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Chaoping Xing

Publications and source records attributed to Chaoping Xing.

81 records · Page 5Linked to original sources
arXiv2012

Cumulative Distance Enumerators of Random Codes and their Thresholds

Cumulative weight enumerators of random linear codes are introduced, their asymptotic properties are studied, and very sharp thresholds are exhibited; as a consequence, it is shown that the asymptotic Gilbert-Varshamov bound is a very sharp threshold point for the density of the linear codes whose relative distance is greater than a given positive number. For arbitrary random codes, similar settings and results are exhibited; in particular, the very sharp threshold point for the density of the codes whose relative distance is greater than a given positive number is located at half the asymptotic Gilbert-Varshamov bound.

cs.IT↗
arXiv2012

Folded Codes from Function Field Towers and Improved Optimal Rate List Decoding

We give a new construction of algebraic codes which are efficiently list decodable from a fraction $1-R-\eps$ of adversarial errors where $R$ is the rate of the code, for any desired positive constant $\eps$. The worst-case list size output by the algorithm is $O(1/\eps)$, matching the existential bound for random codes up to constant factors. Further, the alphabet size of the codes is a constant depending only on $\eps$ - it can be made $\exp(\tilde{O}(1/\eps^2))$ which is not much worse than the lower bound of $\exp(Ω(1/\eps))$. The parameters we achieve are thus quite close to the existential bounds in all three aspects - error-correction radius, alphabet size, and list-size - simultaneously. Our code construction is Monte Carlo and has the claimed list decoding property with high probability. Once the code is (efficiently) sampled, the encoding/decoding algorithms are deterministic with a running time $O_\eps(N^c)$ for an absolute constant $c$, where $N$ is the code's block length. Our construction is based on a linear-algebraic approach to list decoding folded codes from towers of function fields, and combining it with a special form of subspace-evasive sets. Instantiating this with the explicit "asymptotically good" Garcia-Stichtenoth tower of function fields yields the above parameters. To illustrate the method in a simpler setting, we also present a construction based on Hermitian function fields, which offers similar guarantees with a list and alphabet size polylogarithmic in the block length $N$. Along the way, we shed light on how to use automorphisms of certain function fields to enable list decoding of the folded version of the associated algebraic-geometric codes.

cs.IT↗
arXiv2010

New Results on Two Hypercube Coloring Problems

In this paper, we study the following two hypercube coloring problems: Given $n$ and $d$, find the minimum number of colors, denoted as $χ'_{d}(n)$ (resp. $χ_{d}(n)$), needed to color the vertices of the $n$-cube such that any two vertices with Hamming distance at most $d$ (resp. exactly $d$) have different colors. These problems originally arose in the study of the scalability of optical networks. Using methods in coding theory, we show that $χ'_{4}(2^{r+1}-1)=2^{2r+1}$, $χ'_{5}(2^{r+1})=4^{r+1}$ for any odd number $r\geq3$, and give two upper bounds on $χ_{d}(n)$. The first upper bound improves on that of Kim, Du and Pardalos. The second upper bound improves on the first one for small $n$. Furthermore, we derive an inequality on $χ_{d}(n)$ and $χ'_{d}(n)$.

math.CO↗
arXiv2009

New informations on the structure of the functional codes defined by forms of degree $h$ on non-degenerate Hermitian varieties in $\mathbb{P}^{n(\mathbb{F}_q)$}

We study the functional codes of order $h$ defined by G. Lachaud on $\mathcal{X} \subset {\mathbb{P}}^n(\mathbb{F}_q)$ a non-degenerate Hermitian variety. We give a condition of divisibility of the weights of the codewords. For $\mathcal{X}$ a non-degenerate Hermitian surface, we list the first five weights and the corresponding codewords and give a positive answer on a conjecture formulated on this question. The paper ends with a conjecture on the minimum distance and the distribution of the codewords of the first $2h+1$ weights of the functional codes for the functional codes of order $h$ on $\mathcal{X} \subset {\mathbb{P}}^n(\mathbb{F}_q)$ a non-singular Hermitian variety.

math.AG↗
arXiv2009

Intersection of two quadrics with no common hyperplane in $\mathbb{P}^{n}(\mathbb{F}_q)$}}

Let $\mathcal{Q}_1$ and $\mathcal{Q}_2$ be two arbitrary quadrics with no common hyperplane in ${\mathbb{P}}^n(\mathbb{F}_q)$. We give the best upper bound for the number of points in the intersection of these two quadrics. Our result states that $| \mathcal{Q}_1\cap \mathcal{Q}_2|\le 4q^{n-2}+π_{n-3}$. This result inspires us to establish the conjecture on the number of points of an algebraic set $X\subset {\mathbb{P}}^n(\mathbb{F}_q)$ of dimension $s$ and degree $d$: $|X(\mathbb{F}_q)|\le dq^s+π_{s-1}$.

math.CO↗
arXiv2009

Cyclic Codes and Sequences from a Class of Dembowski-Ostrom Functions

Let $q=p^n$ with $p$ be an odd prime. Let $0\leq k\leq n-1$ and $k\neq n/2$. In this paper we determine the value distribution of following exponential(character) sums \[\sum\limits_{x\in \bF_q}ζ_p^{\Tra_1^n(αx^{p^{3k}+1}+βx^{p^k+1})}\quad(α\in \bF_{p^m},β\in \bF_{q})\] and \[\sum\limits_{x\in \bF_q}ζ_p^{\Tra_1^n(αx^{p^{3k}+1}+βx^{p^k+1}+\ga x)}\quad(α\in \bF_{p^m},β,\ga\in \bF_{q})\] where $\Tra_1^n: \bF_q\ra \bF_p$ and $\Tra_1^m: \bF_{p^m}\ra\bF_p$ are the canonical trace mappings and $ζ_p=e^{\frac{2πi}{p}}$ is a primitive $p$-th root of unity. As applications: (1). We determine the weight distribution of the cyclic codes $\cC_1$ and $\cC_2$ over $\bF_{p^t}$ with parity-check polynomials $h_2(x)h_3(x)$ and $h_1(x)h_2(x)h_3(x)$ respectively where $t$ is a divisor of $d=\gcd(n,k)$, and $h_1(x)$, $h_2(x)$ and $h_3(x)$ are the minimal polynomials of $π^{-1}$, $π^{-(p^k+1)}$ and $π^{-(p^{3k}+1)}$ over $\bF_{p^t}$ respectively for a primitive element $π$ of $\bF_q$. (2). We determine the correlation distribution among a family of m-sequences.

cs.IT↗
arXiv2009

Cyclic Codes and Sequences from Kasami-Welch Functions

Let $q=2^n$, $0\leq k\leq n-1$ and $k\neq n/2$. In this paper we determine the value distribution of following exponential sums \[\sum\limits_{x\in \bF_q}(-1)^{\Tra_1^n(αx^{2^{3k}+1}+βx^{2^k+1})}\quad(α,β\in \bF_{q})\] and \[\sum\limits_{x\in \bF_q}(-1)^{\Tra_1^n(αx^{2^{3k}+1}+βx^{2^k+1}+\ga x)}\quad(α,β,\ga\in \bF_{q})\] where $\Tra_1^n: \bF_{2^n}\ra \bF_2$ is the canonical trace mapping. As applications: (1). We determine the weight distribution of the binary cyclic codes $\cC_1$ and $\cC_2$ with parity-check polynomials $h_2(x)h_3(x)$ and $h_1(x)h_2(x)h_3(x)$ respectively where $h_1(x)$, $h_2(x)$ and $h_3(x)$ are the minimal polynomials of $π^{-1}$, $π^{-(2^k+1)}$ and $π^{-(2^{3k}+1)}$ respectively for a primitive element $π$ of $\bF_q$. (2). We determine the correlation distribution among a family of binary m-sequences.

cs.IT↗
arXiv2005

Codes for Key Generation in Quantum Cryptography

As an alternative to the usual key generation by two-way communication in schemes for quantum cryptography, we consider codes for key generation by one-way communication. We study codes that could be applied to the raw key sequences that are ideally obtained in recently proposed scenarios for quantum key distribution, which can be regarded as communication through symmetric four-letter channels.

quant-ph↗