Carrier frequency offset and channel estimation for MIMO OFDM systems

A new preamble structure is designed for MIMO OFDM systems, which not only can be used for frequency synchronization but also can be used for channel estimation. Modulatable orthogonal polyphase sequence is utilized in training symbol design regarding of its correlation properties. Two correlations are used to get carrier frequency offset (CFO) estimation. The channel estimation is achieved by measuring the correlation between the received training sequence and the locally generated training sequence. From analysis, it is shown that the accuracy of CFO estimation is close to the Cramer-Rao lower bound. The MSE of channel estimation coincides with the lower bound of the MSE based on minimum mean square error (MMSE) criterion.