Research On Synchronization And Channel Estimation For MIMO-OFDM System

With the development of wireless communication system, the lack of frequency resource is the most central problem that hinders the development of the wireless communication. Therefore, how to develop and make use of limited frequency resources and improve the efficiency of bandwidth on the basis of reliable transmission becomes one of the key questions of wireless communication technique. OFDM transforms frequency-selective multipath fading channel into flat channel in the frequency domain and reduce the effect of multipath fading. MIMO provides a space multiplex technique which transmits data stream in parallel channels simultaneously and thus increase the system's efficiency. MIMO-OFDM combining MIMO with OFDM, can not only transmit a great deal of high-speed data but also have good antimultipath and antinoise performance.This paper presents thoroughly the theory and technique of OFDM and MIMO separately, and elaborates MIMO-OFDM system including its theory, modeling and key techniques. Subsequently the author analyses the cause and influence of frequency offset that bring the inter channel interference in the MIMO-OFDM system. The paper describes classical Schmidl&Cox algorithms, gives its simulation results in multipath channel and evaluates its performances of carrier synchronization and compares.Channel design and estimation in MIMO-OFDM is another vital problem. The paper introduces several methods of channel estimation in MIMO-OFDM and explicates LS time-domain estimation method. The author simulates two-dimension methods using LS and MMSE algorithms and analyses performance difference between two estimation algorithms when different Doppler frequency is introduced.