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2011 3rd International Conference on communication Systems and networks, COMSNETS 2011

作者： Issing, Jochen Reuschly, Stefan Dressler, Falko Färbery, Nikolaus Dept. Computer Science 7 Computer Networks and Communication Systems Friedrich-Alexander-University Erlangen Germany Multimedia Transport Group Fraunhofer Institute for Integrated Circuits Erlangen Germany

ISBN: (纸本)9781424489534

We present an integrated approach for flexible playout adaptation for high quality audio transmission over impaired network connections. The key concept of our framework is a continuous measurement of the transmission delay, the delay variation, and packet loss. Based on these measurements, the adaptive playout control employs audio time stretching using audio concealment and frame dropping techniques to keep the low delay requirements. In the literature, playout adaptation techniques have mainly been considered for voice over IP, using silence periods between talkspurts, or for high quality audio transmission over dedicated network links. To the best of our knowledge, our playout algorithm is the first achieving low delay high quality audio streaming over impaired network connections for both music and speech. We used a significant number of network traces to estimate the variation of the network quality in DSL, WLAN, UMTS and GPRS links and to update the parameters of our playout adaptation technique. Experimental results clearly indicate that our system provides very high accuracy for the desired accepted late loss rate and achieves a fast playout adaptation, even for rapidly changing network conditions. © 2011 IEEE.

关键词： Audio acoustics

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Simulative performance evaluation of the simTD Self Organizing Traffic Information System

Simulative performance evaluation of the simTD Self Organizi...

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IFIP Annual Mediterranean Ad Hoc Networking Workshop

作者： Eckhoff, David Gansen, Tobias Manz, Robert Thum, Daniela Klages, Oliver Sommer, Christoph Computer Networks and Communication Systems Dept. of Computer Science University of Erlangen Germany AUDI AG/Audi Electronics Venture GmbH Germany C4c Engineering GmbH Germany

ISBN: (纸本)9781457709005

The simTD (Safe and Intelligent Mobility: Test Field Germany) research project is another step towards bringing Car-to-X technology to marketability. One of its envisioned applications is a Traffic Information System (TIS) based on self-generated maps for vehicles not equipped with digital maps. To assure reliable operation, the function itself, its performance and the effect of its input parameters was simulatively evaluated before it was validated on real vehicles. In this paper we demonstrate how to adequately parameterize and evaluate such a TIS. We find feasible values for the input parameters for the creation of self-generated maps to ensure solid operation of the function. We further contribute to the community and other projects using similar TIS deployments by introducing applicable metrics for TIS evaluation in general and show our findings for the simTD research project. © 2011 IEEE.

关键词： Function evaluation

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High repetition rate high average power all-normal dispersion Yb: Fiber ring laser

High repetition rate high average power all-normal dispersio...

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作者： Yang, Hongyu Li, Peng Wang, Xi Li, Chen Wang, Aimin Zhang, Zhigang State Key Laboratory of Advanced Optical Communication System and Networks School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

ISBN: (纸本)9781557529107

关键词： Ring lasers

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Sub-40 fs Er:Fiber laser

Sub-40 fs Er:Fiber laser

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作者： Zhang, Zhigang Zong, Weijian Li, Chen Ma, Ding Zhou, Chun Wang, Aimin State Key Laboratory of Advanced Optical Communication System and Networks School of Electronics Engineering and Computer Science University of Beijing Beijing 100871 China

ISBN: (纸本)9781557529107

关键词： Ring lasers

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Self-healing optical access networks (SHOAN) operated by optical switching technologies

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IEEE Transactions on Network and Service Management 2011年第3期8卷 234-244页

作者： Huang, Anpeng Liu, Siyu Xie, Linzhen Chen, Zhangyuan Mukherjee, Biswanath State Key Lab. of Advanced Optical Communication Systems and Networks China Wireless Communications Lab. PKU-UCLA Joint Research Institute Peking University Beijing 100871 China Department of Computer Science University of California Davis United States

An optical access network should offer low-cost reliable services to its end users. To address this problem, an optimal solution is needed which can turn an optical access architecture into a self-healing system. Hence, we propose the Self-Healing Optical Access Network (SHOAN), in which two or more optical access architectures are partners of each other, and they are interconnected by elementary optical crossbar switches into a simple mesh network. In SHOAN, the crossbar switches can keep each access architecture as an independent and closed system for only serving its own end users in normal state. But the crossbars become open in fault scenarios. Whenever a failure occurs in the network, the fault can be monitored and affected services can be recovered by the partner of the access architecture that is affected. Such an interconnected optical access network can withstand failures in its transmission paths, and recover network services in a self-healing way. Compared to existing solutions (e.g., dual-home architecture), illustrative examples demonstrate that SHOAN has many desirable properties: (1) it is robust because risks are disjointed, (2) it is reliable because service recovery is given top priority, and (3) it has low cost because redundant backup components are not necessary since the partner's resources act as backup resources. Analysis results show that SHOAN can minimize disruption duration and network cost for broadband access services. © 2011 IEEE.

关键词： Cost benefit analysis

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A computationally inexpensive empirical model of IEEE 802.11p radio shadowing in urban environments

A computationally inexpensive empirical model of IEEE 802.11...

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Annual Conference on Wireless On Demand Network Systems and Services (WONS)

作者： Christoph Sommer David Eckhoff Reinhard German Falko Dressler Computer Networks and Communication Systems Department of Computer Science University of Erlangen Germany

We present a realistic, yet computationally inexpensive simulation model for IEEE 802.11p radio shadowing in urban environments. Based on real world measurements using IEEE 802.11p/DSRC devices, we estimated the effect that buildings and other obstacles have on the radio communication between vehicles. Especially for evaluating safety applications in the field of Vehicular Ad Hoc networks (VANETs), stochastic models are not sufficient for evaluating the radio communication in simulation. Motivated by similar work on WiFi measurements, we therefore created an empirical model for modeling buildings and their properties to accurately simulate the signal propagation. We validated our model using real world measurements in a city scenario for different types of obstacles. Our simulation results show a very high accuracy when compared with the measurement results, while only requiring a marginal overhead in terms of computational complexity.

关键词： Buildings Computational modeling Mathematical model Shadow mapping Attenuation Predictive models Loss measurement

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Cooperative Awareness at Low Vehicle Densities: How Parked Cars Can Help See through Buildings

Cooperative Awareness at Low Vehicle Densities: How Parked C...

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2011 IEEE Global Telecommunications Conference - GLOBECOM 2011

作者： David Eckhoff Christoph Sommer Reinhard German Falko Dressler Computer Networks and Communication Systems Department of Computer Science University of Erlangen Germany Computer and Communication Systems Institute of Computer Science University of Innsbruck Austria

Many safety applications in Intelligent Transportation Systems (ITS) require vehicles to be aware of the presence of nearby cars, but - especially in urban and suburban regions - buildings and other obstacles may block radio transmissions. In the literature, multi-hop relaying by neighboring cars has been demonstrated to perform well at disseminating safety broadcasts in the presence of obstacles. At night, in areas with low traffic density, or when the penetration rate of Car-2-X devices is low, however, there are likely to be too few relaying cars available. This again leads to the problem that vehicles which are not in line-of-sight frequently cannot be sensed either. To the best of our knowledge, we are the first to help overcome this problem by utilizing parked cars as relay nodes. We study the effectiveness and the necessity of this approach with the help of extensive simulative studies and real life experiments. We show how, for scenarios with few equipped cars, the utilization of parked cars proves crucial to support safety applications. When disseminating safety critical events in a realistic scenario, parked cars can increase cooperative awareness by over 40% in total.

关键词： Vehicles Peer to peer computing Relays Safety Buildings Attenuation High definition video

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Broadband SESAM for mode locked Yb:fiber lasers

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Chinese science Bulletin 2011年第13期56卷 1348-1351页

作者： CHEN LingLing ZHANG Meng WANG Xi LI WenChao WEI Yun MA YunFeng FAN ZhongWei NIU Gang YU Jin LIU Yang ZHANG Xue ZHANG ZhiGang Institute of Quantum Electronics State Key Laboratory of Advanced Optical Communication System and Networks School of Electronics Engi- neering and Computer Science Peking University Beijing 100871 China Academy of Opto-Electronics of Chinese Academy of Sciences Beijing 100080 China

We report a semiconductor saturable absorber mirror (SESAM) with phase shift *** SESAM shows a uniform low-intensity reflectivity and a modulation depth up to 12% for the wavelength from 1000 to 1100 nm.A linear cavity all-normal dispersion Yb-doped fiber laser has proved its mode locking performance for the wavelength of both 1030 nm and 1064 nm.

关键词：掺镱光纤激光器 SESAM 模式锁定半导体可饱和吸收镜宽带波长锁定调制深度正常色散

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On routing and transmission-range determination of multi-bit-rate signals over mixed-line-rate WDM optical networks for carrier ethernet

On routing and transmission-range determination of multi-bit...

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作者： Batayneh, Marwan Schupke, Dominic A. Hoffmann, Marco Kirstaedter, Andreas Mukherjee, Biswanath Department of Optical Ethernet IPITEK Inc. Carlsbad CA 92008 United States Multi-Layer Networks and Resilience Nokia Siemens Networks Munich 81541 Germany Institute of Communication Networks and Computer Engineering University of Stuttgart Stuttgart 70174 Germany Department of Computer Science University of California Davis Davis CA 95616 United States

Ethernet's success in local area networks (LANs) is fueling the efforts to extend its reach to cover metro and long-haul networks. This new Ethernet is refereed to as Carrier Ethernet. Among the various transport infrastructures for realizing Carrier Ethernet, wavelength-division multiplexing (WDM) optical network is a strong candidate for this purpose. Optical transmission rates per channel are increasing from 10 to 40 Gb/s and even 100 Gb/s, and they can also coexist in the same fiber. Along with the flexibility associated with such a network with mixed-line rates (MLR), signal-related constraints at high rates become a challenge for cost-efficient routing. Among these issues is the maximum nonregenerated optical distance that a signal can travel before its quality degrades or maximum transmission range (TR). TR is rate-dependent: The higher the rate, the shorter the range. While high-rate pipes may require signal regeneration to restore the signal's quality, they support more traffic and, hence, can save resources. We study the problem of cost-efficient routing of multi-bit-rate (1/10/40/100 Gb/s) Ethernet tunnels using MLR over a carrier's WDM optical network with signal-transmission-range constraints. We studied the effect of TR for mixed-rate signals (10/40/100 Gb/s) on the network's cost to determine the optimal TR of each bit rate. We present an analytical model based on a mixed-integer linear program (MILP) to determine the optimal TR of a small network. Since MILP has scalability constraints that makes it hard or sometimes impossible to solve for real network topologies, we propose a graph-based solution that constructs a mixed-line-rate auxiliary (MLR-AUX) graph to capture the network's heterogeneity and a weight-assignment approach that allows the routing to be cost-efficient. Our algorithms were tested on a U.S. nationwide network topology. We found that it is possible to reduce the network's cost by using short TR and that the optimal TR depends strong

关键词： Light transmission

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Power efficient femtocell distribution strategies

Power efficient femtocell distribution strategies

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19th International Conference on Software, Telecommunications and computer networks, SoftCOM 2011

作者： Haddad, Yoram Mirsky, Yisroel Jerusalem College of Technology Computer Science and Networks Department Jerusalem Israel Ben Gurion University of the Negev Dept. of Communication Syst. Eng. Beer-Sheva Israel

ISBN: (纸本)9789532900262

Reducing our power consumption is an urgent issue which has important economical and ecological benefits. By using femtocell technology the mobile network can become far more energy efficient than it is today. In this paper, we describe what femtocell technology is and introduce outdoor femtocell distribution strategies that can save the network power. We also compare the usage of typical short-range base stations in place of femtocells and show that femtocells are more efficient. The results of the introduced strategies show that significant power savings of up to 92% can be achieved on a per-macrocell basis if implemented. © 2011 University of Split.

关键词： Femtocell

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