Research of time-frequency synchronization in MIMO-OFDM system

A time-frequency synchronization scheme and a kind of multi-input multi-output orthogonal frequency-division multiplexing(MIMO-OFDM) training sequency are proposed from the point of time-frequency joint-design. The time synchronization is accomplished by the symmetric conjugate of the training sequence in time domain, and the frequency synchronization is finished by the good autocorrelation of the training symbol in frequency domain. Comparing with the conventional schemes, this proposed scheme gives very accurate estimates of symbol timing and carrier frequency offset, and provides a very wide acquisition range for the carrier frequency offset, up to (-N/2, N/2) theoretically. The simulation results show that comparing with the conventional schemes, under multipath fading channels, this scheme has higher timing offset estimation precision, particularly obviously when the signal to noise ratio (SNR) is small, and while frequency offset estimation mean square error (MSE) is 1×10^-4, approximately 3 dB can be improved.