Code-Aided Adaptive Decorrelator for IQ Imbalance Compensation in Iterative Receivers for Flat Fading Channels

Long convergence times associated with adaptive algorithms are not practical in burst mode communications for synchronization and channel estimation tasks including IQ imbalance parameters. This motivates one to find techniques to increase the rate of convergence of the learning algorithm. We propose a novel acquisition aid that is also low in complexity to the adaptive decorrelator for IQ imbalance compensation. The acquisition aid is an estimator that is embedded in the iterative detector and passes the estimated IQ imbalance parameters back to the compensation filter controlled by the adaptive decorrelator. The resulting adaptive decorrelator with acquisition aid can converge on the first packet and resumes in the tracking mode and offers steady-state performance superior to that offered by the estimator. The proposed adaptive decorrelator aided by the embedded estimator is blind in the sense that it does not require any training symbols nor tones. The performance is simulated for 64QAM under flat fading channel conditions.