"On the use of fixed-point approximations for wireless network performance analysis"
Speaker: Merkourios Karaliopoulos
Date: 13 February 2009 Time: 09:00-11:00
Location: STEP-C Seminar Room, Building B (1st floor), FORTH, Heraklion, Crete
Host: Maria Papadopouli


The talk evolves around the use of fixed-point methods as a general framework for the performance analysis of communication protocols over wireless networks. We draw on formulations derived for wired networks and expand them to accommodate properties that are more frequently, though not exclusively, met in wireless networks including error-prone, broadcast and MAC-shared links, link asymmetry, and transport protocol mechanisms such as TCP proxies.

We provide examples for the use of the method in the context of closed-loop TCP traffic over Bandwidth on Demand satellite networks under two different resource scheduling schemes; the first one is based on the Collision-Free Demand Assignment Multiple Access (CF-DAMA) protocol, which provides no guarantees, whereas the second one caters for proportional differentiation of traffic classes over the network. In both cases, the analytical results are compared against simulation results. We demonstrate the applicability of fixed-point techniques to the study of interactions between protocols at different layers of the protocol stack, giving pointers to related work in the literature. The last part of the talk discusses the limitations of the method as well as directions of future work.


Merkouris Karaliopoulos is a Senior Researcher and Lecturer at the Computer Engineering and Networks Laboratory of the Swiss Federal institute of Technology in Zurich (ETH Zurich), Switzerland. His research interests lie in the general area of wireless networking spanning both infrastructure and self-organizing network paradigms; their current focus is on routing and reliable transport mechanisms and their interaction with the radio access layers, and network resilience to node misbehaviors.

He was awarded his diploma in electrical and computer engineering from Aristotle University of Thessaloniki, Greece, in 1998 and a PhD degree in broadband satellite networking from the University of Surrey, UK, in 2004. In parallel with his PhD studies, he was employed as a Research Associate in a series of European projects evolving around Satellite Digital Multimedia Broadcasting (SDMB), a hybrid satellite-terrestrial system designed by the now called Thales Alenia Space for broadcasting content to mobile users all over Europe. Prior to joining ETH Zurich in April 2007, he spent one year as a Postdoctoral Researcher in the Computer Science department of the University of North Carolina, Chapel Hill, USA, working on measurement-driven engineering of large-scale wireless local area networks.

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