Novel Adaptive Receiver for Multilevel Quadrature Amplitude Modulated Signals

The paper presents a novel and robust adaptive receiver that jointly estimates the fading amplitude distortion induced by Rayleigh fading channels, as well as the carrier phase noise that is contributed by the receiver local oscillator (LO) and the fading channel. The amplitude fading estimate is used by a novel phase estimator which also involves data detection. The phase noise estimate is input to a Kalman filter which then provides the predicted phase to the reference carrier oscillator such that the carrier phase estimation error remains small even in the presence of fading and channel phase noise impairments. The amplitude and final phase estimates are then used to detect the data symbols. The paper presents detailed results on both the tracking phase error variance and bit error rate results when the proposed method is applied to the case of QPSK modulation. However, the proposed method is applicable to most of the other digital modulation techniques unlike some other phase tracking techniques of the literature.