Joint transmitter and receiver I/Q imbalance estimation in presence of carrier frequency offset

© 2015 IEEE. This paper proposes a simple frequency domain joint transmitter and receiver I/Q imbalance estimation method which exploits the phase rotation introduced by carrier frequency offset. Using two frequency domain training sequences inserted in each transmission frame, the transmitter and receiver I/Q imbalances can be jointly estimated over multiple frames. The transmitter I/Q imbalance parameter can be fed back to the transmitter for I/Q imbalance pre-compensation, whereas the receiver I/Q imbalance can be compensated locally followed by conventional frequency domain equalization. Numerical simulation results show that the image rejection ratios for both transmitter and receiver after I/Q imbalance compensation can be improved to over 50 dB which is necessary for multichannel systems with high order modulation and wide transmission bandwidth

Low-complexity estimation of CFO and frequency independent I/Q mismatch for OFDM systems

CFO and I/Q mismatch could cause significant performance degradation to OFDM systems. Their estimation and compensation are generally difficult as they are entangled in the received signal. In this paper, we propose some low-complexity estimation and compensation schemes in the receiver, which are robust to various CFO and I/Q mismatch values although the performance is slightly degraded for very small CFO. These schemes consist of three steps: forming a cosine estimator free of I/Q mismatch interference, estimating I/Q mismatch using the estimated cosine value, and forming a sine estimator using samples after I/Q mismatch compensation. These estimators are based on the perception that an estimate of cosine serves much better as the basis for I/Q mismatch estimation than the estimate of CFO derived from the cosine function. Simulation results show that the proposed schemes can improve system performance significantly, and they are robust to CFO and I/Q mismatch

Low-Complexity Estimation of CFO and Frequency Independent I/Q Mismatch for OFDM Systems

CFO and I/Q mismatch could cause significant performance degradation to OFDM systems. Their estimation and compensation are generally difficult as they are entangled in the received signal. In this paper, we propose some low-complexity estimation and compensation schemes in the receiver, which are robust to various CFO and I/Q mismatch values although the performance is slightly degraded for very small CFO. These schemes consist of three steps: forming a cosine estimator free of I/Q mismatch interference, estimating I/Q mismatch using the estimated cosine value, and forming a sine estimator using samples after I/Q mismatch compensation. These estimators are based on the perception that an estimate of cosine serves much better as the basis for I/Q mismatch estimation than the estimate of CFO derived from the cosine function. Simulation results show that the proposed schemes can improve system performance significantly, and they are robust to CFO and I/Q mismatch.</p