Results 1 - 10 of 1,093

Stochastic relaxation, Gibbs distributions and the Bayesian restoration of images.

by Stuart Geman , Donald Geman - IEEE Trans. Pattern Anal. Mach. Intell. , 1984
"... Abstract-We make an analogy between images and statistical mechanics systems. Pixel gray levels and the presence and orientation of edges are viewed as states of atoms or molecules in a lattice-like physical system. The assignment of an energy function in the physical system determines its Gibbs di ..."
Abstract - Cited by 5126 (1 self) - Add to MetaCart
Abstract-We make an analogy between images and statistical mechanics systems. Pixel gray levels and the presence and orientation of edges are viewed as states of atoms or molecules in a lattice-like physical system. The assignment of an energy function in the physical system determines its Gibbs

Snakes, Shapes, and Gradient Vector Flow

by Chenyang Xu, Jerry L. Prince - IEEE TRANSACTIONS ON IMAGE PROCESSING , 1998
"... Snakes, or active contours, are used extensively in computer vision and image processing applications, particularly to locate object boundaries. Problems associated with initialization and poor convergence to boundary concavities, however, have limited their utility. This paper presents a new extern ..."
Abstract - Cited by 755 (16 self) - Add to MetaCart
external force for active contours, largely solving both problems. This external force, which we call gradient vector flow (GVF), is computed as a diffusion of the gradient vectors of a gray-level or binary edge map derived from the image. It differs fundamentally from traditional snake external forces

Performance Comparison between Traditional and Gray-mapped 16-QAM Scheme with OFDM

by Kazi Mohitul Islam, Habib Muhammad, Nazir Ahmad, Chowdhury Akram Hossain - in both AWGN and Rayleigh Fading Channel”, International Journal of Computer and Information Technology (IJCIT , 2011
"... Abstract—Orthogonal Frequency Division Multiplexing (OFDM) using M-ary Quadrature Amplitude Modulation (QAM) is a very common approach in multicarrier communication. With the increasing demand of multimedia communication, the concept of OFDM was introduced. In this paper, we have shown a comparative ..."
Abstract - Cited by 1 (0 self) - Add to MetaCart
comparative analysis between the traditional binary mapped 16-QAM and gray mapped 16-QAM scheme with OFDM in both AWGN and Rayleigh fading channel. We have chosen the parameters SER vs SNR for binary mapping and BER vs SNR for Gray mapping for the performance analysis as these two are the most important

Laplacian eigenmaps and spectral techniques for embedding and clustering.

by Mikhail Belkin , Partha Niyogi - Proceeding of Neural Information Processing Systems, , 2001
"... Abstract Drawing on the correspondence between the graph Laplacian, the Laplace-Beltrami op erator on a manifold , and the connections to the heat equation , we propose a geometrically motivated algorithm for constructing a representation for data sampled from a low dimensional manifold embedded in ..."
Abstract - Cited by 668 (7 self) - Add to MetaCart
retrieval and data mining, one is often confronted with intrinsically low dimensional data lying in a very high dimensional space. For example, gray scale n x n images of a fixed object taken with a moving camera yield data points in rn: n2 . However , the intrinsic dimensionality of the space of all images

On the Distribution of Extrinsic L-values in Gray-mapped 16-QAM ∗

by Alex Alvarado
"... In this paper we address the issue of probabilistic modelling of the extrinsic L-values, used as reliability metrics in the context of bit interleaved coded modulation with iterative demapping (BICM-ID). Starting with a simple piece-wise linear model of the L-values obtained via the max-log approxim ..."
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-log approximation, we derive the expressions for the cumulative distribution functions of the L-values, that differentiated produce the desired forms of the probability density functions for Gray-mapped 16-QAM. To illustrate the usefulness of our analytical expressions we applied them to efficiently compute the so

Performance of Iterative MAP Receiver for MIMO-OFDM Channels with Anti-Gray Mapping

by Sajid Ahmed, T. Ratnarajah, Mathini Sellathurai, S. Ahmed, T. Ratnarajah, M. Sellathurai, C. F. N. Cowan , 2008
"... All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately. ..."
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All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.

On the distribution of L-values in gray-mapped M 2 -QAM signals: Exact expressions and simple approximations

by Alex Alvarado, Leszek Szczecinski, Rodolfo Feick, Luciano Ahumada - in IEEE Global Commun. Conf , 2007
"... Abstract — In this paper we develop formulas for the probability density function (PDF) of the reliability metrics in bitinterleaved coded modulation (BICM) for arbitrary M 2-ary quadrature amplitude modulation (M 2-QAM) with Gray mapping. The advantage of this approach over an entirely general one ..."
Abstract - Cited by 5 (3 self) - Add to MetaCart
Abstract — In this paper we develop formulas for the probability density function (PDF) of the reliability metrics in bitinterleaved coded modulation (BICM) for arbitrary M 2-ary quadrature amplitude modulation (M 2-QAM) with Gray mapping. The advantage of this approach over an entirely general one

Distribution of L-values in Gray-mapped M 2 -QAM: Closed-form approximations and applications

by Alex Alvarado, Student Member, Leszek Szczecinski, Senior Member, Senior Member, Luciano Ahumada - IEEE Trans. Commun , 2009
"... Abstract — In this paper we develop closed form approximations for the probability density function (PDF) of the reliability metrics (L-values) in bit-interleaved coded modulation (BICM). The expressions are valid for M 2-ary quadrature amplitude modulations (M 2-QAM) with Gray mapping when the metr ..."
Abstract - Cited by 3 (1 self) - Add to MetaCart
Abstract — In this paper we develop closed form approximations for the probability density function (PDF) of the reliability metrics (L-values) in bit-interleaved coded modulation (BICM). The expressions are valid for M 2-ary quadrature amplitude modulations (M 2-QAM) with Gray mapping when

SIC based Multi-user Turbo Detector for Non Gray Mapping in Distributed Antenna Systems

by Shahid Khattak, Wolfgang Rave, Gerhard Fettweis, Vodafone Stiftungslehrstuhl, Mobile Nachrichtensysteme, Technische Universität Dresden Dresden
"... Abstract — This paper deals with the multi-user detection for non Gray mappings in an uplink-OFDM system. Joint multiuser detection is made possible through the use of distributed antenna systems. An MMSE based V-BLAST strategy is used to detect the user data. We study performance of bitinterleaved ..."
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Abstract — This paper deals with the multi-user detection for non Gray mappings in an uplink-OFDM system. Joint multiuser detection is made possible through the use of distributed antenna systems. An MMSE based V-BLAST strategy is used to detect the user data. We study performance of bitinterleaved

Black-box and Gray-box Strategies for Virtual Machine Migration

by Timothy Wood, Prashant Shenoy, Arun Venkataramani, Mazin Yousif , 2007
"... Virtualization can provide significant benefits in data centers by enabling virtual machine migration to eliminate hotspots. We present Sandpiper, a system that automates the task of monitoring and detecting hotspots, determining a new mapping of physical to virtual resources and initiating the nece ..."
Abstract - Cited by 211 (7 self) - Add to MetaCart
Virtualization can provide significant benefits in data centers by enabling virtual machine migration to eliminate hotspots. We present Sandpiper, a system that automates the task of monitoring and detecting hotspots, determining a new mapping of physical to virtual resources and initiating
Results 1 - 10 of 1,093