- Date & Time: Friday, June 3, 2011; 11:00 AM
Speaker: Prof. Namrata Vaswani, Iowa State University
MERL Host: Petros T. Boufounos Abstract - In this talk, I will discuss our recent work on Recursive Sparse Recovery (RecSparsRec) and show how it provides novel solutions to two very different problems in dynamic imaging. RecSparsRec refers to recursive approaches to causally recover a time sequence of signals/images from a greatly reduced number of measurements (compared to existing approaches), by utilizing their sparsity.
The motivating application for RecSparsRec is fast recursive dynamic magnetic resonance imaging (MRI) for real-time applications like MRI-guided surgery. MRI is a technique for cross-sectional imaging that acquires Fourier projections of the cross-section to be reconstructed, one-at-a-time. Thus, the ability to accurately reconstruct using fewer measurements directly translates into reduced scan times. This, along with online (causal) and fast (recursive) reconstruction algorithms, can enable real-time imaging of fast changing physiological phenomena, and thus make real-time MRI feasible. Cross-sectional images of the brain, heart, or other organs are known to be wavelet sparse. Our recent work was the first to observe that, in a time sequence, their sparsity pattern changes quite slowly. Using this fact, we were able to reformulate the RecSparsRec problem as one of sparse reconstruction with partially known support. We introduced a simple, but very powerful, approach called!
Modified-CS that achieves provably exact reconstruction (in the noise-free case) and whose error is provably stable over time (in the noisy case), with using much fewer measurements than existing work. Our preliminary experiments indicate that Modified-CS needs roughly 5-times fewer measurements than existing MR scanner technology and 1.5-times fewer than existing research literature.
I will briefly also discuss our ongoing work on the difficult video analysis problem of separating foreground moving objects from a background scene that is itself is changing and dong this in real-time. This can be posed as a recursive robust principal components analysis (PCA) problem in the presence of correlated sparse outliers or equivalently, as a problem of recursive sparse recovery in the presence of very large, but ``low rank" noise (noise with a low rank covariance matrix).
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- Date & Time: Thursday, June 2, 2011; 12:00 PM
Speaker: Ramesh Annavajjala, MERL
MERL Host: Philip V. Orlik Abstract - For orthogonal frequency-division multiplexing (OFDM) based wireless systems, a resource block (RB) in a two-dimensional time-frequency plane is defined as a data block spanned by a number of consecutive OFDM symbols over a number of consecutive subcarriers. Traditionally, RBs contain modulation symbols for data transmission and pilot symbols for channel estimation.
In this talk, I present a novel approach to RB designs for OFDM systems with multiple antennas at the transmitter and the receiver (i.e., MIMO-OFDM). The proposed approach, termed resource block embedding, does not require explicit pilot symbols to estimate the channel at the receiver, and hence reduces the channel estimation overhead significantly. I describe, in detail, the encoding and decoding algorithms for our proposed embedded resource blocks (ERB) for single-user single-antenna transmission, two transmitter antenna Alamouti code, four transmitter antenna stacked Alamouti code, and multi-stream spatial multiplexing. I also outline construction of ERBs for multi-user MIMO systems.
This is a joint work with Phil Orlik and Jin Zhang.
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- Date: Sunday, May 1, 2011
MERL Contact: Anthony Vetro Brief - Anthony Vetro is Guest Editor for the Special Issue on Distributed Image Processing and Communications of the IEEE Signal Processing Magazine.
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- Date: Friday, April 1, 2011
MERL Contact: Anthony Vetro Brief - Anthony Vetro is Guest Editor for the Special Issue on 3D Media & Displays of the Proceedings of the IEEE.
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- Date: Monday, October 4, 2010 - Wednesday, October 6, 2010
Location: St Malo, France
MERL Contact: Anthony Vetro Brief - MERL is a sponsor for the 2010 edition of the IEEE Multimedia Signal Processing Workshop.
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- Date: Sunday, August 29, 2010 - Wednesday, September 1, 2010
Location: Boston, MA Brief - MERL is a sponsor for the 2010 edition of the IEEE International Conference on Advanced Video and Signal-Based Surveillance. AVSS is a forum bringing together participants from the worlds of research, industry and government agencies sharing interest in various forms of surveillance.
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- Date & Time: Sunday, September 21, 2008; 10:00 AM - 5:00 PM
Location: Brisbane, Australia Brief - MERL is a sponsor for SAPA 2008, the third ISCA Tutorial and Research Workshop on Statistical And Perceptual Audition, to be held in Brisbane, Australia, in September 2008. The workshop is co-organized by MERL researcher Bhiksha Raj.
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- Date & Time: Saturday, September 16, 2006; 9:00 AM - 6:00 PM
Location: Pittsburgh, PA Brief - MERL is a sponsor for SAPA 2006, the second ISCA Tutorial and Research Workshop on Statistical And Perceptual Audition, to be held in Pittsburgh, PA, in September 2006. The workshop is co-organized by MERL researchers Bhiksha Raj and Paris Smaragdis.
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- Date: Tuesday, July 12, 2005 - Friday, July 15, 2005
Location: Beijing, China
MERL Contact: Anthony Vetro Brief - Anthony Vetro is the Special Session Co-Chair of VCIP 2005, the IEEE Visual Communications and Image Processing Conference.
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- Date & Time: Sunday, October 3, 2004; 9:00 AM - 6:00 PM
Location: Jeju, Korea Brief - MERL is a sponsor for SAPA 2004, the first ISCA Tutorial and Research Workshop on Statistical and Perceptual Audio Processing, to be held in Jeju, Korea, in October 2004. The workshop is co-organized by MERL researchers Bhiksha Raj and Paris Smaragdis.
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