A navigation signal simulation method based on time delay and power controllability

Abstract

The present invention discloses a navigation signal simulation method based on time delay and power controllability. The method includes: Step S1, performing position calculation on the visible satellite system based on a given receiver device to obtain the baseband observables of the visible satellite signals and the visible motion state of the given receiver device; Step S2, calculating the spoofing range Δρ based on the visible motion state of the given receiver device; Step S3, using the baseband observables of the visible satellite signals and the spoofing range Δρ as input variables to input into a mathematical simulation software for simulation to obtain a simulated spoofing signal; Step S4, inputting the spoofing signal into the given receiver device; Step S5, verifying a preset spoofing scheme by comparing the visible motion state of the given receiver device with the visible motion state in the spoofing scenario. The present invention can generate spoofing signals of different dimensions under different spoofing paths. The simulation scheme has a high degree of flexibility, is convenient, and can verify the simulation results in real time.

Description

Technical Field

[0001] The present invention relates to the field of navigation signal simulation, and specifically to a navigation signal simulation method based on controllable time delay and power. Background Art

[0002] The satellite navigation system can meet the positioning needs of users. However, satellite signals may cause abnormal positioning solutions under malicious interference. Therefore, problems related to the analysis of positioning performance in different complex scenarios are involved in the satellite navigation system. Conducting signal simulation and further positioning analysis under different scenarios has become a hot topic and a difficult point. Analyzing the positioning performance of the satellite navigation system in different scenarios through a simulator is a difficult problem in the field of navigation signal simulation.

[0003] As an inevitable malicious interference among interferences, spoofing interference has complex and changeable problems in the simulation stage and spoofing stage of spoofing signals. Therefore, generating designed interference with a certain intention through a simulator and verifying its spoofing results are currently difficult points. Summary of the Invention

[0004] The purpose of the present invention is to provide a navigation signal simulation method based on controllable time delay and power to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions to solve the problems raised in the above background art.

[0006] Design a preset spoofing scheme for the target receiver according to actual requirements, plan the movement range of the preset spoofing receiver according to the movement trajectory, and execute the preset spoofing scheme based on the designed spoofing range Δρ: Let the target receiver and the preset spoofing receiver move according to the movement trajectory. First, receive and decode the baseband observables of the visible satellites obtained by the established receiver, perform positioning calculation based on the baseband observables to obtain the movement state of the established receiver, use the movement state of the established receiver as the real signal, flexibly adjust the scheme according to power and phase, adjust the power and phase of the real signal and the spoofing signal based on the preset spoofing range Δρ, and on the simulation server, generate spoofing signals in the digital navigation satellite mathematical simulator based on the changes in the power and phase of the real signal and the spoofing signal, and complete the closed-loop simulation processing of the entire navigation and control loop.

[0007] Specifically as follows: A navigation signal simulation method based on controllable time delay and power, including:

[0008] Step S1, perform position calculation on the visible satellite system based on the established receiver device to obtain the baseband observables of the visible satellite signals and the visible movement state of the established receiver device;

[0009] Step S2: Calculate the spoofing range Δρ based on the visible motion state of the established receiver device;

[0010] Step S3: Use the baseband observables of the visible satellite signals and the spoofing range Δρ as input variables to input into mathematical simulation software for simulation to obtain spoofing signals;

[0011] Step S4: Input the spoofing signals into the established receiver device;

[0012] Step S5: Verify the preset spoofing scheme by comparing the visible motion state of the established receiver device and the visible motion state under the spoofing scenario.

[0013] Further, let the baseband observables be where PRN is the satellite number, τ is the satellite transmission delay, is the satellite transmission carrier phase, f is the Doppler frequency, and CNo is the satellite signal transmission power; let the visible motion state be [t, x, y, z, v], where [t] is the signal transmission time and [x, y, z, v] are the positioning solution coordinates of the established receiver device.

[0014] Further, set the initial visible motion state of the established receiver device to [0, 0, 0, 0, 0].

[0015] Further, in step S2, based on the positioning error δ1 of the established receiver device at different times after continuous positioning for 30S, set the spoofing error δ2, and then obtain the spoofing range Δρ by adding the spoofing error δ2 to the positioning error δ1 of the established receiver device.

[0016] Further, step S3 includes:

[0017] Step S31: The established receiver device generates a spoofing delay Δτ based on the baseband observables of the visible satellites according to the two-dimensional search method, with of the correlator spacing of the established receiver device as the search step size;

[0018] Step S32: Generate a weighted power P according to the search step size a ;

[0019] Step S33: Based on the satellite transmission delay and the weighted power P a Execute simulation according to the simulation frequency points and scenario parameters in the signal simulator at a rhythm to generate observation data and telegram data, and package them into DDS data packets and send them to the FPGA; the scenario parameters include simulation time, carrier trajectory, and ephemeris parameters;

[0020] Step S34: The DDS kernel generates digital baseband signals according to the DDS data packets issued by the mathematical simulation software;

[0021] Step S35: The DA chip converts the digital baseband signal into an analog baseband signal, and then performs up-conversion and power control through an external radio frequency module to output a simulated spoofing signal.

[0022] Further, in step S31, it includes:

[0023] Step S311: Set the correlator spacing D of a given receiver device;

[0024] Step S312: Based on the transmission delay τ of the real satellite signal, at as the search step size within the delay range, generate a spoofing delay with a step of M, and the specific spoofing delay is Or Further, step S32 includes: By adjusting the transmission delay of the spoofing signal, when it is completely synchronized with the real satellite signal, from the weighted power P a Calculate the power P of the spoofing signal through the weighting rule s , based on the power P of the spoofing signal s and the signal simulator generate a simulated spoofing signal, where P s = w a ×P a , w a is the weighting coefficient, N is the number of visible satellites, N and K are positive integers, and K < N.

[0025] Further, step S4 includes:

[0026] Step S41: Record the moment k when the spoofing signal is generated;

[0027] Step S42: Then store the visible motion state after adding the spoofing signal at different moments to obtain [t k , x k , y k , z k , v k .

[0028] Further, the method for verifying the preset spoofing scheme in step S5 includes:

[0029] Step S51: Calculate the average visible motion state [x 1 , y 1 , z 1 , v 1 based on the motion data within 30S in the interference-free scenario after the given receiver device has been continuously positioned for 30S;

[0030] Step S52: adding the visible motion state after the deception signal is added [t k ,x k ,y k ,z k ,v k ] and the average visible motion state [x 1 ,y 1 ,z 1 ,v 1 ]Perform comparative verification of preset deception schemes.

[0031] Beneficial Effects

[0032] Baseband observations based on decoded information from a given satellite navigation receiver Decode information on a given satellite navigation receiver according to the reference delay phase and reference power according to the preset step Based on [τ, CNo] in the preset deception scheme, the deception delay phase and power are adjusted to obtain the delay and power [τ+Δτ, CNo+ΔCNo] of the deception signal; wherein the Δτ and ΔCNo in the delay and power [τ+Δτ, CNo+ΔCNo] of the deception signal are generated according to the reference delay phase and reference power according to the preset step on the basis of [τ, CNo] in the decoding information of the established satellite navigation receiving device [τ+Δτ, CNo+ΔCNo]. Deception signals of different dimensions can be generated under different deception paths. The simulation scheme is highly flexible, convenient and can verify the simulation results in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the simulation method flow of the present invention.

[0034] Figure 2 It is a schematic diagram of the preset deception method in the present invention.

[0035] Figure 3 Schematic diagram of the deception simulation process.

[0036] Figure 4 This is a comparison chart of simulation positioning results with and without deceptive interference. DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example:

[0039] like Figure 1 As shown, this embodiment provides a navigation signal simulation method based on controllable delay and power, and the specific implementation method is as follows:

[0040] Step S1: Perform position solution on the visible satellite system based on a given receiver device to obtain the baseband observables of the visible satellite signals and the visible motion state of the given receiver device;

[0041] Let the baseband observables be where PRN is the satellite number, τ is the satellite transmission delay, is the satellite transmission carrier phase, f is the Doppler frequency, and CNo is the satellite signal transmission power; let the visible motion state be [t, x, y, z, v], where [t] is the signal transmission time, and [x, y, z, v] are the positioning solution coordinates of the given receiver device. Let the initial visible motion state of the given receiver device be set to [0, 0, 0, 0, 0].

[0042] Step S2: Calculate the spoofing range Δρ based on the visible motion state of the given receiver device; set the spoofing error δ2 based on the positioning error δ1 of the given receiver device at different times after continuous positioning for 30S, and then add the spoofing error δ2 to the positioning error δ1 of the given receiver device to obtain the spoofing range Δρ.

[0043] Step S3: Use the baseband observables of the visible satellite signals and the spoofing range Δv as input variables to input into a mathematical simulation software for simulation to obtain a simulated spoofing signal;

[0044] Step S31: The given receiver device generates a spoofing delay Δτ based on the baseband observables of the visible satellite according to the two-dimensional search method, with of the correlator spacing of the given receiver device as the search step size; including:

[0045] Step S311: Set the correlator spacing D of the given receiver device;

[0046] Step S312: Based on the transmission delay τ of the real satellite signal, generate a spoofing delay with a step of M within the delay range according to as the search step size. The specific spoofing delay is or Step S32: Generate a weighted power P a according to the search step size; by adjusting the transmission delay of the spoofing signal, when it is completely synchronized with the real satellite signal, the power P a of the spoofing signal is calculated by the weighted rule from the weighted power P s . Based on the power P s of the spoofing signal and the signal simulator, generate a simulated spoofing signal, where P s = w a ×P a , w a is the weighting coefficient, N is the number of visible satellites, N and K are positive integers, and K < N.

[0047] Step S33: Based on the satellite transmission delay and the weighted power P a Execute simulations according to the simulation frequency points and scenario parameters in the signal simulator at regular intervals, generate observation data and telemetry data, and package them into DDS data packets for transmission to the FPGA; the scenario parameters include simulation time, vehicle trajectory, and ephemeris parameters.

[0048] Step S34: The DDS kernel generates a digital baseband signal based on the DDS data packet sent by the mathematical simulation software.

[0049] Step S35: The DA chip converts the digital baseband signal into an analog baseband signal, and then performs upconversion and power control through an external radio frequency module to output a simulated spoofing signal.

[0050] As Figure 3 shown, taking a set of visible satellites PRN1, PRN3, PRN20, PRN22 in the GPS navigation system as an example, execute the preset spoofing scheme based on the decoding information of the established receiver device, and the established receiver user can be spoofed to the preset spoofing range Δρ.

[0051] First, based on a set of baseband observables of the visible satellite PRN3 decoded by the established receiver device the corresponding assignment results can be obtained, with a time delay of 3.4 chips and a carrier-to-noise ratio of 40 dB-Hz; in the model of the interference-free signal x a (t):

[0052]

[0053] where x a (t) is the interference-free signal, a is the true signal, g is the gth visible satellite, G represents the total number of visible satellites, A g is the signal power; D g (t) is the navigation data bit information; C g (t) represents the C / A code of the gth satellite signal; τ g is the time delay of the spreading code of the received satellite signal relative to the local C / A code; f 0 is the carrier frequency; is the initial phase of the carrier.

[0054] Based on the results of the correlator of the receiver performing coherent integration according to the established correlation interval:

[0055]

[0056] is the autocorrelation function of the C / A code of the g-th satellite signal; Δτ k+1 and Δf 0,k+1 are the code phase error and the carrier frequency error respectively; sinc is the sinc-shaped function; is the carrier of the RF signal transmission; exp is the mathematical complex function; T coh is the coherent integration time; is the carrier phase error; e is the measurement noise; P g (n) is the correlation accumulation result of the g-th satellite under a single antenna. Therefore, in the absence of synchronous interference, the correlation accumulation result of the g-th satellite under a single antenna is Pa(n):

[0057]

[0058] When the tracking loop is under spoofing attack, a mixed signal x a+s (t) containing the spoofing signal is introduced on the basis of the real satellite signal. After that, due to the introduction of the spoofing correlation result, a tracking error occurs in the tracking loop. The result of the coherent accumulation performed by the correlator of the receiver at the established correlation interval is as follows:

[0059]

[0060]

[0061] Based on the transmission delay τ g of the g-th satellite, when a spoofing delay is generated at the observation time k, a spoofing correlation accumulation component will be introduced into P g (n) at the observation time k + 1

[0062]

[0063] is the coherent accumulation component caused by synchronous spoofing interference; Similarly, the early code correlation accumulation result E g (n) and the correlation accumulation result l g (n) of the late code can be obtained;

[0064] Therefore, by generating spoofing interference within 3 / 2D of the real satellite signal, a certain interference component can be introduced into the correlation result of the real satellite signal. The discriminator of traditional receivers on the current market is designed as

[0065]

[0066] Actually, the discriminator output is the modulus value, that is

[0067] Taking P g (n)E g (n)lg (n) Substitute into the formula The discriminator output result δτ can be obtained.

[0068] When there is no interference, the output of the phase discriminator is where is the predicted value of the time delay at time k, is the time delay error at time k, is the loop error at time k. After introducing spoofing interference at the spoofing time k, when there is spoofing interference, the discriminator output is The spoofing interference introduces certain correlation components which will cause the discriminator to distort (as shown in Figure 3 ) and thus introduce a certain spoofing error c is the speed of light propagation rate, is the carrier frequency; based on the initial motion state of the established receiver device, by adjusting the transmission time delay of the spoofing signal, as the moment of complete synchronization with the real satellite signal, based on the power P of the satellite signal at the current time k a Introduce the power P of the spoofing signal through the power weighting rule s = w a ×P a ; where where the constant K decreases as the number of spoofed satellites in the actual application scenario increases, and K is less than the number of visible satellites N. Through the spoofing error Δρ generated by the simulation signal of the present invention s can approximate the preset spoofing range Δρ under ideal conditions.

[0069] Step S4, input the spoofing signal into the established receiver device; including:

[0070] Step S41: Record the time k when the spoofing signal is generated;

[0071] Step S42: Then store the visible motion state after adding the spoofing signal according to different times to obtain [t k , x k , y k , z k , v k .

[0072] As shown in Figure 2 , satellite positioning depends on four satellites. Based on the transmission time delay of the satellite signal, a positioning solution equation based on the least squares method is established to obtain the 3D position coordinates of the receiver at different times, and store them in the form of an array at different times [t, x, y, z, v]; under the condition that the number of visible satellites meets the basic positioning requirements and there is no external interference during the satellite transmission process, the positioning service can be satisfied.

[0073] Taking a visible satellite PRN3 as an example, when the transmission delay of the signal reaching the ground is controllable, the receiver can be deceived to a certain position. Therefore, based on the baseband observables of the decoded information of the established satellite navigation receiving device In the transmission delay τ and carrier power CNo, by performing designed adjustments, the user can be deceived in a controllable manner within the scope of the preset deception scheme. Through the preset deception scheme of this solution, purposeful and controllable deception can be performed on the user.

[0074] Step S5: Verify the preset deception scheme by comparing the visible motion states of the established receiver device and the visible motion states in the deception scenario. It includes:

[0075] Step S51: Calculate the average visible motion state [x 1 , y 1 , z 1 , v 1 based on the motion data within 30S in the interference-free scenario after the established receiver device has been continuously positioned for 30S;

[0076] Step S52: Compare the visible motion state [t k , x k , y k , z k , v k after adding the deception signal with the average visible motion state [x 1 , y 1 , z 1 , v 1 to verify the preset deception scheme.

[0077] Under the condition permitted by the preset spoofing scheme, the receiver user can be spoofed to a preset target range according to the preset spoofing scheme. When the receiver and the spoofing signal source are fixed in real-time solution, the interference-free signal and the mixed signal with interference are respectively sent into the receiver, and the root mean square errors δ1 and δ2 are respectively obtained by statistically analyzing the positioning errors in the two positioning scenarios; when the spoofing source is certain, based on the preset spoofing scheme, the position solution of the spoofing information is performed based on the simulated spoofing signal. By comparing with the positioning result of the interference-free signal and the position of the spoofing source, it is found that based on the preset spoofing scheme, the interference-free signal can be adjusted by adjusting the transmission delay and power of the real satellite signal, and the established receiver device can be spoofed to within a certain preset spoofing range Δρ based on the position information coordinates [x, y, z, v] of the established receiver device, and the tentative coordinates are [x + Δx, y + Δy, z + Δz, v + Δv]; by comparing and analyzing the positioning results in the above real positioning scenario and the preset spoofing scenario, the spoofing result under certain spoofing conditions can be obtained. This positioning result based on the preset spoofing scenario is predictable and controllable.

[0078] As Figure 4 shown, the three-dimensional positioning solution result of the established receiver device user is position A: [205, 306, 160, 0.6]; the baseband observables of the relevant visible satellites are read through the signal simulator, and the preset spoofing scheme is implemented within a range of 300 m around the positioning solution position [205, 306, 160, 0.6] of the established receiver device. Based on the relevant interval D of the correlator in the established receiver device on the basis of the transmission delay τ of the real satellite signal step size to adjust the transmission delay and cyclically adjust the weighted power coefficient w of the spoofing signal according to the transmission delay a , adjust w according to the continuously decreasing weighting method based on the number of visible satellites N a , through the weighted power P a multiply w a to obtain the spoofing signal power P s , according to the preset position of the preset spoofing scheme, increase the transmission delay and spoofing power of the spoofing signal on the basis of the established real satellite signal to obtain a preset spoofing signal; in the simulator, according to the frequency of the GPS system and the spoofing observables of the spoofing signal, the spoofing signal is obtained according to the modulation method of the GPS signal in the signal simulator.

[0079] As Figure 4As shown, the spoofing signal obtained according to the preset spoofing scheme is sent into the receiver device, and based on the state [205, 306, 160, 0.6] of the established receiver device, a spoofing signal is simulated through a preset spoofing range Δρ of 50 m, and a positioning solution result [205, 306, 200, 0.6] with the preset spoofing signal added is obtained. By comparing the above positioning results, it can be obtained that in the preset spoofing scheme, the established receiver user can be spoofed to the preset spoofing position.

[0080]

[0081] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A navigation signal simulation method based on controllable delay and power, characterized in that , including the following steps: Step S1: Based on a given receiver device, a position solution is performed on the visible satellite system to obtain a baseband observation of the visible satellite signal and a visible motion state of the given receiver device; assuming that the baseband observation is Among them, PRN is the satellite number, τ is the satellite transmission delay, is the satellite transmission carrier phase, f is the Doppler frequency, and CNo is the satellite signal transmission power; let the visible motion state be [t, x, y, z, v], where [t] is the signal transmission time, and [x, y, z, v] is the positioning solution coordinate of the given receiver device; Set the initial visible motion state of the given receiver device to [0,0,0,0,0]; Step S2, calculating the deception range Δρ based on the visible motion state of the established receiver device; setting the deception error δ2 based on the positioning error δ1 at different times after the established receiver device is continuously positioned for 30S, and then adding the deception error δ2 to the positioning error δ1 of the established receiver device to obtain the deception range Δρ; Step S3, inputting the baseband observation amount of the visible satellite signal and the deception range Δρ as input variables into mathematical simulation software, performing simulation, and obtaining a simulated deception signal, including: Step S31: The predetermined receiver device searches for the baseband observations of the visible satellites in a two-dimensional manner with the predetermined receiver device correlator spacing. Generate a deceptive delay Δτ for the search step, including: Step S311, setting the correlator spacing D of the predetermined receiver device; Step S312: Based on the transmission delay τ of the real satellite signal, The search step is A deceptive delay with a step of M is generated within the delay range. The specific deceptive delay is or Step S32: Generate a weighted power P according to the search step length a ,include: By adjusting the transmission delay of the spoofed signal, when it is completely synchronized with the real satellite signal, the weighted power P a The power P of the deceptive signal is calculated by the weighted rule s , based on the power P of the spoofing signal s The signal simulator generates a simulated spoof signal, where P s =w a ×P a ,w a is the weighting coefficient, N is the number of visible satellites, N and K are positive integers, and K <N; Step S33: based on the satellite transmission delay and weighted power P a According to the simulation frequency and scenario parameters in the signal simulator, the simulation is performed in beats to generate observation data and telegram data, and packaged into DDS data packets and sent to the FPGA; the scenario parameters include simulation time, carrier trajectory, and ephemeris parameters; Step S34, the DDS kernel generates a digital baseband signal according to the DDS data packet sent by the mathematical simulation software; Step S35, the DA chip converts the digital baseband signal into an analog baseband signal, and then performs up-conversion and power control through an external RF module to output a simulated spoofing signal; Step S4, inputting the spoof signal into a predetermined receiver device, comprising: Step S41: Record the time k when the spoofing signal is generated; Step S42: The visible motion state after adding the deceptive signal is stored at different times to obtain [t k ,x k ,y k ,z k ,v k ]; Step S5, verifying the preset deception scheme by comparing the visual motion state of the established receiver device with the visual motion state in the deception scenario, including: Step S51: Calculate the average visible motion state [x1, y1, z1, v1] based on the motion data within 30 seconds in an interference-free scenario after the established receiver device continuously locates for 30 seconds; Step S52: adding the visible motion state after the deception signal is added [t k ,x k ,y k ,z k ,v k ] and the average visible motion state [x1,y1,z1,v1] performs comparison and verification of the preset deception scheme.

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