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Contact:
Marcus Greferath
School of Math. Sciences
University College Dublin
Belfield, Dublin 4, Ireland
Phone:
+353-1-716-2588 (UCD)
+353-85-153-0951 (mobile)
Joachim Rosenthal
Institut of Mathematics
University of Zurich
Winterthurerstrasse 190
8057 Zurich, Switzerland
Phone:
+41-44-63 55884 (office)
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ITW 2010 Dublin
IEEE Information Theory Workshop
Dublin, August 30 - September 3, 2010
Low-density codes
Mon 30 Aug, 14.40-16.00, Room 1
Contributed session
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Dung Viet Nguyen, Bane Vasić, Michael Marcellin, and Shashi Kiran Chilappagari
Structured LDPC Codes from Permutation Matrices Free of Small Trapping Sets
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Abstract:
This paper introduces a class of structured low-density parity-check
(LDPC) codes whose parity check matrices are arrays of permutation
matrices. The permutation matrices are obtained from Latin squares
and form a finite field under some matrix operations. They are
chosen so that the Tanner graphs do not contain subgraphs harmful to
iterative decoding algorithms. The construction of
column-weight-three codes is presented. Although the codes are
optimized for the Gallager A/B algorithm over the binary symmetric
channel (BSC), their error performance is very good on the additive
white Gaussian noise channel (AWGNC) as well.
Mon 30 Aug, 14.40-15.00, Room 1
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David G. M. Mitchell, Roxana Smarandache, Michael Lentmaier, and Daniel J. Costello, Jr.
Quasi-Cyclic Asymptotically Regular LDPC Codes
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Abstract:
Families of asymptotically regular LDPC block code ensembles
can be formed by terminating (J,K)-regular protograph-based LDPC
convolutional codes. By varying the termination length, we obtain a
large selection of LDPC block code ensembles with varying code
rates, minimum distance that grows linearly with block length, and
capacity approaching iterative decoding thresholds, despite the fact
that the terminated ensembles are almost regular. In this paper, we
investigate the properties of the quasi-cyclic (QC) members of such
an ensemble. We show that an upper bound on the minimum Hamming
distance of members of the QC sub-ensemble can be improved by
careful choice of the component protographs used in the code
construction. Further, we show that the upper bound on the minimum
distance can be improved by using arrays of circulants in a graph
cover of the protograph.
Mon 30 Aug, 15.00-15.20, Room 1
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David F. Hayes, Sarah J. Johnson, and Steven R. Weller
Irregular Repeat-Accumulate-Like Codes with Improved Error Floor Performance
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Abstract:
In this paper, we present a new class of iteratively decoded error
correction codes. These codes, which are a modification of
irregular repeat-accumulate (IRA) codes, are termed generalized IRA
(GIRA) codes, and are designed for improved error floor performance.
GIRA codes are systematic, easily encodable, and are decoded with
the sum-product algorithm. In this paper we present a density
evolution algorithm to compute the threshold of GIRA codes, and find
GIRA degree distributions which produce codes with good thresholds.
We then propose inner code designs and show using simulation results
that they improve upon the error floor performance of IRA codes.
Mon 30 Aug, 15.20-15.40, Room 1
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Lorenzo Cappellari
Lossy Source Compression of Non-Uniform Binary Sources Using GQ-LDGM Codes
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Abstract:
In this paper, we study the use of GF(q)-quantized LDGM codes for
binary source coding. By employing quantization, it is possible to
obtain binary codewords with a non-uniform distribution. The
obtained statistics is hence suitable for optimal, direct
quantization of non-uniform Bernoulli sources. We employ a
message-passing algorithm combined with a decimation procedure in
order to perform compression. The experimental results based on
GF(q)-LDGM codes with regular degree distributions yield
performances quite close to the theoretical rate-distortion bounds.
Mon 30 Aug, 15.40-16.00, Room 1
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