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International Symposium on Electronics in Marine (ELMAR)

作者： Ioannis Chatzigiannakis Vasiliki Liagkou Paul G. Spirakis Department of Computer Engineering and Informatics University of Patras Patras Greece Research Academic Computer Technology Institute Patras Greece

ISBN: (纸本)9781424433643

Designing wireless sensor networks is inherently complex; many aspects such as energy efficiency, limited resources, decentralized collaboration, fault tolerance have to be tackled. To be effective and to produce applicable results, fundamental research has to be tested, at least as a proof-of-concept, in large scale environments, so as to assess the feasibility of the new concepts, verb their large scale effects (not only at technological level, but also as for their foreseeable implications on users, society and economy) and derive further requirements, orientations and inputs for the research. In this paper we focus on the problems of interconnecting existing testbed environments via the Internet and providing a virtual unifying laboratory that will support academia, research centers and industry in their research on networks and services. In such a facility important issues of trust, security, confidentiality and integrity of data may arise especially for commercial (or not) organizations. In this paper we investigate such issues and present the design of a secure and robust architectural model for interconnecting testbeds of wireless sensor networks.

关键词： Testing Wireless sensor networks Large-scale systems Energy efficiency Collaboration Fault tolerance IP networks Web and internet services Data security Robustness

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A novel power counting mechanism for enhanced MBMS performance in UMTS networks

IFIP Advances in Information and Communication Technology

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IFIP Advances in Information and Communication technology 2008年 284卷 57-68页

作者： Alexiou, Antonios Bouras, Christos Rekkas, Evangelos Computer Engineering and Informatics Department University of Patras Greece Research Academic Computer Technology Institute 26500 Rio Patras Greece

ISBN: (纸本)9780387848389

One of the key objectives of Universal Mobile Telecommunications System (UMTS) is the realization of enhanced end-user experience through the provision of rich multimedia services, ensuring in parallel an economical delivery cost for service providers. Multimedia Broadcast/Multicast Services (MBMS) framework of UMTS epitomizes the increasing popularity of such applications by efficiently delivering multimedia traffic to a large number of users and optimizing the radio interface of UMTS networks. For exploiting resource efficiency, MBMS specifications consider the Counting Mechanism which decides whether it is more economic to deliver MBMS multicast traffic over point-to-point (PTP) or point-to multipoint (PTM) bearers. However, the necessity to further improve MBMS resource efficiency and integrate new technologies such as High Speed Downlink Packet Access (HSDPA) stresses the need for an advanced Counting Mechanism. To this direction, in this paper we propose a novel Power Counting Mechanism which performs optimal power resource utilization and incorporates the HSDPA broadband extension of UMTS for enhanced performance. © 2008, IFIP International Federation for Information Processing. All rights reserved.

关键词： Universal Mobile Telecommunications System

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Channel estimation techniques for half-duplex cooperative communication systems

Channel estimation techniques for half-duplex cooperative co...

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International Symposium on Wireless Pervasive Computing (ISWPC)

作者： Aris S. Lalos Athanasios A. Rontogiannis Kostas Berberidis Department of Computer Engineering & Informatics and CTI Research & Development University of Patras Patras Greece National Observatory of Athens Institute of Space Applications and Remote Sensing Athens Greece

In this work we present efficient channel estimation algorithms for wideband detect-and-forward (DF) based relay networks. A generalization of a recently proposed transmission model is utilized and the analysis is completely performed in the frequency domain (FD). It is shown that all channels in the network from any node to the destination/receiver node can be blindly estimated up to a phase ambiguities vector, related to the source to destination channel frequency response. Hence, by utilizing a small number of pilot symbols, phase ambiguities can be effectively resolved. As verified by computer simulations, the proposed methods exhibit high estimation accuracy even for a short training sequence, and outperform direct training-based channel estimation. A performance study of the proposed schemes in high SNR conditions is also presented and verified through computer simulations.

关键词： Channel estimation Relays Performance analysis computer simulation Frequency domain analysis Phase estimation Frequency response Wireless networks Protocols computer networks

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Semi-blind channel estimation schemes based on a cooperative form of the cross relation criterion

Semi-blind channel estimation schemes based on a cooperative...

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International Symposium on Wireless Pervasive Computing (ISWPC)

作者： Christos Mavrokefalidis Kostas Berberidis Athanasios A. Rontogiannis Department of Computer Engineering and Informatics & CTI-Research & Development University of Patras Patras Greece Institute for Space Applications and Remote Sensing National Observatory of Athens Athens Greece

In this paper, two channel estimation schemes are derived for specific cooperative scenarios. Both schemes are based on the cross-relation criterion that has been extensively studied in the (semi-) blind literature. As shown in the paper, in a cooperative system, the channel estimator can be constructed in a natural way either by fractionally-spaced or symbol-spaced samples. We investigate the performance of these two schemes using semi-analytic arguments accompanied by corresponding experimental results.

关键词： Channel estimation Protocols Cooperative systems Relays informatics Application software Remote sensing Observatories Chromium Costs

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EEG signal analysis during miss operation in BCI system

EEG signal analysis during miss operation in BCI system

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SICE Annual Conference

作者： Junpei Kaminaka Tomonari Yamaguchi Miyo Taniguchi Kana Ohmori Sinya Watanabe Katsuhiro Inoue Gert Pfurtscheller Department of Systems Innovation and Informatics Factory of Computer Science and Systems Engineering Kyushu Institute of Technology Fukuoka Japan Department of Medical Informatics Institute of Biomedical Engineering Graz University of Technology Graz Austria

ISBN: (纸本)9784907764302

In this paper, electroencephalograph (EEG) signals recorded during miss operation of brain computer interface (BCI) system was analyzed. As a result, a feature difference between miss operation and normal operation was found at the low frequency component and the event-related potential (ERP) such as P300. Therefore a possibility of the modification of miss operation was confirmed.

关键词： EEG AR-model Brain computer interface Motor imagery Brain-computer Interfaces Electroencephalography Surgery Signal analysis normal operation

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Numerical and symbolic state space realizations of linear systems with algebraic loops

Numerical and symbolic state space realizations of linear sy...

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IEEE International Symposium on computer Aided Control System Design (CACSD)

作者： Masanobu Koga Satoru Anan Kentaro Yano Department of Systems Design and Informatics Faculty of Computer Science and Systems Engineering Kyushu Institute of Technology Fukuoka Japan

ISBN: (纸本)9781424422210

This paper proposes a method which gives a state space realization of the linear systems with algebraic loops not only in numerical format but also in symbolic format and guarantees that the order of the system is preserved. The method uses an adjacency matrix in graph theory for the modeling of the control systems and uses the matrix inversion lemma to calculate the inverse of matrix symbolically and to obtain the symbolic state space realizations. We have developed a new software platform for modeling and simulation of control systems using the proposed method.

关键词： Control systems USA Councils

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Fast arbiters for on-chip network switches

Fast arbiters for on-chip network switches

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IEEE International Conference on computer Design: VLSI in computers and Processors, (ICCD)

作者： Giorgos Dimitrakopoulos Nikos Chrysos Kostas Galanopoulos Institute of Computer Science (ICS) Foundation for Research and Technology Hellas FORTH Crete Greece Computer Engineering and Informatics Department University of Patras Patras Greece

The need for efficient implementation of simple crossbar schedulers has increased in the recent years due to the advent of on-chip interconnection networks that require low latency message delivery. The core function of any crossbar scheduler is arbitration that resolves conflicting requests for the same output. Since, the delay of the arbiters directly determine the operation speed of the scheduler, the design of faster arbiters is of paramount importance. In this paper, we present a new bit-level algorithm and new circuit techniques for the design of programmable priority arbiters that offer significantly more efficient implementations compared to already-known solutions. From the experimental results it is derived that the proposed circuits are more than 15% faster than the most efficient previous implementations, which under equal delay comparisons, translates to 40% less energy.

关键词： Network-on-a-chip Switches Fabrics Virtual colonoscopy Processor scheduling Delay Circuits Routing Packet switching Buffer storage

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Interpretation of Source Code Clusters in Terms of the ISO/IEC-9126 Maintainability Characteristics

Interpretation of Source Code Clusters in Terms of the ISO/I...

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(CSMR) European Conference on Software Maintenance and Reengineering

作者： Yiannis Kanellopoulos Christos Tjortjis Ilja Heitlager Joost Visser Computer Engineering and Informatics Department University of Patras Greece School of Computer Science University of Manchester Institute of Science and Technology UK Software Improvement Group Netherlands

Clustering is a data mining technique that allows the grouping of data points on the basis of their similarity with respect to multiple dimensions of measurement. It has also been applied in the software engineering domain, in particular to support software quality assessment based on source code metrics. Unfortunately, since clusters emerge from metrics at the source code level, it is difficult to interpret the significance of clusters at the level of the quality of the entire system. In this paper, we propose a method for interpreting source code clusters using the ISO/IEC 9126 software product quality model. Several methods have been proposed to perform quantitative assessment of software systems in terms of the quality characteristics defined by ISO/IEC 9126. These methods perform mappings of low-level source code metrics to high-level quality characteristics by various aggregation and weighting procedures. We applied such a method to obtain quality profiles at various abstraction levels for each generated source code cluster. Subsequently, the plethora of quality profiles obtained is visualized such that conclusions about different quality problems in various clusters can be obtained at a glance.

关键词： Software quality ISO standards IEC standards Software systems Object oriented modeling Clustering algorithms Data mining Software measurement Quality assessment Software standards

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New architectures for optical packet switching using QD-SOAs for multi-wavelength buffering

New architectures for optical packet switching using QD-SOAs...

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IEEE Workshop on High Performance Switching and Routing

作者： Kyriakos Vlachos Wojciech Kabacinski Slawomir Weclewski LComputer Engineering & Informatics Department and Research Academic Computer Technology Institute University of Patras Rio Greece Poznan University of Technology Poland

We present two architectures for implementing optical buffers. Both use multi-wavelength selective elements like quantum dot semiconductor optical amplifiers (QD-SOAs) as multi-wavelength converters and fixed-length delay lines that are combined to form both an output queuing and a parallel buffer switch design. The output queuing buffer design requires less active devices (QD-SOA) when implementing large buffers, but the parallel buffer design becomes more profitable, when the number of wavelength channels that can be simultaneously processed by the wavelength selective switches (QD-SOAs) increases. This is because the number of active devices depends only on the buffer size. We also proposed scheduling algorithm to resolve packet contention in parallel buffer architecture and carried out a simulation considering mean packet delay, maximum buffer occupancy and packet loss probability.

关键词： Optical packet switching Optical buffering Optical switches Delay lines Optical wavelength conversion Feedforward systems Dairy products Optical fiber networks Quantum dots Scheduling algorithm

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Performance study of the Mobile IPv6 protocol and its variations

Performance study of the Mobile IPv6 protocol and its variat...

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International Symposium on Communication Systems, Networks and Digital Signal Processing, CNSDSP

作者： George Aristomenopoulos Christos Bouras Kostas Stamos Computer Engineering and Informatics Department University슠of슠Patras Greece Computer Engineering and Informatics Department University of Patras Patras Greece Research Academic Computer Technology Institute N.Kazantzaki Str. Patras Univ. GR-26500 Rion Greece

In this paper, we use the OMNET++ simulator in order to evaluate the performance of the basic mobile IPv6 protocol and some of its proposed variations. The most important metric we are interested in is the handover latency, which is measured for various combinations of the proposed mobile IPv6 variations and then this metric is used, combined with factors such as the complexity of the implementation, in order to evaluate and identify the best possible configuration for the operation of the protocol.

关键词： Mobile communication Manganese Protocols Mobile computing Internet Force Object oriented modeling

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