Research And Application On MIMO-OFDM Synchronization Techniques

MIMO-OFDM technology is suitable for requirements of high-speed communications as a new generation of mobile communication core technology. However, MIMO-OFDM system is very sensitive to synchronization error. Timing error will lead to inter-symbol interference and frequency offset can introduce the inter-carrier interference, both results in the decline of system performance. So accurate timing synchronization and frequency offset of MIMO-OFDM system are very important.This thesis focuses on the synchronization algorithms in MIMO-OFDM systems. In the thesis the influence of timing offset and carrier frequency offset on OFDM system is analyzed first, and different synchronization algorithms are introduced. Then the synchronization algorithms are mainly researched, because of Schenk's algorithm has a peak value plateau, its timing synchronization is inaccurate, a modified algorithm that use the CAZAC sequence and TSTD are developed. Finally the frame and flow chart of computer simulation are introduced, the simulation are carried out to validate the performance of modified algorithm in different conditions.The results of computer simulation demonstrated that the modified algorithm has correct timing synchronization because of using the auto correlation characteristic of CAZAC sequence; the right probability of timing synchronization can achieve 97% when SNR is more than 5dB. In lower SNR, the MSE value of modified algorithm is close to the theoretical value; their performance is comparative in higher SNR. In the same condition, the modified algorithm enhanced the performance of timing synchronization and frequency offset. when the frequency offset is 0.1, 0.2 of sub-carrier spacing, and 10kHz, and UE speed is 0km/h, 60km/h, and 120km/h, the modified algorithm can estimate the frequency offset accurately.