On the Study of End-to-End IQ Imbalance Problem in OFDM Systems

In this paper, we study the IQ imbalance effects of OFDM systems at both transmitter and receiver sides. The two sided IQ imbalance model in multipath fading channel is setup. Based on this model, the end-to-end estimation and compensation schemes are proposed. The transmitter IQ imbalance is first considered and a self-calibration scheme is proposed to compensate the imbalance before transmission. Following that, we study the IQ imbalance problem at receiver. The amplitude and phase imbalances are estimated from the correlation function. Then the channel frequency response is estimated in pairs by MLE. Finally, we study three different kinds of detection schemes, including direct zero-forcing (DZF), joint detection equalizer (JDE), and successive interference cancelation (SIC). Computer simulations are conducted to evaluate the performance of the proposed schemes. It is shown that the proposed schemes are reliable and feasible for practical implementation.