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Exploitation des antennes multiples pour l'optimisation dans les réseaux sans fil

Abstract : Recent advances in antennas processing and microelectronics have helped for the emergence of smart antennas and their use in public telecommunication systems. This technology allows sophisticated signal processing and provides significant performance benefits such as increased spectral efficiencies, reduced power consumption, interference cancellation, increased communication reliability and better connectivity. Smart antennas represent a broad variety of antenna technologies that significantly differ in terms of performance and transceiver complexity. The different antennas technologies include switched-beam antennas, adaptive array antennas and multiple-input multiple-output (MIMO) systems. The latter is already being implemented in latest generation equipments and standards like 3GPP-LTE and IEEE 802.11n. The focus of this thesis is to explore the various capabilities of smart antennas and to propose new mechanisms and systems for their use. In particular, we were interested in exploiting two multi-antenna systems' capabilities: spatial multiplexing and beamforming. In the first part of this thesis, we propose a new dynamic beamforming technique for mobile ad hoc networks, based on the LCMV beamformer. Mobiles nodes derive the weight vectors to form dynamic beams more adapted to their mobility parameters. The proposed scheme allows to form dynamic beams with less complexity but more adapted to possible uncertainty on mobile node locations.. Performance evaluations show that the proposed approach enhances system capacity and connectivity while reducing localization overhead and beam forming complexity. In the second part of this thesis, we design and evaluate a joint stream control and link TDMA-based scheduling algorithm (SCLS) for MIMO wireless mesh networks. SCLS is a cross layer resource allocation scheme that selects links to be activated simultaneously and determines the optimal number of streams to be used on each of them. This selection is based on streams' channel gains, traffic demands and interference levels. The proposed algorithm optimizes both the frame length and network capacity and throughput. In the third part, a joint Angle of Arrival (AOA), Angle of Departure (AOD) and Delay of Arrival algorithm, based on the Capon Beamformer, is proposed. These physical parameters of the received signals are needed to develop advanced antenna systems and other applications such as localization in indoor environments.The proposed algorithm reduces both complexity and computation time compared to subspace-based existing methods. The proposed approach works even if the number of multipaths exceeds the number of antenna elements.
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  • HAL Id : tel-00995412, version 1

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Ismehene Chahbi. Exploitation des antennes multiples pour l'optimisation dans les réseaux sans fil. Autre [cs.OH]. Institut National des Télécommunications, 2011. Français. ⟨NNT : 2011TELE0008⟩. ⟨tel-00995412⟩

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