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IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks, DySPAN

作者： Hyoil Kim Kang G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

We address the problem of rapidly discovering spectrum opportunities for seamless service provisioning for secondary users (SUs) in cognitive radio networks (CRNs). Specifically, we propose an efficient sensing-sequence that incurs a small opportunity-discovery delay by considering (1) the probability that a spectrum band (or a channel) may be available at the time of sensing, (2) the duration of sensing on a channel, and (3) the channel capacity. We derive the optimal sensing-sequence for channels with homogeneous capacities, and a suboptimal sequence for channels with heterogeneous capacities for which the problem of finding the optimal sensing-sequence is shown to be NP-hard. To support the proposed sensing-sequence, we also propose a channel-management strategy that optimally selects and updates the list of backup channels. A hybrid of maximum likelihood (ML) and Bayesian inference is also introduced for flexible estimation of ON/OFF channel-usage patterns and prediction of channel availability when sensing produces infrequent samples. The proposed schemes are evaluated via in-depth simulation. For the scenarios we considered, the proposed suboptimal sequence is shown to achieve close-to-optimal performance, reducing the opportunity-discovery delay by up to 47% over an existing probability-based sequence. The hybrid estimation strategy is also shown to outperform the ML-only strategy by reducing the overall opportunity-discovery delay by up to 34%.

关键词： Sensors Channel capacity Delay Algorithm design and analysis Availability Channel estimation Maximum likelihood estimation

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Fermi LAT observations of cosmic-ray electrons from 7 GeV to 1 TeV

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Physical Review D 2010年第9期82卷 092004-092004页

作者： M. Ackermann M. Ajello W. B. Atwood L. Baldini J. Ballet G. Barbiellini D. Bastieri B. M. Baughman K. Bechtol F. Bellardi R. Bellazzini F. Belli B. Berenji R. D. Blandford E. D. Bloom J. R. Bogart E. Bonamente A. W. Borgland T. J. Brandt J. Bregeon A. Brez M. Brigida P. Bruel R. Buehler T. H. Burnett G. Busetto S. Buson G. A. Caliandro R. A. Cameron P. A. Caraveo P. Carlson S. Carrigan J. M. Casandjian M. Ceccanti C. Cecchi Ö. Çelik E. Charles A. Chekhtman C. C. Cheung J. Chiang A. N. Cillis S. Ciprini R. Claus J. Cohen-Tanugi J. Conrad R. Corbet M. DeKlotz C. D. Dermer A. de Angelis F. de Palma S. W. Digel G. Di Bernardo E. do Couto e Silva P. S. Drell A. Drlica-Wagner R. Dubois D. Fabiani C. Favuzzi S. J. Fegan P. Fortin Y. Fukazawa S. Funk P. Fusco D. Gaggero F. Gargano D. Gasparrini N. Gehrels S. Germani N. Giglietto P. Giommi F. Giordano M. Giroletti T. Glanzman G. Godfrey D. Grasso I. A. Grenier M.-H. Grondin J. E. Grove S. Guiriec M. Gustafsson D. Hadasch A. K. Harding M. Hayashida E. Hays D. Horan R. E. Hughes G. Jóhannesson A. S. Johnson R. P. Johnson W. N. Johnson T. Kamae H. Katagiri J. Kataoka M. Kerr J. Knödlseder M. Kuss J. Lande L. Latronico M. Lemoine-Goumard M. Llena Garde F. Longo F. Loparco B. Lott M. N. Lovellette P. Lubrano A. Makeev M. N. Mazziotta J. E. McEnery J. Mehault P. F. Michelson M. Minuti W. Mitthumsiri T. Mizuno A. A. Moiseev C. Monte M. E. Monzani E. Moretti A. Morselli I. V. Moskalenko S. Murgia T. Nakamori M. Naumann-Godo P. L. Nolan J. P. Norris E. Nuss T. Ohsugi A. Okumura N. Omodei E. Orlando J. F. Ormes M. Ozaki D. Paneque J. H. Panetta D. Parent V. Pelassa M. Pepe M. Pesce-Rollins V. Petrosian M. Pinchera F. Piron T. A. Porter S. Profumo S. Rainò R. Rando E. Rapposelli M. Razzano A. Reimer O. Reimer T. Reposeur J. Ripken S. Ritz L. S. Rochester R. W. Romani M. Roth H. F.-W. Sadrozinski N. Saggini D. Sanchez A. Sander C. Sgrò E. J. Siskind P. D. Smith G. Spandre P. Spinelli Ł. Stawarz T. E. Stephens M. S. Strickman A. W. Strong D. J. Suson H. Tajima H. Takahashi T. Takahash W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics and SLAC National Accelerator Laboratory Stanford University Stanford California 94305 USA Santa Cruz Institute for Particle Physics Department of Physics and Department of Astronomy and Astrophysics University of California at Santa Cruz Santa Cruz California 95064 USA Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy Laboratoire AIM CEA-IRFU/CNRS/Université Paris Diderot Service d’Astrophysique CEA Saclay 91191 Gif sur Yvette France Istituto Nazionale di Fisica Nucleare Sezione di Trieste I-34127 Trieste Italy Dipartimento di Fisica Università di Trieste I-34127 Trieste Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova I-35131 Padova Italy Dipartimento di Fisica “G. Galilei” Università di Padova I-35131 Padova Italy Department of Physics Center for Cosmology and Astro-Particle Physics The Ohio State University Columbus Ohio 43210 USA Istituto Nazionale di Fisica Nucleare Sezione di Roma “Tor Vergata” I-00133 Roma Italy Dipartimento di Fisica Università di Roma “Tor Vergata” I-00133 Roma Italy Istituto Nazionale di Fisica Nucleare Sezione di Perugia I-06123 Perugia Italy Dipartimento di Fisica Università degli Studi di Perugia I-06123 Perugia Italy Centre d’Étude Spatiale des Rayonnements CNRS/UPS BP 44346 F-30128 Toulouse Cedex 4 France Dipartimento di Fisica “M. Merlin” dell’Università e del Politecnico di Bari I-70126 Bari Italy Istituto Nazionale di Fisica Nucleare Sezione di Bari 70126 Bari Italy Laboratoire Leprince-Ringuet École Polytechnique CNRS/IN2P3 Palaiseau France Department of Physics University of Washington Seattle Washington 98195-1560 USA Institut de Ciencies de l’Espai (IEEC-CSIC) Campus UAB 08193 Barcelona Spain INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica I-20133 Milano Italy Department of Physics Royal Institute of Technology (KTH) AlbaNova SE-106 91 Sto

We present the results of our analysis of cosmic-ray electrons using about 8×106 electron candidates detected in the first 12 months on-orbit by the Fermi Large Area Telescope. This work extends our previously published cosmic-ray electron spectrum down to 7 GeV, giving a spectral range of approximately 2.5 decades up to 1 TeV. We describe in detail the analysis and its validation using beam-test and on-orbit data. In addition, we describe the spectrum measured via a subset of events selected for the best energy resolution as a cross-check on the measurement using the full event sample. Our electron spectrum can be described with a power law ∝E−3.08±0.05 with no prominent spectral features within systematic uncertainties. Within the limits of our uncertainties, we can accommodate a slight spectral hardening at around 100 GeV and a slight softening above 500 GeV.

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Searches for cosmic-ray electron anisotropies with the Fermi Large Area Telescope

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Physical Review D 2010年第9期82卷 092003-092003页

作者： M. Ackermann M. Ajello W. B. Atwood L. Baldini J. Ballet G. Barbiellini D. Bastieri K. Bechtol R. Bellazzini B. Berenji E. D. Bloom E. Bonamente A. W. Borgland A. Bouvier J. Bregeon A. Brez M. Brigida P. Bruel R. Buehler T. H. Burnett S. Buson G. A. Caliandro R. A. Cameron P. A. Caraveo S. Carrigan J. M. Casandjian C. Cecchi Ö. Çelik E. Charles A. Chekhtman C. C. Cheung J. Chiang S. Ciprini R. Claus J. Cohen-Tanugi J. Conrad A. Cuoco C. D. Dermer A. de Angelis F. de Palma S. W. Digel G. Di Bernardo E. do Couto e Silva P. S. Drell R. Dubois C. Favuzzi S. J. Fegan W. B. Focke M. Frailis Y. Fukazawa S. Funk P. Fusco D. Gaggero F. Gargano S. Germani N. Giglietto P. Giommi F. Giordano M. Giroletti T. Glanzman G. Godfrey D. Grasso I. A. Grenier J. E. Grove S. Guiriec M. Gustafsson D. Hadasch A. K. Harding K. Hayashi E. Hays R. E. Hughes G. Jóhannesson A. S. Johnson W. N. Johnson T. Kamae H. Katagiri J. Kataoka M. Kerr J. Knödlseder M. Kuss J. Lande L. Latronico S.-H. Lee M. Lemoine-Goumard M. Llena Garde F. Longo F. Loparco M. N. Lovellette P. Lubrano A. Makeev M. N. Mazziotta J. E. McEnery J. Mehault P. F. Michelson T. Mizuno A. A. Moiseev C. Monte M. E. Monzani E. Moretti A. Morselli I. V. Moskalenko S. Murgia T. Nakamori M. Naumann-Godo P. L. Nolan E. Nuss T. Ohsugi A. Okumura N. Omodei E. Orlando J. F. Ormes D. Paneque J. H. Panetta D. Parent V. Pelassa M. Pepe M. Pesce-Rollins F. Piron T. A. Porter S. Profumo S. Rainò R. Rando M. Razzano A. Reimer O. Reimer T. Reposeur J. Ripken S. Ritz M. Roth H. F.-W. Sadrozinski A. Sander T. L. Schalk C. Sgrò J. Siegal-Gaskins E. J. Siskind D. A. Smith P. D. Smith G. Spandre P. Spinelli M. S. Strickman A. W. Strong D. J. Suson H. Takahashi T. Takahashi T. Tanaka J. B. Thayer J. G. Thayer D. J. Thompson L. Tibaldo D. F. Torres G. Tosti A. Tramacere Y. Uchiyama T. L. Usher J. Vandenbroucke V. Vasileiou N. Vilchez V. Vitale A. P. Waite P. Wang B. L. Winer K. S. Wood Z. Yang T. Ylinen G. Zaharijas M. Ziegler W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics and SLAC National Accelerator Laboratory Stanford University Stanford California 94305 USA Santa Cruz Institute for Particle Physics Department of Physics and Department of Astronomy and Astrophysics University of California at Santa Cruz Santa Cruz California 95064 USA Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy Laboratoire AIM CEA-IRFU/CNRS/Université Paris Diderot Service d’Astrophysique CEA Saclay 91191 Gif sur Yvette France Istituto Nazionale di Fisica Nucleare Sezione di Trieste I-34127 Trieste Italy Dipartimento di Fisica Università di Trieste I-34127 Trieste Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova I-35131 Padova Italy Dipartimento di Fisica “G. Galilei ” Università di Padova I-35131 Padova Italy Istituto Nazionale di Fisica Nucleare Sezione di Perugia I-06123 Perugia Italy Dipartimento di Fisica Università degli Studi di Perugia I-06123 Perugia Italy Dipartimento di Fisica “M. Merlin” dell’Università e del Politecnico di Bari I-70126 Bari Italy Istituto Nazionale di Fisica Nucleare Sezione di Bari 70126 Bari Italy Laboratoire Leprince-Ringuet École polytechnique CNRS/IN2P3 Palaiseau France Department of Physics University of Washington Seattle Washington 98195-1560 USA Institut de Ciencies de l’Espai (IEEC-CSIC) Campus UAB 08193 Barcelona Spain INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica I-20133 Milano Italy NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA Department of Physics and Center for Space Sciences and Technology University of Maryland Baltimore County Baltimore Maryland 21250 USA Space Science Division Naval Research Laboratory Washington D.C. 20375 USA George Mason University Fairfax Virgin

The Large Area Telescope on board the Fermi satellite (Fermi LAT) detected more than 1.6×106 cosmic-ray electrons/positrons with energies above 60 GeV during its first year of operation. The arrival directions of these events were searched for anisotropies of angular scale extending from ∼10° up to 90°, and of minimum energy extending from 60 GeV up to 480 GeV. Two independent techniques were used to search for anisotropies, both resulting in null results. Upper limits on the degree of the anisotropy were set that depended on the analyzed energy range and on the anisotropy’s angular scale. The upper limits for a dipole anisotropy ranged from ∼0.5% to ∼10%.

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Online drift correction in wireless sensor networks using spatio-temporal modeling

Online drift correction in wireless sensor networks using sp...

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International Conference on Information Fusion

作者： Maen Takruri Sutharshan Rajasegarar Subhash Challa Christopher Leckie Marimuthu Palaniswami Centre for Real-Time Information Networks (CRIN) University of Technology Sydney Australia Department of Electrical and Electronic Engineering ARC Special Research Center for Ultra-Broadband Information Networks Australia Victoria Research Laboratory NICTA Australia Department of Computer Science and Software Engineering University of Melbourne Australia

Wireless sensor networks are deployed for the purpose of sensing and monitoring an area of interest. Sensors in the sensor network can suffer from both random and systematic bias problems. Even when the sensors are properly calibrated at the time of their deployment, they develop drift in their readings leading to erroneous inferences being made by the network. The drift in this context is defined as a slow, unidirectional, long-term change in the sensor measurements. In this paper we present a novel algorithm for detecting and correcting sensors drifts by utilising the spatio-temporal correlation between neigbouring sensors. Based on the assumption that neighbouring sensors have correlated measurements and that the instantiation of drift in a sensor is uncorrelated with other sensors, each sensor runs a support vector regression algorithm on its neigbourspsila corrected readings to obtain a predicted value for its measurements. It then uses this predicted data to self-assess its measurement and detect and correct its drift using a Kalman filter. The algorithm is run recursively and is totally decentralized. We demonstrate using real data obtained from the Intel Berkeley laboratory that our algorithm successfully suppresses drifts developed in sensors and thereby prolongs the effective lifetime of the network.

关键词： Support vector machines Mathematical model Temperature measurement Equations Kalman filters Training time measurement

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Energy-Aware Scheduling of real-time Tasks in Wireless Networked Embedded Systems

Energy-Aware Scheduling of Real-Time Tasks in Wireless Netwo...

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real-time Systems Symposium (RTSS)

作者： G. Sudha Anil Kumar G. Manimaran Z. Wang Real-Time Computing and Networking Laboratory Department of Electrical and Computer Engineering Iowa State University Ames IA USA

Recent technological advances have opened up several distributed real-time applications involving battery-driven embedded devices with local processing and wireless communication capabilities. Energy management is the key issue in the design and operation of such systems. In this paper, we consider a single-hop networked real-time embedded system where each node supports both dynamic voltage scaling (DVS) and dynamic modulation scaling (DMS) power management techniques to tradeoff time for energy savings. In this model, we address the problem of scheduling periodic complex tasks where each task consists of several precedence constrained message passing sub-tasks. Our contributions towards this problem are twofold. First, we analyze the system level energy-time tradeoffs considering both the computation and communication workloads by defining a novel energy gain metric. We then present static (centralized) and dynamic (distributed) energy gain based slack allocation algorithms which reduce the total energy consumption, while guaranteeing the ready time, deadline and precedence constraints. We compare the performance of the proposed algorithms with several baseline algorithms through simulation studies. Our results show that the proposed algorithms perform significantly better than the baseline algorithms for the simulated conditions. Finally, we identify several interesting energy-aware research problems in the area of networked real-time embedded systems.

关键词： real time systems Embedded system Energy management Wireless communication Dynamic voltage scaling Voltage control Computer network management Power system management Power system modeling Processor scheduling

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Energy-aware scheduling with deadline and reliability constraints in wireless networks

Energy-aware scheduling with deadline and reliability constr...

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International Conference on Broadband Networks (BroadNets)

作者： G. Sudha Anil Kumar G. Manimaran Z. Wang Real Time Computing and Networking Laboratory Department of Electrical and Computer Engineering Iowa State University Ames IA USA

ISBN: (纸本)9781424414321

In this paper, we address the problem of scheduling a set of periodic real-time messages in a wireless network with the objective of minimizing the total energy consumption while meeting deadline and reliability constraints. We formally prove that this problem is NP-hard and solve it in two stages. First, we consider a simple model that assumes that the wireless channel is completely reliable and the network is fully provisioned. Using the technique of employing multiple hop-by-hop transmissions instead of a single direct hop transmission as the basis, we prove that the strategy of choosing the hop distances such that they are equidistant is optimal in terms of energy consumption under the deadline constraint. Based on the intuition provided by the optimal strategy, we present heuristic scheduling algorithms for a more realistic wireless channel model and network condition. Our simulation results show that the proposed scheduling algorithms provide significant energy savings over the baseline algorithms

关键词： Wireless networks Energy consumption Scheduling algorithm Wireless application protocol Throughput Access protocols Streaming media Resource management Processor scheduling Computer network reliability

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A Fast Block Mode Decision Algorithm using a Block Correlation in H.264/AVC

A Fast Block Mode Decision Algorithm using a Block Correlati...

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IEEE International Symposium on Consumer Electronics (ISCE)

作者： Jong-Ho Kim Byung-Gyu Kim Chang-Sik Cho Computer software & Engineering Dept University of Science and Technology Norway Real-time Multimedia Research Laboratory Electronics and Telecommunications Research Institute South Korea

The recent video coding standard H.264/AVC show extremely higher coding efficiency compare to any other previous standards. Although H.264/AVC can achieve over 50% of bit rate saving with same quality using the rate-distortion process, but it brings high computational complexity. In this paper, we propose an algorithm that can reduce the complexity of the codec by reducing the block mode decision process adaptively. In this paper an efficient method is proposed to reduce the inter mode decision coding complexity using the direct prediction methods based on inter block correlation and adaptive rate distortion cost threshold for early stopping. The intra mode decision complexity is also reduced using the early intra skip method. The experimental results show that the proposed algorithm can achieve up to 43.85~74.12% speed up ratio with a little PSNR loss. Increment in bit requirement is also not much noticeable.

关键词： Automatic voltage control Image coding Rate-distortion Video coding Costs Computational complexity software standards Telecommunication standards Codecs Motion estimation

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On accurate measurement of link quality in multi-hop wireless mesh networks

On accurate measurement of link quality in multi-hop wireles...

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12th Annual International Conference on Mobile computing and Networking, MOBICOM 2006

作者： Kim, Kyu-Han Shin, Kang G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2121 United States

ISBN: (纸本)1595932860

This paper presents a highly efficient and accurate link-quality measurement framework, called EAR (Efficient and Accurate link-quality monitoR), for multi-hop wireless mesh networks, that has several salient features. First, it exploits three complementary measurement schemes: passive, cooperative, and active monitoring. EAR maximizes the measurement accuracy by (i) dynamically and adaptively adopting one of these schemes and (ii) opportunistically exploiting the unicast application traffic present in the network, while minimizing the measurement overhead. Second, EAR effectively identifies the existence of wireless link asymmetry by measuring the quality of each link in both directions of the link, thus improving the utilization of network capacity by up to 114%. Finally, its reliance on both the network layer and the IEEE 802.11-based device driver solutions makes EAR easily deployable in existing multi-hop wireless mesh networks without system recompilation or MAC firmware modification. EAR has been evaluated extensively via both n.s-2-based simulation and experimentation on our Linux-based implementation. Both simulation and experimentation results have shown EAR to provide highly accurate link-quality measurements with minimum overhead. Copyright 2006 ACM.

关键词： Wireless telecommunication systems

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SMRP: Fast restoration of multicast sessions from persistent failures

SMRP: Fast restoration of multicast sessions from persistent...

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2005 International Conference on Dependable Systems and Networks

作者： Wu, Jian Shin, Kang G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan

The growing reliance of networked applications on timely and reliable data transfer requires the underlying networking infrastructure to provide adequate services even in the presence of "persistent" failures (e.g., broken links/routers). It is much more difficult to meet this requirement for multicast sessions than for unicast communications because any on-tree component failure may often cause simultaneous service disruptions to multiple receivers. This paper presents a new multicast routing protocol, called the Survivable Multicast Routing Protocol (SMRP), which facilitates fast recovery of multicast sessions in face of persistent failures via local detour paths. Our evaluation results show that SMRP trades end-to-end delay and resource usage for short, and hence fast, recovery paths. For example, under a certain set of parameter values, SMRP shortens the recovery path by 20% with only a 5% increase of end-to-end delay and resource usage. Moreover, several design enhancements have made SMRP efficient, robust, flexible and scalable. © 2005 IEEE.

关键词： Multicasting

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Energy-efficient self-adapting online linear forecasting for wireless sensor network applications

Energy-efficient self-adapting online linear forecasting for...

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2nd IEEE International Conference on Mobile Ad-hoc and Sensor Systems, MASS 2005

作者： Lim, Jai-Jin Shin, Kang G. Real-Time Computing Laboratory Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122 United States

ISBN: (纸本)0780394666

New energy-efficient linear forecasting methods are proposed for various sensor network applications, including in-network data aggregation and mining. The proposed methods are designed to minimize the number of trend changes for a given application-specified forecast quality metric. They also self-adjust the model parameters, the slope and the intercept, based on the forecast errors observed via measurements. As a result, they incur O(1) space and time overheads, a critical advantage for resource-limited wireless sensors. An extensive simulation study based on real-world and synthetic time-series data shows that the proposed methods reduce the number of trend changes by 20%-50% over the existing well-known methods for a given forecast quality metric. That is, they are more predictive than the others with the same forecast quality metric. © 2005 IEEE.

关键词： Telecommunication networks

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