Deception Jamming Recognition Method and System Based on Auxiliary of Airport-Approaching Aircraft

Abstract

A method and system for identifying spoofing jamming based on the assistance of an airspace vehicle, the method comprising: directly obtaining a signal to be identified, and obtaining a first pseudorange between the ground anti-jamming navigation receiver and the GNSS satellite by analyzing the signal to be identified; directly obtaining a navigation enhancement signal broadcast by the airspace vehicle, and obtaining a second pseudorange between the ground anti-jamming navigation receiver (3) and the GNSS satellite (1) by analyzing the navigation enhancement signal; calculating a difference between the first pseudorange and the second pseudorange; when the difference is less than a preset difference threshold, determining that the signal to be identified is a navigation signal of the GNSS satellite (1), and when the difference is greater than or equal to the difference threshold, determining that the signal to be identified is a spoofing jamming signal of the interference source.

Description

Technical Field

[0001] The present invention relates to the field of navigation anti-interference, and particularly to a spoofing interference recognition method and system based on an airship-assisted navigation. Background Art

[0002] With the gradual construction of the global satellite navigation system and the rapid development of navigation and positioning technologies, the accuracy of satellite navigation and positioning is becoming increasingly precise, and satellite navigation services will play a more important role in society and daily life. However, inevitably, during the propagation of satellite navigation signals, the navigation signals received by ground navigation receivers are always subject to intentional or unintentional interference, resulting in incorrect positioning results of the receivers. Therefore, the secure application of satellite navigation systems has gradually attracted the attention of the general public.

[0003] The artificial interference received by satellite navigation signals is divided into two categories: jamming interference and spoofing interference. Jamming interference mainly affects the normal reception of real signals by receiving devices by transmitting high-power noise interference signals to submerge the real target signals, such as by transmitting electromagnetic noise with a signal power stronger than the navigation signal. Currently, significant results have been achieved for jamming interference, and technologies such as adaptive space-time filtering and array antennas can be used to suppress it. Spoofing interference is relatively more complex and difficult to eliminate than jamming interference. Spoofing interference creates false signals deliberately, which are similar in structure to real navigation signals, enabling receivers to capture spoofing signals unconsciously, thereby achieving a spoofing effect. According to the generation method of spoofing interference signals, it can be divided into repeat-back spoofing interference, generated spoofing interference, and hybrid spoofing interference that utilizes both methods simultaneously, and the form of its interference signals is the same as or similar to GNSS signals.

[0004] After a GNSS receiver receives a spoofing interference signal, it will obtain incorrect satellite position information and incorrect pseudorange information, thereby calculating a positioning result with a large error. The key to suppressing spoofing interference lies in identifying whether the received signal is a spoofing interference signal. If a certain signal in the receiver is identified as a spoofing interference signal, the receiver can directly eliminate it. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, in response to the need for spoofing interference recognition technology in navigation electronic countermeasure warfare, and in combination with the advantages of overflight aircraft, the present invention uses overflight aircraft to broadcast navigation enhancement signals to assist in realizing GNSS spoofing interference recognition. On the one hand, the ground anti-jamming navigation receiver directly receives GNSS signals and obtains the first pseudorange through acquisition, tracking, synchronization, decoding, etc. On the other hand, the ground anti-jamming navigation receiver can preliminarily determine its approximate position by receiving the navigation enhancement signal from the overflight aircraft and measuring the direction-of-arrival information of the navigation enhancement signal at the same time, and can estimate the approximate positions of visible GNSS satellites according to the GNSS message relayed by the overflight aircraft. The second pseudorange is calculated based on the position of the ground terminal and the position of the GNSS. Compare the first pseudorange with the second pseudorange. If the difference between the first pseudorange and the second pseudorange exceeds a preset threshold, it is considered that the directly received GNSS satellite signal is an interference signal and can be directly eliminated; otherwise, it is considered a real GNSS signal.

[0006] The object of the present invention is achieved through the following technical solutions:

[0007] A spoofing interference recognition method based on overflight aircraft assistance provided by an embodiment of the present invention includes the steps of:

[0008] Obtain the signal to be recognized; wherein, the signal to be recognized includes the navigation signal of GNSS satellites directly obtained by the ground anti-jamming navigation receiver or the interference signal of the interference source directly obtained by the ground anti-jamming navigation receiver;

[0009] Obtain the navigation enhancement signal of the overflight aircraft, where the overflight aircraft is not interfered by the interference source or can eliminate the interference of the interference source;

[0010] Analyze the signal to be recognized to obtain the first pseudorange between the ground anti-jamming navigation receiver and the GNSS satellite;

[0011] Analyze the navigation enhancement signal to obtain the second pseudorange between the ground anti-jamming navigation receiver and the GNSS satellite;

[0012] Calculate the difference between the first pseudorange and the second pseudorange; and

[0013] When the difference is less than the preset difference threshold, determine that the signal to be recognized is the navigation signal of the GNSS satellite.

[0014] In one embodiment, the GNSS satellite includes any one of the four satellite navigation constellations of GPS, BDS, GLONASS, and GALILEO.

[0015] In one embodiment, the navigation enhancement signal uses quadrature phase shift keying modulation, and the signal format of the navigation enhancement signal is expressed as:

[0016]

[0017] where P is the transmission signal power of the aerial vehicle, C I (t) and C Q (t) are the spread spectrum codes for ranging modulated on the I and Q branches respectively, D I (t) and D Q (t) are the navigation messages modulated on the I and Q branches respectively, D I (t) includes the position and clock error of the aerial vehicle, D Q (t) includes forwarding the navigation message of the GNSS satellite, f 0 represents the carrier frequency of the navigation enhancement signal of the aerial vehicle, and t represents the time variable.

[0018] In one embodiment, parsing the signal to be recognized to obtain the first pseudorange includes:

[0019] Obtaining the reception time of the signal to be recognized;

[0020] Obtaining the code phase of the signal to be recognized by acquisition and tracking;

[0021] Obtaining the navigation message of the signal to be recognized by synchronization and decoding; wherein, the navigation message of the signal to be recognized includes information for positioning such as time information, GNSS satellite orbit parameters, ionospheric delay, etc., and the position and clock error of the GNSS satellite can be obtained through the navigation message of the signal to be recognized.

[0022] Obtaining the transmission time of the signal to be recognized according to the code phase of the signal to be recognized; and

[0023] Obtaining the first pseudorange according to the reception time of the signal to be recognized, the clock error of the ground anti-jamming navigation receiver, the transmission time of the signal to be recognized, and the clock error of the GNSS satellite.

[0024] In one embodiment, parsing the navigation enhancement signal to obtain the second pseudorange includes:

[0025] Parsing the navigation enhancement signal to obtain the position of the aerial vehicle and the third pseudorange between the ground anti-jamming navigation receiver and the aerial vehicle;

[0026] Adopting a DOA estimation algorithm to obtain the direction of arrival of the navigation enhancement signal;

[0027] Obtaining the position of the ground anti-jamming navigation receiver according to the direction of arrival of the navigation enhancement signal, the position of the aerial vehicle, and the third pseudorange between the ground anti-jamming navigation receiver and the aerial vehicle.

[0028] Estimate the position of the GNSS satellite according to the navigation message of the GNSS satellite being relayed; and

[0029] Calculate the second pseudorange according to the position of the ground anti-jamming navigation receiver and the position of the GNSS satellite.

[0030] In one embodiment, obtaining the direction of arrival of the navigation enhancement signal by using the DOA estimation algorithm includes: obtaining the direction of arrival of the navigation enhancement signal by using the Multiple Signal Classification algorithm (MUSIC algorithm), where the direction of arrival of the navigation enhancement signal includes the elevation angle θ and the azimuth angle of the navigation enhancement signal

[0031] In one embodiment, the calculation method of the position of the aerial vehicle and the third pseudorange between the ground anti-jamming navigation receiver and the aerial vehicle includes:

[0032] Obtain the reception time of the navigation enhancement signal;

[0033] Capture and track to obtain the code phase of the navigation enhancement signal;

[0034] Synchronize and decode to obtain the navigation message of the navigation enhancement signal; wherein, the message of the navigation enhancement signal includes the position and clock offset of the aerial vehicle, and the navigation message of the GNSS satellite being relayed;

[0035] Obtain the transmission time of the navigation enhancement signal according to the code phase of the navigation enhancement signal; and

[0036] Obtain the third pseudorange according to the reception time of the navigation enhancement signal, the clock offset of the ground anti-jamming navigation receiver, the transmission time of the navigation enhancement signal, and the clock offset of the aerial vehicle.

[0037] In one embodiment, the jamming source is set within a set range of the ground anti-jamming navigation receiver, and the jamming source is used to generate spoofing interference signals.

[0038] A spoofing interference identification system based on aerial vehicle assistance provided by an embodiment of the present invention includes: a GNSS satellite, an aerial vehicle, and a ground anti-jamming navigation receiver that are communicatively connected to each other; wherein, the ground anti-jamming navigation receiver is configured to perform the following steps:

[0039] Obtain a signal to be identified; wherein, the signal to be identified includes the navigation signal of the GNSS satellite directly obtained by the ground anti-jamming navigation receiver or the interference signal of the jamming source directly obtained by the ground anti-jamming navigation receiver;

[0040] Obtain the navigation enhancement signal of the aerial vehicle, where the aerial vehicle is not interfered by the interference source or can eliminate the interference of the interference source;

[0041] Analyze the signal to be recognized to obtain the first pseudorange between the ground anti-jamming navigation receiver and the GNSS satellite;

[0042] Analyze the navigation enhancement signal to obtain the second pseudorange between the ground anti-jamming navigation receiver and the GNSS satellite;

[0043] Calculate the difference between the first pseudorange and the second pseudorange; and

[0044] When the difference is less than a preset difference threshold, determine that the signal to be recognized is the navigation signal of the GNSS satellite. Brief Description of the Drawings

[0045] Figure 1 The figure shows a flowchart of a spoofing interference recognition method based on an aerial vehicle assistant provided by an embodiment of the present invention.

[0046] Figure 2 The figure shows a flowchart of a method for directly receiving GNSS satellite signals to obtain the first pseudorange provided by an embodiment of the present invention.

[0047] Figure 3 The figure shows a flowchart of a method for obtaining the second pseudorange based on an aerial vehicle assistant provided by an embodiment of the present invention.

[0048] Figure 4 The figure shows a schematic diagram of a method for obtaining the position of the ground anti-jamming navigation receiver (3) provided by an embodiment of the present invention.

[0049] Figure 5 The figure shows a flowchart of a method for directly receiving a navigation enhancement signal to obtain the third pseudorange provided by an embodiment of the present invention.

[0050] Figure 6 The figure shows a flowchart of a DOA estimation method based on a two-dimensional MUSIC algorithm provided by an embodiment of the present invention.

[0051] Figure 7 The figure shows a schematic diagram of a spoofing interference recognition system based on an aerial vehicle assistant provided by an embodiment of the present invention. Detailed Embodiments

[0052] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will further describe the embodiments of the present invention in detail with reference to the accompanying drawings.

[0053] A method for identifying spoofing jamming assisted by an over-air vehicle, the method comprising: directly obtaining a signal to be identified, and obtaining a first pseudo-range between the ground anti-jamming navigation receiver and the GNSS satellite by parsing the signal to be identified; directly obtaining a navigation enhancement signal broadcast by the over-air vehicle, and obtaining a second pseudo-range between the ground anti-jamming navigation receiver 3 and the GNSS satellite 1 by parsing the navigation enhancement signal; calculating a difference between the first pseudo-range and the second pseudo-range; when the difference is less than a preset difference threshold, determining that the signal to be identified is a navigation signal of the GNSS satellite 1, and when the difference is greater than or equal to the difference threshold, determining that the signal to be identified is a spoofing jamming signal of the interference source.

[0054] Figure 1 The following shows a flowchart of the method for identifying spoofing jamming assisted by an over-air vehicle provided by an embodiment of the present application. As Figure 1 shown, the method includes the following steps:

[0055] Step 100: Obtain a signal to be identified.

[0056] The signal to be identified includes a navigation signal of the GNSS satellite 1 directly obtained by the ground anti-jamming navigation receiver 3 or an interference signal of the interference source 4 directly obtained by the ground anti-jamming navigation receiver 3;

[0057] The GNSS satellite 1 includes any one of the four satellite navigation constellations of GPS, BDS, GLONASS, and GALILEO. The navigation signal transmitted by the GNSS satellite 1 is structurally divided into three levels: carrier wave, pseudo-code, and data code (i.e., navigation message). The pseudo-code is periodic and has good autocorrelation and cross-correlation performance. Since the pseudo-code is also used as a ranging code in GNSS, it is also called a ranging code. The code phase information refers to the phase information of the pseudo-code modulated on the navigation signal. The data code is a binary code carrying the navigation message in the GNSS navigation signal. The navigation receiver demodulates the carrier wave and despreads the pseudo-code of the received navigation signal to obtain the data code, and then finally compiles the data code into a navigation message according to the format of the navigation message. The GNSS navigation message contains important information for positioning such as time information, GNSS satellite orbit parameters, and ionospheric delay.

[0058] Since the signals transmitted by GNSS satellites are high-frequency signals, and currently available signal processing devices cannot directly process high-frequency signals, in the embodiments of the present application, after receiving the high-frequency signals of GNSS navigation satellites, the high-frequency signals are converted into baseband signals to meet the requirements of signal processing. It should be understood that the embodiments of the present application may select different methods to obtain navigation signals according to the needs of actual application scenarios. For example, high-frequency navigation signals may be obtained through a third-party device, or high-frequency navigation signals may be obtained by a third-party device and converted into directly processable baseband signals, and then the navigation signals are directly sent to a signal processing device (such as the above-mentioned ground anti-jamming navigation receiver, etc.). As long as the signal processing device can obtain available navigation signals, the specific methods for obtaining navigation signals in the embodiments of the present application are not limited.

[0059] Step 110: Obtain the navigation enhancement signal of the aerial vehicle.

[0060] The aerial vehicle 2 broadcasts the navigation enhancement signal, which is not interfered by the interference source 4. The navigation enhancement signal uses quadrature phase shift keying modulation, and the signal format of the navigation enhancement signal is expressed as:

[0061]

[0062] where P is the transmission signal power of the aerial vehicle 2, C I (t) and C Q (t) are the spreading codes for ranging modulated on the I and Q branches respectively, D I (t) and D Q (t) are the navigation messages modulated on the I and Q branches respectively, D I (t) includes the position and clock error of the aerial vehicle 2, D Q (t) includes the navigation message of the GNSS satellite 1 being relayed, f 0 represents the carrier frequency of the navigation enhancement signal of the aerial vehicle, and t represents the time variable.

[0063] Step 120: Analyze the signal to be recognized to obtain the first pseudo-range between the ground anti-jamming navigation receiver and the GNSS satellite.

[0064] The ground anti-jamming navigation receiver directly receives the signal to be recognized, and through signal processing of the signal to be recognized, the first pseudo-range between the ground anti-jamming navigation receiver 3 and the GNSS satellite is obtained.

[0065] Step 130: Analyze the navigation enhancement signal to obtain the second pseudo-range between the ground anti-jamming navigation receiver (3) and the GNSS satellite.

[0066] The ground anti-jamming navigation receiver directly receives the navigation enhancement signal, obtains the forwarded GNSS navigation message by performing signal processing on the navigation enhancement signal, and obtains the second pseudo-range between the ground anti-jamming navigation receiver 3 and the GNSS satellite with the assistance of the forwarded GNSS navigation message.

[0067] Step 140: Calculate the difference between the first pseudo-range and the second pseudo-range.

[0068] Calculate the difference between the first pseudo-range and the second pseudo-range; the second pseudo-range is obtained with the assistance of the aerial vehicle 2, and the aerial vehicle 2 is not interfered by the interference source 4 or has eliminated the interference of the interference source 4. Therefore, the second pseudo-range has high reliability, and the second pseudo-range can be used as a reference standard for the first pseudo-range, and the first pseudo-range is compared with the second pseudo-range by differential.

[0069] Step 150: When the difference is less than a preset difference threshold, determine that the signal to be identified is the navigation signal of the GNSS satellite.

[0070] Preset a difference threshold, compare the difference between the first pseudo-range and the second pseudo-range with the preset difference threshold. When the difference is less than the preset difference threshold, determine that the signal to be identified is the navigation signal of the GNSS satellite 1.

[0071] In some embodiments, as Figure 2 shown, step 120 may include the following sub-steps:

[0072] Step 121: Obtain the reception time of the signal to be identified;

[0073] The ground anti-jamming navigation receiver 3 obtains the signal to be identified, and reads the reception time of the signal to be identified according to the clock of the ground anti-jamming navigation receiver 3, which is the reception time of the signal to be identified; there will be a clock difference between the clock of the ground anti-jamming navigation receiver 3 and the standard time, which is the clock difference of the ground anti-jamming navigation receiver 3.

[0074] In some embodiments, the standard time is GPS time, BDS time, UTC time, etc.

[0075] Step 122: Obtain the code phase of the signal to be identified;

[0076] The ground anti-jamming navigation receiver 3 obtains the code phase of the signal to be identified after capturing and tracking the signal to be identified.

[0077] The code phase of the signal to be recognized refers to the position of the latest received piece of pseudo-code in a full cycle of pseudo-code. Its value is between 0 and L1, and is usually not an integer, where L1 is the number of chips in a full cycle of pseudo-code.

[0078] Step 123: Obtain the navigation message of the signal to be recognized

[0079] Obtain the navigation message of the signal to be recognized through synchronization and decoding; wherein, the navigation message of the signal to be recognized includes information for positioning such as time information, GNSS satellite orbit parameters, ionospheric delay, etc. The position and clock offset of the GNSS satellite can be obtained through the navigation message of the signal to be recognized.

[0080] The navigation message of the signal to be recognized is arranged in a data stream in the form of frames and sub-frames. Each satellite sends the navigation message frame by frame, and when sending each frame of the message, the satellite sends it in the form of sub-frames one after another.

[0081] In some embodiments, the navigation message of the signal to be recognized consists of several frames, each frame consists of several sub-frames, each sub-frame consists of several words, each word consists of several bits, and each bit corresponds to several pseudo-code cycles.

[0082] Step 124: Obtain the transmission time of the signal to be recognized

[0083] Obtain the transmission time of the signal to be recognized according to the code phase of the signal to be recognized. The calculation formula is as follows:

[0084] t (s)＝ TOW1+(N1*w1+b1)×T b1 +(code_cycle1+code_ph1 / code_chip1)×T code_cycle1

[0085] Where t (s) is the transmission time of the signal to be recognized, in seconds, TOW1 is the time within a week in seconds in each sub-frame, w1 is the number of words in the complete navigation message data code received in the current sub-frame, N1 is the number of bits in each word, b1 is the number of bits received in the current word, code_cycle1 is the number of full-week messages received in the current bit, code_ph1 is the current code phase, code_chip1 is the number of chips in a code cycle, T b1 is the length of each bit, in seconds, T code_cycle1 is the length of each code week, in seconds.

[0086] Step 125: Obtain the first pseudo-range

[0087] Based on the reception time of the signal to be recognized, the clock error of the ground anti-jamming navigation receiver 3, the transmission time of the signal to be recognized, and the clock error of the GNSS satellite 1, the first pseudo-range is obtained.

[0088] ρ 1 = c * [(t u1 + δ tu ) - (t (s) + δ ts )]

[0089] where c is the speed of light, t u1 is the reception time of the signal to be recognized, δ tu is the clock error of the ground anti-jamming navigation receiver 3, t (s) is the transmission time of the signal to be recognized, and δ ts is the clock error of the GNSS satellite 1.

[0090] In some embodiments, as Figure 3 shown, step 130 may include the following sub-steps:

[0091] Step 131: Obtain the position of the near-space aircraft 2 and the third pseudo-range

[0092] The ground anti-jamming navigation receiver 3 obtains the navigation enhancement signal, performs signal processing on the navigation enhancement signal, and obtains the position of the near-space aircraft 2 and the third pseudo-range between the ground anti-jamming navigation receiver 3 and the near-space aircraft 2;

[0093] Step 132: Obtain the direction of arrival of the navigation enhancement signal

[0094] The direction of arrival of the navigation enhancement signal is obtained by using a DOA estimation algorithm. The direction of arrival of the navigation enhancement signal includes the elevation angle θ and the azimuth angle of the navigation enhancement signal

[0095] Since the power of the navigation enhancement signal is relatively high, the direction of arrival information of the signal can be measured by using a DOA estimation algorithm through an array antenna. The DOA estimation can estimate the elevation angle θ and the azimuth angle of the signal arrival direction based on the characteristic that the radiation energy of the navigation enhancement signal in the space is the largest under the condition of known array manifold

[0096] Step 133: Obtain the position of the ground anti-jamming navigation receiver 3

[0097] Based on the elevation angle θ and the azimuth angle of the navigation enhancement signal The position of the aerial vehicle 2 and the third pseudorange between the ground anti-jamming navigation receiver 3 and the aerial vehicle 2 are obtained to acquire the position of the ground anti-jamming navigation receiver 3;

[0098] In one embodiment, as Figure 4 shown, the following relational expression is obtained according to the spatial geometric relationship:

[0099]

[0100]

[0101] d·cosθ = z 1 -z 2

[0102] In the formula, (x 1 , y 1 , z 1 ) are the position coordinates of the aerial vehicle 2 in a certain coordinate system, d is the third pseudorange, and θ is the elevation angle and azimuth angle of the navigation enhancement signal where the elevation angle θ is the angle between the navigation enhancement signal and the Z-axis, and its value range is 0 to 90 0 , and the azimuth angle is the angle between the projection of the navigation enhancement signal on the XY plane and the X-axis, and its value range is 0 to 360 0 .

[0103] The position (x 2 , y 2 , z 2 ) of the ground anti-jamming navigation receiver (3) can be calculated and obtained

[0104]

[0105]

[0106] z 2 = z 1 -d·cos θ

[0107] Step 134: Obtain the position of the GNSS satellite 1

[0108] According to the navigation message relayed by the GNSS satellite 1, the position (x s , y s , z s ) of the GNSS satellite 1 is estimated;

[0109] Step 135: Obtain the second pseudorange

[0110] The second pseudorange is calculated based on the position of the ground anti-jamming navigation receiver 3 and the position of the GNSS satellite 1.

[0111]

[0112] where Δt is the pseudorange deviation caused by ionospheric delay, tropospheric delay, and the clock error of the GNSS satellite 1. The ionospheric delay, tropospheric delay, and the clock error of the GNSS satellite 1 are corrected using an ionospheric model, a tropospheric model, and a satellite clock error model respectively to obtain the second pseudorange. Where, (x s (t), y s (t), z s (t)) is the position of the GNSS satellite 1 at time t, and (x 2 (t), y 2 (t), z 2 (t)) is the position of the ground anti-jamming navigation receiver 3 at time t.

[0113] In some embodiments, as Figure 5 shown, step 131 may include the following sub-steps:

[0114] Step 501: Obtain the reception time of the navigation enhancement signal;

[0115] The ground anti-jamming navigation receiver 3 obtains the navigation enhancement signal, and reads the reception time of the navigation enhancement signal according to the clock of the ground anti-jamming navigation receiver 3, which is the reception time of the navigation enhancement signal; there will be a clock error between the clock of the ground anti-jamming navigation receiver 3 and the standard time, which is the clock error of the ground anti-jamming navigation receiver 3;

[0116] In some embodiments, the standard time is GPS time, BDS time, UTC time, etc.

[0117] Step 502: Obtain the code phase of the navigation enhancement signal;

[0118] The ground anti-jamming navigation receiver 3 obtains the code phase of the navigation enhancement signal after capturing and tracking the navigation enhancement signal;

[0119] The code phase of the navigation enhancement signal refers to the position of the latest received momentary pseudocode in a whole cycle of pseudocode, and its value is between 0 and L2, and is usually not an integer, where L2 is the number of chips contained in a whole cycle of pseudocode.

[0120] Step 503: Obtain the navigation message of the navigation enhancement signal

[0121] Synchronize and decode to obtain the navigation message of the navigation enhancement signal; wherein, the navigation message of the navigation enhancement signal includes information for positioning such as time information, GNSS satellite orbit parameters, ionospheric delay, etc. The position and clock offset of the over-air vehicle 2, as well as the navigation message of the GNSS satellite 1 being relayed, can be obtained through the navigation message of the navigation enhancement signal.

[0122] The navigation message of the navigation enhancement signal is arranged as a data stream in the structure of frames and sub-frames. Each satellite sends the navigation message frame by frame, and when sending each frame of the message, the satellite sends it sub-frame by sub-frame.

[0123] In some embodiments, the navigation message of the navigation enhancement signal consists of several frames, each frame consists of several sub-frames, each sub-frame consists of several words, each word consists of several bits, and each bit corresponds to several pseudo-code periods.

[0124] Step 504: Obtain the transmission time of the navigation enhancement signal

[0125] Obtain the transmission time of the navigation enhancement signal based on the code phase of the navigation enhancement signal. The calculation formula is as follows:

[0126] t (A) = TOW2 + (N2 * w2 + b2) × T b2 + (code_cycle2 + code_ph2 / code_chip2) × T code_cycle2

[0127] where t (A) is the transmission time of the navigation enhancement signal, in seconds, TOW2 is the time within a week in seconds in each sub-frame, w2 is the number of words in the complete navigation message data code received in the current sub-frame, N2 is the number of bits contained in each word, b2 is the number of bits received in the current word, code_cycle2 is the number of full-week messages received in the current bit, code_phase2 is the current code phase, code_chip2 is the number of chips contained in one code period, T b2 is the length of each bit, in seconds, T code_cycle2 is the length of each code week, in seconds.

[0128] Step 505: Obtain the third pseudo-range

[0129] Obtain the third pseudo-range based on the reception time of the navigation enhancement signal, the clock offset of the ground anti-jamming navigation receiver 3, the transmission time of the navigation enhancement signal, and the clock offset of the over-air vehicle 2.

[0130] d = c * [(tu2 +δ tu )-(t (A) +δ tA )]

[0131] where d represents the third pseudo-range, c is the speed of light, t u2 is the reception time of the navigation enhancement signal, δ tu is the clock error of the ground anti-jamming navigation receiver 3, t (A) is the transmission time of the navigation enhancement signal, δ tA is the clock error of the aerial vehicle 2.

[0132] In some embodiments, the two-dimensional MUSIC algorithm is used for DOA estimation to obtain the direction of arrival of the navigation enhancement signal, including the elevation angle θ and azimuth angle of the navigation enhancement signal As Figure 6 shown, step 132 may include the following sub-steps:

[0133] Step 601: Calculate the covariance matrix

[0134] In one embodiment, an array antenna is used to receive the incident signal, the incident signal includes the navigation enhancement signal, the number of array elements of the array antenna is M, and the number of signal sources is N. Then the signal expression received by M array elements is:

[0135] X 1 = AS + N

[0136] where S is the received signal, N is the received noise, and A is the steering vector of M×N dimensions.

[0137] The covariance matrix is:

[0138] R xx = X 1 X 1 H / L

[0139] where L is the number of snapshots.

[0140] Step 602: Perform eigenvalue decomposition on the covariance matrix to obtain eigenvalues and eigenvectors respectively.

[0141] Step 603: Set a threshold, compare the eigenvalues with the threshold, and determine the number of incident signals based on the number of eigenvalues greater than the threshold;

[0142] Step 604: Construct the noise subspace according to the eigenvectors, and obtain the spatial spectrum function according to the steering vector and the noise subspace;

[0143] Step 605: Perform two-dimensional peak search on the spatial spectrum function. According to the positions of the maximum points, the pitch angle θ and azimuth angle of the signal can be estimated.

[0144] Figure 7 The figure shows a schematic diagram of a spoofing interference recognition system based on an over-air vehicle assistance provided by an embodiment of the present application. As Figure 7 shown, the system includes the following components:

[0145] GNSS satellite 701: It includes any one of the four satellite navigation constellations of GPS, BDS, GLONASS, and GALILEO, and broadcasts GNSS satellite navigation signals.

[0146] Over-air vehicle 702: Receives and processes GNSS satellite 701, modulates the GNSS satellite navigation message together with its own position, time, motion speed and other parameters onto the navigation enhancement signal, and broadcasts it to the ground anti-jamming navigation receiver 703. The signal power of the navigation enhancement signal is 15 dB to 20 dB higher than that of the GNSS satellite navigation signal; the over-air vehicle 2 is not interfered by the interference source 4 or can eliminate the interference of the interference source 4.

[0147] Ground anti-jamming navigation receiver 703: Receives and processes the GNSS satellite navigation signal broadcast by GNSS satellite 701 and the navigation enhancement signal, and uses the assistance of the over-air vehicle 702 to complete the recognition of spoofing interference signals.

[0148] Interference source 704: Broadcasts spoofing interference signals of GNSS satellite navigation signals to the ground anti-jamming navigation receiver 703 to interfere with it.

[0149] The content not detailed in the specification of the present invention belongs to the well-known technology of those skilled in the art.

[0150] Although the present invention has been disclosed above with preferred embodiments, it is not used to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and decorations made to the above embodiments according to the technical essence of the present invention without departing from the technical solution of the present invention all belong to the protection scope of the technical solution of the present invention.

Claims

1. A method for identifying deceptive jamming assisted by an airspace vehicle, characterized in that, it includes the following steps: Obtain the signal to be identified; wherein, the signal to be identified includes the navigation signal of the GNSS satellite (1) directly obtained by the ground anti-jamming navigation receiver (3) or the interference signal of the interference source (4) directly obtained by the ground anti-jamming navigation receiver (3); Obtain the navigation enhancement signal of the airspace vehicle (2), wherein the airspace vehicle (2) is not interfered by the interference source (4) or can eliminate the interference of the interference source (4); Analyze the signal to be identified to obtain the first pseudorange between the ground anti-jamming navigation receiver (3) and the GNSS satellite (1); Analyze the navigation enhancement signal to obtain the second pseudorange between the ground anti-jamming navigation receiver (3) and the GNSS satellite (1), including: Analyze the navigation enhancement signal to obtain the position of the airspace vehicle (2) and the third pseudorange between the ground anti-jamming navigation receiver (3) and the airspace vehicle (2); Adopt the DOA estimation algorithm to obtain the direction of arrival of the navigation enhancement signal; According to the direction of arrival of the navigation enhancement signal, the position of the airspace vehicle (2), and the third pseudorange between the ground anti-jamming navigation receiver (3) and the airspace vehicle (2), obtain the position of the ground anti-jamming navigation receiver (3); Estimate the position of the GNSS satellite (1) according to the navigation message relayed by the GNSS satellite (1); Calculate the second pseudorange according to the position of the ground anti-jamming navigation receiver (3) and the position of the GNSS satellite (1); Calculate the difference between the first pseudorange and the second pseudorange; When the difference is less than a preset difference threshold, determine that the signal to be identified is the navigation signal of the GNSS satellite (1).

2. The method for identifying deceptive jamming assisted by an airspace vehicle according to claim 1, characterized in that, it further includes: When the difference is greater than or equal to the difference threshold, determine that the signal to be identified is the interference signal of the interference source (4).

3. The method for identifying deceptive jamming assisted by an airspace vehicle according to claim 1, characterized in that, the GNSS satellite (1) includes any one of the four satellite navigation constellations of GPS, BDS, GLONASS, and GALILEO.

4. The method for identifying deceptive jamming assisted by an airspace vehicle according to claim 1, characterized in that, the navigation enhancement signal adopts quadrature phase shift keying modulation, and the signal format of the navigation enhancement signal is expressed as: where P is the transmission signal power of the aerial vehicle (2), C I (t) and C Q (t) are the spread spectrum codes modulated on the I and Q branches for ranging respectively, D I (t) and D Q (t) are the navigation messages modulated on the I and Q branches respectively, D I (t) includes the position and clock error of the aerial vehicle (2), D Q (t) includes the navigation message relaying the GNSS satellite (1), f 0 represents the carrier frequency of the navigation augmentation signal of the aerial vehicle, and t represents the time variable.

5. The method for identifying deceptive jamming assisted by an airspace vehicle according to claim 1, characterized in that, the step of analyzing the signal to be identified to obtain the first pseudorange between the ground anti-jamming navigation receiver (3) and the GNSS satellite (1) includes: Obtain the reception time of the signal to be identified; Obtain the code phase of the signal to be identified by acquisition and tracking; Synchronize and decode to obtain the navigation message of the signal to be recognized; wherein, the navigation message of the signal to be recognized includes time information, the operating orbit parameters of GNSS satellite (1), and ionospheric delay, and the position and clock offset of GNSS satellite (1) can be obtained through the navigation message of the signal to be recognized; Obtain the transmission time of the signal to be recognized according to the code phase of the signal to be recognized; Obtain the first pseudorange according to the reception time of the signal to be recognized, the clock offset of the ground anti-jamming navigation receiver (3), the transmission time of the signal to be recognized, and the clock offset of GNSS satellite (1).

6. The spoofing interference recognition method based on an over-air vehicle assistance according to claim 1, characterized in that, the obtaining the direction of arrival of the navigation enhancement signal by using a DOA estimation algorithm includes: The multiple signal classification algorithm is used to obtain the direction of arrival of the navigation enhancement signal, and the direction of arrival of the navigation enhancement signal includes the elevation angle θ and the azimuth angle of the navigation enhancement signal 7. The spoofing interference recognition method based on an over-air vehicle assistance according to claim 1, characterized in that, the calculation method of the position of the over-air vehicle (2) and the third pseudorange between the ground anti-jamming navigation receiver (3) and the over-air vehicle (2) includes: Obtain the reception time of the navigation enhancement signal; Capture and track to obtain the code phase of the navigation enhancement signal; Synchronize and decode to obtain the navigation message of the navigation enhancement signal; wherein, the message of the navigation enhancement signal includes the position and clock offset of the over-air vehicle (2), and the forwarded navigation message of GNSS satellite (1); Obtain the transmission time of the navigation enhancement signal according to the code phase of the navigation enhancement signal; and Obtain the third pseudorange according to the reception time of the navigation enhancement signal, the clock offset of the ground anti-jamming navigation receiver (3), the transmission time of the navigation enhancement signal, and the clock offset of the over-air vehicle (2).

8. The spoofing interference recognition method based on an over-air vehicle assistance according to claim 1, characterized in that, the interference source (4) is set within the set range of the ground anti-jamming navigation receiver (3), and the interference source (4) is used to generate a spoofing interference signal.

9. A spoofing interference recognition system based on an over-air vehicle assistance, characterized in that, comprises: GNSS satellite (1), over-air vehicle (2), and ground anti-jamming navigation receiver (3) that are communicatively connected to each other; wherein, the ground anti-jamming navigation receiver (3) uses the spoofing interference recognition method described in any one of claims 1 to 8 to recognize the signal to be recognized.

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