Joint Estimation of Carrier Frequency Offset and I/Q Imbalance for Direct Conversion OFDM System with Constrained Preambles

This paper addresses a joint estimation method for carrier frequency offset (CFO) and I/Q imbalance using constrained preamble. Because existing methods can not guarantee correct solutions within all range of CFO, we derive two constraints of phase rotation adjusted to repetition patterns. Using these constraints, proposed estimators can find the optimal estimate of CFO, and low complexity I/Q imbalance estimation is possible in all range of CFO with no exceptions. Numerical results show the importance of these constraints for joint estimation and, proposed scheme can achieve almost same bit error rate performance with perfect estimation scheme.