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IEEE International Conference on Communications Workshops, ICC

作者： R. E. Irwin L. A. DaSilva Wireless Virginia Tech Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University USA

Dynamic spectrum access (DSA) holds the promise for more efficient utilization of the spectrum, while requiring greater cooperation between PHY, MAC, and NET layers to allocate resources and dynamically react to changing network conditions. In this paper, we propose channel assignment based on routing decisions (CARD), a mechanism that combines channel assignment and topology control so that at any given time the cognitive network self-organizes into the topology that is best suited to support the current offered traffic. CARD is a distributed mechanism, and each network node relies on local information only. We show that CARD results in an improvement in route length (and, thus, end-to-end delay), aggregate network capacity, and, in some situations, energy efficiency.

关键词： Routing Communication system traffic control Network topology Physical layer Media Access Protocol Energy efficiency Interference Resource management Aggregates Process design

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Spatially-resolved photoluminescence study of high indium content InGaN LED structures

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physica status solidi c 2010年第7‐8期7卷

作者： G. Tamulaitis J. Mickevičius D. Dobrovolskas E. Kuokštis M. Shur M. Shatalov J. Yang R. Gaska Semiconductor Physics Department and Institute of Applied Research Vilnius University Sauletekio 9-III 10222 Vilnius Lithuania Department of Electrical Computer and Systems Engineering and Center of Integrated Electronics Rensselaer Polytechnic Institute 110 Eighth Street Troy New York 12180 USA Sensor Electronic Technology Inc. 1195 Atlas Rd. Columbia SC USA

Spatially and spectrally resolved photoluminescence (PL) of green light-emitting diode (LED) structure with InGaN multiple quantum wells was studied using confocal and scanning near field optical microscopy techniques. Inhomogeneous distribution of PL intensity on the scale of 200 nm has been observed. The PL bands peaked at approximately 492 nm and 502 nm in bright and dark areas, respectively. The spot-to-spot variation of the peak position of the main PL band was in the range of ∼30 nm for the bright and ∼50 nm for the dark areas. The highest PL intensity in the bright areas was observed in the spots with PL band peaked at ∼492 nm, while emission intensity in dark areas had no correlation with the PL band spectral position. The inhomogeneous PL intensity distribution is explained by inhomogeneous distribution of nonradiative recombination centers, in contrast to a fairly constant tail states density (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

关键词： InGaN quantum wells defects SNOM photoluminescence LEDs

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Queuing Network Models for Multi-Channel P2P Live Streaming Systems

Queuing Network Models for Multi-Channel P2P Live Streaming ...

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IEEE Annual Joint Conference: INFOCOM, IEEE computer and Communications Societies

作者： D. Wu Y. Liu K. Ross Department of Computer & Information Science Polytechnic Institute of New york University Brooklyn NY USA Department of Electrical & Computer Engineering Polytechnic Institute of New york University Brooklyn NY USA

In recent years there have been several large-scale deployments of P2P live video systems. Existing and future P2P live video systems will offer a large number of channels, with users switching frequently among the channels. In this paper, we develop infinite-server queueing network models to analytically study the performance of multi-channel P2P streaming systems. Our models capture essential aspects of multi-channel video systems, including peer channel switching, peer churn, peer bandwidth heterogeneity, and Zipf-like channel popularity. We apply the queueing network models to two P2P streaming designs: the isolated channel design (ISO) and the View-Upload Decoupling (VUD) design. For both of these designs, we develop efficient algorithms to calculate critical performance measures, develop an asymptotic theory to provide closed-form results when the number of peers approaches infinity, and derive near- optimal provisioning rules for assigning peers to groups in VUD. We use the analytical results to compare VUD with ISO. We show that VUD design generally performs significantly better, particularly for systems with heterogeneous channel popularities and streaming rates.

关键词： Streaming media ISO Switches computer networks Large-scale systems Bandwidth Delay Communications Society Information science USA Councils

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A novel scheme for the compression and classification of hyperspectral images

A novel scheme for the compression and classification of hyp...

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Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing, WHISPERS

作者： Bei Xie Tamal Bose Erzsebet Merenyi Wireless Virginia Tech Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University Blacksburg VA USA Electrical and Computer Engineering Rice University Houston TX USA

Since hyperspectral images are very large, it is desirable to compress them before transmission. After receiving the compressed image, decompression is applied before performing image classification and other operations. In this paper, a new processing scheme is proposed, where image transform and quantization are applied for image compression at the transmitter and classification is performed directly on the compressed data at the receiver. The advantage of this scheme is that fewer computations are needed. computer simulations are performed on hyperspectral imagery.

关键词： Image coding Hyperspectral imaging Hyperspectral sensors Image classification Discrete cosine transforms Pulse modulation Discrete transforms Compression algorithms Artificial neural networks Quantization

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Enhancing the computing efficiency of power system dynamic analysis with PSS_E

Enhancing the computing efficiency of power system dynamic a...

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IEEE International Conference on Systems, Man and Cybernetics

作者： Ke Meng Zhao Yang Dong Kit Po Wong Department of Electrical Engineering Hong Kong Polytechnic University Hong Kong China School of Electrical Electronic and Computer Engineering University of Western Australia Perth Australia

Power system simulator for engineering (PSS_E) has gained great success in power energy industry for its powerful simulation and analysis functions. Along with market deregulation, power system planning and stability analysis warrants more effective and fast techniques due to the ever expanding large-scale interconnection of power networks. Running large-scale system multiple case studies on PSS_E will cost intensive time and efforts. In this paper, we accelerate PSS_E dynamic simulations with EnFuzion based distributed computing technique. This approach is proved to be effective by testing with 39-bus New England power system ¿n-1¿ and ¿n-1-1¿ contingency analysis. The results show that the simulation process can be speeded dramatically and the total elapsed time can be reduced proportionally with the increase of computer nodes.

关键词： Power system analysis computing Power system dynamics Power system simulation Computational modeling Power system interconnection Power system planning Analytical models Large-scale systems Power engineering computing Power system stability

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Dynamic rate and FEC adaptation for video multicast in multi-rate wireless networks

Dynamic rate and FEC adaptation for video multicast in multi...

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International Conference on Testbeds and Research Infrastructures for the Development of Networks and Communities (TRIDENTCOM)

作者： Ozgu Alay Caleb Li Anurag Rai Thanasis Korakis Yao Wang Shivendra Panwary Dept. of Electrical and Computer Engineering Polytechnic Institute of NYU Brooklyn NY USA Department of Computer Science and Engineering Indian Institute of Technology Kanpur India

Video multicast over Wireless Local Area Networks (WLANs) faces many challenges due to varying channel conditions and limited bandwidth. A promising solution to this problem is the use of packet level Forward Error Correction (FEC) mechanisms. However, the adjustment of the FEC rate is not a trivial issue due to the dynamic wireless environment. This decision becomes more complicated if we consider the multi-rate capability of the existing wireless LAN technology. In this paper, we propose a novel method which dynamically adapts the transmission rate and FEC for video multicast over multirate wireless networks. In order to evaluate the system experimentally, we implemented a prototype using open source drivers and socket programming. Our experimental results show that the proposed system significantly improves the multicast system performance.

关键词： Wireless networks Forward error correction Bandwidth Wireless LAN Error correction Media Access Protocol computer networks Streaming media Automatic repeat request Transmitters

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Bistatic synthetic aperture radar imaging for arbitrary trajectories in the presence of noise and clutter

Bistatic synthetic aperture radar imaging for arbitrary traj...

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Airborne Intelligence, Surveillance, Reconnaissance (ISR) Systems and Applications VI

作者： Swoboda, John Yarman, Can Evren Yazici, Birsen MITRE Corporation Bedford MA 01730-1420 United States Houston Technology Center WesternGeco-Schlumberger Houston TX 77042 United States Electrical Computer and System Engineering Department Rensselaer Polytechnic Institute Troy NY 12180 United States

ISBN: (纸本)9780819475732

We present an analytic, filtered-backprojection (FBP) type inversion method for bistatic synthetic aperture radar (BISAR) when the measurements have been corrupted by noise and clutter. The inversion method uses microlocal analysis in a statistical setting to design a backprojection filter that reduces the impact of noise and clutter while preserving the fidelity of the target image. We assume an isotropic single scattering model for the electromagnetic radiation that illuminates the scene of interest. We assume a priori statistical information on the target, clutter and noise. We demonstrate the performance of the algorithm and its ability to better resolve targets through numerical simulations. ©2009 SPIE.

关键词： Synthetic aperture radar

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NBC: Network-based cache coherence protocol for multistage NoCs

NBC: Network-based cache coherence protocol for multistage N...

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International SoC Design Conference, ISOCC

作者： Najla Alfaraj H. Jonathan Chao Mohamed Zahran Electrical and Computer Engineering Department Polytechnic Institute of New York University Brooklyn NY USA Electrical and Computer Engineering Department City College and Graduate Center City University of New York New York USA

ISBN: (纸本)9781424450343;9781424450350

Cache coherence is one of the main factors that can complicate the design of Network On Chip (NoC) due to the large volume of control traffic NoCs generate. With the demand to build a scalable multicore system, this problem has become more urgent to resolve. The snooping-based approach, in spite of its simplicity, cannot scale, while the directory-based approach has better scalability but involves synchronization and message exchange, resulting in a larger latency. This paper describes an efficient directory-based cache coherence protocol for a multi-stage multicore system. The protocol decouples the directories from level-2 caches and places them in the multi-stage network. It achieves two advantages over the traditional directory-based protocol in lowering the latency by almost half due to the placement of the directories, and allowing multipath routing to better load balance the traffic and thus reduce congestion. Control message multicasting and acknowledgment message aggregation are used in the network to speed up the completion of cache coherence operations. We have applied our proposed protocol on a fat-tree topology network. The simulation results based on synthesis traffic and Splash2 trace traffic show that our NBC scheme outperforms the traditional directory-based approach.

关键词： Niobium compounds Network-on-a-chip Communication system traffic control Traffic control Multicore processing Delay Scalability Routing protocols Network topology Network synthesis

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Flatbed scanner identification based on dust and scratches over scanner platen

Flatbed scanner identification based on dust and scratches o...

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Ahmet Emir Dirik Husrev Taha Sencar Nasir Memon Electrical & Computer Engineering Department Polytechnic Institute of New York University Brooklyn NY USA Computer Engineering Department TOBB University of Economics and Technology Ankara Turkey Computer & Information Science Department Polytechnic Institute of New York University Brooklyn NY USA

In this paper, a novel individual source scanner identification scheme is proposed. The scheme uses traces of dust, dirt, and scratches over scanner platen on scanned images to characterize a source scanner. The efficacy of the proposed scheme is substantiated with experimental analysis. The robustness of the scheme to the JPEG compression is also investigated. Experimental results show that proposed scheme could be used to match a scanned image to its source.

关键词： Cleaning Image analysis Glass Fingerprint recognition Forensics Robustness Image coding Pollution measurement Optical reflection Chemicals

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Efficient computation of level sets for path planning

Efficient computation of level sets for path planning

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2009 IEEE/RSJ International Conference on Intelligent Robots and Systems

作者： Bin Xu Daniel J. Stilwell Andrew Kurdila Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University Blacksburg VA USA Department of Mechanical Engineering Virginia Polytechnic Institute and State University Blacksburg VA USA

We propose an efficient method for updating a path that was computed using level-set methods. Our approach is suitable for autonomous vehicles navigating in a static environment for which an a priori map of the environment is inaccurate. When the autonomous vehicle detects a new obstacle, our algorithm replans an optimal route without recomputing the entire path. Computational costs when planning paths with level set methods are due to creation of the level set. Once the level set has been computed, the optimal path is simply gradient descent down the level set. Our approach is based on formal analysis of how the level set changes when a new obstacle is detected. We show that in many practical cases, only a small portion of the level set needs to be re-computed when a new obstacle is detected. Simulation examples are presented to validate the effectiveness of the proposed method.

关键词： Level set Path planning Remotely operated vehicles Mobile robots Vehicle detection Costs Navigation Computational efficiency Vehicle dynamics Land vehicles

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