As a multi-carrier modulation scheme, Orthogonal Frequency Division Multiplexing (OFDM)

technique can achieve high data rate in frequency-selective fading channels by splitting a

broadband signal into a number of narrowband signals over a number of subcarriers, where

each subcarrier is more robust to multipath. The wireless communication system with multiple

antennas at both the transmitter and receiver, known as multiple-input multiple-output

(MIMO) system, achieves high capacity by transmitting independent information over different

antennas simultaneously. The combination of OFDM with multiple antennas has been

considered as one of most promising techniques for future wireless communication systems.