Hardness of approximation results for the problem of finding the stopping distance in tanner graphs

  • Authors:
  • K. Murali Krishnan;L. Sunil Chandran

  • Affiliations:
  • Department of Computer Science and Automation, Indian Institute of Science, Bangalore, India;Department of Computer Science and Automation, Indian Institute of Science, Bangalore, India

  • Venue:
  • FSTTCS'06 Proceedings of the 26th international conference on Foundations of Software Technology and Theoretical Computer Science
  • Year:
  • 2006

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Abstract

Tanner Graph representation of linear block codes is widely used by iterative decoding algorithms for recovering data transmitted across a noisy communication channel from errors and erasures introduced by the channel. The stopping distance of a Tanner graph T for a binary linear block code C determines the number of erasures correctable using iterative decoding on the Tanner graph T when data is transmitted across a binary erasure channel using the code C. We show that the problem of finding the stopping distance of a Tanner graph is hard to approximate within any positive constant approximation ratio in polynomial time unless P=NP. It is also shown as a consequence that there can be no approximation algorithm for the problem achieving an approximation ratio of $2^{(\log n)^{1-\epsilon}}$ for any ε 0 unless NP⊆DTIME(npoly(logn)).