52,010 research outputs found
Optimal locally repairable codes of distance and via cyclic codes
Like classical block codes, a locally repairable code also obeys the
Singleton-type bound (we call a locally repairable code {\it optimal} if it
achieves the Singleton-type bound). In the breakthrough work of \cite{TB14},
several classes of optimal locally repairable codes were constructed via
subcodes of Reed-Solomon codes. Thus, the lengths of the codes given in
\cite{TB14} are upper bounded by the code alphabet size . Recently, it was
proved through extension of construction in \cite{TB14} that length of -ary
optimal locally repairable codes can be in \cite{JMX17}. Surprisingly,
\cite{BHHMV16} presented a few examples of -ary optimal locally repairable
codes of small distance and locality with code length achieving roughly .
Very recently, it was further shown in \cite{LMX17} that there exist -ary
optimal locally repairable codes with length bigger than and distance
propositional to .
Thus, it becomes an interesting and challenging problem to construct new
families of -ary optimal locally repairable codes of length bigger than
.
In this paper, we construct a class of optimal locally repairable codes of
distance and with unbounded length (i.e., length of the codes is
independent of the code alphabet size). Our technique is through cyclic codes
with particular generator and parity-check polynomials that are carefully
chosen
Xing-Ling Codes, Duals of their Subcodes, and Good Asymmetric Quantum Codes
A class of powerful -ary linear polynomial codes originally proposed by
Xing and Ling is deployed to construct good asymmetric quantum codes via the
standard CSS construction. Our quantum codes are -ary block codes that
encode qudits of quantum information into qudits and correct up to
\flr{(d_{x}-1)/2} bit-flip errors and up to \flr{(d_{z}-1)/2} phase-flip
errors.. In many cases where the length
and the field size are fixed and for chosen values of and , where is the designed distance of
the Xing-Ling (XL) codes, the derived pure -ary asymmetric quantum CSS codes
possess the best possible size given the current state of the art knowledge on
the best classical linear block codes.Comment: To appear in Designs, Codes and Cryptography (accepted Sep. 27, 2013
Efficient Systematic Encoding of Non-binary VT Codes
Varshamov-Tenengolts (VT) codes are a class of codes which can correct a
single deletion or insertion with a linear-time decoder. This paper addresses
the problem of efficient encoding of non-binary VT codes, defined over an
alphabet of size . We propose a simple linear-time encoding method to
systematically map binary message sequences onto VT codewords. The method
provides a new lower bound on the size of -ary VT codes of length .Comment: This paper will appear in the proceedings of ISIT 201
On MDS Negacyclic LCD Codes
Linear codes with complementary duals (LCD) have a great deal of significance
amongst linear codes. Maximum distance separable (MDS) codes are also an
important class of linear codes since they achieve the greatest error
correcting and detecting capabilities for fixed length and dimension. The
construction of linear codes that are both LCD and MDS is a hard task in coding
theory. In this paper, we study the constructions of LCD codes that are MDS
from negacyclic codes over finite fields of odd prime power elements. We
construct four families of MDS negacyclic LCD codes of length
, and a family of negacyclic LCD codes
of length . Furthermore, we obtain five families of -ary
Hermitian MDS negacyclic LCD codes of length and four
families of Hermitian negacyclic LCD codes of length For both
Euclidean and Hermitian cases the dimensions of these codes are determined and
for some classes the minimum distances are settled. For the other cases, by
studying and -cyclotomic classes we give lower bounds on the minimum
distance
Multiply Constant-Weight Codes and the Reliability of Loop Physically Unclonable Functions
We introduce the class of multiply constant-weight codes to improve the
reliability of certain physically unclonable function (PUF) response. We extend
classical coding methods to construct multiply constant-weight codes from known
-ary and constant-weight codes. Analogues of Johnson bounds are derived and
are shown to be asymptotically tight to a constant factor under certain
conditions. We also examine the rates of the multiply constant-weight codes and
interestingly, demonstrate that these rates are the same as those of
constant-weight codes of suitable parameters. Asymptotic analysis of our code
constructions is provided
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