Semi-blind Joint Estimation for Frequency Offset and Channel in Multi-user MIMO-OFDM

A semi-blind method is proposed for simultaneously estimating the carrier frequency offsets (CFOs) and channels of an uplink multi-user MIMO-OFDM system. By incorporating the CFOs into the transmitted symbols and channels, the MIMO-OFDM with CFO is re-modeled into a MIMO-OFDM without CFO. The known blind method for channel estimation (Y.H. Zeng and T.S. Ng, 2004) is then directly used for the re-modeled system to obtain the shaped channels with an ambiguity matrix. A dedicated pilot OFDM block for each user is then designed to resolve the CFOs and the ambiguity matrix. As a result, based on the second-order statistics (SOS) of the received signal and one pilot OFDM block, the CFOs and channels are found simultaneously