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14 results on '"Sfikas G."'

6. An Analytic Distance Metric for Gaussian Mixture Models with Application in Image Retrieval.

Author

Sfikas, G., Constantinopoulos, C., Likas, A., and Galatsanos, N. P.

Abstract

In this paper we propose a new distance metric for probability density functions (PDF). The main advantage of this metric is that unlike the popular Kullback-Liebler (KL) divergence it can be computed in closed form when the PDFs are modeled as Gaussian Mixtures (GM). The application in mind for this metric is histogram based image retrieval. We experimentally show that in an image retrieval scenario the proposed metric provides as good results as the KL divergence at a fraction of the computational cost. This metric is also compared to a Bhattacharyya-based distance metric that can be computed in closed form for GMs and is found to produce better results. [ABSTRACT FROM AUTHOR]

Published
2005
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8. Service mapping and QoS provisioning in broadband satellite multimedia networks.

Author

Mertzanis, I., Sfikas, G., Tafazolli, R., and Evans, B.G.

Subjects
BROADBAND communication systems, ASYNCHRONOUS transfer mode, TELECOMMUNICATION satellites
Abstract

This paper focuses on the performance evaluation of broadband multimedia services in S-ATM (Satellite Asynchronous Transfer Mode) systems. The investigation includes service mapping and modelling techniques for both Geostationary (GEO) and non-GEO systems. The queuing performance and the buffer dimensioning of an S-ATM network model assuming that the network arrivals at the edges of this network are self-similar processes is also investigated. A new methodology for creating service classes according to the user-defined performance criteria is developed. Our approach can be used to dynamically regulate the system's call blocking and handoff failure probabilities for different services classes. A new radio resource management scheme, the Adaptive Bandwidth Reservation Scheme (ABRS) is proposed by incorporating two different threshold values for handling the new calls and the handoff requests. Due to the dynamic bandwidth reservation, each service class maintains a Grade of Service (GoS) profile that has been accepted or negotiated during the call set-up phase and is guaranteed for a predefined service period. [ABSTRACT FROM AUTHOR]

Published
2001

9. Satellite-ATM networking and call performance evaluation for multimedia broadband services.

Author

Mertzanis, I., Sfikas, G., Tafazolli, R., and Evans, B. G.

Abstract

Currently, there is a huge increase in the demand for satellite communications operating at the Ka-frequency bands; several different systems have been proposed and are under development worldwide. In this paper, we investigate the design issues for the satellite protocol architecture that best satisfies the interconnection to the Broadband Integrated Services Digital Network (B-ISDN). The latest developments in broadband satellite communications aim to support a wide range of applications. These systems are designed to provide high quality multimedia services to remote user terminals. Furthermore, the mechanism that needs to be implemented in order to satisfy certain Grade Of Service (GoS) and Quality Of Service (QoS) criteria is discussed. A new methodology for the call performance evaluation of the Available Bit Rate (ABR) service class in a satellite Asynchronous Transfer Mode (ATM) network is proposed. Results at call level for different mix of service classes are presented using both analytical and simulation models. The simulation model was developed using OPNET modeller and it was used to record statistics that cannot be easily obtained by analysis. Copyright © 1999 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
1999
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