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Pacific Rim International Symposium on Dependable Computing

作者： Meng-lai Yin Rafael R. Arellano Department of Electrical and Computer Engineering Cal Poly Pomona USA Network Centric Systems Raytheon Advanced Device Center USA

This study is motivated by the unexpected failure of a network-based system during the performance of corrective maintenance. This incident highlights the importance of incorporating network connectivity analysis in maintenance planning. This study shows that it is crucial to consider network connectivity when planning maintenance. Procedures to conduct maintenance planning with network connectivity consideration is proposed and discussed

关键词： Satellite broadcasting Spine network topology Degradation Redundancy Failure analysis Performance analysis Availability Fault tolerant systems Large-scale systems

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Self-stabilizing deterministic time division multiple access for sensor networks

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Journal of Aerospace Computing, Information and Communication 2006年第8期3卷 403-419页

作者： Arumugam, Mahesh Kulkarni, Sandeep S. Michigan State University East Lansing MI 48824 Software Engineering and Network Systems Laboratory Department of Computer Science and Engineering Michigan State University East Lansing MI 48824

An algorithm for time division multiple access (TDMA) is found to be applicable in converting existing distributed algorithms into a model that is consistent with sensor networks. Such a TDMA service needs to be self-stabilizing so that in the event of corruption of assigned slots and clock drift, it recovers to states from where TDMA slots are consistent. Previous self-stabilizing solutions for TDMA are either randomized or assume that the topology is known upfront and cannot change. Thus, the question of feasibility of self-stabilizing deterministic TDMA algorithm where the topology is unknown remains open. In this paper, we present a self-stabilizing deterministic algorithm for TDMA in networks where a sensor is only aware of its neighbors. To our knowledge, this is the first such algorithm that achieves these properties. Moreover, this is the first algorithm that demonstrates the feasibility of stabilization-preserving deterministic transformation of a program in shared-memory model on an arbitrary topology into a program that is consistent with the sensor network model. © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Time division multiple access

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An Adaptive Jitter Buffer Play-Out Scheme to Improve VoIP Quality in Wireless networks

An Adaptive Jitter Buffer Play-Out Scheme to Improve VoIP Qu...

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MILCOM, Military Communications Conference

作者： Kevin M. McNeill Mingkuan Liu Jeffrey J. Rodriguez BAE Systems Network Enabled Solutions Reston VA USA Department of Electrical and Computer Engineering University of Arizona Tucson Tucson AZ USA

Extension of the infrastructure supporting network-centric operations to the tactical edge relies primarily on wireless communications. The nature of these communications ensures that the channel will vary dramatically due to environmental and propagation effects, as well as potential interferers. Tactical operations introduce additional impairment due to mobility. With convergence to Internet protocol (IP) centric networking, voice communications at the tactical edge will be increasingly dependent on voice over IP (VoIP). In a packet-based protocol such as IP, two critical factors affecting latency sensitive applications such as VoIP are end-to-end delay and packet loss. Making a tradeoff between these two factors is of prime consideration in designing the jitter buffer playout scheme. Since voice packets are delayed in the network randomly, the jitter buffer is required to maintain consistently spaced playout of voice samples. A deep buffer protects against packet loss due to late arrival of packets. However, a deep buffer introduces mouth-to-ear delay that ultimately degrades the perceived voice quality. We describe an algorithm for dynamically estimating network delay using time series models. This enables the VoIP application to manage the jitter buffer to maintain a minimum playout buffer, while keeping the packet loss rate above a minimal threshold to maintain consistent voice quality. Our proposed algorithm limits sensitivity to short-term delay jitter and is very reactive to bursty network traffic. Simulation results show an improvement of 11% to 15% using metrics based on the subjective ITU E-model (R-factor) when compared against currently used playout methods. The improvement gain from the proposed method may be of particular significance for the challenges of supporting bursty dynamic changing wireless communication channel.

关键词： Jitter Wireless networks Wireless communication Protocols Delay estimation Potential well Convergence IP networks Internet telephony Protection

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A scalable VoIP platform based on MGCP/H.323 interworking and QoS management capabilities

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WSEAS Transactions on Communications 2006年第2期5卷 210-217页

作者： Dagiuklas, T. Ioannou, K. Garmpis, A. Department of Telecommunications and Network Systems TEI of Messologi Nafpaktos Greece Department of Electrical and Computer Engineering University of Patras Rio Patra Greece Department of Applied Informatics in Management and Economy Technological Educational Institution of Messolonghi Messolonghi 30100 Greece

This paper presents a lightweight VoIP platform based on H.323/MGCP interworking and QoS capabilities. The lightweight feature is accomplished by introducing two new schemes in the platform;the use of the SCTP as a transport protocol to convey H.323 signaling and the use of the Compressed-RTP as a compressed implementation of the RTP. The MGCP/H.323 interworking provides the platform with the essential scalability so that many different VoIP scenarios can be implemented. The whole architecture consists of a Call Agent that provide central management to the whole system and of a Media Gateway that is desponsible for carrying out all the essential media transformation. Finally the VoIP platform uses a QoS management module in order to guarantee certain level of voice quality to the users. This module is able to deal with situations where the network load is significantly affected by the voice packets produced by the proposed platform. The whole architecture bears many innovative characteristics and presents the way for a normal interworking of all these modules. Furthermore, it takes into account that many products in the market are already based in either H.323 or MGCP and tries to propose a way for a smooth co-operation between these two protocols.

关键词： Voice/data communication systems

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On Packet Aggregation Mechanisms for Improving VoIP Quality in Mesh networks

On Packet Aggregation Mechanisms for Improving VoIP Quality ...

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IEEE Conference on Vehicular Technology (VTC)

作者： Kyungtae Kim S. Ganguly R. Izmailov Sangjin Hong IP Network and Distributed Systems NEC Laboratories America Princeton NJ USA IP Network and Distributed Systems NEC Laboratories America Princeton NJ Department of Electrical and Computer Engineering State University of NY at Stony Brook Stony Brook NY USA

Performance in multihop wireless networks is known to degrade with the number of hops for both TCP and UDP traffic. For VoIP, the wireless network presents additional challenges as the perceived quality is dependent on loss, delay and jitter. Furthermore, small size of VoIP packets aggravates network utilization of the 802.11 based wireless mesh network. In this work, we evaluate the packet aggregation algorithms to reduce VoIP protocol overhead, compare the aggregation algorithms and propose a distributed packet aggregation mechanism. The experimental results demonstrates that the proposed distributed packet aggregation algorithm improves the VoIP quality and results in significant increase in the number high quality VoIP calls supported over multihop mesh

关键词： Internet telephony Intelligent networks Mesh networks Wireless mesh networks Protocols Spread spectrum communication Bandwidth Laboratories Costs Adaptive algorithm

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Impact of IPSec Overhead on Web Application Servers

Impact of IPSec Overhead on Web Application Servers

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International Conference on Advanced Computing and Communications (ADCOM)

作者： S. P. Meenakshi S. V. Raghavan School of Computing Sciences Vellore of Institute of Technology Vellore India Network Systems Laboratory Department of Computer Science and Engineering Indian Institute of Technology Madras Chennai India

IPSec provides Maturity solutions to various network based applications i.e., web applications. Implementing the, IPSec in network layer includes significant bandwidth and processing time, overhead to application traffic. The upperlayer protocols such as TCP and UDP behaviour is also influenced by these overheads. In war work, we have studied the impact of IPSee on the metrics: Round Trip Time, Average Burst Size and Available Bandwidth for IPv4 and IPv6 network ***-MD5 authentication algorithm, advanced encryption standard encryption algorithm, and deflate comperession algorithm are used for the protocols of IPSec. From the characterized metrics and computed overheads we analyze tile impact of IPSec on connection handling capacity of web application servers by considering the user behaviour on web page requests.

关键词： Protocols Bandwidth Telecommunication traffic Authentication Traffic control network servers Cryptography Web pages Time measurement Application software

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Track and vehicle condition monitoring during normal operation using reduced sensor sets

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HKIE Transactions Hong Kong Institution of Engineers 2006年第1期13卷 47-53页

作者： Weston, P.F. Li, P. Ling, C.S. Goodman, C.J. Goodall, R.M. Roberts, C. Department of Electronic Electrical and Computer Engineering University of Birmingham United Kingdom Department of Engineering University of Leicester United Kingdom Department of Electronic and Electrical Engineering Loughborough University United Kingdom Rail Research UK University of Birmingham Department of Electronic Electrical and Computer Engineering United Kingdom Department of Engineering University of Leicester United Kingdom Department of Mechanical Engineering University of Bristol United Kingdom Traction Systems Denmark Rail Research UK Universities Centre for Rail Systems Research United Kingdom IEE United Kingdom Railway Engineering Professional Network Management Team United Kingdom

The Enhanced Rail Contribution by Increased Reliability (ERCIR) project aimed to enhance availability by condition monitoring of the track and vehicle suspension from in-service trains. In this project, the possibility of instrumenting an inservice train is explored, with emphasis on using a minimal sensor set for the detection and diagnosis of track and vehicle faults. The use of a bogie-mounted pitch rate gyro to observe mean vertical track geometry is novel, as is using a bogie-mounted yaw rate gyro to observe mean lateral alignment as well as the more usual longer wavelength track curvature. Mathematical algorithms are developed to detect vehicle suspension faults and track irregularities. The suspension faults considered are changes in secondary lateral and anti-yaw dampers, and changes in effective conicity. Sudden changes are detected and diagnosed using a Kalman filter-based innovation approach;gradual changes in damping coefficients and effective conicity are detected by parameter estimation using a Rao-Blackwellised particle filter. Observable track geometry irregularities include mean vertical and lateral alignment irregularities, as well as crosslevel and twist faults. This paper finally describes the results of trials carried out on two different railway vehicles, using the data obtained to assess the validity of the fault detection algorithms.

关键词： Railroad tracks

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Experimental demonstration of a simple time-of-flight rangefinder based on semiconductor optical amplifier

Experimental demonstration of a simple time-of-flight rangef...

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Optical Fiber Communication (OFC) Conference

作者： B.S. Gopalakrishnapillai K.L. Lee A.J. Lowery M. Premaratne S. Shinada N. Wada T. Miyazaki A. Nirmalathas C. Lim Department ofElectrical and Electronics Engineering University of Melbourne Parkville VIC Australia Advanced Computing and Simulation Laboratory AXL Department ofElectrical and Computer Systems Engineering Monash University Clayton VIC Australia Department of Electrical and Electronics Engineering University of Melbourne Parkville VIC Australia Information and Network Systems Department National Institute ofInformation and Communications Technology NICT Incorporated Administrative Agency Koganei Tokyo Japan

We propose a unique design of a time-of-flight laser ranger that detects the distance and reflectivity of a target based on cross-gain modulation between counter-propagating pulses in a semiconductor optical amplifier... 详细信息

ISBN: (纸本)1557528020

关键词： Semiconductor optical amplifiers Pulse amplifiers Optical pulses Optical interferometry Optical receivers Semiconductor lasers Stimulated emission High speed optical techniques Optical sensors Pulse measurements

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Stochastic user behaviour modelling and network simulation for resource management in cooperation with mobile telecommunications and broadcast networks

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International Journal of Mobile Communications 2006年第1期4卷 97-117页

作者： Centonza, Angelo Taylor, Gareth A. Itagaki, Takebumi Owens, Thomas J. Cosmas, John Song, Yong-Hua School of Engineering and Design Brunel University Kingston Lane Uxbridge Middlesex UB8 3PH United Kingdom Department of Electronics and Computer Engineering Brunel University West London United Kingdom Brunel University United Kingdom Institute of Teaching and Learning Australia Department of Multimedia Systems Brunel University United Kingdom Brunel Research Institute of Network Systems United Kingdom

The latest generations of telecommunications networks have been designed to deliver high data rates, providing flexible communication capabilities that can enable high-quality video images. However, these new generations of telecommunications networks are interference-limited, impairing their performance in cases of heavy traffic and high usage. One way to lift this constraint would be for the mobile telecommunications network operators to obtain the cooperation of a broadcast network operator so that at times when the service demand is too high, the service can be transferred to the broadcast network. This paper proposes a way for UMTS network operators to forecast the traffic associated with high-demand services intended to be deployed on the UMTS network and when demand requires to transfer it to a cooperating DVB-T network. The paper aims to justify cooperation between UMTS and DVB-T networks clearly showing how using a DVB-T network as a support to UMTS can increase the revenue generated by both networks. Copyright © 2006 Inderscience Enterprises Ltd.

关键词： Mobile telecommunication systems

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WLC05-1: A Cognitive Radio (CR) System Employing A Dual-Stage Spectrum Sensing Technique : A Multi-Resolution Spectrum Sensing (MRSS) and A Temporal Signature Detection (TSD) Technique

WLC05-1: A Cognitive Radio (CR) System Employing A Dual-Stag...

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IEEE Globecom 2006

作者： Y. Hur J. Park W. Woo J. S. Lee K. Lim C.-H. Lee H. S. Kim Joy Laskar Department of Computer and Digital Systems Engineering University of Sao Paulo Sao Paulo SP Brazil University of Sao Paulo Department of Research and Development (R & D) National Education and Research Network (RNP) Rio de Janeiro RJ Brazil

Spectrum sensing technology is most vital to the implementation of a CR system using dynamic spectrum resource management. This paper suggested a CR system architecture with a wideband dual-stage spectrum sensing technique - a coarse and a fine spectrum sensing. Specifically, a coarse spectrum sensing technique adopted wavelet transforms in this architecture to provide a multi-resolution spectrum sensing (MRSS) feature. Analog implementation of the MRSS block offers wideband, low-power, and real-time operation. A fine spectrum sensing technique used the beneficial properties of auto-correlation in time domain - temporal signature detection (TSD). This TSD technique enables identifying the unique signature feature of each specific signal type. Moreover, this feature detection technique in time domain realizes simple and fast spectrum-detection compared to spectral feature detection methods.

关键词： Cognitive radio Chromium computer vision Signal processing Wideband Autocorrelation Resource management Frequency Digital modulation Wavelet transforms

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