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|All Authors / Contributors:||
Seyed Mohammad Sajad Sadough; Alain Sibille; Pierre Duhamel; Université de Paris-Sud. Faculté des Sciences d'Orsay (Essonne).
|Notes:||Thèse rédigée entièrement en anglais.
Résumé étendu en français (p. VII - XXIX).
|Description:||1 vol. (XLVIII-162 p.) : ill. ; 30 cm.|
|Responsibility:||Seyed Mohammad Sajad Sadough ; [sous la direction de] Alain Sibille [et de] Pierre Duhamel.|
The aim of this thesis is to study the problem of iterative data detection in an ultra wideband (UWB) OFDM system, where the receiver disposes only of an imperfect (and possibly poor) estimate of the unknown channel parameters. First, we propose an efficient receiver jointly estimating the channel and the transmitted symbols in an iterative manner. This receiver is based on a wavelet representation of the unknown channel and exploits the sparseness property of UWB channels in the wavelet domain to reduce the receiver's computational complexity. Second, we rely on the statistics characterizing the quality of the channel estimation as a mean to integrate the imperfect channel knowledge into the design of iterative receivers. In this way, we formulate an improved maximum likelihood (ML) detection metric taking into account the presence of channel estimation errors. A modified iterative MAP detector is derived by an appropriate use of this metric. The results are compared to those obtained by using the classical mismatched ML detector, which uses the channel estimate as if it was the perfect channel. Furthermore, we calculate the achieved throughputs associated to both improved and mismatched ML detectors, in terms of achievable outage rates. Finally, we propose an improved low-complexity iterative detector based on soft parallel interference cancellation and linear MMSE filtering where we takes into account the presence of channel estimation errors in the formulation of the detector. The important point is that the performance improvements reported in this thesis are obtained while imposing practically no additional complexity to the receiver.