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41 results on '"Vergados, D."'

7. A two‐step authentication framework for Mobile ad hoc networks

Author

Komninos, N., Vergados, D. D., and Douligeris, C.

Subjects
QA76
Abstract

The lack of fixed infrastructure in ad hoc networks causes nodes to rely more heavily on peer nodes for communication. Nevertheless, establishing trust in such a distributed environment is very difficult, since it is not straightforward for a node to determine if its peer nodes can be trusted. An additional concern in such an environment is with whether a peer node is merely relaying a message or if it is the originator of the message. In this paper, we propose an authentication approach for protecting nodes in mobile ad hoc networks. The security requirements for protecting data link and network layers are identified and the design criteria for creating secure ad hoc networks using several authentication protocols are analyzed. Protocols based on zero knowledge and challenge response techniques are presented and their performance is evaluated through analysis and simulation.

Published
2007

8. Two‐Step Authentication in Mobile Ad Hoc Networks

Author

Komninos, N., Vergados, D. D., and Douligeris, C.

Subjects
QA75
Abstract

The lack of fixed infrastructure in ad hoc networks causes nodes to rely more heavily on peer nodes for communication. Nevertheless, establishing trust in such a distributed environment is very difficult, since it is not straightforward for a node to determine if its peer nodes can be trusted. An additional concern in such an environment is with whether a peer node is merely relaying a message or if it is the originator of the message. In this paper, we propose an authentication approach for protecting nodes in mobile ad hoc networks. The security requirements for protecting data link and network layers are identified and the design criteria for creating secure ad hoc networks using several authentication protocols are analyzed. Protocols based on zero knowledge and challenge response techniques are presented and their performance is evaluated through analysis and simulation.

Published
2006

23. A QoE-driven adaptation scheme for video content delivery in LTE networks

Author

Vergados, D. J., Sgora, A., Michalas, A., Vergados, D. D., Laulajainen, J. -P, and Jiang, Y.

Subjects
LTE, wireless networks, AHP, QoE
Abstract

The Long-Term Evolution (LTE) standard is a promising solution to mobile connectivity. It provides high data rates at a relatively low cost. At the same time, video traffic has so far outpaced other traffic types in growth, making it the dominant traffic type in current wireless networks. In this paper we study the concept of Quality of Experience (QoE) for video traffic in LTE systems. Since video users are more annoyed by unpredictable disruptions than overall reduced video fidelity, we developed an adaptive video coding scheme that aims to improve QoE in LTE networks. In the proposed model users of the same quality class are classified into a number of service levels providing different QoE satisfaction thresholds to their members. The QoE driven adaptation scheme adapts the rate of the transmitted video, so that the QoE experienced by the users remains in satisfactory levels. Two different policies for transmission rate adaptation are studied, namely the adaptive and the coordinated approach. The level of the transmission rate for both policies is regulated by the linear slow start and/or the exponential increase. Simulation results showed that the proposed algorithm for the both transmission rate adaptation policies succeeds in minimizing packet loss and delay in the video transmission, by adjusting the video resolution.

26. Performance of maximum-ratio combining-enabled heterodyne detection for free-space optical systems under mixture-Gamma fading channels and pointing errors.

Author

Miridakis, N. I., Vergados, D. D., and Michalas, A.

Subjects
*OPTICAL communications, *HETERODYNE detection, *TURBULENCE, *RADIO transmitter fading, *BIT error rate
Abstract

The performance of maximum-ratio combining for free-space optical systems using heterodyne detection is analytically studied. The analysis includes the joint effect of turbulence- and misalignment-induced channel fading. Particularly, novel closed-form expressions regarding the scintillation index, outage probability and average bit-error rate are derived. Based on these results, some useful outcomes are manifested, such as the system diversity order, the crucial role of diversity branches, and the impact of composite channel fading onto the system performance. [ABSTRACT FROM AUTHOR]

Published
2017
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39. Sliding Windows: A Software Method Suitable for Real-Time Inspection of Textile Surfaces.

Author

Anagnostopoulos, C., Anagnostopoulos, I., Vergados, D., Kayafas, E., and Loumos, V.

Abstract

There is a strong interest in expert systems to assist in complex defect identification procedures. To increase accuracy, attempts are made to enhance traditional human inspection by automated visual systems, which employ cameras and image processing routines. This paper presents a detailed description of a fast algorithm for defect detection in textile surfaces and an evaluation of the experimental results for 137 digitized images of representative defects in woven fabrics collected from a larger sample provided by textile companies.

Published
2004

40. The Wisconsin breast cancer problem: Diagnosis and TTR/DFS time prognosis using probabilistic and generalised regression information classifiers.

Author

Anagnostopoulos I, Anagnostopoulos C, Vergados D, Rouskas A, and Kormentzas G

Subjects
Biopsy, Needle, Disease-Free Survival, Female, Humans, Prognosis, Survival Analysis, Breast Neoplasms diagnosis, Breast Neoplasms pathology, Models, Statistical, Neural Networks, Computer
Abstract

This study addresses the breast cancer diagnosis and prognosis problem by employing two neural network architectures with the Wisconsin diagnostic and prognostic breast cancer (WDBC/WPBC) datasets. A probabilistic approach is dedicated to solve the diagnosis problem, detecting malignancy among cases (instances) as derived from fine needle aspirate (FNA) tests, while the second architecture estimates the time interval that possibly contains the right endpoint of disease-free survival (DFS) of the patient. The accuracy of the neural classifiers reaches nearly 98% for the diagnosis and 93% for the prognosis problem, while the prognostic recurrence predictions were evaluated using survival analysis through the Kaplan-Meier approximation method. Both architectures were compared with other similar approaches. The robustness and real-time response of the proposed classifiers were further tested over the web as a potential integrated web-based decision support system.

Published
2006
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41. A modelling and simulation framework for compound medical applications in regional healthcare networks.

Author

Kormentzas G, Maglogiannis I, Vassis D, and Vergados D

Subjects
Europe, Humans, Medical Records Systems, Computerized, Models, Theoretical, North Sea, Telemedicine, Computer Communication Networks, Delivery of Health Care
Abstract

Regional healthcare information networks have already started to grow across Europe, in order to cover local healthcare provision needs, especially in isolated regions, where there is often no availability of central general hospitals. The paper discusses a modelling and simulation framework for the design of regional healthcare information networks running compound medical and QoS-sensitive applications. The proposed framework decomposes the compound medical applications into combinations of elementary traffic profiles, assesses appropriate values to the traffic parameters of the assigned models and defines suitable simulation scenarios. The simulation results are analysed and finally lead to reliable bandwidth estimations of the links of the healthcare information network under design. The proposed framework has been thoroughly validated through its application for the design of a healthcare network in the islands of the North Aegean Sea, running actual compound medical applications in the context of a national research project.

Published
2005
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