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5th International Conference on Wireless communications, Networking and Mobile Computing, WiCOM 2009

作者： Feng, Wang Dou, Li Yuping, Zhao State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University Beijing China

ISBN: (纸本)9781424436934

This paper analyzes the non-persistent Carrier Sense Multiple Access (CSMA) mechanism, and simulates its application in IEEE 802.15.4. We find that throughputs are relevant to the normalized propagation delay and the Basic Time Period (BTP) of slotted CSMA. The throughputs of slotted and unslotted CSMA are almost equal when the normalized propagation delay is much less than 1 and the BTP is equal to the propagation delay. Moreover, for slotted CSMA, the BTP selection should be cautious because an unsuitable BTP will make the performance of the protocol worse. In IEEE 802.15.4, the normalized propagation delay is much less than 1, so it is inappropriate for the usage of a Slotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism whose BTP is 20 symbols. Finally, we compare the performance of slotted and unslotted CSMA/CA in IEEE 802.15.4 and verify the conclusion by simulation. ©2009 IEEE.

关键词： Carrier sense multiple access

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Plasmonic Corrugated Horn Structure for Optical Transmission Enhancement

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Chinese Physics Letters 2009年第12期26卷 122-124页

作者：李光元蔡琳肖峰徐安士 State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronic Engineering and Computer Science Peking University Beijing 100871 Centre of Excellence for MicroPhotonic Systems (COMPS) Electron Science Research Institute Edith Cowan University 270 Joondalup Drive Joondalup WA 6027 Australia

We propose and theoretically analyze a plasmonic corrugated horn structure for enhanced optical transmission. It makes use of the enhancement of unidirectional propagating surface plasmon polaritons at oblique incidence. Geometric parameters such as the groove depth and width are optimized. Analysis shows that it presents a better performance than the bull＇s eye structure for a small number of grooves.

关键词： Chinese climate network complex systems small world community

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The negative refraction of the 2D triangular lattice of air hole in silicon

The negative refraction of the 2D triangular lattice of air ...

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Photonics and Optoelectronics Meetings (POEM) 2009 - Optoelectronic Devices and Integration

作者： Wu, Chaojun Wu, Jun Hong, Tingting Li, Yanping Wang, Ziyu State Key Laboratory on Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

ISBN: (纸本)9780819479051

We study numerically the focusing effects when a Gaussian beam pass through a two-dimensional photonic crystal consisting of triangular structure of air holes. By using plane wave expansion (PWE) and finite difference time domain (FDTD) methods, we find the width of convergent beam is about 2m. Meanwhile, the focusing effects also are influenced by the Gaussian half-width, the numbers of the layers and the incident angle. The structure can be used for light-coupling and near-field scan image application. © 2009 Copyright SPIE - The International Society for Optical Engineering.

关键词： Photonic crystals

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Channel estimation for pilot-aided OFDM systems in single frequency network

Channel estimation for pilot-aided OFDM systems in single fr...

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2009 15th Asia-Pacific Conference on communications, APCC 2009

作者： Wu, Yiling Zhao, Yuping Li, Dou State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

ISBN: (纸本)9781424447855

In single frequency network (SFN), there exist some special long delay spread channels as well as conventional multi-path channels. For pilot-aided orthogonal frequency division multiplex (OFDM) systems, channel estimation is usually accomplished by interpolation with pilots. However, few pilot subcarriers exist within coherent bandwidth under the long delay spread channels in SFN. In this case, conventional interpolation methods cannot work properly. This paper proposes a sinewave based frequency domain interpolation method for channel estimation of pilot-aided OFDM systems in SFN. As simulation results show, the proposed method gives accurate channel estimation under the long delay spread channels, whereas the mismatched wiener interpolation filter (WIF) estimates channel response inaccurately. Moreover, the proposed method performs well under conventional multi-path channels, especially for systems which adopt high order modulations. ©2009 IEEE.

关键词： Channel estimation

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A modified Q-parameter anti-collision scheme for RFID systems

A modified Q-parameter anti-collision scheme for RFID system...

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2009 International Conference on Ultra Modern Telecommunications and Workshops

作者： Yinghua, Cui Yuping, Zhao State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

ISBN: (纸本)9781424439416

EPC Q scheme is a very popular protocol in RFID, in which the reader uses parameter Q to vary the slot number that tags can select. In this paper, we propose a new algorithm based on this scheme. We first propose a fast and efficient tag estimation method according to stochastic analyses on the first three slots of each frame, then propose a new ALOHA based multi-branch anti-collision scheme. Both theoretical analysis and simulation results indicate the proposed scheme can improve a lot than the standard EPC Q algorithm and the modification is slight. ©2009 IEEE.

关键词： Stochastic systems

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XPM statistics in 100% pre-compensated WDM transmission for different modulation formats and transmission fibres

XPM statistics in 100% pre-compensated WDM transmission for ...

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2009 14th OptoElectronics and communications Conference, OECC 2009

作者： Fan, Zhang State Key Lab. of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

XPM statistics in 100% pre-compensated WDM transmission depends on bit rates, transmission fibres and modulation formats. XPM in DPSK systems shows much less stochastic than that in OOK systems. © 2009 IEEE.

ISBN: (纸本)9781424441037

关键词： Stochastic systems

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A simulation approach for the design of safety-relevant automotive multi-ECU systems

A simulation approach for the design of safety-relevant auto...

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IEEE International Conference on System of systems Engineering (SoSE)

作者： Thomas Herpel Reinhard German Department of Computer Science 7-Computer Networks and Communication Systems University Erlangen-Nuünberg Erlangen Germany

Modern cars comprise tens of electronic control units, interconnected via automotive bus systems towards a specific system-of-systems inside the vehicle. Safety-relevant applications which are realized by these networked embedded controllers require a sophisticated process of system design. The appropriate choice of communication infrastructure and parameters at an early stage of system development significantly influences the overall application performance and reliability. Therefore, we propose the employment of distinct, well-proven system modeling techniques, using discrete event simulation and the Unified Modeling Language with real-time extensions. Our approach allows modeling the relevant aspects of in-car communication even before the first prototype vehicle is built up. Various design alternatives can easily be investigated without time- and manpower-consuming real-world system tests, yielding trustworthy results for a broad variety of aspects of automotive in-car communication. In cooperation with the German car manufacturer Audi, we applied our methodology for design of a networked airbag control system.

关键词： Automotive engineering communication system control Control systems Vehicles Telecommunication network reliability Employment Discrete event simulation Unified modeling language Real time systems Prototypes

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A differentiated QoS aware multipath routing algorithm for optical burst switched networks

A differentiated QoS aware multipath routing algorithm for o...

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Network Architectures, Management, and Applications VII

作者： Chi, Yuan Zhang, Zhenrong Li, Zhengbin Anshi, Xu State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University Beijing China School of Computer Electronics and Information Guangxi University Nanning Guangxi China

ISBN: (纸本)9780819480354

Optical burst switching (OBS) is thought to be the best way to adapt the bursty IP traffic over optical WDM networks. It provides statistical multiplexing gains and avoids long end to end setup time of traditional virtual circuit configuration. However, under the current and foreseeable limitations of optical technology, performance of OBS is mainly hampered at network nodes by burst contention. The contention is serious constraints on the capacity of OBS networks. A leading source of contention is the congestion at congested links where a limited number of wavelengths are shared by a lot of bursts. These congested links are stemming from burst routing algorithms. In this paper, we studied on routing path competition phenomenon. We proposed a differentiated QoS aware multipath routing algorithm for OBS networks. This algorithm is evaluated through extensive numerical studies over a typical topology--the 14-node NSFnet. Results show that it outperforms the existing algorithms in terms of burst blocking probability and link utilization. © 2009 SPIE-OSA-IEEE.

关键词： Optical burst switching

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Self-localization capable mobile sensor nodes

Self-localization capable mobile sensor nodes

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IEEE International Conference on Technologies for Practical Robot Applications (TePRA)

作者： Juergen Eckert Kemal Koeker Philipp Caliebe Falko Dressler Reinhard German Computer Networks and Communication Systems Department of Computer Science University of Erlangen Germany

ISBN: (纸本)9781424449910

Position sensing systems for indoor environments have one common problem: The setup effort of the whole system. GPS-supported localization is simple and fast to implement and the reference grid is ubiquitous. However, in locations where the signals of GPS are not available, e.g. indoor, or where the technique is not accurate enough, other position sensing systems have to be used. Usually, a reference grid will be provided by an administrator: Reference points must be deployed and programmed with the correct location information. Especially for temporary installations and dynamic surroundings the setup costs are very high. In our work, we developed a robotic platform, which is capable of deploying itself autonomously and which can operate as a mobile reference point equipped with ultra sound transmitters. Relying on a combination of two controllers and an odometry system, the platform is able to drive on a complex spline-like trace using only a few supporting points. We also investigated the problem for the localization system itself. The detection field of our ultra sound based system is a full hemisphere. Within this domain, we can measure the distances between nodes exploiting the time of flight technique as well as the angle of arrival. Finally, the system can also be used as a sonar system for passive obstacles detection.

关键词： Sonar detection Indoor environments Global Positioning System Costs Mobile robots Robot sensing systems Transmitters Control systems Spline Time measurement

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Self-organizing network security environments - A simulative analysis

Self-organizing network security environments - A simulative...

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Eurocon

作者： Falko Dressler Lavanya Poondru Tobias Limmer Reinhard German Computer Networks and Communication Systems Department of Computer Science University of Erlangen Germany

We discuss the need for adaptive load control in network security environments in order to cope with the increasing bandwidth requirements. In earlier work, we developed a simple model to study the behavior of feedback loops for self-configuring security environments. We primarily considered the traffic between the monitoring probes, the IDS systems, and associated firewalls. We now enhanced the model to study fully self-organized network security environments in a simulation model. First simulation results outline both the feasibility of the general approach and the possibilities of the simulation model.

关键词： Self-organizing networks Analytical models Programmable control Adaptive control Load flow control Bandwidth Feedback loop communication system traffic control Traffic control Monitoring

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