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arXiv math/0309081math.COcs.ITmath.IT
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非对称二元覆盖码

Asymmetric binary covering codes

Joshua N. Cooper, Robert B. Ellis, Andrew B. Kahng

摘要:

一个长度为n,半径为R的非对称二元覆盖码是n-立方体Q_n的子集C,使得Q_n中的每个向量x都可以由C中的某个向量c通过将c中至多R1变为0得到,其中R尽可能小。K^+(n,R)被定义为这种码的最小长度。利用非对称球覆盖界和概率方法证明了K^+(n,R)的阶为2^n/n^R,其中R为常数.我们证明了对常数Coradius R',K^+(n,n-R')= R '+1当且仅当n>= R'(R '+1)/2。这两个结果分别推广到近常数R和R '。K^+的各种界限是根据最小码中0或1的总数给出的。最小非对称线性二进制码([n,R]^+码)的维数被确定为min(0,n-R)。最后,我们讨论了公开问题和计算K^+的显式值的技术,并给出了一个最佳已知边界表。

英文摘要:

An asymmetric binary covering code of length n and radius R is a subset C of the n-cube Q_n such that every vector x in Q_n can be obtained from some vector c in C by changing at most R 1's of c to 0's, where R is as small as possible. K^+(n,R) is defined as the smallest size of such a code. We show K^+(n,R) is of order 2^n/n^R for constant R, using an asymmetric sphere-covering bound and probabilistic methods. We show K^+(n,n-R')=R'+1 for constant coradius R' iff n>=R'(R'+1)/2. These two results are extended to near-constant R and R', respectively. Various bounds on K^+ are given in terms of the total number of 0's or 1's in a minimal code. The dimension of a minimal asymmetric linear binary code ([n,R]^+ code) is determined to be min(0,n-R). We conclude by discussing open problems and techniques to compute explicit values for K^+, giving a table of best known bounds.

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