Diversity Techniques for HARQ Transmissions over Frequency-Selective Channels. (Techniques de diversité pour les transmissions HARQ sur des canaux sélectifs en fréquence)

In this thesis, we consider the problem of reliable data packets transmission using singlecarrier signaling over frequency-selective fading channels. Our objective is to design enhanced transceivers with improved detection performance in the absence of channel state information at the transmitter by exploiting the available time-diversity in Chase combining Hybrid Automatic Repeat reQuest (HARQ) protocols. By analyzing the performance of the transmission scheme using an optimal maximumlikelihood receiver, we establish a suitable criterion for the study of system performance based on the statistics of the Euclidean distance at the output of a frequency-selective channel. From this theoretical framework, we propose a novel transmit-diversity scheme between subsequent HARQ transmissions, called phase-precoding, which allows the mitigation of intersymbol interference for slow time-varying channels. Then, with the help of our analytical tools, we revisit another transmit-diversity scheme which is the bit-interleaving diversity scheme. In particular, we emphasize the double advantage o ered by this diversity scheme including the inherent modulation diversity in addition to the intersymbol interference reduction. Subsequently, we perform a comparative study between phase-precoding and bit-interleaving diversity schemes under iterative and non-iterative receiver structures. Finally, we introduce a new adaptive retransmission protocol for a multi-layer transmission scheme for the mitigation of inter-layers interference for rapidly time-varying channels using limited feedback information.