37,310 research outputs found
Automatic-repeat-request error control schemes
Error detection incorporated with automatic-repeat-request (ARQ) is widely used for error control in data communication systems. This method of error control is simple and provides high system reliability. If a properly chosen code is used for error detection, virtually error-free data transmission can be attained. Various types of ARQ and hybrid ARQ schemes, and error detection using linear block codes are surveyed
Engineering autonomous error correction in stabilizer codes at finite temperature
We present an error correcting protocol that enhances the lifetime of
stabilizer code based qubits which are susceptible to the creation of pairs of
localized defects (due to string-like error operators) at finite temperature,
such as the toric code. The primary tool employed is dynamic application of a
local, unitary operator which exchanges defects and thereby translates
localized excitations. Crucially, the protocol does not require any
measurements of stabilizer operators, and therefore can be used to enhance the
lifetime of a qubit in the absence of such experimental resources.Comment: 14 pages, 13 figures. Comments welcome, APS March Meeting session
K44.0000
Continuous quantum error correction by cooling
We describe an implementation of quantum error correction that operates
continuously in time and requires no active interventions such as measurements
or gates. The mechanism for carrying away the entropy introduced by errors is a
cooling procedure. We evaluate the effectiveness of the scheme by simulation,
and remark on its connections to some recently proposed error prevention
procedures.Comment: 8 pages, 5 figures. Published version. Minor change in conten
Design of Raptor Codes in the Low SNR Regime with Applications in Quantum Key Distribution
The focus of this work is on the design of Raptor codes for continuous
variable Quantum key distribution (CV-QKD) systems. We design a highly
efficient Raptor code for very low signal to noise ratios (SNRs), which enables
CV-QKD systems to operate over long distances with a significantly higher
secret key rate compared to conventional fixed rate codes. The degree
distribution design of Raptor codes in the low SNR regime is formulated as a
linear program, where a set of optimized degree distributions are also obtained
through linear programming. Simulation results show that the designed code
achieves efficiencies higher than 94\% for SNRs as low as -20 dB and -30 dB. We
further propose a new error reconciliation protocol for CV-QKD systems by using
Raptor codes and show that it can achieve higher secret key rates over long
distances compared to existing protocols.Comment: The paper has been submitted to IEEE International Communications
Conference (ICC), Kuala Lumpur, Malaysia, May 201
Tailored codes for small quantum memories
We demonstrate that small quantum memories, realized via quantum error
correction in multi-qubit devices, can benefit substantially by choosing a
quantum code that is tailored to the relevant error model of the system. For a
biased noise model, with independent bit and phase flips occurring at different
rates, we show that a single code greatly outperforms the well-studied Steane
code across the full range of parameters of the noise model, including for
unbiased noise. In fact, this tailored code performs almost optimally when
compared with 10,000 randomly selected stabilizer codes of comparable
experimental complexity. Tailored codes can even outperform the Steane code
with realistic experimental noise, and without any increase in the experimental
complexity, as we demonstrate by comparison in the observed error model in a
recent 7-qubit trapped ion experiment.Comment: 6 pages, 2 figures, supplementary material; v2 published versio
Energy Aware Error Control in Cooperative Communication in Wireless Sensor Networks
Due to small size of sensor nodes deployed in Wireless Sensor Networks
(WSNs), energy utilization is a key issue. Poor channel conditions lead to
retransmissions and hence, result in energy wastage. Error control strategies
are usually utilized to accommodate channel impairments like noise and fading
in order to optimize energy consumption for network lifetime enhancement.
Meanwhile, cooperative communication also emerges to be an appropriate
candidate to combat the effects of channel fading. Energy efficiency of
cooperative scheme when applied with Automatic Repeat Request (ARQ), Hybrid-ARQ
(HARQ) and Forward Error Correction (FEC) is investigated in this work.
Moreover, the expressions for energy efficiency of Direct Transmission, Single
Relay Cooperation and Multi Relay Cooperation are also derived. In all, our
work is focused towards energy optimal communication in WSNs. Our results show
that error control strategies with cooperative schemes can significantly
enhance system performance in form of energy optimization.Comment: ACM Research in Adaptive and Convergent Systems (RACS 2013),
Montreal, Canad
Coping with qubit leakage in topological codes
Many physical systems considered promising qubit candidates are not, in fact,
two-level systems. Such systems can leak out of the preferred computational
states, leading to errors on any qubits that interact with leaked qubits.
Without specific methods of dealing with leakage, long-lived leakage can lead
to time-correlated errors. We study the impact of such time-correlated errors
on topological quantum error correction codes, which are considered highly
practical codes, using the repetition code as a representative case study. We
show that, under physically reasonable assumptions, a threshold error rate
still exists, however performance is significantly degraded. We then describe
simple additional quantum circuitry that, when included in the error detection
cycle, restores performance to acceptable levels.Comment: 5 pages, 8 figures, comments welcom
Probability of undetected error after decoding for a concatenated coding scheme
A concatenated coding scheme for error control in data communications is analyzed. In this scheme, the inner code is used for both error correction and detection, however the outer code is used only for error detection. A retransmission is requested if the outer code detects the presence of errors after the inner code decoding. Probability of undetected error is derived and bounded. A particular example, proposed for NASA telecommand system is analyzed
Embedding Noise Prediction into List-Viterbi Decoding using Error Detection Codes for Magnetic Tape Systems
A List Viterbi detector produces a rank ordered list of the N globally best
candidates in a trellis search. A List Viterbi detector structure is proposed
that incorporates the noise prediction with periodic state-metric updates based
on outer error detection codes (EDCs). More specifically, a periodic decision
making process is utilized for a non-overlapping sliding windows of P bits
based on the use of outer EDCs. In a number of magnetic recording applications,
Error Correction Coding (ECC) is adversely effected by the presence of long and
dominant error events. Unlike the conventional post processing methods that are
usually tailored to a specific set of dominant error events or the joint
modulation code trellis architectures that are operating on larger state spaces
at the expense of increased implementation complexity, the proposed detector
does not use any a priori information about the error event distributions and
operates at reduced state trellis. We present pre ECC bit error rate
performance as well as the post ECC codeword failure rates of the proposed
detector using perfect detection scenario as well as practical detection codes
as the EDCs are not essential to the overall design. Furthermore, it is
observed that proposed algorithm does not introduce new error events.
Simulation results show that the proposed algorithm gives improved bit error
and post ECC codeword failure rates at the expense of some increase in
complexity.Comment: 4 pages, 3 figures, Proceedings of the ASME 2013 Conference on
information storage and processing systems (ISPS 2013
CodeNet: Training Large Scale Neural Networks in Presence of Soft-Errors
This work proposes the first strategy to make distributed training of neural
networks resilient to computing errors, a problem that has remained unsolved
despite being first posed in 1956 by von Neumann. He also speculated that the
efficiency and reliability of the human brain is obtained by allowing for low
power but error-prone components with redundancy for error-resilience. It is
surprising that this problem remains open, even as massive artificial neural
networks are being trained on increasingly low-cost and unreliable processing
units. Our coding-theory-inspired strategy, "CodeNet," solves this problem by
addressing three challenges in the science of reliable computing: (i) Providing
the first strategy for error-resilient neural network training by encoding each
layer separately; (ii) Keeping the overheads of coding
(encoding/error-detection/decoding) low by obviating the need to re-encode the
updated parameter matrices after each iteration from scratch. (iii) Providing a
completely decentralized implementation with no central node (which is a single
point of failure), allowing all primary computational steps to be error-prone.
We theoretically demonstrate that CodeNet has higher error tolerance than
replication, which we leverage to speed up computation time. Simultaneously,
CodeNet requires lower redundancy than replication, and equal computational and
communication costs in scaling sense. We first demonstrate the benefits of
CodeNet in reducing expected computation time over replication when accounting
for checkpointing. Our experiments show that CodeNet achieves the best
accuracy-runtime tradeoff compared to both replication and uncoded strategies.
CodeNet is a significant step towards biologically plausible neural network
training, that could hold the key to orders of magnitude efficiency
improvements.Comment: Currently under revie
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