7,312 research outputs found
Maximum Distance Separable Codes for Symbol-Pair Read Channels
We study (symbol-pair) codes for symbol-pair read channels introduced
recently by Cassuto and Blaum (2010). A Singleton-type bound on symbol-pair
codes is established and infinite families of optimal symbol-pair codes are
constructed. These codes are maximum distance separable (MDS) in the sense that
they meet the Singleton-type bound. In contrast to classical codes, where all
known q-ary MDS codes have length O(q), we show that q-ary MDS symbol-pair
codes can have length \Omega(q^2). In addition, we completely determine the
existence of MDS symbol-pair codes for certain parameters
Frequency permutation arrays
Motivated by recent interest in permutation arrays, we introduce and
investigate the more general concept of frequency permutation arrays (FPAs). An
FPA of length n=m lambda and distance d is a set T of multipermutations on a
multiset of m symbols, each repeated with frequency lambda, such that the
Hamming distance between any distinct x,y in T is at least d. Such arrays have
potential applications in powerline communication. In this paper, we establish
basic properties of FPAs, and provide direct constructions for FPAs using a
range of combinatorial objects, including polynomials over finite fields,
combinatorial designs, and codes. We also provide recursive constructions, and
give bounds for the maximum size of such arrays.Comment: To appear in Journal of Combinatorial Design
Structured optical receivers to attain superadditive capacity and the Holevo limit
When classical information is sent over a quantum channel, attaining the
ultimate limit to channel capacity requires the receiver to make joint
measurements over long codeword blocks. For a pure-state channel, we construct
a receiver that can attain the ultimate capacity by applying a single-shot
unitary transformation on the received quantum codeword followed by
simultaneous (but separable) projective measurements on the
single-modulation-symbol state spaces. We study the ultimate limits of
photon-information-efficient communications on a lossy bosonic channel. Based
on our general results for the pure-state quantum channel, we show some of the
first concrete examples of codes and structured joint-detection optical
receivers that can achieve fundamentally higher (superadditive) channel
capacity than conventional receivers that detect each modulation symbol
individually.Comment: 4 pages, 4 figure
Lectures on Designing Screening Experiments
Designing Screening Experiments (DSE) is a class of information - theoretical
models for multiple - access channels (MAC). We discuss the combinatorial model
of DSE called a disjunct channel model. This model is the most important for
applications and closely connected with the superimposed code concept. We give
a detailed survey of lower and upper bounds on the rate of superimposed codes.
The best known constructions of superimposed codes are considered in paper. We
also discuss the development of these codes (non-adaptive pooling designs)
intended for the clone - library screening problem. We obtain lower and upper
bounds on the rate of binary codes for the combinatorial model of DSE called an
adder channel model. We also consider the concept of universal decoding for the
probabilistic DSE model called a symmetric model of DSE.Comment: 66 page
Locally Encodable and Decodable Codes for Distributed Storage Systems
We consider the locality of encoding and decoding operations in distributed
storage systems (DSS), and propose a new class of codes, called locally
encodable and decodable codes (LEDC), that provides a higher degree of
operational locality compared to currently known codes. For a given locality
structure, we derive an upper bound on the global distance and demonstrate the
existence of an optimal LEDC for sufficiently large field size. In addition, we
also construct two families of optimal LEDC for fields with size linear in code
length.Comment: 7 page
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