Research On Classification And Identification Of GNSS Interference Based On Multi-identificers

Global Navigation Satellite System(GNSS)is a cornerstone for numerous applications in modern society.Because of the long traveling distance,however,the power of the spatial satellite signals arriving the ground decreases significantly.It means that GNSS signals are vulnerable to lots of radio frequency interference,which definitely threaten the reliability and availability of GNSS applications.Hence,it is of great importance to improve the anti-interference ability of GNSS.Considering the various types of interference,classification and identification of interference signals are the essential requirements before realizing targeted and efficient anti-interference techniques.Therefore,with GPS L1 as an example,the interference mechanisms,identification methods and classification strategies of both jamming and spoofing attacks have been studied in this study.The effects of common jamming(continuous wave,sweep wave and pulse modulated continuous wave)and spoofing are investigated in-depthly.The analysis results show that jamming could distort the power spectrum density(PSD)of GNSS intermediate frequency(IF)signal,while spoofing attacks distort correlation function at baseband stage rather than PSD of IF signal.Besides,continuous wave(CW)interference with ?-70 dBm-power and sweep wave(SW)interference with ?-60dBm-power sharply degrade the acquisition and tracking performance of GNSS receivers.Differently,the performances degrade gradually with increasing power under pulse interference.Moreover,jamming with different strength has been classified into four threat levels,namely extremely weak,weak,strong,and extremely strong levels.Then,according to the distorted PSD caused by jamming,a frequency estimation algorithm based on shifted cumulative spectral power(SCSP)is proposed to detect the jamming and figure out interference bandwidth.To estimate the period of jamming,time-frequency analysis is used and improved by a proposed integrating spectrum-based de-nosing method and a block binarization filter.The de-nosing method reduces the estimation error of extremely weak jamming and the filter leads to successful estimation of extremely weak broadband jamming.Therefore,identification and parameters estimation of jamming scheme based on SCSP and time-frequency analysis is implemented eventually.Experimental results show that identification rate of CW or SW above-90 dBm is higher than 99%.The frequency estimation errors of CW and SW above-80 dBm are less than 5%,and the period estimation error of SW is nearly 0.The identification rate of short period(1ms)pulse interference above-80 dBm is more than 92%,the estimation errors of frequency and period are close to 0,and the estimation error of duty cycle is below 6.9%.Different from the jamming,spoofing attacks are unable to distort the signals' PSD.It leads to obvious distortations on correlation function except for the cases of strong spoofing attacks and small relative spoofing delay.Therefore,inertial information is researched to identify spoofing attacks in the exceptions.Based on the analysis of spoofing effects on the performance of GNSS/INS(inertial navigation system)loosely coupled integration systems,kalman innovation are adopted to identify spoofing attack.The results show that the identification rate of meaconing(MEAC)attack with ?7 m-position offset or lifted-of-aligned(LOA)attack with ?0.2 m/s-velocity offset,which correspond to over 12 m relative pseudorange and over 0.35m/s relative pseudorange drift rate respectively,is more than 92%.Besides,GNSS receivers based on parameter estimation have difficulty in distinguishing spoofing signals while these signals could be estimated by these receivers.Hence,a spoofing identification strategy based on rate of pseudorange difference is researched,which is proved by tests and the results illustrate that the possibility of identifying spoofing pseudorange with ?1m/s relative pseudorange drift rate successfully is over 95%.Finally,considering the practical situation that the type of received GNSS interference is unknown,a multi-identifier of GNSS jamming and spoofing is designed and realized.The test results show that proposed GNSS interference classification and identification scheme is capable of detecting and then identifying types of interference effectively.Meanwhile,this scheme can provide significant parameters related to interference characters,which definitely improve the adaptability of lots of anti-interference methodologies.