805 research outputs found
Design and Analysis of Ternary m-sequences with Interleaved Structure by d-Transform
Multilevel sequences find more and more applications in modern modulation schemes [4QPSK, 8QPSK,16QAM..]Â for the 3G ,4G system air interface [1,2].Furthermore, in modern cryptography they are also widerly used. It is also interesting to point out that the length L of these sequences are composite numbers( L=NS),that means the sequence can be easily implemented by interleaving S subsequences, each of length S.Therefore, the methods to develop multilevel sequence with interleaved structure draw a lot of attentions [3, 4]. In this contribution, a method for design and analysis of ternary m-sequences with interleaved structure is presented, based on the d-transform, Which turns out to be a very effective and versal tool for this purpose. Simulations have been made to verify the theory. We first introduce d-transform and its properties and then work out the procedure to design an interleaving sequence in d-transform. Keywords: d-transform,q-ary sequences, interleaved sequence
Indications that "codon boundaries" are physico-chemically defined and that protein-folding information is contained in the redundant exon bases
BACKGROUND: All the information necessary for protein folding is supposed to be present in the amino acid sequence. It is still not possible to provide specific ab initio structure predictions by bioinformatical methods. It is suspected that additional folding information is present in protein coding nucleic acid sequences, but this is not represented by the known genetic code. RESULTS: Nucleic acid subsequences comprising the 1st and/or 3rd codon residues in mRNAs express significantly higher free folding energy (FFE) than the subsequence containing only the 2nd residues (p < 0.0001, n = 81). This periodic FFE difference is not present in introns. It is therefore a specific physico-chemical characteristic of coding sequences and might contribute to unambiguous definition of codon boundaries during translation. The FFEs of the 1st and 3rd residues are additive, which suggests that these residues contain a significant number of complementary bases and that may contribute to selection for local RNA secondary structures in coding regions. This periodic, codon-related structure-formation of mRNAs indicates a connection between the structures of exons and the corresponding (translated) proteins. The folding energy dot plots of RNAs and the residue contact maps of the coded proteins are indeed similar. Residue contact statistics using 81 different protein structures confirmed that amino acids that are coded by partially reverse and complementary codons (Watson-Crick (WC) base pairs at the 1st and 3rd codon positions and translated in reverse orientation) are preferentially co-located in protein structures. CONCLUSION: Exons are distinguished from introns, and codon boundaries are physico-chemically defined, by periodically distributed FFE differences between codon positions. There is a selection for local RNA secondary structures in coding regions and this nucleic acid structure resembles the folding profiles of the coded proteins. The preferentially (specifically) interacting amino acids are coded by partially complementary codons, which strongly supports the connection between mRNA and the corresponding protein structures and indicates that there is protein folding information in nucleic acids that is not present in the genetic code. This might suggest an additional explanation of codon redundancy
A constrained Potts antiferromagnet model with an interface representation
We define a four-state Potts model ensemble on the square lattice, with the
constraints that neighboring spins must have different values, and that no
plaquette may contain all four states. The spin configurations may be mapped
into those of a 2-dimensional interface in a 2+5 dimensional space. If this
interface is in a Gaussian rough phase (as is the case for most other models
with such a mapping), then the spin correlations are critical and their
exponents can be related to the stiffness governing the interface fluctuations.
Results of our Monte Carlo simulations show height fluctuations with an
anomalous dependence on wavevector, intermediate between the behaviors expected
in a rough phase and in a smooth phase; we argue that the smooth phase (which
would imply long-range spin order) is the best interpretation.Comment: 61 pages, LaTeX. Submitted to J. Phys.
Raising the ClaSS of Streaming Time Series Segmentation
Ubiquitous sensors today emit high frequency streams of numerical
measurements that reflect properties of human, animal, industrial, commercial,
and natural processes. Shifts in such processes, e.g. caused by external events
or internal state changes, manifest as changes in the recorded signals. The
task of streaming time series segmentation (STSS) is to partition the stream
into consecutive variable-sized segments that correspond to states of the
observed processes or entities. The partition operation itself must in
performance be able to cope with the input frequency of the signals. We
introduce ClaSS, a novel, efficient, and highly accurate algorithm for STSS.
ClaSS assesses the homogeneity of potential partitions using self-supervised
time series classification and applies statistical tests to detect significant
change points (CPs). In our experimental evaluation using two large benchmarks
and six real-world data archives, we found ClaSS to be significantly more
precise than eight state-of-the-art competitors. Its space and time complexity
is independent of segment sizes and linear only in the sliding window size. We
also provide ClaSS as a window operator with an average throughput of 538 data
points per second for the Apache Flink streaming engine
New Lower Bounds on the Capacity of Optical Fiber Channels via Optimized Shaping and Detection
Constellation shaping is a practical and effective technique to improve the
performance and the rate adaptivity of optical communication systems. In
principle, it could also be used to mitigate the impact of nonlinear effects,
possibly increasing the information rate beyond the current limit dictated by
fiber nonlinearity. However, this appealing idea is frustrated by the
difficulty of designing an effective shaping strategy that takes into account
the nonlinearity and long memory of the fiber channel, as well as the possible
interplay with other nonlinearity mitigation strategies. As a result, only
little progress has been made so far, while the optimal shaping distribution
and the ultimate channel capacity remain unknown. In this work, we describe a
novel technique to optimize the shaping distribution in a very general setting
and high-dimensional space. For a simplified block-memoryless nonlinear optical
channel, the capacity lower bound obtained by the proposed technique can be
expressed analytically, establishing the conditions for an unbounded growth of
capacity with power. In a more realistic scenario, the technique can be
implemented by a rejection sampling algorithm driven by a suitable cost
function, and the corresponding achievable information rate estimated
numerically. The combination of the proposed technique with an improved
(non-Gaussian) decoding metric yields a new capacity lower bound for the
dual-polarization WDM channel.Comment: Submitted to IEEE Journal of Lightwave Technology on November 30th,
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Synchronization with permutation codes and Reed-Solomon codes
D.Ing. (Electrical And Electronic Engineering)We address the issue of synchronization, using sync-words (or markers), for encoded data. We focus on data that is encoded using permutation codes or Reed-Solomon codes. For each type of code (permutation code and Reed-Solomon code) we give a synchronization procedure or algorithm such that synchronization is improved compared to when the procedure is not employed. The gure of merit for judging the performance is probability of synchronization (acquisition). The word acquisition is used to indicate that a sync-word is acquired or found in the right place in a frame. A new synchronization procedure for permutation codes is presented. This procedure is about nding sync-words that can be used speci cally with permutation codes, such that acceptable synchronization performance is possible even under channels with frequency selective fading/jamming, such as the power line communication channel. Our new procedure is tested with permutation codes known as distance-preserving mappings (DPMs). DPMs were chosen because they have de ned encoding and decoding procedures. Another new procedure for avoiding symbols in Reed-Solomon codes is presented. We call the procedure symbol avoidance. The symbol avoidance procedure is then used to improve the synchronization performance of Reed-Solomon codes, where known binary sync-words are used for synchronization. We give performance comparison results, in terms of probability of synchronization, where we compare Reed-Solomon with and without symbol avoidance applied
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