1,561 research outputs found
Multi-Input Multi-Output Deletion Channel
Cataloged from PDF version of article.We describe a new channel model suitable in certain
applications, namely the multi-input multi-output (MIMO) deletion
channel. This channel models the scenarios where multiple
transmitters and receivers suffering from synchronization errors
are employed. We then consider a coding scheme over such
channels based on a serial concatenation of a low-density parity
check (LDPC) code, a marker code and a layered space-time
code. We design two detectors operating at the bit level which
jointly achieve synchronization for the deletion channel (with the
help of the marker code) and detection for the MIMO channel.
Utilizing the proposed detector together with an LDPC code
with powerful error-correction capabilities, we demonstrate that
reliable transmission over a MIMO deletion channel is feasible
Capacity Bounds and Concatenated Codes Over Segmented Deletion Channels
Cataloged from PDF version of article.We develop an information theoretic characterization
and a practical coding approach for segmented deletion
channels. Compared to channels with independent and identically
distributed (i.i.d.) deletions, where each bit is independently
deleted with an equal probability, the segmentation assumption
imposes certain constraints, i.e., in a block of bits of a certain
length, only a limited number of deletions are allowed to occur.
This channel model has recently been proposed and motivated
by the fact that for practical systems, when a deletion error
occurs, it is more likely that the next one will not appear
very soon. We first argue that such channels are information
stable, hence their channel capacity exists. Then, we introduce
several upper and lower bounds with two different methods in an
attempt to understand the channel capacity behavior. The first
scheme utilizes certain information provided to the transmitter
and/or receiver while the second one explores the asymptotic
behavior of the bounds when the average bit deletion rate is
small. In the second part of the paper, we consider a practical
channel coding approach over a segmented deletion channel.
Specifically, we utilize outer LDPC codes concatenated with inner
marker codes, and develop suitable channel detection algorithms
for this scenario. Different maximum-a-posteriori (MAP) based
channel synchronization algorithms operating at the bit and
symbol levels are introduced, and specific LDPC code designs are
explored. Simulation results clearly indicate the advantages of the
proposed approach. In particular, for the entire range of deletion
probabilities less than unity, our scheme offers a significantly
larger transmission rate compared to the other existing solutions
in the literature
Magnetic superelasticity and inverse magnetocaloric effect in Ni-Mn-In
Applying a magnetic field to a ferromagnetic NiMnIn
alloy in the martensitic state induces a structural phase transition to the
austenitic state. This is accompanied by a strain which recovers on removing
the magnetic field giving the system a magnetically superelastic character. A
further property of this alloy is that it also shows the inverse magnetocaloric
effect. The magnetic superelasticity and the inverse magnetocaloric effect in
Ni-Mn-In and their association with the first order structural transition is
studied by magnetization, strain, and neutron diffraction studies under
magnetic field.Comment: 6 pages, 8 figures. Published in the Physical Review
Magnetic superelasticity and inverse magnetocaloric effect in Ni-Mn-In
Applying a magnetic field to a ferromagnetic NiMnIn
alloy in the martensitic state induces a structural phase transition to the
austenitic state. This is accompanied by a strain which recovers on removing
the magnetic field giving the system a magnetically superelastic character. A
further property of this alloy is that it also shows the inverse magnetocaloric
effect. The magnetic superelasticity and the inverse magnetocaloric effect in
Ni-Mn-In and their association with the first order structural transition is
studied by magnetization, strain, and neutron diffraction studies under
magnetic field.Comment: 6 pages, 8 figures. Published in the Physical Review
One step emission tunable synthesis of PEG coated Ag 2 S NIR quantum dots and the development of receptor targeted drug delivery vehicles thereof
PEGylation of quantum dots (QDs) to decrease their toxicity, increase blood circulation time, reduce non-specific uptake and also to solubilize and stabilize hydrophobic QDs in aqueous medium is a widely used approach and many different methods were developed to achieve this. QDs that are luminescent in the near-infrared region (NIR) have recently emerged as the more appropriate materials for bio-imaging studies. In this work, we describe a single step emission tunable aqueous synthesis of PEGylated Ag2S NIRQDs. They are highly cytocompatible, not only due to the PEG coating but also due to the intrinsic biocompatibility of Ag2S, and prepared in a single step aqueous method using thiolated PEGs as the only coating material. Tuning the emission wavelength within the medical window (775–930 nm) with a quantum yield between 2 and 65% is achieved by changing the reaction variables such as PEG molecular weight, pH and precursor ratios. Ag2S–PEG NIRQDs prepared from 5 kDa MPEG-SH at acidic pH provided a dramatic enhancement in the luminescence intensity. These NIRQDs were also designed with surface functional groups to attach folic acid and loaded with doxorubicin (DOX) which dramatically enhanced the uptake and efficacy of DOX (50% cell death with 15 nM DOX) in FA-receptor overexpressed cancer cell lines (HeLa). They also showed a strong cytoplasmic NIR signal in the in vitro studies, demonstrating great theranostic potential
Multi-input multi-output deletion channel
We describe a new channel model suitable in certain applications, namely the multi-input multi-output (MIMO) deletion channel. This channel models the scenarios where multiple transmitters and receivers suffering from synchronization errors are employed. We then consider a coding scheme over such channels based on a serial concatenation of a low-density parity check (LDPC) code, a marker code and a layered space-time code. We design two detectors operating at the bit level which jointly achieve synchronization for the deletion channel (with the help of the marker code) and detection for the MIMO channel. Utilizing the proposed detector together with an LDPC code with powerful error-correction capabilities, we demonstrate that reliable transmission over a MIMO deletion channel is feasible. © 2012 IEEE
Capacity bounds and concatenated codes over segmented deletion channels
We develop an information theoretic characterization and a practical coding approach for segmented deletion channels. Compared to channels with independent and identically distributed (i.i.d.) deletions, where each bit is independently deleted with an equal probability, the segmentation assumption imposes certain constraints, i.e., in a block of bits of a certain length, only a limited number of deletions are allowed to occur. This channel model has recently been proposed and motivated by the fact that for practical systems, when a deletion error occurs, it is more likely that the next one will not appear very soon. We first argue that such channels are information stable, hence their channel capacity exists. Then, we introduce several upper and lower bounds with two different methods in an attempt to understand the channel capacity behavior. The first scheme utilizes certain information provided to the transmitter and/or receiver while the second one explores the asymptotic behavior of the bounds when the average bit deletion rate is small. In the second part of the paper, we consider a practical channel coding approach over a segmented deletion channel. Specifically, we utilize outer LDPC codes concatenated with inner marker codes, and develop suitable channel detection algorithms for this scenario. Different maximum-a-posteriori (MAP) based channel synchronization algorithms operating at the bit and symbol levels are introduced, and specific LDPC code designs are explored. Simulation results clearly indicate the advantages of the proposed approach. In particular, for the entire range of deletion probabilities less than unity, our scheme offers a significantly larger transmission rate compared to the other existing solutions in the literature. © 1972-2012 IEEE
On capacity and coding for segmented deletion channels
We consider binary deletion channels with a segmentation assumption which appears to be suited for more practical scenarios. Unlike the binary independent and identically distributed (i.i.d.) deletion channel where each bit is independently deleted with an equal probability, the segmentation assumption prohibits certain transmitted bits to be deleted, i.e., in a block of bits of a certain length, only a limited number of deletions can occur. We first propose several upper and lower capacity bounds for the segmented deletion channel. Then we focus on an interleaved concatenation of an outer low-density parity check (LDPC) code with error-correction capabilities and an inner marker code with synchronization capabilities over these channels. With the help of a specifically designed maximum-a-posteriori (MAP) detector, we demonstrate reliable transmission at higher code rates than the existing ones reported in the literature. © 2011 IEEE
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