A new cumulant estimator in multipath fading channels for digital modulation classification

In this study, the authors consider the problem of digital modulation classification in a multipath channel using the cumulant-based method. A new estimator is proposed to estimate the fourth-order cumulant of transmitted symbol in a multipath channel with the help of the fourth-order cross-cumulants of the received symbols. The proposed estimator does not need the estimation of the multipath channel coefficients and is shown to be asymptotically unbiased. The channel order is an important factor to affect the estimator. The impact of the channel order mismatch on the estimator is analysed and it is proved that the estimator keeps unbiased in the case of the overestimation of the channel order. The simulated experiments are made to verify the cumulant-based classifier using the new estimator and the results show that it attains better performance for digital modulation classification than the two existing cumulant-based classifiers in a multipath channel.