Mimo-ofdm System Synchronization Technology

Multiple Input Multiple Output can significantly increase the channel capacity and spectral efficiency of communication system without increasing bandwidth. Orthogonal frequency-division multiplexing can effectively mitigate the effort of frequency-selective fading. Therefore, the MIMO-OFDM system, which is combined with MIMO and OFDM technology, is the core technology of the next generation mobile communication. However, MIMO-OFDM system is fairly sensitive to timing and frequency synchronization error. Time and frequency excursion will lead to inter-symbol interference and inter-carrier interference, and both of them will cause serious decline of system performance.The development, key techniques and basic principles of MIMO-OFDM system are introduced firstly in this paper. Then, synchronization algorithms for SISO-OFDM system and MIMO-OFDM system are discussed in detail, based on the introduction of analysis about the influence of synchronization error on the system. Aiming at the SISO-OFDM system, as to the synchronization algorithm based on Cyclic Prefix, Maximum Likelihood algorithm is introduced,and an improved algorithm is proposed as well,which makes use of the correlation of several symbols. As to the synchronization algorithm based on training sequences, a new training sequence structure and synchronization algorithm is given.and chu sequence is used as sub-carrier of frequency domain. The simulations show that the proposed synchronization scheme has low algorithm complexity and high estimate precision. In the centralized MIMO-OFDM system, shift-orthogonal chu sequences are used as training sequence to improve the Schenk&Zelst's synchronization algorithm and demonstrate the performance of the improved algorithm by simulation. As to the distributed MIMO-OFDM system, aiming at the shortcomings of traditional algorithm, a new training sequence structure and synchronization algorithm are proposed. The simulation results show that the improved algorithm has a better synchronization performance than the conventional algorithm.