Analyse et evaluation des performances d'erreur du codage spatio-temporel en blocs pour des systemes de telecommunications sans-fil dans des canaux a evanouissements (French text)

Nowadays, the great popularity of cordless phones, cellular phones, portable computing demonstrates the importance of wireless communications systems in our society. The next generation of wireless systems is supposed to allow high speed data services and to insure a very good quality of communication anywhere, with the user evolving as well in indoors as in outdoors environment. However the physical limitation of the wireless channel presents a challenge for reliable communications. Indeed, the limited spectrum is desired by many companies and should be shared among the various operators. Besides, time-varying impairments such as noise and multipaths can attenuate strongly the signal during the transmission. Most personal communications and wireless services are meant to be carried in a pocket or a briefcase and must be small and lightweight, which means small batteries. Diversity techniques, such as time, frequency or space diversity, may be used to improve the transmission quality instead of technics demanding significant processing power.; Our work focuses on space and time diversities and especially using space-time block codes (STBC). After introducing digital communications systems and especially channel coding, space-time codes are completely described. Then we deal with the principle and the performances of STBC, the main subject of our work. The influence of several parameters on these performances is analyzed. Quasi-static and fast fading channels are treated as well as gaussian channels. The influence of the imprecise knowledge of the path gains between transmitters and receivers is also analyzed. Finally we conclude our work by analyzing concatenated TCM encoder with STBC. (Abstract shortened by UMI.)...