| With the rapid development of wireless mobile communication, people’s requirements of information transfer are getting higher and higher. With the applications of the third generation mobile communication technology, the global mobility information age is to coming soon. However, the limited spectral resources become a bottleneck restricting the development of mobile communications. The studies of how to improve the system spectral efficiency and channel capacity in wireless mobile communications on a premise that ensuring reliable transmission have become the focus study areas of this subject. The appearance of MIMO-OFDM technology laid the foundation for future broadband wireless mobile communication systems in high-speed data transmission, and became the effective physical layer technology for future development to resolve the tension of spectral resources and efficiency. However, the combination of MIMO and OFDM technologies, it also brings many problems need to be solved.However, the MIMO-OFDM system can proper work on the premise that the ascertain channel state information, ideal symbol timing synchronization and frequency offset. This paper aims to study the key technologies of MIMO-OFDM system synchronization and channel estimation. Through deeply studies on the status quo of domestic and international in system synchronization and channel estimation, it had obtained the suitable system synchronization and channel estimation techniques for STBC-OFDM system, and analysis the entirety performance of this system. The major achievements of this paper are outlined as follows:Firstly, the implementation of MIMO-OFDM system and the effects on system performance in nonideal system synchronization are analyzed. Analysis of MIMO systems, OFDM systems, MIMO-OFDM systems principle and the implementation means of MIMO-OFDM. The STBC-OFDM technologies have been studied. The timing error and carrier frequency error on system performance are analyzed in detail.Secondly, based on cyclic prefix or training sequence synchronization algorithms for MIMO-OFDM system are analyzed. The ML algorithm based on cyclic prefix was detailed analyzed, by simulation analysis obtained that:in Rayleigh fading channels this algorithm is not very good performance. At the same time it had studied the theory and performances of Mody&Stuber algorithm based on orthogonal training sequence. In low SNR channel environment the timing synchronization accuracy of this algorithm is low, thus affecting the overall system performance. Based on above results, based on Zadoff-Chu training sequence synchronization improvement algorithm is proposed, by theoretical analysis and simulation obtained that:in Rayleigh channel the performance of this algorithm is good.Thirdly, the channel estimation technology for MIMO-OFDM system was analyzed. LS algorithm and MMSE algorithm based on training sequence are compared with each other. By simulation obtained that:in this case the Doppler frequency shift is not too large, the performance of MMSE algorithm is superior to LS algorithm. But the influence of MMSE algorithm is greater by Doppler frequency shift, so it’s suitable for the smaller mobility systems.Finally, the simulation of the entirety performance was analyzed in STBC-OFDM system using proposed synchronization algorithm and the MMSE algorithm. Through simulation, these two algorithms in this system reflect a good performance. In low moving speed, multi-user and multi-antennas performance can be ensured. |
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