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arXiv 1005.3729cs.ITcs.DMmath.IT
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Grassmann流形上的压缩感知:一个统一的几何框架

Compressive Sensing over the Grassmann Manifold: a Unified Geometric Framework

Weiyu Xu, Babak Hassibi

摘要:

$\ell_1$极小化常用于求解欠定线性系统的稀疏解。在本文中,我们专注于寻找尖锐的性能界限恢复近似稀疏信号使用$\ell_1$最小化,可能在噪声测量。虽然限制等距属性是强大的分析恢复近似稀疏的信号与噪声测量,已知的界限上可实现的稀疏性(本文中的“稀疏性”是指在一个信号向量的非零或重要元素的集合的大小)。水平可以相当宽松。对于理想稀疏信号,邻域多面体分析能给出精确的边界,但不能很容易地推广到近似稀疏信号。从线性子空间的“平衡性”这一充分必要条件出发,为达到一定的信号恢复精度,给出了一个统一的基于\emph{null space Grassmann angle}的几何框架,用于分析$\ell_1$最小化的性能.通过研究“平衡性”属性,这个统一的框架表征了所考虑的稀疏性和$\ell_{1}$优化的恢复精度之间的尖锐的定量权衡。因此,这推广了理想稀疏信号的相邻多面体结果。除了对\emph{all}稀疏信号的“强”意义下的鲁棒性外,我们还讨论了“弱”和“分段”鲁棒性的概念。我们的结果涉及线性子空间的基本性质,因此可能是独立的数学兴趣。

英文摘要:

$\ell_1$ minimization is often used for finding the sparse solutions of an under-determined linear system. In this paper we focus on finding sharp performance bounds on recovering approximately sparse signals using $\ell_1$ minimization, possibly under noisy measurements. While the restricted isometry property is powerful for the analysis of recovering approximately sparse signals with noisy measurements, the known bounds on the achievable sparsity (The "sparsity" in this paper means the size of the set of nonzero or significant elements in a signal vector.) level can be quite loose. The neighborly polytope analysis which yields sharp bounds for ideally sparse signals cannot be readily generalized to approximately sparse signals. Starting from a necessary and sufficient condition, the "balancedness" property of linear subspaces, for achieving a certain signal recovery accuracy, we give a unified \emph{null space Grassmann angle}-based geometric framework for analyzing the performance of $\ell_1$ minimization. By investigating the "balancedness" property, this unified framework characterizes sharp quantitative tradeoffs between the considered sparsity and the recovery accuracy of the $\ell_{1}$ optimization. As a consequence, this generalizes the neighborly polytope result for ideally sparse signals. Besides the robustness in the "strong" sense for \emph{all} sparse signals, we also discuss the notions of "weak" and "sectional" robustness. Our results concern fundamental properties of linear subspaces and so may be of independent mathematical interest.

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