Identification Of Digital Modulation Signals And Symbol Rate Estimation In Wavelet Domain

This paper mainly studies the application of wavelet transform in automatic identification and symbol rate estimation of digital modulated signals.It extracts the characteristic parameters of the incoming signal by the Haar wavelet,and identifies the modulation type of quadrature amplitude modulation(QAM) signal, phase shift keying(PSK) signal and frequency shift keying(FSK) signal.Further more,the symbol rate estimation of the signal is derived.The main contents are as follows:The first,this paper adopts the variance of the wavelet transform amplitude as the characteristic parameter with and without amplitude normalization of the signal in inter-class identification among QAM,PSK and FSK signals.In ideal case,without applying amplitude normalization,the wavelet transform magnitude of a PSK signal is a constant,while the wavelet transform magnitude of a PSK or QAM signal is a multi-step function;with applying amplitude normalization,the wavelet transform magnitude of a PSK or QAM signal is a constant,while the wavelet transform magnitude of a FSK signal is a multi-step function.Hence the variance of the wavelet transform amplitude of an input signal as a feature to classify the three signals with and without applying amplitude normalization.The second,the amplitude or phase characteristic of wavelet transform is used in intra-class identification among QAM,PSK and FSK signals.In ideal case, the wavelet transform amplitude of M-ary QAM or M-ary FSK signal has M stable levels,and the phase change of neighbour symbols of M-ary PSK signal has M stable levels.The third,the symbol rate of QAM,PSK and FSK signals is estimated by wavelet transform and chirp-z transform.The last,this paper studies how the experimental result is effected by the extension scale of wavelet transform and the number of observing symbols.The simulation result shows that the algorithms mentioned in this paper pose high identification rate and noise-resistance.