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 applyingdirect conversion architecture, low-cost, low-power, small size, and flexible implementation of MIMOOFDM systems can be realized. However, the performance of direct conversion architecture-based MIMOOFDM systems can be seriously affected by RF impairments incling 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 for example, beyond 60 GHz. To achievethe desired high performance of MIMO OFDM, such RF impairments have to be compensated for. In thispaper, the joint compensation of CFO, transmitter and receiver frequency-selective I/Q imbalance, and theMIMO radio channel is investigated. Two preamble-based schemes are proposed for impairment parameterestimation. The proposed preambles are constructed both in time and frequency domains and require muchless overhead than the state-of-the-art designs. Furthermore, much lower computational complexity is allowed,enabling efficient implementation. The advantages and effectiveness of both proposed schemes arecompared and verified by numerical simulations and complexity analysis