| At present, MIMO and OFDM as the main technologies in fourth generation (4G) systems have been adopted by IEEE 802.11a, 802.16e and 3GPP Long Term Evolution (LTE) systems. But for any system which take OFDM as the core technology, the problems of timing and frequency synchronization in the system must be the primary problems to be solved, otherwise the system can not be in utility.This paper mainly studies the timing and frequency synchronization problems of the distributed MIMO-OFDM system and LTE system. Firstly for the timing synchronization of distributed MIMO-OFDM system, in order to overcome the shortcomings of the existing timing algorithm in multipath-fading channel, an improved symbol timing synchronization algorithm based on unequal period and reverse conjugate symmetric synchronization pattern is proposed. Through the simulation, it can be proved that the improved algorithm has the good performance in multipath-fading channel compared to other algorithms. Secondly for the timing synchronization of the LTE system, in order to get over the drawbacks of correlation peak illegibility of traditional ML algorithm in the multipath-fading channel and frequency offset sensitivity of Zadoff-Chu (ZC) sequence full correlation algorithm, an improved timing synchronization algorithm based on ZC sequence subsection correlation is proposed, and availability of the algorithm is demonstrated through the simulation. Lastly for the frequency synchronization of the LTE system, utilizing the phase property of the pilot, a frequency precise synchronization algorithm is proposed. On the base of frequency coarse estimation, this algorithm can estimate the residual frequency offset in the system and reduce error bit rate of the system. The simulation indicates the conclusion. |
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