71,726 research outputs found
On the Error Performance of 8-VSB TCM Decoder for ATSC Terrestrial Broadcasting of Digital Television
The error performance of various 8-VSB TCM decoders for reception of terrestrial digital television is analyzed. In previous work, 8-state TCM decoders were proposed and implemented for terrestrial broadcasting of digital television. In this paper, the performance of a 16-state TCM decoder is analyzed and simulated. It is shown that not only a 16-state TCM decoder outperforms one with 8-states, but it also has much smaller error coefficients
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
Molecular signatures distinguish human central memory from effector memory CD8 T cell subsets
Abstract
Memory T cells are heterogeneous in terms of their phenotype and functional properties. We investigated the molecular profiles of human CD8 naive central memory (TCM), effector memory (TEM), and effector memory RA (TEMRA) T cells using gene expression microarrays and phospho-protein-specific intracellular flow cytometry. We demonstrate that TCM have a gene expression and cytokine signaling signature that lies between that of naive and TEM or TEMRA cells, whereas TEM and TEMRA are closely related. Our data define the molecular basis for the different functional properties of central and effector memory subsets. We show that TEM and TEMRA cells strongly express genes with known importance in CD8 T cell effector function. In contrast, TCM are characterized by high basal and cytokine-induced STAT5 phosphorylation, reflecting their capacity for self-renewal. Altogether, our results distinguish TCM and TEM/TEMRA at the molecular level and are consistent with the concept that TCM represent memory stem cells.</jats:p
An unexpected complication of a percutaneous coronary angioplasty
Takotsubo cardiomyopathy (TCM) is characterized by transient ventricular dysfunction, classically in its apical and mid segments in the absence of coronary lesions, and is often observed after intense stressful events and occasionally associated to an acute medical illness. We describe a case of TCM associated with coronary artery disease and triggered by a percutaneous coronary angioplasty. This case highlights the concept that a medical procedure can lead, in certain conditions, to TCM and provides new interesting insights on the pathophysiology of coronary syndromes
On Optimal TCM Encoders
An asymptotically optimal trellis-coded modulation (TCM) encoder requires the
joint design of the encoder and the binary labeling of the constellation. Since
analytical approaches are unknown, the only available solution is to perform an
exhaustive search over the encoder and the labeling. For large constellation
sizes and/or many encoder states, however, an exhaustive search is unfeasible.
Traditional TCM designs overcome this problem by using a labeling that follows
the set-partitioning principle and by performing an exhaustive search over the
encoders. In this paper we study binary labelings for TCM and show how they can
be grouped into classes, which considerably reduces the search space in a joint
design. For 8-ary constellations, the number of different binary labelings that
must be tested is reduced from 8!=40320 to 240. For the particular case of an
8-ary pulse amplitude modulation constellation, this number is further reduced
to 120 and for 8-ary phase shift keying to only 30. An algorithm to generate
one labeling in each class is also introduced. Asymptotically optimal TCM
encoders are tabulated which are up to 0.3 dB better than the previously best
known encoders
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
UTILIZATION OF TRADITIONAL COMMUNICATION MEDIA (TCM) FOR INNOVATION DISSEMINATION IN OBAFEMI OWODE LOCAL GOVERNMENT AREA OF OGUN STATE
The study examined various traditional communication media (TCM) used by rural farmers as sources of information to improve their production in Obafemi Owode Local Government Area of Ogun State. Data were drawn from a sample of one hundred and twenty (120) randomly selected farmers using a structure interview schedule. The obtained data were described with frequency and analyzed using chi-square test. The results indicated that majority (62.8%) of farmers commonly received innovations through TCM such as discussion groups, market places, agriculture-based festivals, visits, cooperative society, traditional meetings, community elders, village squares, and relations. and found them effective. A significant relationship was established between farmersā perceptions of effectiveness TCM and effectiveness of TCM .The variables that had significant relationship with TCM was socio-cultural lifestyles of farmers (Ļ2 = 49.9, Ī± =0.05) and farmersā level of education (Ļ2=95.58, Ī± =0.05) Based on the findings, it is pertinent to direct deliberate efforts towards the integration of traditional media of communication into the innovation delivery system for rural farmers.Research and Development/Tech Change/Emerging Technologies,
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