Research On Modulation Recognition Of Wireless Signals

Modulation recognition technologies of communication signals are widely used in both civilian and military fields, aiming at identifying the modulation type of the intercepted communication signals in multi-signal environments.The recognized modulation parameters can provide the reference information for the subsequent signal processing and analysis. Especially, modulation recognition plays a fundamental and vital role in the radio monitor.In recent years, modulation recognition has become a much-discussed topic in China and abroad.There have been a large amount of novel recognition algorithms, however, most of which mainly stayed at the stage of theoretical research and simulation.In fact,these algorithms are unsuitable for application in the radio monitor due to the poor performance in real propagation environments.In this paper, we mainly focus on the practical application of the modulation recognition methods.Based on the investigation of recognition algorithms for9typical Ultra-short wave signals in the radio monitor, a more accurate and high stability recognition scheme is proposed.The corresponding modulation recognition software is developed to distinguish the modulation type of real-word collected signals,which shows a good performance. The primary content of this paper is described as follows:For a start, the research background and present situation of modulation recognition technology are introduced.According to the modulation of communication signals, we describe the principles and characteristics of the commonly used analog modulation signals (DSB, FM) and digital modulation signals (MASK, MFSK, MPSK) and then simulate each of these modulation schemes using the MATLAB tools.Then, we research on the recognition statistics parameters based on the feature parameters of communication signals, simulate each of these recognition statistics using the MATLAB tools and obtain the decision threshold. Based on the decision theory, a recognition algorithm is designed to distinguish2ASK, BPSK,4ASK, QPSK,2FSK,4ASK,16QAM signals. The recognition rate achieves97%under the SNR=7.8dB.Moreover, according to the recommendation of ITU-RSM.1600, we study the estimation methods about signal parameters, which mainly includes presence of signal, symbol rate estimation, carrier frequency estimation and emission bandwidth estimation. Three new estimation methods about symbol rate estimation are proposed, such as signal squared spectrum, spectral correlation method and Haar wavelet transform.These new estimation methods are simulated and verified using the MATLAB tools.Finally, we study the modulation recognition algorithm of BPSK, QPSK,8PSK, OQPSK,Ï€/4DQPSK, FSK,4FSK,16QAM,32QAM signals. According to the characteristics of Ultra-short wave signals, a new scheme for modulation recognition system is designed, which applied in the routine Ultra-short waves monitor and obtained fine recognition performance.