Research And Implementation On Modulation Classification And Parameters Estimation Technologies Of Communication Signals Based On Multi-node Cooperation

With the rapid development of wireless communication technologies, the electromagnetic environment becomes more complex and the electromagnetic spectrum monitoring is playing an increasingly important role for optimal management of spectrum resources. Because of the unique advantages, the networked electromagnetic spectrum monitoring get more and more concern. As key technologies of the electromagnetic spectrum monitoring, the research of modulation classification and parameter estimation are largely based on a single node in existing study. How to use multiple nodes to conduct modulation classification and parameter estimation cooperatively in networked monitoring system has become an important issue. This paper focuses on this problem, multi-node cooperative modulation classification and parameter estimation method by using the feature layer information of signal have been researched and related works have been implemented. The main work and innovation of this paper is summarized as the following three aspects:1. Aiming at the limited performance boost in multi-node cooperative method based on signal feature layer in low SNR and the limited energy of monitoring node, an improved method based on higher-order cumulant characteristics is proposed. Firstly, aimming at the signal set {4ASK,2PSK,4PSK,8PSK and 16QAM}, four higher-order cumulant characteristics is extracted.Then the feature set is classified by decision tree classifier and support vector machine classifier in single-node, and the two performance are compared. Secondly, aiming at the shortage of the existing multi-node method, an improved multi-node method combined with the existing higher-order cumulant characteristics is proposed. The cooperative strategic is designed by the anti-noise performance and the feature of compution of higher-order cumulant, which can minimize the average computation amount of nodes under the premise of performance guaranteed. And each feature is extracted only once. Simulation results show that, the performce of improved method is better than the original method in different SNR environment and the amount of compution is reduced.2. Aiming at the poor performance of the existing symbol rate estimation method in low SNR, a feature spectrum which contains the symbol rate information is proposed and the symbol rate is estimated by extracting characteristic lines. A multi-node cooperative symbol rate estimation method based on spectral synthesis is designed, which combined with the property of the feature spectrum, that is the insensitivity to time delay, frequency offset, phase offset.The existence of a discrete spectrum line in symbol rate position of the signal spectrum by signal modulus squared is used to calculate the feature spectrum,which make the different sampling ratio as the abscissa and fourier coefficient modulus as the vertical axis. Search the characteristic line on behalf of the symbol rate by specific method, then an estimation of the symbol rate is obtained. This method is suitable for MASK, MPSK, MQAM signals. Simulation results show that the performance of symbol rate estimation of the method in this paper is better than the wavelet transform method and the cyclostationary method, and the amount of calculation is reduced when compared with the cyclostationary method. Then a multi-node cooperative symbol rate estimation method based on spectral synthesis take advantage of this feature spectrum is presented. The feature spectrums of every sensor node are weighted composed according to the SNR and the synthetic spectrum is used to estimate symbol rate. Simulation results show that the performance of the feature spectral synthesis method is better than the feature value synthesis method and the single-node method.3. An multi-node cooperative electromagnetic spectrum monitoring system is designed and implemented. Based on the previous theoretical studies and combined with the functional requirements of the electromagnetic spectrum monitoring, An multi-node cooperative electromagnetic spectrum monitoring system is designed and implemented. First, according to the indicator of the system, the overall program of the system is designed, including the network structure, the structure of the monitoring node, the processes and hardware platform of the signal processing unit. Aiming at the signal processes, DSP programming of signal detection, modulation classification, parameter estimation algorithm is completed. Combined with system functional requirements, the DSP module interface and multi-task is designed and accordingly debugging work is also done. Finally, functional testing and actual operational testing of the system is tested, results meet the theoretical research and achieve the desired targets, the feasibility of the whole system is verified.