85,398 research outputs found
On the Asymptotic Performance of Bit-Wise Decoders for Coded Modulation
Two decoder structures for coded modulation over the Gaussian and flat fading
channels are studied: the maximum likelihood symbol-wise decoder, and the
(suboptimal) bit-wise decoder based on the bit-interleaved coded modulation
paradigm. We consider a 16-ary quadrature amplitude constellation labeled by a
Gray labeling. It is shown that the asymptotic loss in terms of pairwise error
probability, for any two codewords caused by the bit-wise decoder, is bounded
by 1.25 dB. The analysis also shows that for the Gaussian channel the
asymptotic loss is zero for a wide range of linear codes, including all
rate-1/2 convolutional codes
Extended Non-Binary Low-Density Parity-Check Codes over Erasure Channels
Based on the extended binary image of non-binary LDPC codes, we propose a
method for generating extra redundant bits, such as to decreases the coding
rate of a mother code. The proposed method allows for using the same decoder,
regardless of how many extra redundant bits have been produced, which
considerably increases the flexibility of the system without significantly
increasing its complexity. Extended codes are also optimized for the binary
erasure channel, by using density evolution methods. Nevertheless, the results
presented in this paper can easily be extrapolated to more general channel
models.Comment: ISIT 2011, submitte
Skip-Sliding Window Codes
Constrained coding is used widely in digital communication and storage
systems. In this paper, we study a generalized sliding window constraint called
the skip-sliding window. A skip-sliding window (SSW) code is defined in terms
of the length of a sliding window, skip length , and cost constraint
in each sliding window. Each valid codeword of length is determined by
windows of length where window starts at th symbol for
all non-negative integers such that ; and the cost constraint
in each window must be satisfied. In this work, two methods are given to
enumerate the size of SSW codes and further refinements are made to reduce the
enumeration complexity. Using the proposed enumeration methods, the noiseless
capacity of binary SSW codes is determined and observations such as greater
capacity than other classes of codes are made. Moreover, some noisy capacity
bounds are given. SSW coding constraints arise in various applications
including simultaneous energy and information transfer.Comment: 28 pages, 11 figure
PopCORN: Hunting down the differences between binary population synthesis codes
Binary population synthesis (BPS) modelling is a very effective tool to study
the evolution and properties of close binary systems. The uncertainty in the
parameters of the model and their effect on a population can be tested in a
statistical way, which then leads to a deeper understanding of the underlying
physical processes involved. To understand the predictive power of BPS codes,
we study the similarities and differences in the predicted populations of four
different BPS codes for low- and intermediate-mass binaries. We investigate
whether the differences are caused by different assumptions made in the BPS
codes or by numerical effects. To simplify the complex problem of comparing BPS
codes, we equalise the inherent assumptions as much as possible. We find that
the simulated populations are similar between the codes. Regarding the
population of binaries with one WD, there is very good agreement between the
physical characteristics, the evolutionary channels that lead to the birth of
these systems, and their birthrates. Regarding the double WD population, there
is a good agreement on which evolutionary channels exist to create double WDs
and a rough agreement on the characteristics of the double WD population.
Regarding which progenitor systems lead to a single and double WD system and
which systems do not, the four codes agree well. Most importantly, we find that
for these two populations, the differences in the predictions from the four
codes are not due to numerical differences, but because of different inherent
assumptions. We identify critical assumptions for BPS studies that need to be
studied in more detail.Comment: 13 pages, +21 pages appendix, 35 figures, accepted for publishing in
A&A, Minor change to match published version, most important the added link
to the website http://www.astro.ru.nl/~silviato/popcorn for more detailed
figures and informatio
Numerical and analytical bounds on threshold error rates for hypergraph-product codes
We study analytically and numerically decoding properties of finite rate
hypergraph-product quantum LDPC codes obtained from random (3,4)-regular
Gallager codes, with a simple model of independent X and Z errors. Several
non-trival lower and upper bounds for the decodable region are constructed
analytically by analyzing the properties of the homological difference, equal
minus the logarithm of the maximum-likelihood decoding probability for a given
syndrome. Numerical results include an upper bound for the decodable region
from specific heat calculations in associated Ising models, and a minimum
weight decoding threshold of approximately 7%.Comment: 14 pages, 5 figure
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