Method for preventing spoofing of a satellite navigation by a repeater

Abstract

The application discloses a method for preventing retransmission type satellite navigation deception, which comprises the following steps: firstly, performing multi-correlation peak preliminary detection to identify abnormal signal characteristics; then, performing power analysis on the signal by using a power estimation module, setting a power threshold, and identifying a deception signal by comparison; in order to further improve the identification accuracy, a constellation model is established, and two methods of time of arrival monitoring and autonomous integrity detection are adopted to comprehensively identify retransmission type deception interference; if the two methods both indicate that deception exists, the deception behavior is determined; once it is confirmed that deception interference exists, anti-interference measures are immediately started, such as adjusting receiver parameters, switching antennas and the like, so as to ensure normal operation of the system; meanwhile, the autonomous integrity detection is used to eliminate abnormal signals, so as to ensure the accuracy of positioning information; in addition, the scheme comprehensively monitors the deception interference situation, and records the interference event information in detail, so as to provide strong support for subsequent analysis and processing.

Description

Technical Field

[0001] This invention relates to the field of satellite navigation technology, and in particular to a method for preventing transponder-based satellite navigation spoofing. Background Technology

[0002] Spoofing jamming targets receivers and can be categorized into transponder-based spoofing jamming and generator-based spoofing jamming. Transponder-based jamming alters the time delay of the signal reaching the target receiver, causing it to generate erroneous pseudorange information and resulting in errors in position and clock error calculation. Generator-based spoofing jamming modifies the satellite position information in the received navigation message, causing the receiver to misposition. Summary of the Invention

[0003] This application provides a method for preventing spoofing of transponder satellite navigation systems. This technical solution comprehensively improves the accuracy of spoofing interference identification and enhances the system's anti-interference capability by using methods such as multi-correlation peak detection, power estimation, time of arrival monitoring, and autonomous integrity detection. At the same time, it eliminates abnormal satellite signals, improves the reliability of positioning information, and comprehensively monitors and records spoofing interference, providing strong support for subsequent analysis.

[0004] This application provides a method for preventing transponder satellite navigation spoofing, including:

[0005] S1, perform preliminary multi-correlation peak detection on the signal layer of the navigation satellite signals received by the satellite navigation system to identify possible abnormal signal characteristics;

[0006] S2 uses the power estimation module in the receiver to estimate the power of the received navigation satellite signal and sets a reasonable power threshold. By comparing the signal power with the threshold, spoofing signals can be identified.

[0007] S3 uses known constellation layout and satellite orbital parameters to establish a constellation model. Based on this, it employs two methods—time of arrival monitoring and autonomous integrity detection—to comprehensively identify and respond to relay-type spoofing interference.

[0008] S4. Based on the combined results of arrival time monitoring and autonomous integrity detection, if both methods indicate that there is deception interference, then it is determined that there is deception.

[0009] S5. If the above steps confirm the existence of deceptive interference, anti-interference measures should be initiated immediately, and key information about the interference event should be recorded in detail.

[0010] Preferably, the preliminary detection of multiple correlation peaks specifically includes:

[0011] S11: Perform initial capture processing on the intermediate frequency signal to narrow the capture window range; wherein, the search window time is set to 2 seconds to start the initial capture attempt; determine whether the peak value of the first capture exceeds the preset threshold. If it does not exceed the threshold, repeat the first capture; if it exceeds the threshold, execute S12.

[0012] S12: Based on the code phase obtained in the first capture, set the search window time to 40 milliseconds and perform a second capture; based on the result of the first capture, determine whether the peak value of the second capture exceeds the threshold. If it does not exceed the threshold, perform a second capture again; if it exceeds the threshold, execute S13.

[0013] S13, based on the code phase obtained from the second capture, offset the search starting point by 2046 chips and perform a third capture;

[0014] S14, Analyze the results of the second and third captures;

[0015] Preferably, step S14, analyzing the second and third capture results, includes:

[0016] S141, If ​​the second capture is successful and the third capture is unsuccessful, provided that the conditions for the third capture are reasonable, then the second capture is considered to be a real signal, and the result is transferred to tracking processing;

[0017] S142, If the second and third captures are both successful, after comparing the consistency of the two capture results, it is considered that the third capture is a real signal, and the tracking process is performed.

[0018] S143, In each capture attempt, record all peak values ​​that exceed the preset threshold;

[0019] S144, count the number of peaks exceeding the threshold. If multiple independent peaks exceeding the threshold are detected, it is preliminarily determined that there is deceptive interference.

[0020] Preferably, step S2, identifying spoofing signals through signal power detection, includes:

[0021] S21, The power estimation module integrates the signal over a period of time, calculates and outputs its signal power;

[0022] S22, set the normal operating range to -110dBm to -133dBm, compare the calculated signal power with the normal operating range, and if the signal power exceeds the normal operating range, perform spoofing signal identification.

[0023] Preferably, S22, the spoofing signal identification, includes:

[0024] S221, compares the current branch power with the noise power in the three-way product branch;

[0025] S222, if the current branch power is higher than the noise power threshold and the signal power is greater than the normal operating range, it is determined that there is deceptive interference;

[0026] S223, when the absolute power of the signal is detected to exceed the preset enhanced signal power threshold, it is considered that there is currently suppression-type deception interference;

[0027] S224. Based on the detection results, a corresponding interference label is given. The anti-interference antenna can start space-time anti-interference processing according to the interference label to deal with the detected spoofing signal.

[0028] Preferably, S3, arrival time monitoring, includes:

[0029] S3A1, through simulation calculation, obtains the theoretical normal range of the relative time difference of different satellite signals arriving at the target receiver antenna;

[0030] S3A2 monitors the arrival time of received satellite signals in real time and calculates the difference between the arrival time of each satellite signal and the arrival time of other satellite signals.

[0031] S3A3: If the difference between the arrival time of a satellite signal and the arrival time of other satellite signals exceeds the normal range obtained from the simulation, it is preliminarily determined that the signal is subject to deceptive interference.

[0032] Preferably, in step S3, the autonomous integrity detection includes:

[0033] S3B1 randomly selects 4 out of the 5 received satellites to calculate their position, velocity, and time, and obtains the current position estimate of the target receiver through the calculation;

[0034] S3B2, repeat the above process, perform five different combination calculations on the five satellites to obtain five position results, and compare the consistency of these five calculation results; if there are differences, it indicates that there is deception interference;

[0035] S3B3 identifies and eliminates interfering satellites based on abnormal information.

[0036] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0037] By employing multiple methods, including preliminary detection of multiple correlation peaks, power estimation and threshold comparison, time-of-arrival monitoring, and autonomous integrity detection, spoofing signals are comprehensively identified, significantly improving the accuracy and reliability of identification. Once spoofing interference is detected, anti-interference measures are immediately initiated, such as adjusting receiver parameters and switching antennas, effectively countering various spoofing attacks and ensuring normal system operation. Autonomous integrity detection eliminates abnormal satellite signals, ensuring the accuracy of the calculation results for the remaining satellite signals and providing users with reliable positioning information. Comprehensive monitoring of spoofing interference and detailed recording of key information about interference events provide strong support for subsequent analysis and processing. Attached Figure Description

[0038] Figure 1 This is a flowchart illustrating a method for preventing transponder-based satellite navigation spoofing according to an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the preliminary detection of multiple correlation peaks in an embodiment of the present invention. Detailed Implementation

[0040] To facilitate understanding of the present invention, a more complete description of this application will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of the present invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] Example 1: Figure 1 This is a flowchart illustrating a method for preventing transponder-based satellite navigation spoofing according to an embodiment of the present invention.

[0043] like Figure 1 As shown, a method for preventing transponder-based satellite navigation spoofing includes the following steps:

[0044] S1 performs preliminary multi-correlation peak detection on the signal layer of navigation satellite signals received by satellite navigation in order to identify possible abnormal signal characteristics.

[0045] Specifically, in satellite navigation systems, receivers receive signals from multiple navigation satellites. These signals may be subject to various interferences during transmission, including spoofing interference. Therefore, a preliminary multi-correlation peak detection is first required on the received signals to identify potential interference signals. This preliminary detection typically involves correlating the signal and observing the peak values ​​in the correlation results. If multiple significant peaks appear in the correlation results, it may indicate the presence of spoofing interference.

[0046] Among them, such as Figure 2 The schematic diagram of preliminary detection of multiple correlation peaks shown includes the following steps:

[0047] S11 performs initial capture processing on the intermediate frequency signal, narrowing the capture window range.

[0048] The search window time is set to 2 seconds to begin the first capture attempt. It is then determined whether the peak value of the first capture exceeds a preset threshold. If it does not exceed the threshold, the first capture attempt is repeated; otherwise, step S12 is executed.

[0049] The preset threshold refers to the number of correlation peaks exceeding this threshold during the acquisition process. This threshold is set based on factors such as system performance requirements, signal characteristics, and environmental noise. When the height or intensity of a correlation peak exceeds this threshold, the peak is considered valid and may correspond to a real signal.

[0050] Specifically, the initial acquisition is a crucial step for a satellite navigation receiver to acquire satellite signals. During the initial acquisition, the receiver needs to search for possible code phases and Doppler shifts to find a satellite signal that matches the received signal. To narrow the acquisition window, the search window time can be set to 2 seconds. This means that within the 2-second time window, the receiver will attempt to match all possible combinations of code phases and Doppler shifts. The receiver then determines whether the peak value of the first acquisition exceeds a preset threshold. The threshold is a threshold set according to system requirements and signal characteristics, used to determine the validity of the acquisition result. If the threshold is not exceeded, the first acquisition is repeated; if the threshold is exceeded, step S12 is executed. The threshold setting can be based on parameters such as signal-to-noise ratio (SNR) and bit error rate (BER).

[0051] The relevant calculation formulas for the capture process are as follows: R(τ,∫ d The correlation result represents the relationship between the received signal and the local reference signal at a specific code phase τ and Doppler shift ∫. dThe similarity or matching degree; s(t) is the received signal, that is, the signal received by the satellite navigation receiver from the navigation satellite. The received signal usually contains navigation data, carrier, and pseudocode (or spreading code) components. During the acquisition process, the receiver needs to try to match the pseudocode and carrier frequency in the received signal; * (t-τ) is the conjugate of the local reference signal, representing the complex conjugate of the pseudocode generated by the receiver that matches the received signal and the carrier signal. t-τ represents the time offset of the local reference signal relative to the received signal, i.e., the code phase difference. By adjusting the code phase τ, the receiver can search for and find a pseudocode sequence that matches the received signal. τ is the code phase, representing the time offset between the local reference signal and the received signal. In satellite navigation, due to signal propagation delay and receiver clock errors, the pseudocode sequence in the received signal may have a time offset from the locally generated pseudocode sequence. By searching for different code phase values, the receiver can find a pseudocode sequence that matches the received signal. d Doppler shift refers to the change in signal frequency caused by the relative motion between the receiver and the satellite. When there is relative motion between the receiver and the satellite, the frequency of the received signal will shift; this shift is called Doppler shift. During acquisition, the receiver needs to try different Doppler shift values ​​to find a carrier frequency that matches the received signal. T dt is the integration operation, which means integrating the correlation function over a time range T. Integration can smooth noise in the signal and improve the accuracy of the correlation results. Through integration, the receiver can obtain the correlation results under specific code phase and Doppler frequency shift.

[0052] S12, based on the code phase obtained in the first capture, set the search window time to 40 milliseconds and perform a second capture.

[0053] Based on the result of the first capture, it is determined whether the peak value of the second capture exceeds the threshold. If it does not exceed the threshold, the second capture is performed again; if it does exceed the threshold, S13 is executed.

[0054] Specifically, after a successful initial acquisition, the receiver obtains a preliminary code phase estimate. To further improve acquisition accuracy, a second acquisition can be performed with a search window time set to 40 milliseconds, based on the code phase obtained from the first acquisition. The search range for the second acquisition is narrower, thus allowing for a faster finding of a code phase and Doppler shift combination that better matches the received signal. The receiver then checks if the peak value of the second acquisition exceeds a threshold. If it does not exceed the threshold, the second acquisition is performed again; if it does exceed the threshold, step S13 is executed.

[0055] S13, based on the code phase obtained from the second capture, offset the search starting point by 2046 chips and perform a third capture.

[0056] Specifically, after a successful second acquisition, the receiver obtains a more accurate code phase estimate. To further verify the accuracy of the acquisition result, the search starting point can be adjusted based on the code phase information obtained from the second acquisition, and a third acquisition can be performed at the new starting point. The search range for the third acquisition is 2046 base codes, which is sufficient to cover possible code phase deviations.

[0057] S14, Analyze the results of the second and third captures.

[0058] The analysis of the second and third capture results includes:

[0059] S141, if the second capture is successful and the third capture is unsuccessful, provided that the conditions for the third capture are reasonable, then the second capture is considered to be a real signal, and the result is transferred to tracking processing.

[0060] Among them, reasonable conditions refer to the conventional reasonableness of settings such as search range and threshold settings.

[0061] Specifically, if the second acquisition is successful but the third acquisition is unsuccessful, it may mean that there is no code phase and Doppler shift combination that matches the received signal within the search range of the third acquisition. Therefore, it can be assumed that the second acquisition was of the real signal, and the result can be converted to tracking processing.

[0062] S142, if the second and third captures are both successful, after comparing the consistency of the two capture results, it is considered that the third capture is a real signal, and the tracking process is performed.

[0063] Specifically, if the second and third captures are both successful, and the results of the two captures are consistent to some extent, this may mean that there is a code phase and Doppler shift combination that matches the received signal better within the search range of the third capture. Therefore, it can be assumed that the third capture is of the real signal (or a more accurate signal than the second), and tracking processing can be performed.

[0064] S143, in each capture attempt, records all peak values ​​that exceed the preset threshold.

[0065] S144, count the number of peaks exceeding the threshold. If multiple independent peaks exceeding the threshold are detected, it is preliminarily determined that there is deceptive interference.

[0066] Among them, if multiple correlation peaks larger than the threshold and independent of each other are detected, that is, consecutive peaks not caused by random factors such as noise in the same capture attempt or adjacent capture attempts.

[0067] It should be noted that after recording all peak values ​​exceeding the threshold, the number of these peak values ​​needs to be counted. If multiple related peaks exceeding the threshold are detected, this may indicate the presence of deceptive interference. Normally, only one significant peak should match the received signal. Therefore, deceptive interference can be preliminarily identified, and appropriate countermeasures can be taken.

[0068] S2 uses the power estimation module in the receiver to estimate the power of the received navigation satellite signal and sets a reasonable power threshold. It then identifies spoofing signals by comparing the signal power with the threshold.

[0069] Specifically, identifying spoofing signals through signal power detection includes:

[0070] S21, the power estimation module integrates the signal over a period of time, calculates and outputs its signal power.

[0071] The calculation of signal power includes: the estimation of navigation satellite signal power is mainly based on the magnitude of the integral value of the relevant channel, i.e., the correlation channel output power (COP). Specifically, it is estimated by using the ratio of the power (sum of squares of integral values) of the current branch in the three-way integral branch to the noise power.

[0072] S22, set the normal operating range to -110dBm to -133dBm, compare the calculated signal power with the normal operating range, and if the signal power exceeds the normal operating range, perform spoofing signal identification.

[0073] Among them, deception signal identification includes:

[0074] S221 compares the current branch power with the noise power in the three-way product branch.

[0075] The noise power is obtained by calculating its average value through multiple statistical calculations. The calculation method for noise power is as follows: In the navigation receiver, the A / D analog-to-digital converter has an AGC (Automatic Gain Control) function at the front end, which basically keeps the input signal strength constant. If the A / D uses 3-bit quantization, the probability distribution of the amplitude of the quantized analog input signal is set, and the mean square value of the product of the local carrier signal and the input signal is calculated accordingly. A single calculation may fluctuate significantly due to noise; therefore, multiple statistical calculations are performed to obtain a more accurate noise power estimate.

[0076] S222 If the current branch power is higher than the noise power threshold and the signal power is greater than the normal operating range, it is determined that there is deceptive interference.

[0077] Among them, the noise power threshold uses statistical methods to analyze historical data and determine a reasonable range of power difference as a judgment criterion.

[0078] S223, when the absolute power of the signal is detected to exceed the preset enhanced signal power threshold, it is considered that there is currently suppression-type deception interference.

[0079] S224. Based on the detection results, a corresponding interference label is given. The anti-interference antenna can start space-time anti-interference processing according to the interference label to deal with the detected spoofing signal.

[0080] S3 uses known constellation layout and satellite orbital parameters to establish a constellation model. Based on this, it employs two methods—time of arrival monitoring and autonomous integrity detection—to comprehensively identify and respond to relay-type spoofing interference.

[0081] Specifically, arrival time monitoring includes:

[0082] S3A1, through simulation calculation, obtains the theoretical normal range of the relative time difference of different satellite signals arriving at the target receiver antenna, such as 3 to 5 chips.

[0083] S3A2 monitors the arrival time of received satellite signals in real time and calculates the difference between the arrival time of each satellite signal and the arrival time of other satellite signals.

[0084] S3A3: If the difference between the arrival time of a satellite signal and the arrival time of other satellite signals exceeds the normal range obtained from the simulation (3 to 5 chips), it is preliminarily judged that the signal may be subject to deceptive interference.

[0085] It should be noted that, considering the clock discrepancy between the satellite and the ground receiver, the absolute value of the signal arrival time cannot be effectively limited, but the relative value (i.e., the difference in arrival time) is reasonable and therefore used as a basis for judgment.

[0086] Specifically, autonomous integrity testing includes:

[0087] S3B1 randomly selects 4 out of the 5 received satellites to perform position, velocity, and time (PVT) calculations, and obtains the current position estimate of the target receiver through the calculations.

[0088] S3B2, repeat the above process, perform five different combination calculations on the five satellites to obtain five position results, and compare the consistency of these five calculation results; if there are significant differences, and such differences cannot be explained by normal measurement errors, it indicates that there may be deception interference.

[0089] S3B3 identifies and eliminates interfering satellites based on anomaly information, ensuring the accuracy of the calculation results for the remaining satellite signals to provide reliable positioning information.

[0090] S4. Based on the combined results of arrival time monitoring and autonomous integrity detection, if both methods indicate the presence of deceptive interference, then a deceptive behavior is determined to exist.

[0091] S5. If the above steps confirm the existence of deceptive interference, anti-interference measures should be initiated immediately, and key information about the interference event should be recorded in detail.

[0092] Anti-interference measures include adjusting receiver parameters and switching antennas. Key information includes the time and location of the interference, as well as the type of interference.

[0093] The technical solutions described in the embodiments of this application above have at least the following technical effects or advantages:

[0094] By employing multiple methods, including preliminary detection of multiple correlation peaks, power estimation and threshold comparison, time-of-arrival monitoring, and autonomous integrity detection, spoofing signals are comprehensively identified, significantly improving the accuracy and reliability of identification. Once spoofing interference is detected, anti-interference measures are immediately initiated, such as adjusting receiver parameters and switching antennas, effectively countering various spoofing attacks and ensuring normal system operation. Autonomous integrity detection eliminates abnormal satellite signals, ensuring the accuracy of the calculation results for the remaining satellite signals and providing users with reliable positioning information. Comprehensive monitoring of spoofing interference and detailed recording of key information about interference events provide strong support for subsequent analysis and processing.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preventing transponder-based satellite navigation spoofing, characterized in that, include: S1, Perform preliminary multi-correlation peak detection on the signal layer of the navigation satellite signal received by the satellite navigation system to identify possible abnormal signal characteristics; S11, Perform initial acquisition processing on the intermediate frequency signal to narrow the acquisition window range; Specifically, set the search window time to 2 seconds to start the first acquisition attempt; Determine whether the peak value of the first acquisition exceeds a preset threshold. If it does not exceed the threshold, repeat the first acquisition; if it does exceed the threshold, proceed to S12; S12, Based on the code phase obtained from the first acquisition, set the search window time to 40 milliseconds and perform a second acquisition; Based on the result of the first acquisition, determine whether the peak value of the second acquisition exceeds the threshold. If it does not exceed the threshold, repeat the second acquisition; if it does exceed the threshold, proceed to S13; S13, Based on the code phase obtained from the second acquisition, offset the search starting point by 2046 chips and perform a third acquisition; S14, Analyze the results of the second and third captures; S141, If ​​the second capture is successful and the third capture is unsuccessful, and the conditions for the third capture are confirmed to be reasonable, then the second capture is considered to be a real signal, and the result is transferred to tracking processing; S142, If both the second and third captures are successful, after comparing the consistency of the two capture results, then the third capture is considered to be a real signal, and tracking processing is performed; S143, In each capture attempt, record all peak values ​​exceeding the preset threshold; S144, Count the number of peak values ​​exceeding the threshold. If multiple independent and correlated peaks exceeding the threshold are detected, it is preliminarily determined that deceptive interference exists; S2 uses the power estimation module in the receiver to estimate the power of the received navigation satellite signal and sets a reasonable power threshold. By comparing the signal power with the threshold, spoofing signals can be identified. S3 uses known constellation layout and satellite orbital parameters to establish a constellation model. Based on this, it employs two methods—time of arrival monitoring and autonomous integrity detection—to comprehensively identify and respond to relay-type deception interference. S4. Based on the combined results of arrival time monitoring and autonomous integrity detection, if both methods indicate that there is deception interference, then it is determined that there is deception. S5. If the above steps confirm the existence of deceptive interference, anti-interference measures should be initiated immediately, and key information about the interference event should be recorded in detail.

2. The method for preventing transponder-based satellite navigation spoofing as described in claim 1, characterized in that, S2, which identifies spoofing signals through signal power detection, includes: S21, The power estimation module integrates the signal over a period of time, calculates and outputs its signal power; S22, set the normal operating range to -110dBm to -133dBm, compare the calculated signal power with the normal operating range, and if the signal power exceeds the normal operating range, perform spoofing signal identification.

3. The method for preventing transponder-based satellite navigation spoofing as described in claim 2, characterized in that, S22, the deception signal identification, includes: S221, compares the current branch power with the noise power in the three-way product branch; S222, if the current branch power is higher than the noise power threshold and the signal power is greater than the normal operating range, it is determined that there is deceptive interference; S223, when the absolute power of the signal is detected to exceed the preset enhanced signal power threshold, it is considered that there is currently suppression-type deception interference; S224. Based on the detection results, a corresponding interference label is given. The anti-interference antenna can start space-time anti-interference processing according to the interference label to deal with the detected spoofing signal.

4. The method for preventing transponder-based satellite navigation spoofing as described in claim 1, characterized in that, The S3, arrival time monitoring, includes: S3A1, through simulation calculation, obtains the theoretical normal range of the relative time difference of different satellite signals arriving at the target receiver antenna; S3A2 monitors the arrival time of received satellite signals in real time and calculates the difference between the arrival time of each satellite signal and the arrival time of other satellite signals. S3A3: If the difference between the arrival time of a satellite signal and the arrival time of other satellite signals exceeds the normal range obtained from the simulation, it is preliminarily determined that the signal is subject to deceptive interference.

5. The method for preventing transponder-based satellite navigation spoofing as described in claim 1, characterized in that, In S3, the autonomous integrity detection includes: S3B1 randomly selects 4 out of the 5 received satellites to calculate their position, velocity, and time, and obtains the current position estimate of the target receiver through the calculation; S3B2, repeat the above process, perform five different combination calculations on the five satellites to obtain five position results, and compare the consistency of these five calculation results; if there are differences, it indicates that there is deception interference; S3B3 identifies and eliminates interfering satellites based on abnormal information.

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