Spoofing Detection Based On Model Parameter Identification

Spoofing interference is a serious threat to the global positioning system(GPS)receiver.This kind of interference and the satellite signal can be overlapped in time,frequency and spatial domain.So the spoofing can obtain the same processing gain as well as the real signal and it is hard to be detected.In this paper,a Hammerstein model is applied to model the spoofer or the GPS transmitter and the wireless channel.This dissertation studies spoofing detection from the perspective of system identification.The main works of this thesis are as follows:1 The fundamental principles and research status of spoofing detection and system identification are introduced.On the basis of analyses of spoofer's structure,the nonlinearity distortion of the jammer/transmitter can be modeled as a memoryless polynomial,and the radio frequency wireless channel can be regarded as a FIR filter.Thus,the satellite communications system or the jamming system can be modeled as a Hammerstein model.Then the simulation model is established using MATLAB/Simulink,which is essential to follow-up experiments.2 For the Hammerstein model mentioned above,three classic method of system identification,least square method(LS),least square/singular value decomposition method(LS/SVD)and iterative method,are utilized to estimate parameters of the system model.Then we take the estimated parameters as a feature vector and utilize euclidean distance method to detect the jamming signal.The performance is compared in terms of the running time,average relative error,and detection rate.Simulation results show that the iterative method is more effective than others in the perspective of average relative error and detection rate.But the performance of iterative method is poor when signal-to-noise ratio(SNR)is relative low.3 Because the above methods have some demerits,such as being sensitive to noise and the poor performance in low SNR,bat algorithm(BA)and wolf pack algorithm(WPA)are utilized to obtain the estimated parameters.Since the WPA is easy to be trapped into local optimum,an improved algorithm based on differential evolution strategy is proposed,which named differential evolution wlof pack algorithm(DE-WPA).Simulation results show that although the running time of the DE-WPA is longer than others,it is effective in system identification of Hammerstein model,and it can obtain better estimation precision than others,hence it has better detection performance of GPS spoofing.