An automatic modulation recognition algorithm for spectrum monitoring applications

An algorithm based on a decision-tree approach for the automatic modulation recognition of communications signals is presented. This algorithm can discriminate between continuous wave (CW), amplitude modulation (AM), double sideband suppressed carrier (DSB-SC), frequency modulation (FM), frequency shift keying (FSK), binary phase shift keying (BPSK) and quaternary phase shift keying (QPSK) modulations. Requirements for a priori knowledge of the signals are minimized by the inclusion of an efficient carrier frequency estimator and low sensitivity to variations in the sampling epochs. Computer simulations indicate good performance on an AWGN channel, even at signal-to-noise ratios as low as 5 dB. This compares favorably with the performance obtained with most algorithms based on pattern recognition techniques