Date of Award

Spring 1-1-2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical, Computer & Energy Engineering

First Advisor

Shannon M. Hughes

Second Advisor

Youjian Liu

Third Advisor

Francois Meyer

Fourth Advisor

Lijun Chen

Fifth Advisor

Alireza Doostan

Abstract

In today's world, we often face an explosion of data that can be difficult to handle. Signal models help make this data tractable, and thus play an important role in designing efficient algorithms for acquiring, storing, and analyzing signals. However, choosing the right model is critical. Poorly chosen models may fail to capture the underlying structure of signals, making it hard to achieve satisfactory results in signal processing tasks. Thus, the most accurate and concise signal models must be used.

Many signals can be expressed as a linear combination of a few elements of some dictionary, and this is the motivation behind the emerging field of compressive sensing. Compressive sensing leverages this signal model to enable us to perform signal processing tasks without full knowledge of the data.

However, this is only one possible model for signals, and many signals could in fact be more accurately and concisely described by other models. In particular, in this thesis, we will look at two such models, and show how these other two models can be used to allow signal reconstruction and analysis from partial knowledge of the data.

First, we consider signals that belong to low-dimensional nonlinear manifolds, i.e. that can be represented as a continuous nonlinear function of few parameters. We show how to apply the kernel trick, popular in machine learning, to adapt compressive sensing to this type of sparsity. Our approach provides computationally-efficient, improved signal reconstruction from partial measurements when the signal is accurately described by such a manifold model.

We then consider collections of signals that together have strong principal components, so that each individual signal may be modeled as a linear combination of these few shared principal components. We focus on the problem of finding the center and principal components of these high-dimensional signals using only their measurements. We show experimentally and theoretically that our approach will generally return the correct center and principal components for a large enough collection of signals. The recovered principal components also allow performance gains in other signal processing tasks.

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