Analyse des performances de reseaux cooperatifs a relais multiples

In a cooperative communication system, a set of relay nodes works jointly with a source node in order to forward its information to the destination. This technique permits to increase the reliability of the communication when the direct link is corrupted.;Meanwhile, many cooperation techniques with multiple relays are limited to the model where the relays are single antenna. Moreover, the system models assume a perfect Channel State Information (CSI) at the receiver, which is not the real case for a fading channel. Finally, multi-hop cooperative communication has been treated partially. The authors were limited in their works to double hops networks (generally small number of hops) and to transmissions with space-time coding with unitary code matrices.;In order to rectify these limitations in the system model of cooperative communications with multiple relays, we develop and analyze system models that include each of these constraints.;The first developed system model assumes MIMO relay nodes using AF or DF transmission techniques with a perfect CSI or imperfect CSI at the receivers. The relay nodes exploit distributed space-time coding (to strengthen the communication) or distributed spatial multiplexing (to increase the transmission rate).;Cooperative communications with multiple relays have an important interest in telecommunications. By the presence of multiple relay nodes, point-to-point MIMO properties such as spatial multiplexing and diversity could be exploited in this new type of communications.;To increase the communication reliability at a fixed transmission rate, we propose a decentralized selection technique between space-time coding and spatial multiplexing based on the estimated SNR.;Finally, we develop and analyze the model of a multi-hop cooperative communication. We develop the analysis of the multi-hop (multi-levels) cooperative communication model where the space-time coding is used at one or many relays' levels. The simulation results show the performance gains and the behaviors (in error rates) of the new developed system models. This help us to understand better the behavior of the cooperative system using the proposed transmission techniques and then extract the network structure and transmission technique providing the best error rate performances.