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Utilisation des antennes multiples dans un lien descendant des systèmes sans fils

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Auteur / Autrice : Mari Kobayashi
Direction : Giuseppe Caire
Type : Thèse de doctorat
Discipline(s) : Électronique et communications
Date : Soutenance en 2005
Etablissement(s) : Paris, ENST

Résumé

FR

For point-to-point communication, Multi-Input Multi-Output technology has emerged as an attractive solution to increase the capacity by providing multiplexing gain and/or to improve the link quality by diversity. The first part focuses on the use of multiple antennas to increase the reliability of wireless links via space-time coding (STC). For frequency selective multi-input single-output fading channels, we propose a STC scheme that concatenates trellis-coded modulation with time-reversal orthogonal space-time block coding. Numerical examples show that our scheme offers superior performance at lower complexity than the existing schemes thanks to reduced-state joint equalization and decoding. The second and third parts investigate the use of multiple transmit antennas in a point-to-multipoint downlink system with channel state information at transmitter (CSIT). In the second part, we compare and random "opportunistic" beamforming by restricting ourselves to a rate feedback. We take into account the realistic aspects such as random packet arrivals, correlated block-fading channels, and a feedback delay. The realistic assumption of non-perfect CSIT yields a non-trivial tradeoff between multiuser diversity achieved by opportunistic beamforming and transmit diversity achieved by STC. In the third part, we consider a more qualitative "analog feedback" in which each user sends back its estimated channel without quantizing and coding. We propose a novel method for user selection and linear beamforming that maximizes a weighted sum rate over a beamforming matrix. Over a time-varying channel, our scheme achieves a smaller average delay than the previously considered schemes