The electromagnetic environment is constantly changing. Compared to user-segment defense, the spatial satellite constellation, which is the core of the global navigation satellite system (GNSS), faces more complex threat sources and dynamic jamming scenarios. There is an urgent need for research on evaluating the defensive performance of GNSS in the space segment to ensure its built-in system updates, external facility maintenance, and system security applications. However, effectively evaluating the space-segment defensive performance poses challenges due to the limited existing studies in this field. Therefore, this study presented 25 different threat scenarios using BeiDou navigation satellite system III (BDS-3) as an example and introduced the concept of stability margin to improve existing models for assessing system service performance under non-threatening situations from various perspectives, including constellation status, navigation information quality, spatial signal quality, and service performance evaluation. Consequently, the itemized performance evaluation models of the space-segment defense were proposed for multi-threat scenarios. Furthermore, based on fuzzy comprehensive assessment principles, this study introduced an improved combined assigning method to enhance the weighted product approach, thereby proposing a comprehensive capability evaluation method for the space-segment defense. Experiments demonstrated that these proposed models efficiently determined stability margins against jamming threats for various performances in comparison to existing models, with higher sensitivity toward changes in threat intensity and closer to the theoretical threshold of 0.5. They have effectively assessed the space-segment defensive capability.

Signal Quality Monitoring (SQM) has been widely used as a simple and effective means to detect spoofing attacks on Global Navigation Satellite Systems (GNSS). However, the inherent disadvantages of SQM techniques such as low detection accuracy and poor robustness necessitate the study of new methods. We propose an innovative enhanced SQM method based on the application of a statistical test, known as the Kolmogorov–Smirnov (KS) test, applied to monitor the correlator output of the GNSS receiver to identify the subtle distortions of the correlation function. The simulation results show that the KS test-based method is suitable for detecting spoofing attacks with different power advantages. Compared with seven existing typical spoofing detection methods in applied cases 2, 3, and 7 from the Texas Spoofing Test Battery datasets, the proposed method achieved a higher than 95% detection rate at a false alarm rate of 10%, which is 27.69%, 10.36%, and 6.43% higher than that of the detection method based on weighted second-order central moments, respectively, and the spoofed alarm time delay and computation time are shortened. The proposed method overcomes the performance loss of existing SQM methods and provides excellent detection accuracy and effectiveness, thus, can be used as a potential reliable application solution against spoofing attacks with differing frequency lock modes and power superiorities.

To address the need for real-time solutions when handling kinematic baselines using multi-system and multi-frequency data, where both the rover and reference stations are in motion, we propose a novel non-combined double-difference approach based on extended Kalman filtering. By employing single-difference ambiguity conversion, this approach achieves ambiguity resolution and avoids the frequent alteration of reference satellites in kinematic baselines. Analysis of actual measurement data demonstrates that within a 20 km baseline length range, this algorithm achieves real-time horizontal and vertical baseline accuracies of approximately 1 cm and 2 cm, respectively. The success rate of ambiguity resolution nears 100%, surpassing conventional ionospheric-free double-difference models. Furthermore, as more systems and frequencies are introduced, this proposed method consistently provides superior real-time solutions for kinematic baselines. The practical effectiveness of this approach is further validated through real-flight experiments involving two unmanned aerial vehicles.

Research on the key anti-spoofing technologies is of great significance to resist the increasingly complex threat of spoofing attacks on global navigation satellite system (GNSS) users’ application services. The purpose of detection technologies is to detect spoofing attacks and these are currently relatively mature. However, the current mitigation technologies rely on an antenna array or external sensor information, which is costly and poor in practicability. Therefore, we propose a new detection–estimation–correction anti-spoofing technique based on the vector tracking loop (VTL) structure. This technique effectively utilizes the advantages of the VTL structure to construct equivalent noise bandwidth (ENB) detection statistics to detect spoofing attacks. With the design of 51 sets of correlators in the receiver channel for the first time, the method of estimating and correcting code phase delay error by virtual autocorrelation function (VACF) is proposed, and the effective recovery of receiver navigation and positioning solution is realized by the extended Kalman filter (EKF). The spoofing scene tests of the Texas Spoofing Test Battery (TEXBAT) database show that the proposed anti-spoofing algorithm has a detection probability of more than 90% under the condition of a false alarm rate of 0.1%; the alarm time delay is less than 20 s and the time or position deviation is reduced from 600 m to less than 20 m, which has an excellent performance in detecting and mitigating spoofing attacks. The proposed anti-spoofing technique does not need external information and shows a wide range of potential applicability values for receivers equipped with anti-spoofing attack modules.

The spoofing detection algorithm for a global navigation satellite system/inertial navigation system (GNSS/INS) integrated navigation system based on the innovation rate and robust estimation has limitations such as extensive or invalid detection times, high missed detection rates, and false alarm rates. This study addresses these limitations by proposing a tightly coupled GNSS/INS integration spoofing detection algorithm based on innovation rate optimization and robust estimation. The proposed algorithm improved the normalized innovation of a small step or slow-growing ramp, thereby optimizing its innovation rate test statistics. The proposed approach also reduces the spoofing effect on the innovation rate by adaptively adjusting a gain matrix using robust estimation, thus improving the detection ability further. The simulation results show that the detection time of the proposed algorithm is reduced by 51.9% on average when dealing with small step or slow-growing ramp spoofing. Moreover, the missed detection rate decreases by 58% on average, and the false alarm rate remains at approximately zero. The proposed algorithm is suitable for spoofing detection in unmanned aerial vehicle applications of GNSS/INS integrated navigation systems with the advantages of fast detection and good performance.

全球卫星导航系统(GNSS)/惯性导航系统(INS)的组合导航系统中,GNSS模块易受欺骗干扰的影响,通过开展欺骗干扰对GNSS/INS系统定位性能的影响分析,有助于发掘潜在的GNSS/INS组合系统欺骗干扰检测和抑制方法.将欺骗干扰分为阶跃式位置欺骗、斜坡式位置欺骗、阶跃式速度欺骗和斜坡式速度欺骗四类,根据相应类型的特点建立了欺骗干扰模型,基于该模型理论推导了欺骗干扰影响下位置偏差和速度偏差的变化规律:阶跃式位置欺骗产生阶跃的位置偏差和脉冲的速度偏差;斜坡式位置欺骗产生呈比例变化的位置偏差和阶跃的速度偏差;阶跃式速度欺骗产生阶跃变化的位置和速度偏差;斜坡式速度欺骗产生呈比例变化的位置和速度偏差.仿真结果表明,四类欺骗干扰对应的位置和速度偏差与理论分析一致,通过调整观测噪声矩阵中伪距测量噪声标准差,位置偏差最高减少了34.5％,速度偏差减少了99.5％,有效降低欺骗干扰对位置速度影响的程度.

全球卫星导航系统(GNSS)/惯性导航系统(INS)的组合导航系统常采用松组合与紧组合2种模式,通过分析比较松组合与紧组合在欺骗干扰环境下的导航精度与系统鲁棒性,有助于用户选取最佳的组合模式应对欺骗干扰.首先介绍了GNSS/INS松组合与紧组合的数学模型;然后根据欺骗干扰原理,建立了欺骗模型;最后通过仿真试验,对比分析了松组合与紧组合在欺骗干扰环境下的导航精度与系统鲁棒性.仿真结果表明:在欺骗干扰环境下,紧组合相比松组合的导航精度不具有明显优势,但紧组合的鲁棒性优于松组合.

Being the first mixed-constellation global navigation system, the global BeiDou navigation system (BDS-3) designs new signals, the service performance of which has attracted extensive attention. In the present study, the Signal-in-space range error (SISRE) computation method for different types of navigation satellites was presented. The differential code bias (DCB) correction method for BDS-3 new signals was deduced. Based on these, analysis and evaluation were done by adopting the actual measured data after the official launching of BDS-3. The results showed that BDS-3 performed better than the regional navigation satellite system (BDS-2) in terms of SISRE. Specifically, the SISRE of the BDS-3 medium earth orbit (MEO) satellites reached 0.52 m, slightly inferior compared to 0.4 m from Galileo, marginally better than 0.59 m from GPS, and significantly better than 2.33 m from GLONASS. The BDS-3 inclined geostationary orbit (IGSO) satellites achieved the SISRE of 0.90 m, on par with that (0.92 m) of the QZSS IGSO satellites. However, the average SISRE of BDS-3 geostationary earth orbit (GEO) satellites was 1.15 m, which was marginally inferior to that of the QZSS GEO satellite (0.91 m). In terms of positioning accuracy, the new signals B1C and B2a are considered together with the transition signals B1I and B3I. The overall three-dimensional single-frequency standard point positioning (SPP) accuracy of BDS-3 B1C, B2a, B1I, and B3I gained an accuracy level better than 5 m. Moreover, the B1I signal exhibited the best positioning accuracy in the Asian-Pacific region, while the B1C signal set forth the best positioning accuracy in the other regions. Owing to the advantage in signal frequency, the dual-frequency SPP accuracy of B1C + B2a surpassed that of the transitional signal of B1I + B3I. Since there are more visible satellites in Asia–Pacific, the positioning accuracy of BDS-3 was moderately superior to that of GPS. The precise point positioning (PPP) accuracy of BDS-3 B1C + B2a or B1I + B3I converged to the order of centimeters, marginally inferior to that of the GPS L1 + L2. However, these three combinations had a similar convergence time of approximately 30 min.

欺骗式干扰对卫星导航接收机的影响是多层次的,现已成为接收机用户的一大主要威胁.近些年,学者们提出了许多抗欺骗技术.针对牵引式欺骗攻击,设计了一种信号处理层的抗欺骗技术,提出了基于载噪比的欺骗检测算法.该算法基于假设检验方法,使用信号载噪比为检测统计量,建立了检测模型,实现了欺骗信号检测.仿真实验和实测数据验证了该算法的有效性.实验结果表明,该方法能成功检测大功率优势欺骗干扰和小功率优势欺骗干扰,在虚警率为1×10-3时,检测概率分别达到95％和80％以上.该算法无需外部设备,可低成本地应用到现有的接收机.但对于功率匹配的欺骗干扰,该方法不再可靠,需结合其他的欺骗检测算法来联合检测.

Global navigation satellite system (GNSS) spoofing causes the victim receiver to deduce false positioning and timing data; this notably threatens navigational safety. Thus, anti-spoofing techniques that improve the reliability of GNSS systems, for which interference detection is critical, are essential. Based on the distortion of tracking loop correlation function symmetry of the target receiver caused by gradual adjustment of induced spoofing signals, we proposed a new induced spoofing detection method that uses the weighted second-order central moment (WSCM) difference in the time-domain transient response of multiple correlators of the left and right peaks to obtain the test statistic, theoretically proving that the test statistic follows Gaussian distribution. The Neyman-Pearson hypothesis test method is used to determine the optimal test threshold and determine whether the receiver is being spoofed. The proposed WSCM-based method for spoofing detection was compared with three conventional methods in Scenarios 4 and 7 of the Texas Spoofing Test Battery database, showing that the detection probability of the proposed method is at least 24.15% higher at a false alarm rate of 10% and is more advantageous at lower false alarm rates and the alert time is shortened by at least 30 seconds, enabling at least a 20% faster detection efficiency. The proposed method overcomes the problem of existing methods, which are associated with difficulties in capturing the subtle time-varying effects of the relative carrier phase between the spoofing and authentic signals; thus, it provides excellent detection accuracy and effectiveness, showing broad potential applicability in GNSS spoofing detection.

随着卫星导航技术的发展,GNSS服务易受欺骗干扰已成为现实威胁.本文首先介绍了GNSS/INS组合导航抗欺骗式干扰技术背景,包括欺骗式干扰技术的概念、方式和案例等;其次深入分析和总结了国内外GNSS/INS组合导航系统抗欺骗式干扰技术研究现状与展望;最后进行了总结和思考.

针对传统的新息抗差估计欺骗检测算法对缓慢增长的斜坡式欺骗检测时间较长甚至检测不敏感等问题,提出了一种GNSS/INS紧组合的新息优化抗差估计欺骗检测算法.所提出的算法对缓慢增长的斜坡式的新息检测量进行了优化,结合抗差估计自适应调整增益矩阵并合理选择"检测窗口",进一步提高了对缓慢增长的斜坡式欺骗干扰的检测效率和检测性能.仿真结果表明,在检测单通道0.1 m/s缓慢增长的斜坡式欺骗时,所提算法检测时间较新息抗差估计欺骗检测算法平均缩短了30％以上,漏检率为0;在检测多通道时,检测时间平均缩短了30％,漏检率为0,虚警率平均降低了18.5％.所提算法在检测缓慢增长的斜坡式欺骗干扰时,具有检测快、漏检率和虚警率低的优势,对无人机应用领域具有重要意义.

在INS/GNSS组合导航系统中常采用基于新息的欺骗检测算法.针对现有算法对同步式欺骗干扰的检测时间较长、漏警率和误警率较高的问题,提出了一种基于新息速率抗差估计的INS/GNSS组合导航系统欺骗检测算法.该算法将Kalman滤波估计得到的新息速率作为检测量来判断是否存在欺骗干扰,并利用抗差估计削弱欺骗干扰对新息序列的影响,通过调整等价权函数的参数进一步提高算法的检测能力.仿真结果表明:该算法对诱导速率为0.1 m/s的同步式欺骗干扰的检测时间缩短了60％以上,在3路以下的卫星信号被欺骗时,通过选择合适的检测门限,误警率和漏警率均能维持在4％以内.

For classical TCAR(three carrier ambiguity resolution) algorithm is affected by ionospheric delay and measurement noise, it is difficult to reliably fix ambiguity at medium and long baselines. An improved TCAR algorithm which takes the influence of ionospheric delay into account and has good adaptive robustness is proposed. On the basis of the non-geometric TCAR model, ionospheric delay is obtained by linearly combining extra-wide-lane with fixed ambiguity, and then wide-lane ambiguity is solved. Solving narrow-lane ambiguity by adaptive robust filtering by constructing optimal combination observation, which can effectively improve the fixed success rate of narrow-lane ambiguity and reduce the adverse effects of gross error. Experimental results show that the improved TCAR algorithm can guarantee a high fixed correct rate of wide-lane ambiguity, effectively improve fixed success rate of narrow-lane ambiguity, and has a good ability to resist gross error.

BDS-3 is a global satellite navigation system independently built by China. Its performance level and performance comparison with other satellite navigation systems have an important impact on the follow-up promotion and application. In this paper, the signal in space range error (SISRE) is used as a key performance index of the system. Taking the multi-system precise orbit and clock offset provided by GFZ as the standard, the comparison and evaluation method of satellite orbit, satellite clock offset and SISRE is given. Based on the measured data of three months from January to March 2020, the accuracy improvement of BDS-3 relative to BDS-2 is verified, and the performance comparison between BDS-3, GPS, Galileo and GLONASS is analyzed emphatically. The results show that the accuracy level of BDS-3 is significantly higher than that of BDS-2 both in satellite orbit and in satellite clock offset. The orbit accuracy of BDS-3 in the R, T and N direction is 0.07 m, 0.30 m and 0.26 m respectively, which is at the optimal level among the four global systems. The satellite clock offset accuracy is 1.83 ns, which is basically the same as that of GPS, superior to GLONASS, but slightly worse than Galileo. In terms of the signal in space range error, if only orbit error is considered, BDS-3 SISRE(orb) is averagely 0.08 m. Next, Galileo SISRE(orb) is 0.26 m, GPS SISRE(orb) is 0.57 m, and GLONASS SISRE(orb) is 0.98 m. If the orbit and clock error are considered comprehensively, the average SISRE of BDS-3 is 0.50 m, which is slightly lower than 0.38 m of Galileo, better than 0.58 m of GPS, and significantly better than 2.35 m of GLONASS.

As Global Navigation Satellite System (GNSS) spoofing techniques are highly stealthy and pose a tremendous risk to targets using GNSS technology, studies on GNSS spoofing techniques have been in the spotlight. If the accurate position and velocity of the target receiver can be obtained, the target receiver can be covertly spoofed during the signal tracking stage using synchronous lift-off spoofing. However, it is often difficult to accurately obtain the position and velocity of a target in real GNSS spoofing scenarios. To address this problem, To study the effects of spoofing signals’ power (relative to the real signal), code pulling rate, carrier Doppler shift, initial code phase difference, and carrier phase difference on the efficacy of spoofing, the intrusion of receiver’s signal tracking loop by spoofing signals is mathematically modeled. Based on the model, an asynchronous lift-off spoofing for GNSS receivers in the signal tracking stage is proposed. Theoretical analysis and experimental results show that the new method resulted in stable Doppler frequency variations, short fluctuations in carrier-to-noise ratio (C/N) and signal lock time, and gentle changes to the receiver’s 3D Earth-Centered Earth Fixed (ECEF) coordinates, when the target’s position and velocity were approximately known during the intrusion period. The proposed spoofing method is highly feasible and could expand the scope of applicability of lift-off spoofing.

针对GNSS/SINS/摄影测量组合导航中某个子系统发生故障时,整个导航系统易受到故障数据污染的问题,提出了一种基于快速强跟踪AUKF的双状态卡方(χ2)检测数据融合方法.首先,采用快速强跟踪AUKF算法进行滤波;然后,引入卡方检验通过检测UKF子滤波器输出的状态向量来定位故障参数;最后,采用强跟踪滤波准确跟踪状态矢量突变以增强系统鲁棒性,并根据自适应因子实时调整预测协方差阵以修正增益矩阵,使滤波结果不受异常信息的干扰.将提出的改进算法与常规算法分别应用于无人机着陆导航系统,结果显示:与传统UKF相比,提出的算法得到的位置误差减少了62.6％以上;与强跟踪UKF相比,导航误差也至少减小了32.6％.

Satellite navigation spoofing has become a central issue of jamming technology research because of its serious threat and ability to conceal itself. Increasingly, targets are equipped with more robust GNSS/IMU systems and normalized innovation squared (NIS) is used to detect interference. Therefore, it is harder to implement covert trajectory spoofing on a GNSS/IMU system than a GNSS-only target. In practice, spoofing is needed to control unknown targets. Therefore, covert trajectory spoofing for GNSS/IMU targets is an important issue. Hence, using the information fusion of a GNSS/IMU system, the influence of spoofing on loosely coupled GNSS/IMU positioning is derived. To avoid ill-posed equations when introducing a measurement deviation, a Kalman gain matrix local regularization method is proposed to accurately determine the measurement deviation. To avoid triggering the NIS detection alarm, the range that enables the introduced measurement deviation to remain concealed is calculated. Then, a two-step trajectory guidance algorithm is proposed to quickly guide the target onto the spoofing trajectory. The simulation results show that the proposed trajectory spoofing algorithm can guide a loosely coupled GNSS/IMU target along a spoofing trajectory without triggering the NIS detection alarm. The proposed method can remain concealed and has good theoretical and practical application value.

针对全球卫星导航系统(Global Navigation Satellite System,GNSS)信号中部分周跳难以探测的问题,在三维坐标系中分析了不敏感周跳的产生及分布,研究了探测阈值对不敏感周跳的影响,进而研究了多个组合量联合探测周跳的效果,提出了针对不敏感周跳的组合系数选取方法.该方法根据不敏感周跳的探测量构建组合系数的函数模型,在所有可能的三频无几何相位(geometry free combination,GF)组合系数中选取最敏感的组合系数,可探测3个频点上跳变量相近的不敏感周跳.北斗三频实测数据证实,多个GF组合有效提升了不敏感周跳的探测概率,数量以两个为宜,选取的组合量有效提升了不敏感周跳的探测概率.

针对目前有关GPS欺骗干扰技术的研究较少涉及GPS时间欺骗干扰,且因实验条件限制,难以构建与重放实际欺骗场景,因此不同场景GPS时间欺骗对目标接收机影响仍不明确的问题,基于TEXBAT(Tex-as Spoofing Test Battery)提供的3组不同场景GPS时间欺骗数据集,建立了GPS时间欺骗模型,分析了欺骗过程中存在的两种相位对齐模式对欺骗行为的影响;利用自编软件对采集的欺骗场景的原始高保真数字实时数据进行数据处理,分别得到目标接收机受欺骗与未受欺骗时的接收机钟差及钟差变化率、多普勒频率与载噪比、载波相位与接收机天线位置随时间的变化情况;深入分析了不同场景GPS时间欺骗对目标接收机的影响.实验结果表明,不同场景GPS时间欺骗将从不同角度有效影响GPS定时结果,所得结论将为GPS时间欺骗与抗欺骗技术提供重要参考.