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

作者： R. Yu C.C. Ko S. Rahardja X. Lin ASTAR Laboratories for Information Technology Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore Laboratories for Information Technology Agency for Science Technology and Research Singapore

This paper presents a bit-plane coding algorithm for Laplacian distributed sources that are commonly encountered in signal compression applications. By exploiting the statistical characteristics of the sources, the proposed algorithm achieves a rate-distortion performance that is essentially comparable to an optimal nonscalable scalar quantizer, while at the same time operates at a complexity level suitable for most practical implementations.

关键词： Laplace equations Image coding Scalability Video compression laboratories Information technology Application software Rate-distortion Compression algorithms Bandwidth

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Eigenfunctional expansion of dyadic Green's functions in gyrotropic media using cylindrical vector wave functions

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Progress in Electromagnetics Research 2003年 43卷 101-121页

作者： Li, L.-W. Lim, N.-H. Yin, W.-Y. Kong, J.-A. Department of Electrical and Computer Engineering National Universityof Singapore Kent Ridge Singapore Temasek Laboratories National Universityof Singapore Kent Ridge Singapore Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 United States

This paper presents a novel eigenfunction expansion of the electric-type dyadic Green's function for an unbounded gyrotropic medium in terms of the cylindrical vector wave functions. The unbounded Green dyadics are formulated based on the Ohm-Rayleigh method, orthogonalityof the vector wave functions, and the newly formulated curl and divergence of dyadic identities. The irrotational part of the Green's function is obtained from the residual theorem. Unlike some of the published work where some assumptions are made prior to the formulation, the irrotational dyadic Green's function in this paper is formulated rigorouslybased on the idea given by Tai.

关键词： Wave functions

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Wide-angle radar imaging using time-frequency distributions

Wide-angle radar imaging using time-frequency distributions

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作者： Lanterman, A.D. Munson Jr., D.C. Wu, Y. Sch. of Elec./Computer Engineering Georgia Institute of Technology Mail Code 0250 Atlanta GA 30332 United States Coordinated Science Laboratory Department of Electrical Engineering Univ. Illinois at Urbana-Champaign Urbana IL 61801 United States DSO National Laboratories Singapore 118230 Singapore

Low-frequency radar systems provide some attractive advantages in a few niche applications, such as foliage penetration and covert operation. In low-frequency imaging systems, data must be collected over a wide range of angles to obtain cross-range resolution comparable to that obtainable from a competing small-angle high-frequency system. The reflectivity of a target varies with aspect angle;although this variation is usually ignored by traditional radar imaging algorithms, it sometimes cannot be neglected in wide-angle scenarios. To account for aspect dependence of reflectivity, time-frequency transforms have been invoked to generate a series of images corresponding to different look angles;these images may be considered individually or synthesised into a single image. A simple theoretical analysis with a point scatter illustrates why the angular dependence needs explicit consideration. The potential of time-frequency methods is illustrated via simulations.

关键词： Radar

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OPCA: robust interdomain policy routing and traffic control

OPCA: robust interdomain policy routing and traffic control

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IEEE Conference on Open Architectures and Network Programming

作者： S. Agarwal Chen-Nee Chuah R.H. Katz IP & Interworking Division Sprint Advanced Technology Laboratories USA Computer Science Division University of California Berkeley USA Department of Electrical & Computer Engineering University of California Davis USA

An increasing number of ASes have been connecting to the Internet through the BGP inter-domain routing protocol. With increasing stress on the scale of this system and increasing reliance on Internet connectivity, more participants demand additional functionality from interdomain routing that BGP cannot handle. For example, we believe that the recent trend towards multihomed stub networks exhibits a likely intent to achieve fault tolerant and load balanced connectivity to the Internet. However, BGP today offers route fail-over times as long as 15 minutes, and very limited control over incoming traffic across multiple wide area paths. More research literature and news media are calling for stemming malicious or erroneous routing announcements. We propose a policy control architecture, OPCA, that runs as an overlay network on top of BGP. OPCA allows an AS to make route change requests at other, remote ASes to achieve faster route fail-over and provide capabilities to control traffic entering the local AS. The proposed architecture and protocol will co-exist and interact with the existing routing infrastructure and will allow for a scalable rollout of the protocol.

关键词： Robust control Traffic control Routing protocols Internet Communication system traffic control Joining processes Stress Fault tolerance IP networks IEEE news

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Understanding TCP fairness over wireless LAN

Understanding TCP fairness over wireless LAN

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

作者： S. Pilosof Ramachandran Ramjee D. Raz Y. Shavitt Prasun Sinha Department of Computer Science Technion-Israel Institute of Technology Haifa Israel Bell Laboratories Holmdel NJ USA Department of Electrical Engineering Tel-Aviv University Ramat-Aviv Israel

As local area wireless networks based on the IEEE 802.11 standard see increasing public deployment, it is important to ensure that access to the network by different users remains fair. While fairness issues in 802.11 networks have been studied before, this paper is the first to focus on TCP fairness in 802.11 networks in the presence of both mobile senders and receivers. In this paper, we evaluate extensively through analysis, simulation, and experimentation the interaction between the 802.11 MAC protocol and TCP. We identify four different regions of TCP unfairness that depend on the buffer availability at the base station, with some regions exhibiting significant unfairness of over 10 in terms of throughput ratio between upstream and downstream TCP flows. We also propose a simple solution that can be implemented at the base station above the MAC layer that ensures that different TCP flows share the 802.11 bandwidth equitably irrespective of the buffer availability at the base station.

关键词： Wireless LAN Base stations Bandwidth Media Access Protocol Wireless networks Analytical models Throughput Femtocell networks computer science USA Councils

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Transport properties of polycrystalline Si/sub 0.8/Ge/sub 0.2/ thin films for micro power generators

Transport properties of polycrystalline Si/sub 0.8/Ge/sub 0....

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International Conference on Thermoelectrics (ICT)

作者： M. Takashiri T. Borca-Tasciuc O. Olubuyide A. Jacquot J. Hoyt G. Chen Mechanical Engineering Department Massachusetts Institute of Technology Cambridge MA USA Research Division Komatsu Limited Hiratsuka Kanagawa Japan Department of Mechanical Aerospace and Nuclear Engineering Rensselaer Polytechnic Institute Troy NY USA Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA USA LPM UMR CNRS-INPL-UHP 7556 Ecole des Mines Nancy France

The transport properties of polycrystalline Si/sub 0.8/Ge/sub 0.2/ thin films are studied for their potential applications in micro power generators. These thin films are deposited by low-pressure chemical deposition (LPCVD). The doping is carried out by boron and phosphorus ion implantation, followed by annealing in nitrogen ambient. The concentration of boron and phosphorus 4.3x10/sup 19/ cm/sup -3/, and 8.7x10/sup 19/ cm/sup -3/, respectively. The thermoelectric transport properties of these thin films are measured, including electrical conductivity, Seebeck coefficient, and thermal conductivity. The electrical conductivity is measured by a 4 point-probe method. The Seebeck coefficient is measured by applying a temperature gradient along the in-plane direction, and evaluating the resulting voltage. The thermal conductivity is measured by a 3/spl omega/ method in the cross-plane direction.

关键词： Thermal conductivity Conductivity measurement Boron Electric variables measurement Semiconductor thin films Power generation Sputtering Chemicals Doping Ion implantation

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Algorithms for computing QoS paths with restoration

Algorithms for computing QoS paths with restoration

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

作者： Y. Bejerano Y. Breitbart A. Orda Rajeev Rastogi A. Sprintson Bell Laboratories Lucent Technologies Inc. Murray Hill NJ USA Department of Computer Science Kent University Kent OH USA Department of Electrical Engineering Technion-Israel Institute of Technology Haifa Israel

There is a growing interest among service providers to offer new services with quality of service (QoS) guaranties that are also resilient to failures. Supporting QoS connections requires the existence of a routing mechanism, that computes the QoS paths, i.e., paths that satisfy QoS constraints (e.g., delay or bandwidth). Resilience to failures, on the other hand, is achieved by providing, for each primary QoS path, a set of alternative QoS paths used upon a failure of either a link or a node. The above objectives, coupled with the need to minimize the global use of network resources, imply that the cost of both the primary path and the restoration topology should be a major consideration of the routing process. We undertake a comprehensive study of problems related to finding suitable restoration topologies for QoS paths. We consider both bottleneck QoS constraints, such as bandwidth, and additive QoS constraints, such as delay and jitter. This is the first study to provide a rigorous solution, with proven guarantees, to the combined problem of computing QoS paths with restoration. It turns out that the widely used approach of disjoint primary and restoration paths is not an optimal strategy. Hence, the proposed algorithms construct a restoration topology, i.e., a set of bridges, each bridge protecting a portion of the primary QoS path. This approach guaranties to find a restoration topology with low cost when one exists. In addition to analysis, we test our approach also by way of simulations. The simulation results demonstrate that our proposed approximation algorithms identify QoS restoration paths whose cost is significantly smaller than those provided by alternative approaches.

关键词： Quality of service Costs Routing Delay Bandwidth Network topology Bridges Resilience Jitter Protection

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A novel CAM/RAM based buffer manager for next generation IP routers 1

A novel CAM/RAM based buffer manager for next generation IP ...

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1st IEEE International Workshop on Electronic Design, Test and Applications

作者： Dou, C Jiang, SJ Leu, KC Department of Electrical Engineering National Yunlin University of Science and Technology Taiwan Computer and Communications Research Laboratories ITRI Taiwan

ISBN: (纸本)0769514537

This paper proposes an integrated CAM/RAM based buffer manager for next-generation IP routers. Buffer allocation is accomplished by inspecting the length field in the IP header of an incoming packet, the wasted buffer area is optimized, and the hardware implementation is simple. The data buffer is configured according to the cumulative packet size distribution observed from the underlying network thus increases the efficiency of the memory utilization. The buffer manager also supports the multicast management in an elaborate manner. In addition, it supports different-sized block movement of the packet data between the data buffer and the transmission media. Finally, it need not have to maintain the free buffer list, i.e., enormous and repeated 'insert' and 'delete' operations of pointers in a linked list are eliminated.

关键词： Managers

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Guest editorial

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IEEE Journal on Selected Areas in Communications 2002年第4期20卷 653-655页

作者： Chan, Vincent W. S. Elwalid, Anwar Ji, Chuanyi Yemini, Yacham Lea, Chin-Tau Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science Cambridge MA 02139 United States Bell Laboratories Lucent Technologies Department of Mathematics of Networks and Systems Murray Hill NJ 07974 United States Georgia Institute of Technology Department of Electrical and Computer Engineering Atlanta GA 30332 United States Columbia University Department of Computer Science New York NY 10027 United States

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Distance/motion-based segmentation under heavy background noise

Distance/motion-based segmentation under heavy background no...

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IEEE Symposium on Intelligent Vehicle

作者： Yajun Fang I. Masaki B. Horn Electrical Engineering and Computer Science Department Massachusetts Institute of Technology Cambridge MA USA Mlicrosystems Technology Laboratories Electrical Engineering and Computer Science Department Massachusetts Institute of Technology Cambridge MA USA

Typical segmentation algorithms are challenged by background noise and the variation of object sizes and object positions in video frames. In this paper, we propose a new object segmentation method based on both motion and distance information to increase segmentation reliability and to suppress background noise. Two new concepts are described in this paper. First proposed is a new distance-based background detection algorithm to remove the impact of noisy background without using reference frames. The second proposed is a new depth/motion-based segmentation that can accurately capture objects of different sizes. The algorithm introduced successfully increases the accuracy and reliability of object segmentation and motion detection.

关键词： Background noise Object detection Image edge detection Object segmentation Target tracking Road transportation Detection algorithms Motion detection Robustness Optical detectors

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