Download or read book Conception Et Optimisation de Protocoles D'accès Multiple Au Canal Pour Les Réseaux Ad Hoc Sans Fil written by Hicham Anouar and published by . This book was released on 2006 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main subjects of this thesis are the design, analysis, and optimization of multiple access control protocols for wireless ad hoc networks, and the study of fundamental limitations in time delay estimation of ultra wideband signals. For single hop networks, we focus on deriving optimal backoff schemes that maximize the overall network throughput. We further look only for quasi- blind schemes that require only information about the network size. This information is simple to obtain in single hop networks. For this, we consider slotted ALOHA and the IEEE 802.11 decentralized coordination protocols. In the second part of this thesis we address MAC protocol design and enhancement for multihop networks. We introduce a modified handshaking scheme to guarantee full protection of ongoing transmissions in IEEE 802.11 DCF protocol. We analyze the performance of the resulting protocol, and we propose a distributed algorithm based on stochastic approximations theory to control the backoff window length of each node in order to maximize the network throughput. The use of multiple channels in wireless ad hoc networks may provide some performance advantages by reducing collisions and enabling more concurrent transmissions. We propose then a new ALOHA-like protocol for multi-channel multihop networks. The new protocol operates without channel assignment and achieves high performance without carrier sensing. In the perspective of using UWB signaling for future ad hoc networks, we study the performance of some coherent and non-coherent time delay estimators. The obtained results are crucial for protocol design, synchronization, and localization purposes.