26,339 research outputs found
Relaxed Recovery Conditions for OMP/OLS by Exploiting both Coherence and Decay
We propose extended coherence-based conditions for exact sparse support
recovery using orthogonal matching pursuit (OMP) and orthogonal least squares
(OLS). Unlike standard uniform guarantees, we embed some information about the
decay of the sparse vector coefficients in our conditions. As a result, the
standard condition (where denotes the mutual coherence and
the sparsity level) can be weakened as soon as the non-zero coefficients
obey some decay, both in the noiseless and the bounded-noise scenarios.
Furthermore, the resulting condition is approaching for strongly
decaying sparse signals. Finally, in the noiseless setting, we prove that the
proposed conditions, in particular the bound , are the tightest
achievable guarantees based on mutual coherence
Term-Specific Eigenvector-Centrality in Multi-Relation Networks
Fuzzy matching and ranking are two information retrieval techniques widely used in web search. Their application to structured data, however, remains an open problem. This article investigates how eigenvector-centrality can be used for approximate matching in multi-relation graphs, that is, graphs where connections of many different types may exist. Based on an extension of the PageRank matrix, eigenvectors representing the distribution of a term after propagating term weights between related data items are computed. The result is an index which takes the document structure into account and can be used with standard document retrieval techniques. As the scheme takes the shape of an index transformation, all necessary calculations are performed during index tim
Channel Aided Interference Alignment
Interference alignment (IA) techniques mostly attain their degrees of freedom
(DoF) benefits as the number of channel extensions tends to infinity.
Intuitively, the more interfering signals that need to be aligned, the larger
the number of dimensions needed to align them. This requirement poses a major
challenge for IA in practical systems. This work evaluates the necessary and
sufficient conditions on channel structure of a fully connected interference
network with time-varying fading to make perfect IA feasible within limited
number of channel extensions. We propose a method based on the obtained
conditions on the channel structure to achieve perfect IA. For the case of
user interference channel, it is shown that only one condition on channel
coefficients is required to make perfect IA feasible at all receivers. IA
feasibility literature have mainly focused on network topology so far. In
contrast, derived channel aiding conditions in this work can be considered as
the perfect IA feasibility conditions on channel structure.Comment: 20 pages, 4 figure. arXiv admin note: text overlap with
arXiv:0901.4379 by other author
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