3,597 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
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
Comment on "Probing the equilibrium dynamics of colloidal hard spheres above the mode-coupling glass transition"
In the Letter [PRL 102, 085703 (2009)] Brambilla, et al. claimed to observe
activated dynamics in colloidal hard spheres above the critical packing
fraction of mode coupling theory (MCT). By performing microscopic MCT
calculations, we show that polydispersity in their system shifts the critical
packing fraction above the value determined by van Megen et al. for less
polydisperse samples, and that the data agree with theory except for, possibly,
the highest packing fraction.Comment: Comment in print in Phys. Rev. Lett.; for accompanying reply see
arXiv Brambilla et al. (Monday 18.10.2010
Punctured Trellis-Coded Modulation
In classic trellis-coded modulation (TCM) signal constellations of twice the
cardinality are applied when compared to an uncoded transmission enabling
transmission of one bit of redundancy per PAM-symbol, i.e., rates of
when denotes the cardinality of the signal
constellation. In order to support different rates, multi-dimensional (i.e.,
-dimensional) constellations had been proposed by means of
combining subsequent one- or two-dimensional modulation steps, resulting in
TCM-schemes with bit redundancy per real dimension. In
contrast, in this paper we propose to perform rate adjustment for TCM by means
of puncturing the convolutional code (CC) on which a TCM-scheme is based on. It
is shown, that due to the nontrivial mapping of the output symbols of the CC to
signal points in the case of puncturing, a modification of the corresponding
Viterbi-decoder algorithm and an optimization of the CC and the puncturing
scheme are necessary.Comment: 5 pages, 10 figures, submitted to IEEE International Symposium on
Information Theory 2013 (ISIT
Domain-wall melting as a probe of many-body localization
Motivated by a recent optical-lattice experiment by Choi et al.[Science 352,
1547 (2016)], we discuss how domain-wall melting can be used to investigate
many-body localization. First, by considering noninteracting fermion models, we
demonstrate that experimentally accessible measures are sensitive to
localization and can thus be used to detect the delocalization-localization
transition, including divergences of characteristic length scales. Second,
using extensive time-dependent density matrix renormalization group
simulations, we study fermions with repulsive interactions on a chain and a
two-leg ladder. The extracted critical disorder strengths agree well with the
ones found in existing literature.Comment: 4+2 pages, 4+2 figure
On Recognizing Things
AbstractIn this paper, travelogues and scientific reports on the exploration of Central Africa (ca 1875-1914) are read against a background of renewed interest in the anthropology of material culture. Of special interest is what these sources reveal about the epistemic, political, and economic conditions of collecting «ethnographic objects». Concentrating on the concept of recognition and its denial, the paper argues that objects found their place in Western museums and schemes of interpretation to the extent that they were dematerialized; decontextualization was constitutive of ethnographic objects and their collection. Comparing ethnographic objects with ethnic artefacts, commonalities and differences are shown to have been rooted in contrasting, yet inextricably linked, projects of creating identity as well as alterity.RésuméCet article se propose de relire les récits de voyage et rapports scientifiques ayant trait à l’exploration de l’Afrique centrale (ca 1875-1914) en s’appuyant sur le nouvel intérêt qui s’est fait jour en anthropologie pour les cultures matérielles. Ces sources sont d’une importance capitale pour ce qui concerne les conditions économiques, politiques et épistémiques qui ont présidé à la collecte d’objets ethnographiques. Envisageant la notion problématique de re-connaissance, cet article s’attache à montrer que ces objets ou collections ethnographiques ne prennent place dans les musées occidentaux et ne trouvent sens dans les grilles d’interprétation qu’au prix d’une dématérialisation, c’est-à -dire d’une décontextualisation. En les comparant aux artefacts ethniques, les composants communs ou différences paraissent inextricablement liés à des projets contrastés de création d’identité aussi bien que d’affirmation de l’altérité
Canonical tree-decompositions of finite graphs I. Existence and algorithms
We construct tree-decompositions of graphs that distinguish all their
k-blocks and tangles of order k, for any fixed integer k. We describe a family
of algorithms to construct such decompositions, seeking to maximize their
diversity subject to the requirement that they commute with graph isomorphisms.
In particular, all the decompositions constructed are invariant under the
automorphisms of the graph.Comment: 23 pages, 5 figure
-Blocks: a connectivity invariant for graphs
A -block in a graph is a maximal set of at least vertices no two
of which can be separated in by fewer than other vertices. The block
number of is the largest integer such that has a
-block.
We investigate how interacts with density invariants of graphs, such
as their minimum or average degree. We further present algorithms that decide
whether a graph has a -block, or which find all its -blocks.
The connectivity invariant has a dual width invariant, the
block-width of . Our algorithms imply the duality theorem
: a graph has a block-decomposition of width and adhesion if and only if it contains no -block.Comment: 22 pages, 5 figures. This is an extended version the journal article,
which has by now appeared. The version here contains an improved version of
Theorem 5.3 (which is now best possible) and an additional section with
examples at the en
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