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Globecom '00 - IEEE. Global Telecommunications Conference. Conference Record (Cat. No.00CH37137)

作者： H.M. Smith M.W. Mutka Department of Computer Science California Polytechnic State University San Louis Obispo CA USA Department of Computer Science and Engineering Michigan State University East Lansing MI USA

Some type of transmission rate control protocol is required in order to support multicast video applications over the Internet. Previously, we proposed a protocol, the layered multicast control protocol (LMCP), which utilizes both the sender and receiver to control the rate of the video transmission. The sender stripes the video signal across multiple multicast channels, and each receiver selectively adds and drops channels to meet their individual needs. The receivers also send feedback to the sender, and the sender uses this feedback to adjust the transmission rate for each channel. One weakness of this approach is that it did not share the available bandwidth fairly among multiple video applications. In this paper we introduce a new router based approach for determining a video applications fair share of the available network bandwidth. This approach builds on the strengths of the LMCP approach while allowing multiple video applications to share the available bandwidth. This approach requires low overhead on the network routers, scales well to hundreds of video sources and is independent of the number of video receivers. We show through our simulation results that this approach allows the network to be shared fairly among video applications and adjusts gracefully to fluctuations in available bandwidth.

关键词： Teleconferencing Video sharing Videoconference Multicast protocols Bandwidth Process control Feedback computer science Application software Internet

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Dynamic knowledge representation and its applications 9th

Dynamic knowledge representation and its applications

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9th International Conference on Artificial Intelligence: Methodology, Systems, and Applications, AIMSA 2000

作者： Alferes, José Júlio Pereira, Luís Moniz Przymusinska, Halina Przymusinski, Teodor C. Quaresma, Paulo Centro de Inteligência Artificial Univ. Nova de Lisboa CaparicaP-2825-114 Portugal Dept. de Informática Univ. Évora Rua Romão Ramalho 59 ÉvoraP-7000 Portugal Department of Computer Science California State Polytechnic University PomonaCA91768 United States Department of Computer Science and Engineering University of California RiversideCA92521 United States

ISBN: (纸本)3540410449

This paper has two main objectives. One is to show that the dynamic knowledge representation paradigm introduced in [ALP+00] and the associated language LUPS, defined in [APPP99], constitute natural, powerful and expressive tools for representing dynamically changing knowledge. We do so by demonstrating the applicability of the dynamic knowledge representation paradigm and the language LUPS to several broad knowledge representation domains, for each of which we provide an illustrative example. Our second objective is to extend our approach to allow proper handling of conflicting updates. So far, our research on knowledge updates was restricted to a two-valued semantics, which, in the presence of conflicting updates, leads to an inconsistent update, even though the updated knowledge base does not necessarily contain any truly contradictory information. By extending our approach to the three-valued semantics we gain the added expressiveness allowing us to express undefined or noncommittal updates. © Springer-Verlag Berlin Heidelberg 2000.

关键词： Knowledge representation

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A general method for calculating error probabilities over fading channels

A general method for calculating error probabilities over fa...

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IEEE International Conference on Communications (ICC)

作者： A. Annamalai C. Tellambura V.K. Bhargava Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University Falls Church VA USA School of Computer Science and Software Engineering Monash University Clayton VIC Australia Department of Electrical and Computer Engineering University of Victoria Victoria BC Canada

This paper presents a general method for calculating the average error rates and outage performance of a broad class of coherent, differentially coherent and noncoherent communication systems with/without diversity reception in a myriad of fading environments. Unlike the moment generating function (MGF) technique, the proposed characteristic function (CHF) method based on Parseval's theorem enables us to unify the average error rate analysis of different modulation formats and all commonly used predetection diversity techniques (i.e., maximal-ratio combining (MR), equal-gain combining (EG), selection diversity (SD), switched diversity (SW) and hybrid diversity systems) in a single common framework. The CHF method also lends itself to the averaging of the conditional error probability (CEP) involving the complementary incomplete Gamma function and the confluent hypergeometric function over fading amplitudes, which heretofore resisted to a simple form. As an aside, we show previous results as special instances of our unified framework.

关键词： Fading Diversity reception Error analysis Modulation Error probability Signal analysis Fourier transforms computer errors computer science software engineering

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Multiscale Coherent Structures and Broadband Waves due to Parallel Inhomogeneous Flows

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Physical Review Letters 2000年第20期85卷 4285-4285页

作者： Valeriy V. Gavrishchaka Gurudas I. Ganguli Wayne A. Scales Steven P. Slinker Christopher C. Chaston James P. McFadden Robert E. Ergun Charles W. Carlson Science Applications International Corporation McLean Virginia Plasma Physics Division Naval Research Laboratory Washington D.C. Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University Blacksburg Virginia Space Sciences Laboratory University of California Berkeley California Department of Astrophysical and Planetary Science Laboratory for Atmospheric and Space Physics Colorado University Boulder Colorado

Linear theory analysis and particle-in-cell simulations show that a spatial transverse gradient in the ion drift parallel to the magnetic field, dVdi/dx≤Ωi, where Ωi is the ion cyclotron frequency, can generate a broadband multimode spectrum extending from ω≪Ωi to ω≫Ωi. Nonlinearly, these waves lead to multiscale spatially coherent structures, substantial cross-field transport, ion energization, and phase-space diffusion. Large spikes are formed in the parallel electric field time series. These signatures are similar to the Fast Auroral Snapshot satellite observations in the upward current region.

关键词： .generate coherent structures drift Plasma Physics Inhomogeneous upward time series electric fields ion beams

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Exact analysis of equal-gain diversity systems over fading channels

Exact analysis of equal-gain diversity systems over fading c...

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IEEE Conference on Vehicular Technology (VTC)

作者： A. Annamalai Jing Su C. Tellambura Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University Falls Church VA USA Mobile Communications Technology Center Mitsubishi Wireless Communications San Diego CA USA School of Computer Science and Software Engineering Monash University Clayton VIC Australia

Performance evaluation of equal-gain (EG) diversity systems is notoriously difficult-a classical problem dating back to Lord Rayleigh himself almost a century ago. A number of references to this problem and to its difficulty can be found in the research literature and textbooks. In this paper, we derive exact analytical expressions for the EG receiver performance in Rayleigh, Rician, Nakagami-m and Nakagami-q fading channels in terms of the Appell hypergeometric function. Our methodology and analytical framework can readily handle any order of diversity as well as arbitrary fading statistics (including mixed-fading). The method also applies to a broad class of coherent, differentially coherent and noncoherent modulation formats. For coherent BPSK and BFSK, the solution is particularly simple because a desirable exponential integral representation for the Gaussian probability integral is available.

关键词： Fading Diversity reception Rayleigh channels Modulation Closed-form solution Rician channels Frequency domain analysis Error probability Mobile communication Communications technology

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Symbolic Intersect Detection: A Method for Improving Spatial Intersect Joins

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GeoInformatica 1998年第2期2卷 149-174页

作者： Huang, Yun-Wu Jones, Matthew Rundensteiner, Elke A. IBM T.J. Watson Research Center Hawthorne NY 10532 United States University of Michigan Elec. Eng. and Comp. Science Dept. Ann Arbor MI 48109 United States Worcester Polytechnic Institute Department of Computer Science Worcester MA 01609 100 Institute Road United States National Chiao-Tung University Taiwan Indiana University United States University of Michigan United States IBM T.J. Watson Research Center United States Rice University United States ABD Comp. Sci. Software Syst. R. University of Michigan United States Department of Computer Science Worcester Polytechnic Institute United States Dept. of Elec. Eng. and Comp. Sci. University of Michigan United States Johann Wolfgang Goethe University Frankfurt Germany Florida State University United States University of California Irvine CA United States

Due to the increasing popularity of spatial databases, researchers have focused their efforts on improving the query processing performance of the most expensive spatial database operation: the spatial join. While most previous work focused on optimizing the filter step, it has been discovered recently that, for typical GIS data sets, the refinement step of spatial join processing actually requires a longer processing time than the filter step. Furthermore, two-thirds of the time in processing the refinement step is devoted to the computation of polygon intersections. To address this issue, we therefore introduce a novel approach to spatial join optimization that drastically reduces the time of the refinement step. We propose a new approach called Symbolic Intersect Detection (SID) for early detection of true hits. Our SID optimization eliminates most of the expensive polygon intersect computations required by a spatial join by exploiting the symbolic topological relationships between the two candidate polygons and their overlapping minimum bounding rectangle. One important feature of our SID optimization is that it is complementary to the state-of-the-art methods in spatial join processing and therefore can be utilized by these techniques to further optimize their performance. In this paper, we also develop an analytical cost model that characterizes SID's effectiveness under various conditions. Based on real map data, we furthermore conduct an experimental evaluation comparing the performance of the spatial joins with SID against the state-of-the-art approach. Our experimental results show that SID can effectively identify more than 80% of the true hits with negligible overhead. Consequently, with SID, the time needed for resolving polygon intersect in the refinement step is improved by over 50% over known techniques, as predicted by our analytical model.

关键词： Spatial databases Spatial joins Spatial query processing True hit detection

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The consensus glossary of temporal database concepts - february 1998 version

Lecture Notes in Computer Science (including subseries Lectu...

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Lecture Notes in computer science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 1998年 1399卷 367-405页

作者： Jensen, Christian S. Dyreson, Curtis E. Bohlen, Michael Clifford, James Elmasri, Ramez Gadia, Shashi K Grandi, Fabio Hayes, Pat Jajodia, Sushil Käfer, Wolfgang Kline, Nick Lorentzos, Nikos Mitsopoulos, Yannis Montanari, Angelo Nonen, Daniel Peressi, Elisa Pernici, Barbara Roddick, John F Sarda, Nandlal L Scalas, Maria Rita Segev, Arie Snodgrass, Richard T Soo, Mike D. Tansel, Abdullah Tiberio, Paolo Wiederhold, Gio Aalborg University Department of Computer Science Fredrik Bajers Vej 7E Aalborg ØDK-9220 Denmark Computer Science Dept Aalborg University Denmark Computer Science Dept James Cook University Australia Computer Science Engineer¬ing Dept University of Texas at Arlington United States Computer Science Dept Iowa State University United States CIOC-CNR DEIS University of Bologna Italy Beckman Institute United States In¬formation and Software Systems Engineering Dept George Mason University United States Mercedes Benz Agricultural University of Athens Greece Informatics Laboratory Agricultural University of Athens Greece Infor¬matics Laboratory Agricultural University of Athens Greece Dip. di Matematica e Informatica Universita di Udine Italy Computer Science Dept Concordia University Canada Dip. di Matematica e Informatica Universita di Udine Italy Electronic Engineering and Information Sciences Dept Politecnico di Milano Italy School of Computer and Information Science University of South Australia Australia Computer Science and Engineering Dept Indian Institute of Technology Bombay India University of Bologna Italy School of Business Adm. and Computer Science Research Dept University of California United States Computer Science Dept Uni¬versity of Arizona United States Computer Science and Engineering Dept University of South Florida United States Bernard M. Baruch College City University of New York United States CIOC-CNR DEIS University of Bologna Italy Computer Science Dept Stanford University United States

This document1 contains definitions of a wide range of concepts specific to and widely used within temporal databases. In addition to providing definitions, the document also includes explanations of concepts as well as discussions of the adopted names. The consensus effort that lead to this glossary was initiated in Early 1992. Earlier versions appeared in SIGMOD Record in September 1992 and March 1994. The present glossary subsumes all the previous documents. The glossary meets the need for creating a higher degree of consensus on the definition and naming of temporal database concepts. Two sets of criteria are included. First, all included concepts were required to satisfy four relevance criteria, and, second, the naming of the concepts was resolved using a set of evaluation criteria. The concepts are grouped into three categories: concepts of general database interest, of temporal database interest, and of specialized interest. © Springer-Verlag Berlin Heidelberg 1998.

关键词： Database systems

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A Hierarchical Path View Model for Path Finding in Intelligent Transportation Systems

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GeoInformatica 1997年第2期1卷 125-159页

作者： Huang, Yun-Wu Jing, Ning Rundensteiner, Elke A. University of Michigan United States Chagsha Institute of Technology China Worcester Polytechnic Insitute United States National Chiao-Tung University Taiwan Indiana University United States Dept. of Elec. Eng. and Comp. Sci. University of Michigan United States Changsha Institute of Technology Changsha China State Education Commission China Department of Electrical Engineering Changsha Institute of Technology China Johann Wolfgang Goethe University Frankfurt Germany University of California Irvine CA United States IEEE ACM United States Department of Computer Science Worcester Polytechnic Institute United States

Effective path finding has been identified as an important requirement for dynamic route guidance in Intelligent Transportation Systems (ITS). Path finding is most efficient if the all-pair (shortest) paths are precomputed because path search requires only simple lookups of the precomputed path views. Such an approach however incurs path view maintenance (computation and update) and storage costs which can be unrealistically high for large ITS networks. To lower these costs, we propose a Hierarchical Path View Model (HPVM) that partitions an ITS road map, and then creates a hierarchical structure based on the road type classification. HPVM includes a map partition algorithm for creating the hierarchy, path view maintenance algorithms, and a heuristic hierarchical path finding algorithm that searches paths by traversing the hierarchy. HPVM captures the dynamicity of traffic change patterns better than the ITS path finding systems that use the hierarchical A* approach because: (1) during path search, HPVM traverses the hierarchy by dynamically selecting the connection points between two levels based on up-to-date traffic, and (2) HPVM can reroute the high-speed road traffic through local streets if needed. In this paper, we also present experimental results used to benchmark HPVM and to compare HPVM with alternative ITS path finding approaches, using both synthetic and real ITS maps that include a large Detroit map ( > 28,000 nodes). The results show that the HPVM incurs much lower costs in path view maintenance and storage than the non-hierarchical path precomputation approach, and is more efficient in path search than the traditional ITS path finding using A* or hierarchical A* algorithms.

关键词： Digital map databases Intelligent transportation systems Path queries Path search

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RBF growing algorithm applied to the equalization and co-channel interference rejection problem

RBF growing algorithm applied to the equalization and co-cha...

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International Joint Conference on Neural Networks (IJCNN)

作者： I. Howitt J.H. Reed V. Vemuri T.C. Hsia Department of Electrical & Computer Engineering University of California Davis CA USA Mobile and Portable Radio Research Group Bradley Department of Electrical Engineering Virginia Polytechnic Institute and State University Blacksburg VA USA Department of Applied Science University of California Livermore CA USA

Recently the RBF network has been successfully applied to a number of communication signal processing problems, including equalization and co-channel interference rejection. Determining the number and locations of the centers is an important but usually neglected issue. A growing RBF algorithm for determining the number and location of the centers is presented and the performance is compared to a RBF with prescribed centers. The growing algorithm's advantages are its limited need for prior information and its ability to better utilize the allocated centers. As an example, the growing algorithm reduced the number of centers by more than a factor of 2/sup 31/ over the prescribed method to achieve a desired performance for an equalization and interference rejection application.< >

关键词： Interchannel interference Signal processing algorithms Clustering algorithms Radial basis function networks Vector quantization computer networks Feeds Neural networks Parameter estimation state-space methods

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A standard simulation environment: a review of preliminary requirements 94

A standard simulation environment: a review of preliminary r...

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Simulation Winter Conference

作者： M.A.F. Wagner S. Sevinc O. Tanir P.L. Haigh J.D. Arthur R.E. Nance H.D. Schwetman SysTech Software Solutions Annandale VA USA Knowledge Systems Group Basser University of Sydney Australia Quality Engineering and Research (QER) Group Longueuil QUE Canada High Performance Software Inc. Dayton OH USA Systems Research Center Department of Computer Science Virginia Polytechnic Institute and State University Blacksburg VA USA Mesquite Software Inc. Austin TX USA

ISBN: (纸本)9780780321090

The concept of a simulation environment combines different aspects of the simulation process into one complete powerful tool. The environment should provide the necessary state-of-the-art advances and concepts that a modeler may require during the simulation development and execution process. The "environment" requirements must address the end user needs while minimizing the necessity of learning a new language. The requirements must specify the useful features, independent of different platforms and implementation languages. Hence the opportunity exists for standardization of environments. The paper opens a discussion on challenges and rewards awaiting the simulation community with the advent of a standard environment.

关键词： Power system modeling Computational modeling computer simulation Standardization Knowledge based systems Australia Knowledge engineering software performance Drives computer science

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