23,785 research outputs found
Low Complexity Decoding for Higher Order Punctured Trellis-Coded Modulation Over Intersymbol Interference Channels
Trellis-coded modulation (TCM) is a power and bandwidth efficient digital
transmission scheme which offers very low structural delay of the data stream.
Classical TCM uses a signal constellation of twice the cardinality compared to
an uncoded transmission with one bit of redundancy per PAM symbol, i.e.,
application of codes with rates when denotes the
cardinality of the signal constellation.
Recently published work allows rate adjustment for TCM by means of puncturing
the convolutional code (CC) on which a TCM scheme is based on.
In this paper it is shown how punctured TCM-signals transmitted over
intersymbol interference (ISI) channels can favorably be decoded. Significant
complexity reductions at only minor performance loss can be achieved by means
of reduced state sequence estimation.Comment: 4 pages, 5 figures, 3 algorithms, accepted and published at 6th
International Symposium on Communications, Control, and Signal Processing
(ISCCSP 2014
An efficient length- and rate-preserving concatenation of polar and repetition codes
We improve the method in \cite{Seidl:10} for increasing the finite-lengh
performance of polar codes by protecting specific, less reliable symbols with
simple outer repetition codes. Decoding of the scheme integrates easily in the
known successive decoding algorithms for polar codes. Overall rate and block
length remain unchanged, the decoding complexity is at most doubled. A
comparison to related methods for performance improvement of polar codes is
drawn.Comment: to be presented at International Zurich Seminar (IZS) 201
Low Complexity Decoding for Punctured Trellis-Coded Modulation Over Intersymbol Interference Channels
Classical trellis-coded modulation (TCM) as introduced by Ungerboeck in
1976/1983 uses a signal constellation of twice the cardinality compared to an
uncoded transmission with one bit of redundancy per PAM symbol, i.e.,
application of codes with rates when denotes the
cardinality of the signal constellation. The original approach therefore only
comprises integer transmission rates, i.e., , additionally, when transmitting over an intersymbol interference
(ISI) channel an optimum decoding scheme would perform equalization and
decoding of the channel code jointly. In this paper, we allow rate adjustment
for TCM by means of puncturing the convolutional code (CC) on which a TCM
scheme is based on. In this case a nontrivial mapping of the output symbols of
the CC to signal points results in a time-variant trellis. We propose an
efficient technique to integrate an ISI-channel into this trellis and show that
the computational complexity can be significantly reduced by means of a reduced
state sequence estimation (RSSE) algorithm for time-variant trellises.Comment: 4 pages, 7 pictured, accepted for 2014 International Zurich Seminar
on Communication
Block-Transitive Designs in Affine Spaces
This paper deals with block-transitive - designs in affine
spaces for large , with a focus on the important index case. We
prove that there are no non-trivial 5- designs admitting a
block-transitive group of automorphisms that is of affine type. Moreover, we
show that the corresponding non-existence result holds for 4- designs,
except possibly when the group is one-dimensional affine. Our approach involves
a consideration of the finite 2-homogeneous affine permutation groups.Comment: 10 pages; to appear in: "Designs, Codes and Cryptography
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