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Optical DQPSK System Performance Evaluation Using Equivalent Differential Phase in Presence of Receiver Imperfections

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Journal of Lightwave Technology 2010年第12期28卷 1735-1744页

作者： Costa, Nelson M.S. Cartaxo, Adolfo V.T. Group of Research on Optical Fiber Telecommunication Systems Instituto de Telecomunicações Department of Electrical and Computer Engineering Instituto Superior Técnico 1049-001 Lisboa Portugal Nokia Siemens Networks Portugal S.A. 2720-093 Amadora Portugal

The performance evaluation of optical differential quadrature phase-shift keying (DQPSK) systems through numerical simulation using a Gaussian approach (GA) for the equivalent differential phase (EDP) statistics is analyzed. It is shown that the GA describes quite accurately the probability density function (PDF) of EDP for a large range of DQPSK receiver (RX) imperfections. A semi-analytical simulation method (SASM) for bit error probability (BEP) evaluation based on the GA for the EDP is derived, proving to be quite accurate in presence of RX imperfections. The SASM takes into account the signal-noise beat variance dependence on signal waveform distortion and arbitrary optical and electrical filtering frequency responses. Closed-form expressions for the mean and standard deviation of EDP are derived which allows evaluating the DQPSK system performance in a quite time-efficient manner. Discrepancies not exceeding 0.1 dB on the optical SNR penalty estimated by the SASM for a BEP of 10⁻⁴ when compared with Monte Carlo simulation are observed for the majority of the acceptable RX imperfections. Only the time-misalignment of the signals at the balanced detector input leads to higher discrepancies but not exceeding 0.3 dB even for considerable time-misalignment. © 2010 IEEE

关键词： Differential quadrature phase-shift keying (DQPSK) equivalent differential phase receiver imperfections semi-analytical simulation method

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Using ontologies in case-based activity recognition

Using ontologies in case-based activity recognition

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作者： Knox, Stephen Coyle, Lorcan Dobson, Simon Systems Research Group School of CS and Informatics UCD Dublin Ireland Lero - The Irish Software Engineering Research Centre University of Limerick United Kingdom School of Computer Science Universty of St Andrews United Kingdom

ISBN: (纸本)9781577354475

Pervasive computing requires the ability to detect user activity in order to provide situation-specific services. Case-based reasoning can be used for activity recognition by using sensor data obtained from the environment. Pervasive computing systems can grow to be very large, containing many users, sensors, objects and situations, thus raising the issue of scalability. This paper presents a case-based reasoning approach to activity recognition in a smart home setting. An analysis is performed on scalability with respect to case storage, and an ontology-based approach is proposed for case base maintenance. We succeeded in reducing the casebase size by a factor of one thousand, while increasing the accuracy in recognising some activities. Copyright © 2010, Association for the Advancement of Artificial Intelligence (***). All rights reserved.

关键词： Scalability

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A delay-sensitive strategy for real-time monitoring in wireless sensor networks

A delay-sensitive strategy for real-time monitoring in wirel...

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International Conference on Telecommunications (ICT)

作者： João B. Borges Neto Pedro F. Ribeiro Neto Rossana M. C. Andrade Group of Computer Networks Software Engineering and Systems Federal University of Ceará Fortaleza Ceara Brazil Group of Software Engineering State University of Rio Grande do Norte Mossoro Rio Grande do Norte Brazil

Advances in the research of Wireless Sensor networks (WSN) have allowed their use for several purposes, including monitoring of critical and dangerous environments. Applications in these environments share the need of operation without human intervention, which imposes autonomy and efficiency in executing their tasks, even under critical environmental conditions. Besides the traditional WSN physical limitations, their utilization as a source of collecting data in challenging environments requires the ability to support real-time observations of the monitoring environment. These observations should consider not only environment unpredictability with respect to mobility but also the variable amount of nodes and collected data. To deal with that, in this paper we propose a delay-sensitive strategy, which aims to enable WSN for monitoring challenging environments, taking into account real-time data constraints as well as mobility and limitations of the sensor nodes. This strategy is implemented in a new routing protocol, called PROST.

关键词： Monitoring Wireless sensor networks Road accidents Vehicle safety Protocols Traffic control Road safety Telecommunication traffic Road vehicles Global Positioning System

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UML model-driven detection of performance bottlenecks in Concurrent Real-Time software

UML model-driven detection of performance bottlenecks in Con...

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International Symposium on Performance Evaluation of computer & Telecommunication Systems SPECTS

作者： Vahid Garousi Software Engineering Research Group (SERG) Department of Electrical and Computer Engineering University of Calgary Calgary AB Canada

A UML-driven technique for detection of performance bottlenecks in concurrent real-time systems is presented. The approach is based on comprehensive analysis of control flow in two types of UML 2.x behavioral models: sequence diagrams and interaction overview diagrams. The technique takes an input the runtime durations of tasks and uses the Program Evaluation and Review Technique (PERT) to pinpoint performance bottlenecks in UML-based control flow information of a concurrent real-time system. Since design UML models are usually developed and are available already for most object-oriented systems, the technique prevents the need to construct specific-purpose performance models such as Layered Queuing networks. Application of the technique on an example control software system demonstrates the applicability and effectiveness of the technique in pinpointing performance bottlenecks.

关键词： Unified modeling language Object oriented modeling Analytical models Real time systems Runtime Flow graphs

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A metric for measuring the degree of entity-centric service cohesion

A metric for measuring the degree of entity-centric service ...

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IEEE International Conference on Service-Oriented Computing and Applications (SOCA)

作者： A. Rostampour A. Kazemi F. Shams A. Zamiri P. Jamshidi Automated Software Engineering Research Group Electrical and Computer Engineering Faculty Shahid Beheshti University Tehran Iran

Most of the focus in business process modeling (BPM) is on activity-centric; however an emerging approach in the field is entity-centric which benefits from various enhancements in contrast to former approaches. As a consequence, entity-centric business services as the external view of a group of business processes within an organization are getting more importance in contrast to the other types of business services. These types of services are more powerful than task-centric services in terms of being more reusable, and needing less effort to redesign and redevelop when satisfying new requirements. Therefore, it is critical to quantitatively measure structural properties of such services. Since entity-centric design approaches are emerging in service-oriented paradigm, there is no comprehensive metric to measure the degree of service cohesion. This paper aims to address this issue by providing a novel cohesion metric that takes into account the relations between the entities used by shared operations. The metric are empirically evaluated in a small-scaled controlled study.

关键词： Business Correlation software Object oriented modeling software measurement software engineering

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Measured performance of a memory-efficient segment-based packet-combining scheme

Measured performance of a memory-efficient segment-based pac...

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IFIP Wireless Days, WD

作者： Danil Kipnis Tobias Jacob Andreas Willig Telecommunication Networks Group Technical University Berlin Germany Department of Computer Science and Software Engineering University of Canterbury Christchurch New Zealand

Packet-combining schemes are an attractive improvement to ARQ schemes, since they allow receivers to keep the good parts of an otherwise erroneous packet and use these with good parts from subsequent packets to allow for quicker decoding. In the previous paper a memory-efficient hard-decision packet combining scheme has been described and analysed, which relies on intermediate checksums spread into the user data part of a packet. In this paper we provide experimental data on the performance of the proposed packet-combining scheme, showing that a significant percentage of the wireless links found in a large indoor wireless testbed (the TKN TWIST testbed) indeed benefits from introducing such a packet-combining scheme.

关键词： Receivers Wireless sensor networks Transmitters Automatic repeat request Wireless communication Power measurement Transceivers

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Teaching software engineering from a collaborative perspective: Some Latin-American experiences

Teaching software engineering from a collaborative perspecti...

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21st International Workshop on Database and Expert Systems Applications, DEXA 2010

作者： Giraldo, Fáber D. Collazos, César A. Ochoa, Sergio F. Zapata, Sergio De Clunie, Gisela Torres System and Computer Engineering Department University of Quindío Armenia IDIS Research Group University of Cauca Popayan Colombia Computer Science Department University of Chile Santiago Chile Informatics Institute National University of San Juan San Juan Argentina Software Engineering Department Technological University of Panama Panama City Panama

ISBN: (纸本)9780769541747

Teaching software engineering has been recognized as an important challenge for computer science undergraduate programs. Instruction in such area requires not only to deliver theoretical knowledge, but also to perform practical experiences that allow students to assimilate and apply such knowledge. This paper presents some results of two computer-Supported Collaborative Learning (CSCL) experiences that involved students of software engineering courses from four Latin American Universities. The obtained results were satisfactory and indicate the reported collaborative activity could be appropriate to address teaching software engineering. © 2010 IEEE.

关键词： E-learning

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An Open Modern software Testing Laboratory Courseware – An Experience Report

An Open Modern Software Testing Laboratory Courseware – An ...

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Conference on software engineering Education & Training (CSEE&T)

作者： Vahid Garousi Software Quality Engineering Research Group (SoftQual) Department of Electrical and Computer Engineering Schulich School of Engineering University of Calgary AB Canada

In order to effectively teach software testing students how to test real-world software, the software tools, exercises, and lab projects chosen by testing educators should be practical and realistic. However, there are not many publicly-available realistic testing courseware for software testing educators to adapt and customize. Even for the existing testing lab exercises developed and/or used by the educators, there are various drawbacks, e.g.: (1) They are not usually kept up-to-date with the most recent testing tools and technologies, e.g., JUnit, (2) They are not built based on realistic/real-world Systems Under Test (SUTs), but rather use ¿toy¿ examples (SUTs). The above needs were the main motives for the author and his team at the University of Calgary to modernize the lab exercises of an undergraduate software testing course. This paper presents the designed lab courseware, and the experiences learned from using the courseware in the University of Calgary. It is hoped (and expected) that other software testing educators start to use this laboratory courseware and find it useful for their instruction and training needs.

关键词： software testing Laboratories Courseware System testing software tools software engineering software quality computer science education Large-scale systems computer industry

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Advanced gaze visualizations for three-dimensional virtual environments 10

Advanced gaze visualizations for three-dimensional virtual e...

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ACM Symposium on Eye-Tracking research and Applications, ETRA 2010

作者： Stellmach, Sophie Nacke, Lennart Dachselt, Raimund User Interface and Software Engineering Group Faculty of Computer Science Otto-von-Guericke-Universität Magdeburg D-39106 Magdeburg Germany Game Systems and Interaction Research Laboratory School of Computing Blekinge Institute of Technology SE-37225 Ronneby Sweden

ISBN: (纸本)9781605589947

Gaze visualizations represent an effective way for gaining fast insights into eye tracking data. Current approaches do not adequately support eye tracking studies for three-dimensional (3D) virtual environments. Hence, we propose a set of advanced gaze visualization techniques for supporting gaze behavior analysis in such environments. Similar to commonly used gaze visualizations for two-dimensional stimuli (e.g., images and websites), we contribute advanced 3D scan paths and 3D attentional maps. In addition, we introduce a models of interest timeline depicting viewed models, which can be used for displaying scan paths in a selected time segment. A prototype toolkit is also discussed which combines an implementation of our proposed techniques. Their potential for facilitating eye tracking studies in virtual environments was supported by a user study among eye tracking and visualization experts. © 2010 ACM.

关键词： Visualization

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An Empirical Evaluation of Regression Testing Based on Fix-Cache Recommendations

An Empirical Evaluation of Regression Testing Based on Fix-C...

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International Conference on software Testing, Verification, and Validation, ICST

作者： Emelie Engström Per Runeson Greger Wikstrand Software Engineering Research Group Dept. of Comp. Science Lund University Lund Sweden Software Engineering Research Group Department of Computer Science Lund University Lund Sweden KnowIT YAHM Sweden AB Lund Sweden

Background: The fix-cache approach to regression test selection was proposed to identify the most fault-prone files and corresponding test cases through analysis of fixed defect reports. Aim: The study aims at evaluating the efficiency of this approach, compared to the previous regression test selection strategy in a major corporation, developing embedded systems. Method: We launched a post-hoc case study applying the fix-cache selection method during six iterations of development of a multi-million LOC product. The test case execution was monitored through the test management and defect reporting systems of the company. Results: From the observations, we conclude that the fix-cache method is more efficient in four iterations. The difference is statistically significant at α = 0.05. Conclusions: The new method is significantly more efficient in our case study. The study will be replicated in an environment with better control of the test execution.

关键词： System testing software testing Fault diagnosis Logic testing Costs software engineering Monitoring Joining processes Iterative methods Embedded system

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