{ "id": "1910.09416", "version": "v1", "published": "2019-10-21T14:45:35.000Z", "updated": "2019-10-21T14:45:35.000Z", "title": "An Improved Linear Programming Bound on the Average Distance of a Binary Code", "authors": [ "Lei Yu", "Vincent Y. F. Tan" ], "comment": "17 pages, 2 figures", "categories": [ "math.CO", "cs.DM", "cs.IT", "math.IT", "math.MG" ], "abstract": "Ahlswede and Katona (1977) posed the following isodiametric problem in Hamming spaces: For every $n$ and $1\\le M\\le2^{n}$, determine the minimum average Hamming distance of binary codes with length $n$ and size $M$. Fu, Wei, and Yeung (2001) used linear programming duality to derive a lower bound on the minimum average distance. However, their linear programming approach was not completely exploited. In this paper, we improve Fu-Wei-Yeung's bound by finding a better feasible solution to their dual program. For fixed $0