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Contributions à l'amélioration de la qualité de service dans les réseaux sans fil Wifi

Abstract : Due to their wide proliferation, IEEE 802.11 Wireless Local Area Networks (WLANs) are expected to support multimedia applications such as voice and broadband video transmissions, which normally have a strict bounded transmission delay. The aim of this thesis is to enhance the support of these applications, and so, to improve the Quality of Service (QoS) scheme in IEEE 802.11 WLANs. Firstly, we focus our work on the link adaptation procedure performed over WiFi networks. A new dynamic time-based link adaptation mechanism, called Modified Adaptive Auto Rate Fallback, is proposed. Simulations are performed by means of the Network Simulator 2 and the results show the quality improvement of transmission link. The results also demonstrate that the proposed mechanism outperforms the basic solution in terms of providing support to both acknowledgment-based and time-based rate control decision. In the second part of this thesis, we introduce a new inter-node priority access scheme with the existing Enhanced Distributed Chanel Access of IEEE 802.11e networks. The new technique is based on the junction of a new inter-node priority with the existing inter-frame priority. The simulation results show that the proposed technique improves the basic 802.11e MAC protocol in terms of providing support to both strict priority and weighted fair service. Compared to other solutions, the new model is easier to implement in real systems, has better aggregate throughput and is more stable. As a third part of this work, a novel handoff scheme for IEEE 802.11 WLANs is proposed to reduce handoff latency and to improve the QoS support in multimedia applications. The proposed handoff scheme, called Prevent-Scan Handoff Procedure, uses an early pre-scan phase to avoid probe wait delays during next Handoff occurrence. Through extensive simulations, we prove that the new handoff procedure decreases handoff latency considerably and accelerates handoff by minimizing the time during which the MS remains out of contact with its AP. Therefore, the inter-frame delay incurred is within multimedia applications' delay restrictions. These simulations are carried out over a new IEEE 802.11 handoff simulator to provide performance evaluations. We prove that the new handoff technique achieves both fast and smooth handoff which is requested by multimedia applications.
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https://hal-uphf.archives-ouvertes.fr/tel-03065253
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Submitted on : Monday, December 14, 2020 - 5:37:04 PM
Last modification on : Friday, October 1, 2021 - 8:36:03 AM
Long-term archiving on: : Monday, March 15, 2021 - 8:07:09 PM

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Ahmed-Riadh Rebai. Contributions à l'amélioration de la qualité de service dans les réseaux sans fil Wifi. Informatique [cs]. Université de Valenciennes et du Hainaut-Cambrésis, 2009. Français. ⟨NNT : 2009VALE0035⟩. ⟨tel-03065253⟩

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