Research On Spoofing Detection And Cancellation Of Standalone GNSS Receiver

Global Navigation Satellite System(GNSS)can provide precise positioning and timing services,and plays an important role in aircraft and vehicle navigation,as well as timing of power grid,communication network and stock market transactions.GNSS spoofing can make target receivers relying on GNSS civil signals produce false positioning and timing results without knowing it.Based on the national high technology research and development program(863 Program),the research topics of "GNSS vulnerability analysis and signal transmission environment research" and "urban vehicle online location service technology for active traffic safety",this thesis studies on the detection and cancellation of GNSS spoofing,aiming to enable the receiver to detect the presence of spoofing and eliminate the effects of spoofing when it suffers from GNSS spoofing interference,and finally restore the correct positioning and timing results.This thesis studies the single-source spoofing and intermediate spoofing that are most harmful to GNSS civilian signals in reality.Existing anti-spoofing methods based on multiple sensors,multiple antennas,multiple receivers and external reference stations are costly or require external assistance.High cost is not conducive to the use of these methods in commercial receivers,and the external dependence also reduces the robustness of anti-spoofing.Therefore,it is particularly important to develop low-cost standalone receiver independent anti-spoofing technology which does not rely on other sensors,other receivers and the assistance of external reference stations.High complexity,false alarm caused by multipath interference and the influence of the overlap of spoofing signal and authentic signal correlation preaks on the performance of spoofing cancellation are the problems that need to be solved urgently for the existing receiver independent anti-spoofing methods.Therefore,this thesis studies the independent anti-spoofing technology of the standalone receiver,and realizes the detection and cancellation of spoofing by means of model optimization,signal correlation distribution monitoring,joint time-frequency domain estimation and positioning domain residual detection,which has low complexity,takes into account the ability to distinguish between spoofing scenario and multipath scenario,and ensures the timeliness of spoofing alarm and the timeliness of authentic positioning and timing result recovery.From the standpoint of anti-spoofing of GNSS standalone receiver,this thesis studies receiver anti-spoofing techniques with complete functions of detection and cancellation.After investigating the current status of research on spoofing and anti-spoofing technology,the principles of GNSS spoofing are introduced,the main spoofing related events are listed,the main types of GNSS spoofing are summarized,and the main research content and significance of this thesis are established.The main work and innovations of the thesis are reflected in the following aspects:(1)Aiming at single-source spoofing,a low-complexity anti-spoofing method based on Doppler frequency difference monitoring is proposed.Analysis of the components of the Doppler frequency difference between signals reveals that the Doppler frequency difference between the spoofing signals changes linearly with time when the receiver moves randomly,while the Doppler frequency difference between the authentic signals changes non-linearly with time.The spoofing detection problem is transformed into a linearity detection problem,a hypothesis test is established,and statistics are constructed based on the sequential block processing method.The simulations are conducted to analyze the influencing factors of detection performance and detection performance at different receiver motion speeds.Experiment is conducted to verify the detection performance of the proposed method.Compared with the method based on multi-antenna and multi-receiver,this method reduces the cost;compared with the method based on Doppler correlation of motion receiver,it reduces the calculation of satellite motion Doppler and receiver clock drift,and reduces the complexity.(2)The GNSS intermediate time spoofing detection algorithm is studied.The distribution characteristics of the delay correlation results of the received signal are deduced mathematically.It is revealed that the delay correlation results follow the normal distribution when there is no spoofing,and do not follow the normal distribution when intermediate spoofing exists.The spoofing detection problem is transformed into a normality test problem,and the AD test method is selected to detect spoofing.The simulation analyzes the detection probability under different parameters such as spoofing-authentic power ratio,code delay difference,and Doppler difference.Texas Spoofing Test Battery(TEXBAT),the spoofing data battery shared by the University of Texas at Austin,is used to verify the effectiveness of the proposed method.This method belongs to the pre-despreading method,does not require acquisition and tracking operations,and has low complexity;compared with some existing pre-despreading methods,the performance is improved,and it can also obtain good detection performance when the Doppler difference between the signals does not euqals integer kilohertz;it can detect the existence of spoofing even when the error introduced by the spoofing is small,and has strong alarm timeliness.(3)The spoofing detection method based on dual-peak in frequency domain and relative velocity residuals is studied.The characteristics and spoofing process of intermediate spoofing are introduced in detail.It was revealed that spoofing-authentic Doppler difference will cause dual-peak in the frequency domain,and spoofing detection based on dual-peak in frequency domain is proposed.The influence of multipath is taken into account,and the similarities and differences of dual-peak number and Doppler difference between multipath scenario and spoofing scenario are analyzed,and proposes that the number of dual-peaks and relative velocity residual can be used to distinguish the multipath scenario from spoofing scenario.The calculation method of relative velocity residual is given.Dual-peak recognition and Doppler difference extraction methods are proposed,and the effects of different extraction methods are compared experimentally.Spoofing Detection performance is verified based on TEXBAT.This method can not only detect spoofing but also distinguish spoofing scenario from multipath scenario,and its detection performance will not be affected by spoofing-authentic signal carrier phase difference.(4)Research on GNSS intermediate spoofing cancellation technique.The framework of intermediate spoofing cancellation is given,and the process of spoofing cancellation is introduced.The direct estimation reconstruction method for spoofing signal reconstruction is introduced in detail,and a joint estimation reconstruction method is proposed.The evaluation index of spoofing cancellation performance is given.The influence of the estimation error of the spoofing signal on the spoofing cancellation performance and the spoofing reconstruction and cancellation performance of the direct estimation reconstruction-based method are analyzed by simulation.The spoofing cancellation performance of joint estimation reconstruction-based method is verified based on TEXBAT.This method does not require iterative calculation and has low computational complexity.And it solves the problem of large estimation error caused by the overlap of the authentic signal correlation peak and the spoofing signal correlation peak.