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BEZAHAF Mohamed el Mehdi

PhD graduated
Team : NPA
Departure date : 05/30/2011
http://www-rp.lip6.fr/~bezahaf
Supervision : Serge FDIDA
Co-supervision : IANNONE Luigi

Transparent Mobility Management in a Real Wireless Mesh Environment

Over the last decade, we have witnessed a great success of wireless communications. In our daily life, most of electronic devices are equipped with a wireless interface, allowing users to be more mobile and pervasive. This requires specific communication architectures that respond to the challenges imposed by new user behaviors. Wireless mesh networks fall in this category. Indeed, with their two-tiered architecture, they concentrate routing on a stable wireless backbone, while mobile clients are totally free to move around. In this context, one of the main challenges is to provide an efficient localization service so that clients can communicate with each other in a transparent way. This thesis investigates micro-mobility issues in wireless mesh networks by analyzing mobility management performance on real testbeds through measurements. The contributions are threefold: Enhanced mobility management. Most of existing solutions rely on some variant of full or partial flooding, which causes the well known broadcast storm problem, and very often they need support from end-users' devices. To deal with this latter issue, we propose Enhanced Mobility Management (EMM), a new efficient solution that does not rely on any modification or additional software on client side, thus being totally transparent for end-users. EMM takes advantage of the existing Neighbor Discovery Protocol (NDP) cache to keep track of the latest association and uses this information to trigger an update in order to re-route packets. Measurements show that EMM significantly improve performance of mobility management. DHT-based location management. We design, implement, and test LORD, a new DHT-based scalable location management scheme through logical and experimental evaluation on our wireless mesh testbed. The main features of our proposed scheme are that broadcast packets are totally avoided and node localization is transparent to users. We compare it to our previous flooding-based location scheme (EMM). Our results show improved performance both in terms of percentage of dropped packets and handover latency introduced to re-establish open sessions after a user movement. Link stability. Finally, to study the stability of our DHT approach, we investigate stability of links in wireless environments. We address some interesting questions related to persistence and prevalence of both dominant and sub-dominant routes between nodes in a real deployment. We note that source-destination pairs mostly use the dominant route and the two most sub-dominant routes to communicate. We also investigate the impact of the distance between a source and a destination on stability of routes. It turns out that the longer the distance, the larger the number of sub-dominant routes.
Defence : 12/09/2010 - 11h - Site Jussieu 25-26/105
Jury members :
Thomas NOEL, Professeur, Université Louis Pasteur de Strasbourg [Rapporteur]
Vania CONAN, Chercheur, Thales Communications [Rapporteur]
Pierre SENS, Professeur, UPMC Sorbonne Universités
Djamal ZEGHLACHE, Professeur, INT
Henrik LUNDGREN, Chercheur, Technicolor Lab
Serge FDIDA, Professeur, UPMC Sorbonne Universités
Luigi IANNONE, Chercheur, Deutsche Telekom Laboratories -- Berlin

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