336 research outputs found
On the Design of a Novel Joint Network-Channel Coding Scheme for the Multiple Access Relay Channel
This paper proposes a novel joint non-binary network-channel code for the
Time-Division Decode-and-Forward Multiple Access Relay Channel (TD-DF-MARC),
where the relay linearly combines -- over a non-binary finite field -- the
coded sequences from the source nodes. A method based on an EXIT chart analysis
is derived for selecting the best coefficients of the linear combination.
Moreover, it is shown that for different setups of the system, different
coefficients should be chosen in order to improve the performance. This
conclusion contrasts with previous works where a random selection was
considered. Monte Carlo simulations show that the proposed scheme outperforms,
in terms of its gap to the outage probabilities, the previously published joint
network-channel coding approaches. Besides, this gain is achieved by using very
short-length codewords, which makes the scheme particularly attractive for
low-latency applications.Comment: 28 pages, 9 figures; Submitted to IEEE Journal on Selected Areas in
Communications - Special Issue on Theories and Methods for Advanced Wireless
Relays, 201
Revisiting Complex Moments For 2D Shape Representation and Image Normalization
When comparing 2D shapes, a key issue is their normalization. Translation and
scale are easily taken care of by removing the mean and normalizing the energy.
However, defining and computing the orientation of a 2D shape is not so simple.
In fact, although for elongated shapes the principal axis can be used to define
one of two possible orientations, there is no such tool for general shapes. As
we show in the paper, previous approaches fail to compute the orientation of
even noiseless observations of simple shapes. We address this problem. In the
paper, we show how to uniquely define the orientation of an arbitrary 2D shape,
in terms of what we call its Principal Moments. We show that a small subset of
these moments suffice to represent the underlying 2D shape and propose a new
method to efficiently compute the shape orientation: Principal Moment Analysis.
Finally, we discuss how this method can further be applied to normalize
grey-level images. Besides the theoretical proof of correctness, we describe
experiments demonstrating robustness to noise and illustrating the method with
real images.Comment: 69 pages, 20 figure
The superadditivity effects of quantum capacity decrease with the dimension for qudit depolarizing channels
Quantum channel capacity is a fundamental quantity in order to understand how
good can quantum information be transmitted or corrected when subjected to
noise. However, it is generally not known how to compute such quantities, since
the quantum channel coherent information is not additive for all channels,
implying that it must be maximized over an unbounded number of channel uses.
This leads to the phenomenon known as superadditivity, which refers to the fact
that the regularized coherent information of channel uses exceeds one-shot
coherent information. In this article, we study how the gain in quantum
capacity of qudit depolarizing channels relates to the dimension of the systems
considered. We make use of an argument based on the no-cloning bound in order
to proof that the possible superadditive effects decrease as a function of the
dimension for such family of channels. In addition, we prove that the capacity
of the qudit depolarizing channel coincides with the coherent information when
. We conclude that when high dimensional qudits
experiencing depolarizing noise are considered, the coherent information of the
channel is not only an achievable rate but essentially the maximum possible
rate for any quantum block code.Comment: 7 pages, 2 figure
Classes of sum-of-cisoids processes and their statistics for the modeling and simulation of mobile fading channels
In this paper, we present a fundamental study on the stationarity and ergodicity of eight classes of sum-of-cisoids (SOC) processes for the modeling and simulation of frequency-nonselective mobile Rayleigh fading channels. The purpose of this study is to determine which classes of SOC models enable the design of channel simulators that accurately reproduce the channel’s statistical properties without demanding information on the time origin or the time-consuming computation of an ensemble average. We investigate the wide-sense stationarity, first-order stationarity of the envelope, mean ergodicity, and autocorrelation ergodicity of the underlying random processes characterizing the different classes of stochastic SOC simulators. The obtained results demonstrate that only the class of SOC models comprising cisoids with constant gains, constant frequencies, and random phases is defined by a set of stationary and ergodic random processes. The analysis presented here can easily be extended with respect to the modeling and simulation of frequency-selective single-input single-output (SISO) and multiple-input multiple-output channels. For the case of frequency-selective SISO channels, we investigate the stationarity and ergodicity in both time and frequency of 16 different classes of SOC simulation models. The findings presented in this paper can be used in the laboratory as guidelines to design efficient simulation platforms for the performance evaluation of modern mobile communication systems
Performance enhancement of surface codes via recursive MWPM decoding
The minimum weight perfect matching (MWPM) decoder is the standard decoding
strategy for quantum surface codes. However, it suffers a harsh decrease in
performance when subjected to biased or non-identical quantum noise. In this
work, we modify the conventional MWPM decoder so that it considers the biases,
the non-uniformities and the relationship between , and errors of
the constituent qubits of a given surface code. Our modified approach, which we
refer to as the recursive MWPM decoder, obtains an improvement in the
probability threshold under depolarizing noise. We also obtain
significant performance improvements when considering biased noise and
independent non-identically distributed (i.ni.d.) error models derived from
measurements performed on state-of-the-art quantum processors. In fact, when
subjected to i.ni.d. noise, the recursive MWPM decoder yields a performance
improvement of over the conventional MWPM strategy and, in some
cases, it even surpasses the performance obtained over the well-known
depolarizing channel
Rate compatible modulation for non-orthogonal multiple access
We propose a new Non-Orthogonal Multiple Access (NOMA) coding scheme based on the
use of a Rate Compatible Modulation (RCM) encoder for each user. By properly designing the encoders
and taking advantage of the additive nature of the Multiple Access Channel (MAC), the joint decoder from
the inputs of all the users can be represented by a bipartite graph corresponding to a standard point-topoint RCM structure with certain constraints. Decoding is performed over this bipartite graph utilizing the
sum-product algorithm. The proposed scheme allows the simultaneous transmission of a large number of
uncorrelated users at high rates, while the decoding complexity is the same as that of standard point-to-point
RCM schemes. When Rayleigh fast fading channels are considered, the BER vs SNR performance improves
as the number of simultaneous users increases, as a result of the averaging effect
Network Coding-Based Next-Generation IoT for Industry 4.0
Industry 4.0 has become the main source of applications of the Internet of Things (IoT), which is generating new business opportunities. The use of cloud computing and artificial intelligence is also showing remarkable improvements in industrial operation, saving millions of dollars to manufacturers. The need for time-critical decision-making is evidencing a trade-off between latency and computation, urging Industrial IoT (IIoT) deployments to integrate fog nodes to perform early analytics. In this chapter, we review next-generation IIoT architectures, which aim to meet the requirements of industrial applications, such as low-latency and highly reliable communications. These architectures can be divided into IoT node, fog, and multicloud layers. We describe these three layers and compare their characteristics, providing also different use-cases of IIoT architectures. We introduce network coding (NC) as a solution to meet some of the requirements of next-generation communications. We review a variety of its approaches as well as different scenarios that improve their performance and reliability thanks to this technique. Then, we describe the communication process across the different levels of the architecture based on NC-based state-of-the-art works. Finally, we summarize the benefits and open challenges of combining IIoT architectures together with NC techniques
Periodistes, individualisme o corporativisme
Periodistes, individualisme o corporativism
Decoding algorithms for surface codes
Quantum technologies have the potential to solve computationally hard
problems that are intractable via classical means. Unfortunately, the unstable
nature of quantum information makes it prone to errors. For this reason,
quantum error correction is an invaluable tool to make quantum information
reliable and enable the ultimate goal of fault-tolerant quantum computing.
Surface codes currently stand as the most promising candidates to build error
corrected qubits given their two-dimensional architecture, a requirement of
only local operations, and high tolerance to quantum noise. Decoding algorithms
are an integral component of any error correction scheme, as they are tasked
with producing accurate estimates of the errors that affect quantum
information, so that it can subsequently be corrected. A critical aspect of
decoding algorithms is their speed, since the quantum state will suffer
additional errors with the passage of time. This poses a connundrum-like
tradeoff, where decoding performance is improved at the expense of complexity
and viceversa. In this review, a thorough discussion of state-of-the-art
surface code decoding algorithms is provided. The core operation of these
methods is described along with existing variants that show promise for
improved results. In addition, both the decoding performance, in terms of error
correction capability, and decoding complexity, are compared. A review of the
existing software tools regarding surface code decoding is also provided.Comment: 54 pages, 31 figure
The whole genome sequence of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), reveals insights into the biology and adaptive evolution of a highly invasive pest species
31 p.-11 fig.-2 tab.+ Erratum (2 p.) Papanikolaou, Alexie et al.Background: The Mediterranean fruit fly (medfly), Ceratitis capitata, is a major destructive insect pest due to its broad host range, which includes hundreds of fruits and vegetables. It exhibits a unique ability to invade and adapt to ecological niches throughout tropical and subtropical regions of the world, though medfly infestations have
been prevented and controlled by the sterile insect technique (SIT) as part of integrated pest management programs (IPMs). The genetic analysis and manipulation of medfly has been subject to intensive study in an effort to improve SIT efficacy and other aspects of IPM control.Results: The 479 Mb medfly genome is sequenced from adult flies from lines inbred for 20 generations. A highquality assembly is achieved having a contig N50 of 45.7 kb and scaffold N50 of 4.06 Mb. In-depth curation of more than 1800 messenger RNAs shows specific gene expansions that can be related to invasiveness and host adaptation, including gene families for chemoreception, toxin and insecticide metabolism, cuticle proteins, opsins, and aquaporins. We identify genes relevant to IPM control, including those required to improve SIT.Conclusions: The medfly genome sequence provides critical insights into the biology of one of the most serious and widespread agricultural pests. This knowledge should significantly advance the means of controlling the size and invasive potential of medfly populations. Its close relationship to Drosophila, and other insect species important
to agriculture and human health, will further comparative functional and structural studies of insect genomes that should broaden our understanding of gene family evolutionSupport of this project was provided by the U.S. Department of Agriculture(USDA), Agricultural Research Service (ARS), Animal and Plant Health Inspection Service (APHIS), and National Institute of Food and Agriculture(NIFA)-Biotechnology Risk Assessment Grants Program (grant #2011-39211-30769 to AMH) for funding the initial phase of this project, and to the National Institutes of Health (NIH)-National Human Genome Research Institute (NHGRI) for
funding the medfly genome sequencing, assembly and Maker 2.0 automated annotation as part of the i5K 30 genome pilot project (grant #U54 HG003273 to RAG). The NIH Intramural Research Program, National Library of Medicine funded the NCBI Gnomon annotation and the USDA-National Agricultural Library (NAL)
provided support for the WebApollo curation website, with support for manual curation training (to MM-T) provided by NIGMS (grant #5R01GM080203),NHGRI (grant #5R01HG004483), and the U.S. Department of Energy(contract #DE-AC02-05CH11231). Support was provided for: toxin metabolism and insecticide resistance gene studies from MINECO,Spain (AGL2013-42632-R to FO and PH-C); microRNAs, horizontal gene transfer and bacterial contaminant studies from the European Social Fund and National Strategic Reference Framework-THALES (MIS375869 to KB, GT, AGH, and KM) and the U.S. National Science Foundation(DEB 1257053 to JHW); cuticle protein gene studies from USDA-NIFA(grant #2016-67012-24652 to AJR); sex-determination studies from L.R.
Campania (grant 5/02, 2008 to GS); male reproduction and sexual
differentiation studies from the FAO/IAEA (Technical Contract No: 16966 to GGa) and Cariplo IMPROVE (to FS); and programmed cell death gene studies and genomic data analysis (to MFS) from the Emmy Noether program, DFG(SCHE 1833/1-1) and the LOEWE Center for Insect Biotechnology & Bioresources grant of the Hessen State Ministry of Higher Education, Research and the Arts(HMWK), Germany and from the USDA-NIFA-Biotechnology Risk Assessment Grants Program (grant #2015-33522-24094 to AMH).Peer reviewe
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