Research On Modulation Recognition Of Digital Communication Signals Based On Wavelet Transform

The rapid development of digital communications results in the coexistence of many different communication systems, which leads to a lot of disturbance for the communication among different communication systems. In order to handle variety of modulated signals on the same platform, the modulation recognition technology of communication signals has been widely studied. First, the background and development status of the modulation recognition are introduced,and then according to most recognition algorithms are dealing with base-band signals and have a low recognition rate in low SNR conditions, the paper does the wavelet transform for the received IF signals of MQAM, MFSK, and MPSK, at last gives some modulation recognition algorithms to increases the recognition rate in low SNR conditions. For the inter-class recognition of modulation signals, a method using the signal envelope variance and frequency variance after wavelet transform is proposed for inter-class classification of MQAM, MFSK and MPSK signals. For the intra-class recognition of modulated signals, a method using the corresponding sampling time phase difference information between neighboring symbols after wavelet transform is given for intra-class classification of MPSK signals, a method using the instantaneous frequency information extracted from the wavelet transform phase information is proposed for intra-class classification of MFSK signals, and a method using the distribution characteristics of normalized wavelet transform power for intra-class classification of MQAM signals. Compared with the existing algorithms, it has a higher recognition rate.