Thèse de doctorat en Informatique
Sous la direction de Ramesh Pyndiah.
Soutenue en 2010
à Télécom Bretagne en cotutelle avec Rennes 1 , dans le cadre de École doctorale Mathématiques, télécommunications, informatique, signal, systèmes, électronique (Rennes) , en partenariat avec Université de Rennes 1 (autre partenaire) et de Université européenne de Bretagne (autre partenaire) .
As portable computers and communication terminals become more powerful and are more widely deployed, the demand for very high data rate wireless networks has exploded. An optical wireless (OW) transmission represents an attractive solution for many indoor and home applications. Because of the difficulties and the cost of the phase control and detection in wireless optics, current systems use intensity modulation techniques and direct detection (IM/DD). OW systems offer several advantages including the potential to achieve very high data rates and the immunity to radio frequency (RF) interferences. OW techniques benefit from a wide unregulated bandwidth that can be reused in a dense fashion. However, this bandwidth will be limited by the characteristics of the optical components, the product's availability and the propagation properties. Taking the demand for very high data rates and good link budgets into consideration requires scientific advances in different fields, such as the following : The optical receiver components and their key characteristics The bandwidth efficient modulation schemes allowing high data rates transmissions with limited bandwidth. This dissertation is a contribution to the second field. Particularly, we investigate the adaptation of coded orthogonal frequency division multiplexing (COFDM) and COFDM/OQAM (also referred as COFDM/Offset quadrature amplitude modulation) to OW constraints. The modified COFDM and the modified COFDM/OQAM increase the data rate and mitigate the inter symbol interference (ISI). We also propose spatial division multiplexing techniques combined to these multi-carrier modulations for OW networks. Both, non-iterative and iterative receivers are studied.
A contribution to digital communications studies for optical wireless networks
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