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International Conference on Software, Telecommunications and computer networks (SoftCOM)

作者： Jochen Issing Nikolaus Färber Department Computer Science 7 Computer Networks and Communication Systems Friedrich-Alexander-Universitat Erlangen Germany Multimedia Transport Group Fraunhofer IIS Erlangen Germany

The impact of mouth-to-ear delay on Conversational Quality (CQ) has been subject to manyfold research in the field of telecommunications. However, its dependency on Conversational Interactivity (CI) has not been studied explicitly in a quantitative way. To investigate the impact of both delay and CI, we conducted 48 tests with 96 different participants and controlled the interactivity through different tasks, namely natural conversation (flight), proof reading of text (text), and random number verification (rnv). The control of interactivity is proven to be effective and remains stable for delays from 100 ms to 800 ms. The Speaker Alternation Rate (SAR) is used as the metric for interactivity. It is shown to have a significant impact on CQ after 200ms delay and the effect does not alleviate until 800 ms. The hypothesis is proven using both graphical analysis and statistical evaluation based on a linear model and Analysis of Variance (ANOVA).

关键词： Delay Interrupters Telecommunications Correlation Predictive models Analysis of variance

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High repetition rate all-normal dispersion Yb:fiber laser for minimum pulses

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Chinese Optics Letters 2012年第3期10卷 81-83页

作者：杨弘宇王爱民麻云凤樊仲维牛岗余锦刘洋张雪张志刚 Institute of Quantum Electronics State Key Laboratory of Advanced Optical Communication System and Networks School of Electronics Engineering and Computer SciencePeking University Beijing GK Laser Technology Co. Ltd Academy of Opto-electronics Chinese Academy of Sciences

Simulation and experimental results for high repetition rate all-normal dispersion Yb:fiber ring lasers are demonstrated for the cavity dispersion from 0.01 to 0.025 ps 2 .The simulation shows that the pulse spectrum has the potential to reach>30 nm for the dispersion of 0.014 ps 2 under practical pump power. This potential is proved by the *** spectral width of 30 nm is achieved at the repetition rate of 285 MHz under the 850-mW pump *** output power is 550 mW and dechirped pulse is 78 fs.

关键词： Yb rate High repetition rate all-normal dispersion Yb

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Implementation of secure email server in cloud environment

Implementation of secure email server in cloud environment

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International Conference on computer and communication Engineering, ICCCE

作者： Nadim K. M. Madi Solmaz Salehian Farzaneh Masoumiyan Azizol Abdullah Department of Communication Technology and Networks Faculty of Computer Science and Information Technology Universiti Putra Malaysia Serdang Selangor Darul Ehsan Malaysia

In the recent virtual communication world, the email services play a vital role as a basic content of heterogeneous networking infrastructure. Whereby, multiple platforms are connecting each other. Mail Server refers to computer performing Mail Transfer Agent functions. MTA is software that delivers electronic mail messages from one computer to another, by using client-server application architecture. MTA implements both sender and receiver portions of SMTP (Simple Mail Transfer Protocol). Postfix is a free and open-source MTA which is fast, easy-to-administrator and provide secure communication over Internet. In this paper we focus on the problem of email contents disclosure, and establish a secure mail server by using Postfix in Linux platform and then implement it into a cloud service provider as IaaS (Infrastructure as a Service). Security is provided by tuning a Transport Layer Security (TLS), and SMTP-AUTH which use Simple Authentication and Security Layer (SASL) as a security mechanism and platform.

关键词： Electronic mail Servers Cloud computing Postal services Authentication

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Adaptive modulation and coding for two-way amplify-and-forward relay networks

Adaptive modulation and coding for two-way amplify-and-forwa...

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IEEE International Conference on communications in China (ICCC)

作者： Kun Yang Lingyang Song State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electrical Engineering and Computer Science Peking University Beijing China

In this paper, we introduce an adaptive modulation and coding protocol for all-participate amplify-and-forward relay network systems to achieve a better overall system performance. In the proposed scheme, all the relays are available and have chances to amplify and forward (AF) the signal candidates to the terminals, and for fairness all the relays submit to the same power limitation for the signal amplification. The two source nodes adaptively choose the appropriate modulation and coding scheme based on the information from the feedback channels to ensure that the block error rate (BLER) of the relay system is under the system requirement. Furthermore, we derive closed form expressions for the system performances over Rayleigh Channels, including average spectral efficiency and average BLER. Numerical results show that the analytical results figure out the system performance asymptotically.

关键词： Relays Signal to noise ratio Modulation Approximation methods Encoding Protocols Adaptive systems

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Passive YouTube QoE Monitoring for ISPs

Passive YouTube QoE Monitoring for ISPs

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International Conference on Innovative Mobile and Internet Services in Ubiquitous Computing (IMIS)

作者： Raimund Schatz Tobias Hoßfeld Pedro Casas Telecommunications Research Center Vienna-FTW Vienna Austria Institute of Computer Science Chair of Communication Networks University of Würzburg Wurzburg Germany

Over the last decade, Quality of Experience (QoE) has become the guiding paradigm for enabling a more user-centric understanding of quality of communication networks and services. The intensifying competition among ISPs and the exponentially increasing traffic volumes caused by online video platforms like YouTube is forcing service providers to integrate QoE into their corporate DNA. This paper investigates the problem of YouTube QoE monitoring from an access provider's perspective. To this end, we present three novel methods for in-network measurement of the QoE impairment that dominates user perception in the context of HTTP video-streaming: stalling of playback. Our evaluation results show that it is possible to detect application-level stalling events at high accuracy by using network-level passive probing only. However, only the most complex and most accurate approach can be used for QoE prediction due to the non-linear ties inherent in human quality perception.

关键词： Streaming media YouTube Monitoring Quality of service Approximation methods Data mining Accuracy

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490 MHz spaced optical frequency comb based on an Yb-fiber-ring laser

490 MHz spaced optical frequency comb based on an Yb-fiber-r...

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Conference on Lasers and Electro-Optics

作者： Peng Li Aimin Wang Zhigang Zhang Institute of Quantum Electronics State Key Laboratory of Advanced Optical Communication System and Networks School of Electronics Engineering and Computer Science Peking University

We demonstrate an optical frequency comb based on a 490 MHz femtosecond Yb:fiber laser. The broadened spectrum covers 500 - 1500 nm and the frequency off-set was found to be > 30 dB.

ISBN: (纸本)9781467318396

We demonstrate an optical frequency comb based on a 490 MHz femtosecond Yb:fiber laser. The broadened spectrum covers 500 - 1500 nm and the frequency off-set was found to be > 30 dB.

关键词： Ultrafast lasers Lasers Fiber Metrological Instrumentation

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Collaborative data dissemination in cognitive VANETs with sensing-throughput tradeoff

Collaborative data dissemination in cognitive VANETs with se...

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IEEE International Conference on communications in China (ICCC)

作者： Tianyu Wang Lingyang Song Zhu Han The State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University Beijing China Electrical and Computer Engineering Department University of Houston Houston USA

Vehicular ad hoc networks (VANETs) have recently received considerable attentions for both safety and commercial applications. In this paper, we address popular content distribution (PCD) in VANETs, in which a popular file is downloaded by a group of on-board units (OBUs) passing by a roadside unit (RSU). Due to high speeds and channel fadings, the OBUs may not finish downloading the entire file from the RSU, but only possess several content pieces. In this paper, we propose a cooperative approach using coalitional graph game to establish a peer-to-peer (P2P) network among the OBUs, in which content pieces are exchanged to complete the file downloading process. Further, we adopt cognitive radio (CR) technique for implementing vehicle-to-vehicle (V2V) transmissions. Simulation results show that the proposed algorithm enjoys a better performance in various conditions, compared to the non-cooperative approach, where OBUs randomly response to content requests from other OBUs.

关键词： Sensors Games Heuristic algorithms Vehicles Peer to peer computing Ad hoc networks Fading

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More practical power analysis attack on LFSR based stream ciphers

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Journal of Information and Computational science 2012年第12期9卷 3517-3527页

作者： Jia, Yanyan Hu, Yupu Zhang, Wenzheng Department of Computer Science Xi'an University of Science and Technology Xi'an 710054 China Laboratory of Computer Networks and Information Security Xidian University Xi'an 710071 China Science and Technology on Communication Security Laboratory The 30th Research Institute of China Electronics Technology Group Corporation Chengdu 610041 China

Power analysis attack is a powerful cryptanalytic technique aiming to extract the secret data from a cryptographic device by collecting and analyzing power consumption traces. In this paper, we present a practical power analysis attack on Linear Feedback Shift Registers (LFSR) based stream ciphers. Based on Information Theory, the problem of the power analysis attack is converted into the problem of decoding over a 3-ary symmetric channel. By setting two thresholds, the attack algorithm can significantly eliminate the effect of noise. And therefore, the correctness of decoding is enhanced. Compared with Burman's attack, the proposed attack algorithm is much more practical since the algorithmic noise and electronic noise are taken into account. Simulation results show that when the Signal to Noise Ratio (SNR) is higher than -6.5dB, the algorithm can always be practically performed and effective. © 2012 Binary Information Press.

关键词： Side channel attack

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Interference Alignment with Delayed Differential Feedback for Time-Correlated MIMO Channels

Interference Alignment with Delayed Differential Feedback fo...

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IEEE International Conference on communications

作者： Mingxin Zhou Leiming Zhang Lingyang Song Merouane Debbah Bingli Jiao The State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University SUPELEC Alcatel-Lucent Chair in Flexible Radio

ISBN: (纸本)9781457720529

Interference alignment (IA) has been well recognized as an efficient approach to reduce interference at high signal to noise ratio (SNR). However, it demands global channel state information (CSI) at both transmitters and receivers for precoder design in order to maximize the multiplexing gain. In this paper, we discuss IA with delayed differential CSI feedback for time-correlated multiple input multiple output (MIMO) block fading channels. We consider the impact of distortion caused by channel estimation errors and quantized CSI feedback delay, and thus, find an optimal feedback interval to minimize this distortion, as well as the sum rate performance. Specifically, we derive the minimum differential feedback rate. And with the feedback-channel capacity constraint, we further study the relationship between the average sum rate and the feedback interval. Analytical results are verified by simulations.

关键词： multiple input multiple output systems Feedback capacities constraint high SNR signal to noise ratios distortion INFORMATION ASSURANCE Transmitters interference interference channel estimation Receivers

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A bio-inspired adaptive MANET routing to circumvent congestion nodes

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Tien Tzu Hsueh Pao/Acta Electronica Sinica 2012年第4期40卷 710-716页

作者： Huang, Qiong Yin, Peng-Fei Yang, Xiao-Long Xu, Jie Long, Ke-Ping Key Laboratory of Mobile Communication Technology Chongqing University of Posts and Telecommunications Chongqing 400065 China School of Computer and Communications Engineering University of Science and Technology Beijing Beijing 100083 China Research Centre for Optical Internet and Mobile Information Networks University of Electronic Science and Technology of China Chengdu Sichuan 610054 China

Traditional Ad Hoc network routing protocols are mainly based on the condition "Shortest Path", and possibly form many congestion nodes to cause routing instability and re-routing. To this point, this paper proposed a new bio-inspired adaptive routing protocol (ATAR) based on a mathematic model ARAS which is originally a model for its host Escherichia coli cells to adapt to changes in the availability of a nutrient. In this paper, queue buffer of routing node and hop count of feedback are defined as a new metric, fitness, which represents the comprehensive factor of congestion level and the length of routing path. We map the fitness of neighbors of routing node to the cell volume growth speed in the improved ARAS model, and calculate the state values of neighbors with the model. Then, the routing node selects the next hop according to the maximum. Using this method, we can adaptive to choose a leisurely node as the next hop with shorter path.

关键词： Escherichia coli

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