751 research outputs found
Ultra Low-Complexity Detection of Spectrum Holes in Compressed Wideband Spectrum Sensing
Wideband spectrum sensing is a significant challenge in cognitive radios
(CRs) due to requiring very high-speed analog- to-digital converters (ADCs),
operating at or above the Nyquist rate. Here, we propose a very low-complexity
zero-block detection scheme that can detect a large fraction of spectrum holes
from the sub-Nyquist samples, even when the undersampling ratio is very small.
The scheme is based on a block sparse sensing matrix, which is implemented
through the design of a novel analog-to- information converter (AIC). The
proposed scheme identifies some measurements as being zero and then verifies
the sub-channels associated with them as being vacant. Analytical and
simulation results are presented that demonstrate the effectiveness of the
proposed method in reliable detection of spectrum holes with complexity much
lower than existing schemes. This work also introduces a new paradigm in
compressed sensing where one is interested in reliable detection of (some of
the) zero blocks rather than the recovery of the whole block sparse signal.Comment: 7 pages, 5 figure
Flash memory management system and method utilizing multiple block list windows
The present invention provides a flash memory management system and method with increased performance. The flash memory management system provides the ability to efficiently manage and allocate flash memory use in a way that improves reliability and longevity, while maintaining good performance levels. The flash memory management system includes a free block mechanism, a disk maintenance mechanism, and a bad block detection mechanism. The free block mechanism provides efficient sorting of free blocks to facilitate selecting low use blocks for writing. The disk maintenance mechanism provides for the ability to efficiently clean flash memory blocks during processor idle times. The bad block detection mechanism provides the ability to better detect when a block of flash memory is likely to go bad. The flash status mechanism stores information in fast access memory that describes the content and status of the data in the flash disk. The new bank detection mechanism provides the ability to automatically detect when new banks of flash memory are added to the system. Together, these mechanisms provide a flash memory management system that can improve the operational efficiency of systems that utilize flash memory
Complexity adaptation in H.264/AVC video coder for static cameras
H.264/AVC uses variable block size motion estimation (VBSME)
to improve coding gain. However, its complexity is significant
and fixed regardless of the required quality or of the
scene characteristics. In this paper, we propose an adaptive
complexity algorithm based on using the Walsh Hadamard
Transform (WHT). VBS automatic partition and skip mode
detection algorithms also are proposed. Experimental results
show that 70% - 5% of the computation of H.264/AVC is required
to achieve the same PSNR
Automated detection of block falls in the north polar region of Mars
We developed a change detection method for the identification of ice block
falls using NASA's HiRISE images of the north polar scarps on Mars. Our method
is based on a Support Vector Machine (SVM), trained using Histograms of
Oriented Gradients (HOG), and on blob detection. The SVM detects potential new
blocks between a set of images; the blob detection, then, confirms the
identification of a block inside the area indicated by the SVM and derives the
shape of the block. The results from the automatic analysis were compared with
block statistics from visual inspection. We tested our method in 6 areas
consisting of 1000x1000 pixels, where several hundreds of blocks were
identified. The results for the given test areas produced a true positive rate
of ~75% for blocks with sizes larger than 0.7 m (i.e., approx. 3 times the
available ground pixel size) and a false discovery rate of ~8.5%. Using blob
detection we also recover the size of each block within 3 pixels of their
actual size
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