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Les constellations tournées pour les réseaux sans fil et l'internet des objets sous-marins

Abstract : The exponential growth of the number of communicating objects and the rising demand for wireless services on the one hand, and the need to reduce the energy cost of radio communications with the associated greenhouse gas emissions on the other side, make bandwidth-power efficient techniques, such as rotated constellations, particularly interesting. Indeed, rotated constellations allow better theoretical performance than conventional constellations over fading channels thanks to an inherent Signal Space Diversity (SSD).Nevertheless, several issues prevent wider deployment of this technique. Therefore, in this PhD thesis, we propose several original solutions to face these limitations.First, we study the structural properties of M-QAM constellations rotated with a series of rotation angles α=arctan⁡(1/√M) , so as to propose a low-complexity detection technique for fading channels with or without erasures.Then, we propose two distinct and original techniques to reduce the PAPR of OFDM systems with SSD; first, a blind SLM technique is proposed for which two rotation angles are selected so as to jointly optimize the theoretical bit error rate of the constellations and the theoretical blind decoding performance. In addition, a completely blind interleaving technique is proposed. In order to reduce the blind decoding complexity for this second technique, we rely again on the properties of the M-QAM constellations rotated with α=arctan⁡(1/√M) , to design a low-complexity estimator.Finally, we propose an original phase estimator for rotated constellations based on a low-complexity smoothing approach inspired by the Maximum a Posteriori (MAP) principle. This estimator operates off-line and allows the estimation of randomly time-variable phase shifts through two phase-locked loops. The proposed estimator inherently takes into account the characteristics of rotated constellations, in contrast with conventional estimators, which allows to approach the Cramèr-Rao bound.
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Submitted on : Friday, July 3, 2020 - 1:03:35 AM
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Tarak Arbi. Les constellations tournées pour les réseaux sans fil et l'internet des objets sous-marins. Réseaux et télécommunications [cs.NI]. Institut Polytechnique de Paris, 2020. Français. ⟨NNT : 2020IPPAE002⟩. ⟨tel-02888342⟩

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