In modern parallel storage systems (e. g., cloud storage and data centers), it is important to provide data availability guarantees against disk (or storage node) failures via redundancy coding schemes. One coding sch...
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In modern parallel storage systems (e. g., cloud storage and data centers), it is important to provide data availability guarantees against disk (or storage node) failures via redundancy coding schemes. One coding scheme is X-code, which is double-fault tolerant while achieving the optimal update complexity. When a disk/node fails, recovery must be carried out to reduce the possibility of data unavailability. We propose an X-code-based optimal recovery scheme called minimum-disk-read-recovery (MDRR), which minimizes the number of disk reads for single-disk failure recovery. We make several contributions. First, we show that MDRR provides optimal single-disk failure recovery and reduces about 25 percent of disk reads compared to the conventional recovery approach. Second, we prove that any optimal recovery scheme for X-code cannot balance disk reads among different disks within a single stripe in general cases. Third, we propose an efficient logical encoding scheme that issues balanced disk read in a group of stripes for any recovery algorithm (including the MDRR scheme). Finally, we implement our proposed recovery schemes and conduct extensive testbed experiments in a networked storage system prototype. Experiments indicate that MDRR reduces around 20 percent of recovery time of the conventional approach, showing that our theoretical findings are applicable in practice.
A new stopping rule for turbo codes, the input-output consistency (IOC) check is presented. It is based on an extended maximum a posteriori algorithm that also outputs (hard) extrinsic estimates oil the coded bits. In...
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A new stopping rule for turbo codes, the input-output consistency (IOC) check is presented. It is based on an extended maximum a posteriori algorithm that also outputs (hard) extrinsic estimates oil the coded bits. In parallel, the hard decisions of the info bits are re-encoded and if the two sequences coincide, iterative decoding is stopped. Remarkably. IOC beats other known stopping rules ill terms of error rate and convergence speed, closely approaching ideal 'Genie'-aided decoding.
A new wavelet-based representation method for arbitrarily-shaped image segments is proposed. The method includes an efficient way to select wavelet basis by using the projection onto convex sets algorithm to approxima...
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A new wavelet-based representation method for arbitrarily-shaped image segments is proposed. The method includes an efficient way to select wavelet basis by using the projection onto convex sets algorithm to approximate the given image segment, with improved image quality.
In this study, the authors show that the coding advantage (CA) of quasi-orthogonal space-frequency block codes (QOSFBCs) could be decomposed into two parts, namely intrinsic CA (ICA) and extrinsic CA (ECA). Then, by u...
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In this study, the authors show that the coding advantage (CA) of quasi-orthogonal space-frequency block codes (QOSFBCs) could be decomposed into two parts, namely intrinsic CA (ICA) and extrinsic CA (ECA). Then, by using the ICA, the authors demonstrate that the optimum precoder of the QOSFBCs could be analytically derived without any requirement of the exhaustive search. Then, by improving the ECA, the authors enhance performances of the QOSFBCs efficiently - up to 4 dB. Finally, the authors show that a very fast optimisation process for the QOSFBCs is viable over any arbitrary frequency-selective channel.
All-optical generation of 40 GHz pulse trains with arbitrary binary code patterns from a 10 GHz uniform input pulse train using lattice-form Mach-Zehnder interferometers is experimentally demonstrated. The device is f...
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All-optical generation of 40 GHz pulse trains with arbitrary binary code patterns from a 10 GHz uniform input pulse train using lattice-form Mach-Zehnder interferometers is experimentally demonstrated. The device is fabricated on a silica-based planar lightwave circuit, which is based on a buried channel waveguide structure with an index difference of 1.2%.
Selecting an efficient variable block size mode in H.264 video coding standard for better compression performance is considered. The proposed scheme is based on a 3D recursive search algorithm and takes into account t...
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Selecting an efficient variable block size mode in H.264 video coding standard for better compression performance is considered. The proposed scheme is based on a 3D recursive search algorithm and takes into account the motion vector cost and previous frame information. The best mode for the current macroblock is obtained by analysing the modes for a maximum of four macroblocks in the current and previous frames. An improvement in the encoding time with negligible impact on subjective and quantitative performance has been achieved.
Based on XOR coding, proposed is a proactive broadcasting for wireless broadcast systems where multiple faulty packets can be rectified at the cost of transmitting an additional coded packet. Since it greatly outstrip...
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Based on XOR coding, proposed is a proactive broadcasting for wireless broadcast systems where multiple faulty packets can be rectified at the cost of transmitting an additional coded packet. Since it greatly outstrips the conventional one in terms of BER performance, the proposed scheme can aggressively allocate the transmission rate to compensate for its throughput penalty. Numerical simulations show that the proposed scheme outperforms its conventional counterpart for about 5 dB SNR at a target BER of 10(-3) for an OFDM system.
This paper proposes a dictionary-based code compression technique that maps the source register operands to the nearest occurrence of a destination register in the predecessor instructions. The key idea is that most d...
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This paper proposes a dictionary-based code compression technique that maps the source register operands to the nearest occurrence of a destination register in the predecessor instructions. The key idea is that most destination registers have a great possibility to be used as source registers in the following instructions. The dependent registers can be removed from the dictionary if this information can be specified otherwise. Such destination-source relationships are so common that making use of them can result in much better code compression. After removing the dependent register operands, the original dictionary size can be reduced significantly. As a result, the compression ratio can benefit from: (a) the reduction of dictionary size due to the removal of dependent registers, and (b) the reduction of program encoding due to the reduced number of dictionary entries. A set of programs has been compressed using this feature. The compression results show that the average compression ratio is reduced to 38.41% on average for MediaBench benchmarks compiled for MIPS R2000 processor, as opposed to 45% using operand factorization. (C) 2003 Elsevier Inc. All rights reserved.
In this study, joint source-channel decoding for non-binary source samples is conducted. The non-binary source samples can be modelled as the output of a multi-state Markov chain (MC). As the source samples are direct...
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In this study, joint source-channel decoding for non-binary source samples is conducted. The non-binary source samples can be modelled as the output of a multi-state Markov chain (MC). As the source samples are directly transmitted after channel coding without source compression, the transmitted signals can be highly correlated. At the receiver, the multi-state MC module can be designed to exploit the statistical correlation of source samples to improve the error correcting performance. However, as the number of states is increased, the multi-state MC module requires high computational complexity. To alleviate this problem, a simplified MC module is proposed. In the simplified MC module, the multi-state MC is replaced with multiple number of two-state MCs each of which exploits bit-level correlation of samples. Simulation results demonstrate that the simplified MC module can lead to competitive reduction in the required signal-to-noise ratio in comparison with the multi-state MC module with reduced computational complexity.
We consider the quadratic Gaussian CEO problem, where the goal is to estimate a measure based on several Gaussian noisy observations which must be encoded and sent to a centralized receiver using limited transmission ...
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We consider the quadratic Gaussian CEO problem, where the goal is to estimate a measure based on several Gaussian noisy observations which must be encoded and sent to a centralized receiver using limited transmission rate. For real applications, besides minimizing the average distortion, given the transmission rate, it is important to take into account memory and processing constraints. Considering these motivations, we present a low complexity coding and decoding strategy, which exploits the correlation between the measurements to reduce the number of bits to be transmitted by refining the output of the quantization stage. The CEO makes an estimate using a decoder based on a process similar to majority voting. We derive explicit expression for the CEO's error probability and compare numerical simulations with known achievability results and bounds. (C) 2016 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
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