Abstract
In order to rapidly and automatically identify the modulation level of digital amplitude modulated signals at low signal-to-noise ratio (SNR), a method of identifying the modulation levels of M-ary quadrature amplitude modulation (M-QAM) and M-ary amplitude shift keying (M-ASK) is proposed. In this method, wavelet transform with the optimal scale is used to identify the modulation levels of M-QAM and M-ASK signals. The performance of this method was investigated through simulations. Simulation results show that when the SNR is not lower than −4 dB, the percentage of correct identification of M-QAM is higher than 93 %, and when the SNR is not lower than −10 dB, the percentage of correct identification of M-ASK is higher than 90 %, using only 100 observed symbols. It shows that this method can rapidly acquire good performance at a low SNR.
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