Explicit thresholds for approximately sparse compressed sensing via l1-optimization

  • Authors:
  • Mihailo Stojnic

  • Affiliations:
  • School of Industrial Engineering, Purdue University, West Lafayette, IN

  • Venue:
  • ISIT'09 Proceedings of the 2009 IEEE international conference on Symposium on Information Theory - Volume 1
  • Year:
  • 2009

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Abstract

It is well known that compressed sensing problems reduce to solving large under-determined systems of equations. If we choose the elements of the compressed measurement matrix according to some appropriate probability distribution and if the signal is sparse enough then the l1-optimization can recover it with overwhelming probability (see, e.g, [5], [9], (10)). In fact, [5], [9], [10] establish (in a statistical context) that if the number of measurements is proportional to the length of the signal then there is a sparsity of the unknown signal proportional to its length for which the success of the l1-optimization is guaranteed. In this paper we consider a modification of this standard setup, namely the case of the so-called approximately sparse unknown signals [7], [27]. We determine sharp lower bounds on the values of allowable approximate sparsity for any given number (proportional to the length of the unknown signal) of measurements. We introduce a novel, very simple technique which provides very good values for proportionality constants.