Imperial College London > Talks@ee.imperial > Charlotte B Grady's list > Breaking the coherence barrier - A new theory for compressed sensing

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## Breaking the coherence barrier - A new theory for compressed sensingAdd to your list(s) Download to your calendar using vCal - Dr Anders Hansen, Cambridge University
- Thursday 30 April 2015, 14:00-15:00
- Dennis Gabor Seminar Room, 611, level 6, EEE Dept. .
If you have a question about this talk, please contact Pier Luigi Dragotti. Compressed sensing is based on the three pillars: sparsity, incoherence and uniform random subsampling. In addition, the concepts of uniform recovery and the Restricted Isometry Property (RIP) have had a great impact. Intriguingly, in an overwhelming number of inverse problems where compressed sensing is used or can be used (such as MRI , X-ray tomography, Electron microscopy, Reflection seismology etc.) these pillars are absent. Moreover, easy numerical tests reveal that with the successful sampling strategies used in practice one does not observe uniform recovery nor the RIP . In particular, none of the existing theory can explain the success of compressed sensing in a vast area where it is used. In this talk we will demonstrate how real world problems are not sparse, yet asymptotically sparse, coherent, yet asymptotically incoherent, and moreover, that uniform random subsampling yields highly suboptimal results. In addition, we will present easy arguments explaining why uniform recovery and the RIP is not observed in practice. Finally, we will introduce a new theory that aligns with the actual implementation of compressed sensing that is used in applications. This theory is based on asymptotic sparsity, asymptotic incoherence and random sampling with different densities. This theory supports two intriguing phenomena observed in reality: 1. the success of compressed sensing is resolution dependent; 2. the optimal sampling strategy is signal structure dependent. The last point opens up for a whole new area of research, namely the quest for the optimal sampling strategies. This talk is part of the Charlotte B Grady's list series. ## This talk is included in these lists:Note that ex-directory lists are not shown. |
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