Efficient Joint Estimation and Compensation of CFO, Tx/Rx Frequency-Selective I/Q-Imbalance and the MIMO Radio Channel in OFDM Systems
MIMO OFDM is a very promising technique for future wireless communication systems. By applying direct conversion architecture, low-cost, low-power, small size and flexible implementation of MIMO OFDM systems can be realized. However, the performance of direct conversion architecture based MIMO OFDM systems can be seriously affected by RF impairments incl. Carrier Frequency Offset (CFO) and I/Q-imbalance. While OFDM is sensitive to CFO, direct conversion architecture is sensitive to I/Q-imbalance. Such RF impairments aggravate as the carrier frequency becomes higher e.g. beyond 60 GHz. To achieve the desired high performance of MIMO OFDM, such RF impairments have to be compensated for. In this paper, the joint compensation of CFO, transmitter and receiver frequency-selective I/Q-imbalance and the MIMO radio channel is investigated.