3,942 research outputs found
Off-grid Direction of Arrival Estimation Using Sparse Bayesian Inference
Direction of arrival (DOA) estimation is a classical problem in signal
processing with many practical applications. Its research has recently been
advanced owing to the development of methods based on sparse signal
reconstruction. While these methods have shown advantages over conventional
ones, there are still difficulties in practical situations where true DOAs are
not on the discretized sampling grid. To deal with such an off-grid DOA
estimation problem, this paper studies an off-grid model that takes into
account effects of the off-grid DOAs and has a smaller modeling error. An
iterative algorithm is developed based on the off-grid model from a Bayesian
perspective while joint sparsity among different snapshots is exploited by
assuming a Laplace prior for signals at all snapshots. The new approach applies
to both single snapshot and multi-snapshot cases. Numerical simulations show
that the proposed algorithm has improved accuracy in terms of mean squared
estimation error. The algorithm can maintain high estimation accuracy even
under a very coarse sampling grid.Comment: To appear in the IEEE Trans. Signal Processing. This is a revised,
shortened version of version
Sparse MRI for motion correction
MR image sparsity/compressibility has been widely exploited for imaging
acceleration with the development of compressed sensing. A sparsity-based
approach to rigid-body motion correction is presented for the first time in
this paper. A motion is sought after such that the compensated MR image is
maximally sparse/compressible among the infinite candidates. Iterative
algorithms are proposed that jointly estimate the motion and the image content.
The proposed method has a lot of merits, such as no need of additional data and
loose requirement for the sampling sequence. Promising results are presented to
demonstrate its performance.Comment: To appear in Proceedings of ISBI 2013. 4 pages, 1 figur
Variational Bayesian algorithm for quantized compressed sensing
Compressed sensing (CS) is on recovery of high dimensional signals from their
low dimensional linear measurements under a sparsity prior and digital
quantization of the measurement data is inevitable in practical implementation
of CS algorithms. In the existing literature, the quantization error is modeled
typically as additive noise and the multi-bit and 1-bit quantized CS problems
are dealt with separately using different treatments and procedures. In this
paper, a novel variational Bayesian inference based CS algorithm is presented,
which unifies the multi- and 1-bit CS processing and is applicable to various
cases of noiseless/noisy environment and unsaturated/saturated quantizer. By
decoupling the quantization error from the measurement noise, the quantization
error is modeled as a random variable and estimated jointly with the signal
being recovered. Such a novel characterization of the quantization error
results in superior performance of the algorithm which is demonstrated by
extensive simulations in comparison with state-of-the-art methods for both
multi-bit and 1-bit CS problems.Comment: Accepted by IEEE Trans. Signal Processing. 10 pages, 6 figure
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scAI: an unsupervised approach for the integrative analysis of parallel single-cell transcriptomic and epigenomic profiles.
Simultaneous measurements of transcriptomic and epigenomic profiles in the same individual cells provide an unprecedented opportunity to understand cell fates. However, effective approaches for the integrative analysis of such data are lacking. Here, we present a single-cell aggregation and integration (scAI) method to deconvolute cellular heterogeneity from parallel transcriptomic and epigenomic profiles. Through iterative learning, scAI aggregates sparse epigenomic signals in similar cells learned in an unsupervised manner, allowing coherent fusion with transcriptomic measurements. Simulation studies and applications to three real datasets demonstrate its capability of dissecting cellular heterogeneity within both transcriptomic and epigenomic layers and understanding transcriptional regulatory mechanisms
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