A Novel Blind Recognition Algorithm for Modulated M-QAM Signals

In this paper, we develop an algorithm using Hilbert transform for the blind recognition of QAM signals. Without requiring any prior knowledge of signal parameters, the proposed method employs incoming signal and its Hilbert transform to calculate the instantaneous amplitude of the analytic signal, and then uses subtractive clustering algorithm to find the clustering centers of the instantaneous amplitude. The modulation order (M) of QAM signal is determined according to the number of clustering centers obtained. Computer simulation shows that the proposed method has strong capability for recognition of higher order modulation signals in the presence of additive white Gaussian noise (AWGN).