Etude de la synchronisation temporelle dans les systèmes MIMO-OFDM appliqués aux réseaux mobiles

Abstract : The current wireless communication systems, mobile phones, satellite services and wireless internet networks require a very high data rate and a highly reliable degree. These rates have increased rapidly in the new applications of data transmission of new generation. To take into account the spectrum limitations, the OFDM has been proposed thanks the orthogonality between sub-carriers and the data rate that approaches to the Nyquist-Shannon sampling rate. Furthermore, the antennas technic (MIMO) can provide significant various gains, a diversity gain that improves the link reliability and the spatial multiplexing gain where different data streams are transmitted over different antennas. The combination of these two systems (MIMO and OFDM) allows to exploit the robustness of the link on the frequency-selective channels and uncorrelated channels in space. One of the issue in the combination MIO-OFDM resides on the synchronization methods. The synchronization is divided into sub parts, timing synchronization and frequency synchronization. Timing synchronization is also divided into two parts, firstly, the coarse timing synchronization is used to estimate the beginning of each received frame, and secondly, the fine timing synchronization which detects the beginning of each OFDM symbol in the received frame. The principle of the frequency synchronization is to find the shifted phase between the transmitted frequency and the local frequency at the receiver. In a first part, we have proposed different methods for timing synchronization based on synchronization sequences known at the receiver. We did a study for various existing sequences to compare the efficiencies of each of these sequences in timing synchronization for MIMO-OFDM systems. In a second part, Matlab’s simulations were conducted to study the performance of our proposed methods in multi-paths frequency-selective channels. Simulations results show the acquisition timing synchronization probability in terms of SNR.
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Ali Rachini. Etude de la synchronisation temporelle dans les systèmes MIMO-OFDM appliqués aux réseaux mobiles. Réseaux et télécommunications [cs.NI]. INSA de Rennes, 2014. Français. ⟨NNT : 2014ISAR0001⟩. ⟨tel-01083606⟩

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