Modulation Identification In Wireless Communication Systems

This paper focuses on modulation identification in wireless communication systems.Modulation identification is one of the most significant research topics in communication field,and it plays a very important role in both military and civilian areas,such as communication countermeasure and electronic warfare in military area and spectrum monitoring in civilian area.This paper first introduces wavelet transform theory,and a detailed mathematical derivation and simulaton of three commonly used modulated signal ASK,PSK and QAM is made,and then this paper analyzes the characteristics of the wavelet transform magnitude of the modulated signal.Based on this,the characteristics of the wavelet transform of the digital modulated signals under AWGN channel is analyzed.After that,this paper analyzes the existing modulation identification scheme based on wavelet transform,and the existing problems of the existing scheme are summarized and described.Aiming at these problems,this paper proposes a modulation identification scheme based on peaks-cutting off and wavelet transform with optimal scale.The modulation identification scheme based on peaks-cutting off and wavelet transform with optimal scale proposed by this paper solves two problems that exist in the existing scheme:the existing scheme cannot eliminate the influence of the distinct peaks occurring in the wavelet transform magnitude of the signal,and it also does not select the optimal scale to do wavelet transform.These two problems can influence the identification correct rate of the modulation identification scheme,thus the scheme proposed by this paper will have a better performance.Since the M-ary QAM intraclass modulation identification scheme combines the characteristics of the constellation and wavelet transform magnitude of the signal,thus the QAM intraclass modulation identification scheme proposed by this paper is also called constellation and wavelet transform(constellation-wavelet transform,C-WT)M-ary QAM modulation identification scheme.Verified by calculation and simulation,compared with the existing modulation identification scheme,the interclass modulation identification proposed by this paper is more concise,less time-consuming and easier to identify modulation type.For M-ary QAM intraclass identification,the C-WT scheme can obtain high identification correct rate,and shows higher robust to SNR.