Training Sequence Assisted Frequency Offset Estimation for MIMO OFDM

New frequency domain training sequences are proposed sedfor carrier frequency offset (CFO) estimation in multipleinput multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system over frequency-selective fading channels. By exploiting frequency domain orthogonality of the training sequences, integer CFO (ICFO) can be estimated without matrix inversion operation. With the non-zero pilots in the training sequences uniformly spaced, fractional CFO (FCFO) can be estimated through the roots of a complex polynomial. Moreover, a simplified CFO estimator is also proposed which exploits a geometric mapping to transform the complex polynomial to a real one. Simulation results illustrate the good performances of the CFO estimators assisted by the proposed training sequences.