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Abstract - SPEC-DSP

SPEC-DSP.1	Signal Processing with the Sparseness Constraint B. Rao (University of California, San Diego, USA) An overview is given of the role of the sparseness constraint in signal processing problems. It is shown that this is a fundamental problem deserving of attention. This is illustrated by describing several applications where sparseness of solution is desired. Lastly, a review is given of some of the algorithms that are currently available for computing sparse solutions.
SPEC-DSP.2	Application of Basis Pursuit in Spectrum Estimation S. Chen (IBM, USA); D. Donoho (Stanford University, USA) In this paper, we apply Basis Pursuit, an atomic decomposition technique, for spectrum estimation. Compared with several modern time series methods, our approach can greatly reduce the problem of power leakage: it is able to superresolve; moreover, it works well with noisy and unevenly sampled signals. We present expiriments on bizarrely spaced radial velocity data from one of the newly-discoved extra planetary systems.
SPEC-DSP.3	Parsimony and Wavelet Method for Denoising H. Krim (MIT, USA); J. Pesquet (University Paris Sud, France); I. Schick (GTE Internetworking and Harvard Univ., USA) Some wavelet-based methods for signal estimation in the presence of noise are reviewed in the context of the parsimonious representation of the underlying signal. Three approaches are considered. The first is based on the application of the MDL principle. The robustness of this method is improved in the second approach, by relaxing the assumption of known noise distribution following Huber's work. In the third approach, a Bayesian strategy is adopted in order to incorporate prior information pertaining to the signal of interest; this method is especially useful at low signal-to-noise ratios.
SPEC-DSP.4	Parsimonious Side Propagation P. Bradley, O. Mangasarian (University of Wisconsin-Madison, USA) A fast parsimonious linear-programming-based algorithm for training neural networks is proposed that suppresses redundant features while using a minimal number of hidden units. This is achieved by propagating sideways to newly added hidden units the task of separating successive groups of unclassified points. Computational results show an improvement of 26.53 % and 19.76 % in tenfold cross-validation test correctness over a parsimonious perceptron on two publicly available datasets.
SPEC-DSP.5	Fast Optimal and Suboptimal Algorithms for Sparse Solutions to Linear Inverse Problems G. Harikumar (Tellabs Research, USA); C. Couvreur, Y. Bresler (University of Illinois, Urbana-Champaign, USA) We present two "fast" approaches to the NP-hard problem of computing a maximally sparse approximate solution to linear inverse problems, also known as best subset selection. The first approach, a heuristic, is an iterative algorithm globally convergent to sparse elements of any given convex, compact S C R th. We demonstrate its effectiveness in bandlimited extrapolation and in sparse filter design. The second approach is a polynomial-time greedy sequential backward elimination algorithm. We show that if A has full column rank and e is small enough, then the algorithm will find the sparsest x satisfying II Ax - b II < (or equal to) e, if such exists.
SPEC-DSP.6	Measures and Algorithms for Best Basis Selection K. Kreutz-Delgado, B. Rao (University of California, San Diego, USA) A general framework based on majorization, Schur-concavity, and concavity is given that facilitates the analysis of algorithm performance and clarifies the relationships between existing proposed diversity measures useful for best basis selection. Admissible sparsity measures are given by the Schur-concave functions, which are the class of functions consistent with the partial ordering on vectors known as majorization. Concave functions form an important subclass of the Schur-concave functions which attain their minima at sparse solutions to the basis selection problem. Based on a particular functional factorization of the gradient, we give a general affine scaling optimization algorithm that converges to a sparse solution for measures chosen from within this subclass.
SPEC-DSP.7	Sparse Inverse Solution Methods for Signal and Image Processing Applications B. Jeffs (Brigham Young University, USA) This paper addresses image and signal processing problems where the result most consistent with prior knowledge is the minimum order, or ``maximally sparse'' solution. These problems arise in such diverse areas as astronomical star image deblurring, neuromagnetic image reconstruction, seismic deconvolution, and thinned array beamformer design. An optimization theoretic formulation for sparse solutions is presented, and its relationship to the MUSIC algorithm is discussed. Two algorithms for sparse inverse problems are introduced, and examples of their application to beamforming array design and star image deblurring are presented.
SPEC-DSP.8	Image Denoising Using Multiple Compaction Domains P. Ishwar, K. Ratakonda, P. Moulin, N. Ahuja (University of Illinois, Urbana-Champaign, USA) We present a novel framework for denoising signals from their compact representation in multiple domains. Each domain captures, uniquely, certain signal characteristics better than others. We define confidence sets around data in each domain and find sparse estimates that lie in the intersection of these sets, using a POCS algorithm. Simulations demonstrate the superior nature of the reconstruction (both in terms of mean-square error and perceptual quality) in comparison to the adaptive Wiener filter.

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