Friday, June 14, 2019

matlab - Calculating an incoherence property from sub-optimal sampling patterns


EDIT (after comments and subject matter review)


CS is based on a choice of a sensing basis Φ relative to a representation basis Ψ. Using an "Incoherence Property" μ that measures the correlation between vectors from each basis it has been shown that the CS paradigm can achieve good reconstructions if the incoherence between Φ and Ψ is low. Examples of low μ come from: The spike basis (Φ) and the Fourier basis (Ψ), the noiselet basis (Φ) and the wavelet basis (Ψ), a random matrix (Φ) and a fixed basis (Ψ).


updated question is:



Is there a way to calculate the μ when the user is not able to chose Φ ahead of time to sample the signal, i.e. when the samples are already provided through some arbitrary sampling scheme that is sub-optimal vis-vis CS. My aim is to show/quantify, via μ, that the arbitrary sampling scheme I have been given is sub-optimal if one is expecting CS to work.


ORIGINAL


With respect to Matrix Completion and Compressive Sampling (CS) I'm trying to understand how to calculate an incoherence property μ between two bases Φ and Ψ. Getting this incoherence is important because if Φ and Ψ are highly correlated there is little chance of succesfully reconstructing a signal from sparse samples. It is stated here (page 3) that μ is given by:


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where n represents the number of elements in a matrix M - say an image signal.


I understand Φ to be a sensing basis and Ψ to be a sparse representation basis. I am using uniform random sampling to get a set of a samples from M. But I would also like to try arbitrary sampling patterns. (I'm not using wavelets or noiselets or Fourier coefficients - although I would like to try this eventually)


My question is:


How do I actually obtain Φ and Ψ?




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