System and method for estimation and correction of carrier frequency offset in MIMO-OFDM based wireless communications systems

A method of determining carrier frequency offset (CFO) in OFDM beacon signal in Multi-input Multi-output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) based wireless communication systems, comprising:

• providing a MIMO-OFDM transmitter corresponding to the transmission of a beacon symbol allocated with a predetermined sequence of null subcarriers;
• providing an OFDM receiver corresponding to the beacon symbol transmitted from the transmitter;
• receiving the OFDM beacon signals on at least one receiving antenna and removing a cyclic prefix associated with each received OFDM beacon signal;
• combining the cyclic prefix removed signals using a diversity combining technique;
• converting the combined signals to the frequency domain by a N-point DFT operation including computing at the DFT output the energy content of all the N-subcarriers;
• computing the total energy of designated null subcarrier indices by introducing trial cyclic shifts from 0 to N−1;
• storing the total energy of the designated null subcarriers against the trail integer offset shift in an N-element array;
• and
• conducting a search to identify the minimum energy and the corresponding integer shift which represents the integer frequency offset experienced by the MIMO-OFDM signal.