reliability has become one of the most important metrics for on-chip communications infrastructures in nanoscale technologies. Reduced supply voltages and high clock frequency exacerbate the impact of noise sources such as particle strikes and crosstalk, which can cause transient errors in transmitted data. Manufacturing defects and aging issues can cause permanent errors in the communication links. The modularity of the Networks-on-Chip (NoCs) approach facilitates the exploration of error control techniques for on-chip interconnects and many-cores systems. Unfortunately, error control is not free. Worst-case error management methods are simple but waste energy and bandwidth in favorable noise conditions. Consequently, cost-effective techniques for improving link error resilience are needed. In this work, we propose configurable error control methods to tackle variable transient errors and exploit existing transient error control redundancy for permanent error management, achieving high reliability and low average energy consumption with minor area overhead. To adapt to the variable transient error rates, a configurable error control coding (ECC) scheme is proposed for datalink-layer transient error management. The proposed method can adjust both error detection and error correction capability at runtime by varying the number of redundant wires for parity check bits. The obtained error resilience makes the proposed method suitable for a range of link error rates. Configuring the number of redundant wires to match the noise conditions reduces the average energy consumption in the ECC codec and interconnect link. A hardware efficient implementation for the configurable ECC is presented...

## Error Control Coding for Multi-Frequency Modulation

Ives, Robert W.
Português
Relevância na Pesquisa
47.058955%
Approved for public release; distribution is unlimited.; Multi-frequency modulation (MFM) has been developed at NPS using both quadrature-phase-shift-keyed (QPSK) and quadrature-amplitude-modulated (QAM) signals with good bit error performance at reasonable signal-to-noise ratios. Improved performance can be achieved by the introduction of error control coding. This report documents a Fortran simulation of the implementation of error control coding into an MFM communication link with additive white Gaussian noise. Four Reed-Solomon codes were incorporated, two for 16-QAM and two for 32- QAM modulation schemes. The error control codes used were modified from the conventional Reed-Solomon codes in that one information symbol was sacrificed to parity in order to use a simplified decoding algorithm which requires no iteration and enhances error detection capability. Bit error rates as a function of SNR and EbN0 were analyzed, and bit error performance waa weighed against reduction in information rate to determine the value of the codes.

## Análisis energético del control y el error a sistemas linealizados implementando GPC y DMC; Energetic analysis of control and error to linealized systems implementing GPC and DMC

González T., Juan Pablo; Toro García, Nicolás
Tipo: Artigo de Revista Científica Formato: PDF
Português
Relevância na Pesquisa
47.092207%
En este articulo se muestran los resultados obtenidos al realizar un análisis comparativo de la energía de la señal de control y el error, al implementar dos de los algoritmos más representativos del control predictivo basado en modelos, como lo son el GPC (Control Predictivo Generalizado) y el DMC (Control de Matriz Dinámica) a dos tipos de sistemas diferentes: los tanques acoplados y el motor de corriente continua.

## Iterative Multiuser Detection and Error Control Code Decoding in Random CDMA

Shi, Zhenning; Schlegel, Christian
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.85295%
The combination of forward-error control (FEC) coding with code-division multiple access (CDMA) using random spreading sequences is considered. Such systems can be viewed as serially concatenated, and iterative (turbo) decoding principles can be applied.

## Block Network Error Control Codes and Syndrome-based Complete Maximum Likelihood Decoding

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
47.04358%
In this paper, network error control coding is studied for robust and efficient multicast in a directed acyclic network with imperfect links. The block network error control coding framework, BNEC, is presented and the capability of the scheme to correct a mixture of symbol errors and packet erasures and to detect symbol errors is studied. The idea of syndrome-based decoding and error detection is introduced for BNEC, which removes the effect of input data and hence decreases the complexity. Next, an efficient three-stage syndrome-based BNEC decoding scheme for network error correction is proposed, in which prior to finding the error values, the position of the edge errors are identified based on the error spaces at the receivers. In addition to bounded-distance decoding schemes for error correction up to the refined Singleton bound, a complete decoding scheme for BNEC is also introduced. Specifically, it is shown that using the proposed syndrome-based complete decoding, a network error correcting code with redundancy order d for receiver t, can correct d-1 random additive errors with a probability sufficiently close to 1, if the field size is sufficiently large. Also, a complete maximum likelihood decoding scheme for BNEC is proposed. As the probability of error in different network edges is not equal in general...

## Error Control of Iterative Linear Solvers for Integrated Groundwater Models

Dixon, Matthew; Bai, Zhaojun; Brush, Charles; Chung, Francis; Dogrul, Emin; Kadir, Tariq
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.960225%
An open problem that arises when using modern iterative linear solvers, such as the preconditioned conjugate gradient (PCG) method or Generalized Minimum RESidual method (GMRES) is how to choose the residual tolerance in the linear solver to be consistent with the tolerance on the solution error. This problem is especially acute for integrated groundwater models which are implicitly coupled to another model, such as surface water models, and resolve both multiple scales of flow and temporal interaction terms, giving rise to linear systems with variable scaling. This article uses the theory of 'forward error bound estimation' to show how rescaling the linear system affects the correspondence between the residual error in the preconditioned linear system and the solution error. Using examples of linear systems from models developed using the USGS GSFLOW package and the California State Department of Water Resources' Integrated Water Flow Model (IWFM), we observe that this error bound guides the choice of a practical measure for controlling the error in rescaled linear systems. It is found that forward error can be controlled in preconditioned GMRES by rescaling the linear system and normalizing the stopping tolerance. We implemented a preconditioned GMRES algorithm and benchmarked it against the Successive-Over-Relaxation (SOR) method. Improved error control reduces redundant iterations in the GMRES algorithm and results in overall simulation speedups as large as 7.7x. This research is expected to broadly impact groundwater modelers through the demonstration of a practical approach for setting the residual tolerance in line with the solution error tolerance.; Comment: 13 pages and 1 figure

## Global Error Control in the Runge-Kutta Solution of a Hamiltonian System using the RKQ Algorithm

Prentice, J. S. C.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.996387%
We study the effect of global error control in the numerical solution of Hamiltonian systems. In particular, we apply the RKQ algorithm in the numerical solution of a Hamiltonian system. This algorithm is designed to provide stepwise control of both local and global error. A test problem demonstrates the error control features of RKQ. Good results are obtained, despite the fact that explicit Runge-Kutta methods have been used in RKQ, rather than symplectic Runge-Kutta methods. This simply emphasizes the value of stepwise global error control, as per the RKQ algorithm.

## A Rank-Metric Approach to Error Control in Random Network Coding

Silva, Danilo; Kschischang, Frank R.; Kötter, Ralf
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.86844%
The problem of error control in random linear network coding is addressed from a matrix perspective that is closely related to the subspace perspective of K\"otter and Kschischang. A large class of constant-dimension subspace codes is investigated. It is shown that codes in this class can be easily constructed from rank-metric codes, while preserving their distance properties. Moreover, it is shown that minimum distance decoding of such subspace codes can be reformulated as a generalized decoding problem for rank-metric codes where partial information about the error is available. This partial information may be in the form of erasures (knowledge of an error location but not its value) and deviations (knowledge of an error value but not its location). Taking erasures and deviations into account (when they occur) strictly increases the error correction capability of a code: if $\mu$ erasures and $\delta$ deviations occur, then errors of rank $t$ can always be corrected provided that $2t \leq d - 1 + \mu + \delta$, where $d$ is the minimum rank distance of the code. For Gabidulin codes, an important family of maximum rank distance codes, an efficient decoding algorithm is proposed that can properly exploit erasures and deviations. In a network coding application where $n$ packets of length $M$ over $F_q$ are transmitted...

## Enhanced Algebraic Error Control for Random Linear Network Coding

Yan, Zhiyuan; Xie, Hongmei
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.91034%
Error control is significant to network coding, since when unchecked, errors greatly deteriorate the throughput gains of network coding and seriously undermine both reliability and security of data. Two families of codes, subspace and rank metric codes, have been used to provide error control for random linear network coding. In this paper, we enhance the error correction capability of these two families of codes by using a novel two-tier decoding scheme. While the decoding of subspace and rank metric codes serves a second-tier decoding, we propose to perform a first-tier decoding on the packet level by taking advantage of Hamming distance properties of subspace and rank metric codes. This packet-level decoding can also be implemented by intermediate nodes to reduce error propagation. To support the first-tier decoding, we also investigate Hamming distance properties of three important families of subspace and rank metric codes, Gabidulin codes, Kotter--Kschischang codes, and Mahdavifar--Vardy codes. Both the two-tier decoding scheme and the Hamming distance properties of these codes are novel to the best of our knowledge.

## Straight to the Source: Detecting Aggregate Objects in Astronomical Images with Proper Error Control

Friedenberg, David A.; Genovese, Christopher R.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.996387%
The next generation of telescopes will acquire terabytes of image data on a nightly basis. Collectively, these large images will contain billions of interesting objects, which astronomers call sources. The astronomers' task is to construct a catalog detailing the coordinates and other properties of the sources. The source catalog is the primary data product for most telescopes and is an important input for testing new astrophysical theories, but to construct the catalog one must first detect the sources. Existing algorithms for catalog creation are effective at detecting sources, but do not have rigorous statistical error control. At the same time, there are several multiple testing procedures that provide rigorous error control, but they are not designed to detect sources that are aggregated over several pixels. In this paper, we propose a technique that does both, by providing rigorous statistical error control on the aggregate objects themselves rather than the pixels. We demonstrate the effectiveness of this approach on data from the Chandra X-ray Observatory Satellite. Our technique effectively controls the rate of false sources, yet still detects almost all of the sources detected by procedures that do not have such rigorous error control and have the advantage of additional data in the form of follow up observations...

## Runge-Kutta Methods: Local error control does not imply global error control

Prentice, J. S. C.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.113423%
We study the relationship between local and global error in Runge-Kutta methods for initial-value problems in ordinary differential equations. We show that local error control by means of local extrapolation does not equate to global error control. Our analysis shows that the global error of the higher-order solution is propagated under iteration, and this can cause an uncontrolled increase in the global error of the lower-order solution. We find conditions under which global error control occurs during the initial stages of the RK integration, but even in such a case the global error is likely to eventually exceed the user-defined tolerance.; Comment: Corrections to some absolute values signs in Section 3.2

## The sequential rejection principle of familywise error control

Goeman, Jelle J.; Solari, Aldo
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.961636%
Closed testing and partitioning are recognized as fundamental principles of familywise error control. In this paper, we argue that sequential rejection can be considered equally fundamental as a general principle of multiple testing. We present a general sequentially rejective multiple testing procedure and show that many well-known familywise error controlling methods can be constructed as special cases of this procedure, among which are the procedures of Holm, Shaffer and Hochberg, parallel and serial gatekeeping procedures, modern procedures for multiple testing in graphs, resampling-based multiple testing procedures and even the closed testing and partitioning procedures themselves. We also give a general proof that sequentially rejective multiple testing procedures strongly control the familywise error if they fulfill simple criteria of monotonicity of the critical values and a limited form of weak familywise error control in each single step. The sequential rejection principle gives a novel theoretical perspective on many well-known multiple testing procedures, emphasizing the sequential aspect. Its main practical usefulness is for the development of multiple testing procedures for null hypotheses, possibly logically related...

## Rank Metric Decoder Architectures for Random Linear Network Coding with Error Control

Chen, Ning; Yan, Zhiyuan; Gadouleau, Maximilien; Wang, Ying; Suter, Bruce W.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.91034%
While random linear network coding is a powerful tool for disseminating information in communication networks, it is highly susceptible to errors caused by various sources. Due to error propagation, errors greatly deteriorate the throughput of network coding and seriously undermine both reliability and security of data. Hence error control for network coding is vital. Recently, constant-dimension codes (CDCs), especially K\"otter-Kschischang (KK) codes, have been proposed for error control in random linear network coding. KK codes can also be constructed from Gabidulin codes, an important class of rank metric codes. Rank metric decoders have been recently proposed for both Gabidulin and KK codes, but they have high computational complexities. Furthermore, it is not clear whether such decoders are feasible and suitable for hardware implementations. In this paper, we reduce the complexities of rank metric decoders and propose novel decoder architectures for both codes. The synthesis results of our decoder architectures for Gabidulin and KK codes with limited error-correcting capabilities over small fields show that our architectures not only are affordable, but also achieve high throughput.; Comment: 14 pages, 12 figures, accepted by IEEE Trans. VLSI Syst

## Joint Write-Once-Memory and Error-Control Codes

Ma, Xudong
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.904243%
Write-Once-Memory (WOM) is a model for many modern non-volatile memories, such as flash memories. Recently, several capacity-achieving WOM coding schemes have been proposed based on polar coding. Due to the fact that practical computer memory systems always contain noises, a nature question to ask next is how may we generalize these coding schemes, such that they may also have the error-control capabilities. In this paper, we discuss a joint WOM and error-control coding scheme, which is a generalization of the capacity-achieving WOM codes based on source polarization. In this paper, we prove a sufficient and necessary condition for the noisy reading channel being less noisy than the test channel in data encoding in the polar WOM coding. Such a sufficient and necessary condition is usually satisfied in reality. As a consequence of the sufficient and necessary condition, the high entropy set related to the noisy channel is usually strictly contained in the high entropy set related to the test channel in data encoding. Therefore the low-complexity polar joint WOM and error-control codes are sufficient for most practical coding scenarios.

## Security and BER performance trade-off in wireless communication systems applications

Arnone,L.; González,C.; Gayoso,C.; Castiñeira Moreira,J.; Liberatori,M.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html