Study Of Synchronization In MIMO-OFDM Systems

Achieving high-quality, high-speed mobile multimedia transmission is the goal of mobile communications. OFDM (orthogonal frequency division multiplexing) is considered to be a very effective means to obtain high-speed data transmission. And it uses parallel, low-rate sub-carriers to achieve a high rate of digtal communication. MIMO (multiple-input multiple-output) system applying simultaneously several antennas at transmitter and receiver can improve transmission rate exponentially using random fading and possible multipath transmission.The combination between MIMO and OFDM is regarded as a promising solution for the next generation wireless communication systems.However, synchronization is the key effect which influences the performance of MIMO-OFDM systems.This paper introduces the timing synchronization and frequency synchronization algorithms in MIMO-OFDM systems, the main contents of the dissertation are expressed as follows:This paper proposes an accurate technique for timing and frequency synchronization of multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The technique derives a new preamble signal based on GCL sequences, according with the MIMO-OFDM synchronization. The carrier frequency offset (CFO) estimation is obtained through taking double correlation operations on the preamble signal, and used in the timing synchronization to gain accurate time estimation. The simulation results indicate that at the same SNR, the proposed method can reduce the BER and the frame transmission BER of the system compared to the conventional method.The ML-based CFO is analyzed, and a new CFO method based least squares (LS) is proposed.Then, the performance of LS-based CFO is compared with that of ML-based CFO.The simulation results show that the performce of LS is equivalent to that of ML.Considering the simplicity and low restriction of LS, the LS method can be used to obtain the same CFO as the ML estimates.