On the list-decodability of random linear codes

  • Authors:
  • Venkatesan Guruswami;Johan Hastad;Swastik Kopparty

  • Affiliations:
  • Carnegie Mellon University, Pittsburgh, PA, USA;KTH, Stockholm, Sweden;MIT, Cambridge, MA, USA

  • Venue:
  • Proceedings of the forty-second ACM symposium on Theory of computing
  • Year:
  • 2010

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Abstract

We show that the list-decodability of random linear codes is as good as that of general random codes. Specifically, for every fixed finite field Fq, p ∈ (0,1-1/q) and ε 0, we prove that with high probability a random linear code C in Fqn of rate (1-H_q(p)-ε) can be list decoded from a fraction p of errors with lists of size at most O(1/ε). This also answers a basic open question concerning the existence of highly list-decodable linear codes, showing that a list-size of O(1/ε) suffices to have rate within ε of the "list decoding capacity" 1-Hq(p). The best previously known list-size bound was qO(1/ε) (except in the q=2 case where a list-size bound of O(1/ε) was known). The main technical ingredient in our proof is a strong upper bound on the probability that l random vectors chosen from a Hamming ball centered at the origin have too many (more than Θ(l)) vectors from their linear span also belong to the ball.