CN115825996A - Aircraft independent position verification method based on Doppler frequency shift change quantity - Google Patents
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Abstract
The invention discloses an aircraft independent position verification method based on a Doppler frequency shift change quantity, which comprises the following steps of: establishing a satellite-based ADS-B verification system, and determining the Doppler frequency shift of an aerospace link of an aircraft and a satellite-borne ADS-B receiver in the verification system; analyzing the change amount of Doppler frequency shift in two ways based on the position information of the aircraft and the carrier frequency of the signal; and judging whether the distribution of the change amount of the Doppler frequency shift obeying the total is obviously different or not under the two approaches, if not, judging that the ADS-B signal source is an aircraft flying normally, and if so, judging that the ADS-B signal source is a deception source. The invention effectively solves the problem of false target interference of the satellite-based ADS-B system, does not need to carry out space direction finding on the received signals, and does not need to consider the time synchronization problem among base stations; the influence of carrier frequency offset of a transmitter and a receiver is eliminated; only a single low orbit satellite carrying an ADS-B receiver is needed for monitoring.
Description
Technical Field
The invention belongs to the technical field of verification of independent positions of aircrafts, and particularly relates to a verification method of independent positions of aircrafts based on Doppler frequency shift change quantities.
Background
Satellite-based ADS-B (Automatic Dependent Surveillance-Broadcast) is an important technical means for realizing aircraft monitoring in a wide area. The ADS-B receiver is deployed on a low orbit satellite, receives ADS-B messages broadcast by an aircraft, transmits the ADS-B messages to a ground station through a satellite link, and finally distributes the ADS-B messages to application terminals through a ground network to realize the monitoring of the aircraft. Compared with a foundation monitoring system, the satellite-based ADS-B system has the advantages of wide coverage area, no geographic environment limitation, capability of meeting the requirements of continuous monitoring of aircrafts and the like, and therefore, the satellite-based ADS-B system has wide application prospects in the fields of civil aviation, military aviation and the like.
Because ADS-B works in a broadcasting mode, the format of ADS-B information is disclosed, and no encryption authentication measure is adopted in the system, the ADS-B system has the problem of false target interference and seriously threatens the aviation flight safety.
Therefore, it is necessary to provide an aircraft independent position verification method based on the doppler shift change amount to solve the above problems.
Disclosure of Invention
In view of this, the present invention provides an aircraft independent position verification method based on a doppler shift change amount, which is used to solve the problem of false target interference generated in the prior art due to the fact that a message format is disclosed in a satellite-based ADS-B system and the system does not adopt an encryption and authentication mechanism.
In order to achieve the purpose, the invention provides the following technical scheme:
the invention provides an aircraft independent position verification method based on a Doppler frequency shift change quantity, which comprises the following steps:
s1: establishing a satellite-based ADS-B verification system, and determining the Doppler frequency shift of an aerospace link of an aircraft and a satellite-borne ADS-B receiver in the verification system;
s2: analyzing the change amount of Doppler frequency shift in two ways based on the position information of the aircraft and the carrier frequency of the signal;
s3: and judging whether the distribution of the change amount of the Doppler frequency shift obeying the total is obviously different or not under the two approaches, if not, judging that the ADS-B signal source is an aircraft flying normally, and if so, judging that the ADS-B signal source is a deception source.
Further, in step S1, the Doppler shift f d Calculated by the following formula:
in the formula, f ot The carrier frequency of a transmitting signal of an ADS-B transmitter of an aircraft, c is the speed of light, X, Y and Z respectively represent an X axis, a Y axis and a Z axis of a geocentric geostationary coordinate system, and v sp Is the velocity vector v of the satellite s Velocity vector v with aircraft p Velocity difference vector of r sp Is a position difference vector between a vector OS from a satellite position S to a coordinate system origin O under a geocentric geostationary coordinate system and a vector Op from an aircraft position p to the coordinate system origin O, and theta is a position difference vector r sp And velocity difference vector v sp The included angle of (a).
Further, in step S2, the change Δ f in the doppler shift is based on the route of the aircraft position message d (i) Calculated by the following formula:
{Δf d (i)＝f d (i+1)-f d (i)，i＝1，2...I-1}
wherein I is the number of samples.
Further, in step S2, the amount of change in Doppler shift in the signal carrier frequency-based approach
Extracting carrier frequency estimation values of corresponding signals of ADS-B position information through the satellite-based ADS-B verification system to calculate:
where σ is the error in the carrier frequency estimation.
Further, in step S3, the step of determining whether the distribution of the change amount of the doppler shift in the two ways subject to the population has a significant difference includes:
a1, calculating respectively Δ f d (i) And
empirical distribution function of (2):
wherein, { Δ f d (i) I =1,2.. I-1} is an empirical distribution function:
A2, calculating a test statistic D according to the following formula Observation of ：
A3, according to the test statistic D Observation of And Δ f d (i) And with
The number of samples of (1) is obtained by examining a critical value table by a Chargomorgolov-Smimov (k-s) test or obtaining p by using a p-value approximation formula ks ；
A4, comparison of p ks And the significance level alpha is calculated according to the proportion that alpha =0.05 and p is equal to ks At > alpha,. DELTA.f d (i) And with
There was no significant difference in the overall distribution obeyed when p ks At < alpha,. DELTA.f d (i) And
the overall distribution obeyed has significant differences.
Further, in step S1, the ADS-B signal received by the satellite-borne ADS-B receiver is represented as:
in the formula, P is the received signal power, d (t) is the ADS-B baseband signal, f is the carrier frequency, phi is the initial phase of the carrier, and n (t) is the channel input white Gaussian noise.
Further, the carrier frequency f is determined by the following equation:
f＝f 0 +Δf t +f d +Δf r
in the formula (f) 0 Is the nominal frequency, f, of the ADS-B system 0 ＝1090MHZ，Δf t Carrier frequency offset, f, for aircraft ADS-B transmitter d Doppler shift, Δ f, for relative motion of an aircraft and a satellite-borne ADS-B receiver r The carrier frequency offset is the carrier frequency offset of the satellite-borne ADS-B receiver.
Further, an estimated value of the ADS-B signal carrier frequency f
Calculated by the following formula:
where σ is the error in the carrier frequency estimation.
Further, the change quantity delta f of the Doppler frequency shift is calculated under the approach of the aircraft position information d (i) The method comprises the following steps:
b1: determining, by the verification system, a reception time t of an ADS-B location message p (i) Corresponding ADS-B location message m p (i) Speed message m v (i) Wherein I =1,2, ·, I;
b2: for ADS-B location message m p (i) Decoding and transforming coordinates to obtain the position coordinates { x ] of the aircraft in the geocentric geostationary coordinate system p (i)，y p (i)，z p (i)，i＝1，2，...，I}；
B3: for velocity message m v (i) Decoding and transforming coordinates to obtain a velocity vector { v } of the aircraft in a geocentric geostationary coordinate system p (i)＝(v px (i)，v py (i)，v pz (i))，i＝1，2...I}；
B4: obtaining the position coordinates { x ] of the satellite at the corresponding moment in the geocentric geostationary coordinate system through the verification system s (i)，y s (i)，z s (i) I =1,2.. I } and velocity vector { v } s (i)＝(v sx (i)，v sy (i)，v sz (i))，i＝1，2...I}；
B5: using { x p (i)，y p (i)，z p (i) I =1,2.. 1., I } and { x } s (i)，y s (i)，z s (i) I =1,2.. I } is calculated to obtain a set of position difference vectors { r } sp (i) I =1,2,.., I }; using { v p (i) I =1,2.. 1., I } and { v } s (i) I =1,2.. I } is calculated to obtain a set of velocity difference vectors { v } sp (i)，i＝1，2，...，I}；
B6: position difference vector r sp (i) I =1,2.. I } and a velocity difference vector { v } sp (i) I =1,2.. I } is substituted into the Doppler shift f of the aircraft and satellite-borne ADS-B receiver chain d To obtain { f d (i) I =1,2.. 1, I } and { Δ f d (i)＝fdi+1-fdi，i＝1，2，...，I-1。
Further, the authentication system includes: the space-borne ADS-B receiver is used for receiving the ADS-B signal broadcast by the aircraft to obtain the position, speed and identification information of the aircraft, recording the receiving time and carrier frequency of the ADS-B signal, transmitting the received information to the ground gateway station through an inter-satellite link, obtaining the space position, speed and corresponding time information of a satellite through a GNSS system, transmitting the space position, speed and corresponding time information to the ground gateway station through the inter-satellite data link, transmitting the received information to the ground verification terminal by the ground gateway station, and completing verification of the aircraft position information at the ground verification terminal, wherein the ground application subsystem is used for monitoring the aircraft position information.
The invention has the beneficial effects that:
the invention effectively solves the problem of false target interference of the satellite-based ADS-B system, does not need to carry out space direction finding on the received signals, and has simpler receiving equipment; the time synchronization problem among base stations does not need to be considered; the influence of carrier frequency offset of a transmitter and a receiver is eliminated; the existing ADS-B system protocol architecture does not need to be changed, and the method is easy to fuse with the existing aircraft monitoring system; only a single low orbit satellite carrying the ADS-B receiver is needed for monitoring, and the time synchronization problem among the satellites does not need to be considered.
Additional advantages, objects, and features of the invention will be set forth in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
In order to make the object, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:
FIG. 1 is a schematic diagram of a satellite-based ADS-B verification system according to an embodiment of the invention;
FIG. 2 is a schematic diagram of the position relationship between an aircraft and a satellite according to an embodiment of the present invention;
FIG. 3 is a simulation scenario A of an embodiment of the present invention;
FIG. 4 is a simulation scenario B of an embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating the distribution of different p values of signal sources in a simulation scenario A according to an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating an influence of a frequency estimation error on verification performance in a simulation scenario A according to an embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating an influence of an ADS-B horizontal position error on verification performance in a simulation scenario A according to an embodiment of the present invention;
FIG. 8 is a schematic diagram illustrating an influence of an ADS-B vertical position error on verification performance in a simulation scenario A according to an embodiment of the present invention;
FIG. 9 is a schematic diagram illustrating an influence of a satellite orbit determination error on verification performance in a simulation scenario A according to an embodiment of the present invention;
fig. 10 shows the effect of different data comparison methods on verification performance in the simulation scenario a according to the embodiment of the present invention.
The drawings are numbered as follows: 1. an aircraft; 2. an on-board ADS-B receiver; 3. a ground gateway station; 4. a ground verification terminal; 5. a ground application subsystem.
Detailed Description
As shown in fig. 1 to 10, the present invention provides a method for verifying an independent position of an aircraft based on a change amount of doppler shift, comprising the following steps:
firstly, establishing a satellite-based ADS-B verification system;
the verification system comprises an aircraft 1, a satellite-borne ADS-B receiver 2, a ground gateway station 3, a ground verification terminal 4 and a ground application subsystem 5, wherein the aircraft 1 acquires spatial position and speed information of the aircraft 1 through a GNSS system and broadcasts ADS-B signals in a plaintext broadcasting mode through a 1090 data link, the satellite-borne ADS-B receiver 2 is used for receiving the ADS-B signals broadcast by the aircraft to acquire information such as position, speed and identification of the aircraft 1 and record receiving time and carrier frequency of the ADS-B signals, the received information is transmitted to the ground gateway station 3 through an inter-satellite link, meanwhile, the satellite-borne ADS-B receiver 2 acquires spatial position, speed and corresponding time information of a satellite through the GNSS system and transmits the information to the ground gateway station 3 through the inter-satellite data link, the ground gateway station 3 transmits the received information to the ground verification terminal 4, verification of the position information of the aircraft 1 is completed at the ground verification terminal 4, and the ground application subsystem 5 is used for monitoring the position information of the aircraft 1;
secondly, establishing a signal model, and according to an ADS-B signal expression received by the satellite-borne ADS-B receiver 2 at the time t:
in the formula, P is received signal power, d (t) is an ADS-B baseband signal, f is carrier frequency, phi is the initial phase of the carrier, and n (t) is channel input white Gaussian noise;
wherein the carrier frequency f = f 0 +Δf t +f d +Δf r In the formula, f 0 Is the nominal frequency, f, of the ADS-B system 0 ＝1090MHZ，Δf t Carrier frequency offset, f, for aircraft ADS-B transmitter d Doppler shift, Δ f, for relative motion of an aircraft and a satellite-borne ADS-B receiver r The carrier frequency offset of the satellite-borne ADS-B receiver is obtained;
estimation of the carrier frequency of the ADS-B signal at the same time
Expressed as:
where σ is the error in carrier frequency estimation;
referring to fig. 2, fig. 2 is a position relationship between the aircraft and the satellite at a certain time under the geocentric geostationary coordinate system, where O represents an origin of the geocentric geostationary coordinate system, and X, Y, and Z represent an X axis, a Y axis, and a Z axis of the coordinate system, respectively; at this time, the aircraft is at point p, (x) p ，y p ，z p ) Position coordinates, v, representing the aircraft p ＝(v px ，v py ，v pz ) A velocity vector representing the aircraft at that time; the satellite is located at S point, (x) s ，y s ，z s ) Representing the position coordinates of the satellite, v s ＝(v sx ，v sy ，v sz ) Representing a velocity vector of the satellite; r is sp A position difference vector, v, representing the vector OS and the vector Op sp Representing a velocity vector v s And v p Theta represents a position difference vector r sp And velocity difference vector v sp The included angle of (A);
determining the Doppler frequency shift of the aircraft and the satellite-borne ADS-B receiver link by the following formula:
in the formula (f) ot ＝f 0 +Δf t Carrier frequency of a transmission signal of an aircraft ADS-B transmitter, c is speed of light, f 0 ＞＞Δf t Therefore f is ot ＝1090MHZ；
Thirdly, calculating the change amount [ delta ] f of the Doppler frequency shift in the route based on the aircraft position information d (i)＝f d (i+1)-fdi，i＝1，2，...，I-1；
In the ground verification terminal 4, the receiving time of ADS-B position information is marked as { t } p (i) I =1,2.., I }, the corresponding ADS-B location message is { m } p (i) I =1,2.., I }, the velocity message is { m } v (i)，i＝1，2，..，.I}。
For ADS-B location message m p (i) I =1,2.. I } is decoded and coordinate transformation is carried out to obtain the position coordinate { x } of the aircraft under the geocentric geostationary coordinate system p (i)，y p (i)，z p (i) I =1,2,.., I }; for velocity message m v (i) I =1,2.. The I is decoded and transformed by coordinates, so as to obtain a velocity vector vpi = vpxi, vppy, vpzi, I =1,2.. The I of the aircraft in a geocentric geodesic coordinate system.
Meanwhile, in the ground verification terminal 4, the position coordinates { x ] of the satellite in the geocentric/geostationary coordinate system at the corresponding time can be obtained s (i)，y s (i)，z s (i) I =1,2.. I } and velocity vector { v } s (i)＝(v sx (i)，v sy (i)，v sz (i))，i＝1，2，...，I。
Using { x p (i)，y p (i)，z p (i) I =1,2.. 1., I } and { x } s (i)，y s (i)，z s (i) I =1,2.. I } is calculated to obtain a set of position difference vectors { r } sp (i) I =1,2,.., I }; using { v p (i) I =1,2.. 1., I } and { v } s (i) I =1,2.. I } is calculated to yield a set of velocity difference vectors { v } sp (i)，i＝1，2，...，I}。
Finally, the position difference vector r sp (i) I =1,2,. 1, I } and a velocity difference vector { v } sp (i) I =1,2.. Multidot.i } is substituted into the doppler shift of the aircraft and satellite-borne ADS-B receiver chain to yield { f } d (i) I =1,2.. 1, I } and { Δ f d (i)＝f d (i+1)-fdi，i＝1，2，...，I-1。
Fourthly, calculating the change amount of Doppler frequency shift in the signal carrier frequency path
In the ground verification terminal 4, carrier frequency estimation values of corresponding signals of the ADS-B position information are extracted and recorded as
The Doppler frequency shift change quantity under the signal carrier frequency is obtained by calculation as follows:
since the error in the carrier frequency estimation is small,
the amount of change in the signal carrier frequency is approximately equal to the amount of change in the doppler shift;
fifthly, judging whether the variation of the signal carrier frequency and the variation of the Doppler frequency shift obey the overall distribution have obvious difference, if not, judging that the ADS-B signal source is an aircraft flying normally, and if so, judging that the ADS-B signal source is a deception source;
the method specifically comprises the following steps:
establishing hypothesis one: Δ f d (i) And
the overall distribution obeyed has no significant difference; and assume two: Δ f d (i) And
the overall distributions obeyed are significantly different;
Δ f was calculated by the following formula, respectively d (i) And with
The function of the empirical distribution of (a),
{Δf d (i) I =1,2.., I-1} has an empirical distribution function of
Calculating a test statistic D Observation of ，
According to test statistic D Observation of And Δ f d (i) And
the number of samples of (1) is obtained by examining a critical value table by a Chargomorgoov-Smirnov (k-s) or by using a p-value approximation formula to obtain a p-value, which is denoted as p ks ；
Comparison of p ks And the significance level alpha is calculated according to the proportion that alpha =0.05 and p is equal to ks At > alpha,. DELTA.f d (i) And
there was no significant difference in the overall distribution obeyed when p ks At < alpha,. DELTA.f d (i) And with
The overall distribution obeyed has significant differences.
And finally, constructing a satellite-based ADS-B verification simulation system based on the Doppler frequency shift change quantity, wherein the simulation system comprises: the simulation system comprises an aircraft, a deception source and a satellite, and the table 1 is the main technical parameters of the simulation system.
Table 1 simulation parameter settings
Fig. 3 shows a simulation scenario a generated by satellite simulation software. FIG. 3 includes a randomly generated flight path for 200 aircraft; the trajectory of the satellite; and a spoofing source group containing 200 spoofing sources, located in the region a directly below the center of the track group in the figure. As seen in satellite simulation software, the time that a satellite flies through the whole track group is about 85s, 2 ADS-B position messages and 2 ADS-B speed messages are broadcast by the aircraft per second, and for each track, the satellite-borne ADS-B receiver can receive 170 ADS-B position messages and 170 ADS-B speed messages.
170 pieces of position and speed information corresponding to 200 tracks are derived from satellite simulation software, and are used as track information in an ADS-B message after the ADS-B horizontal position error and the vertical position error are added; meanwhile, 170 positions and speed information of the satellites are derived, and the information is used as satellite orbit information obtained by a GNSS system after satellite orbit determination errors are added; finally, the position coordinates of 200 spoof sources are derived.
Fig. 4 shows a simulation scenario B generated by satellite simulation software. FIG. 4 includes a randomly generated flight path for 200 aircraft; the trajectory of the satellite; and 4 deception source groups containing 200 deception sources, which are respectively positioned at four directions of the south, the east and the north of the track group in the figure.
And (3) obtaining a simulation result by setting simulation parameters and scenes and assuming that ADS-B messages corresponding to 200 tracks are sent by a corresponding aircraft or a certain deception source.
As shown in fig. 5, the simulation results are the simulation results of p-value distribution when the signal sources are different, and fig. 5 shows that when the ADS-B signal source is an aircraft or a deception source, the simulation results show that: 1) When the signal source is an aircraft, 200 p values are all greater than the significance level of 0.05, and the false alarm probability is 0%; 2) When the signal source is a deception source, most of 200 p values are less than the significance level of 0.05, the false alarm probability is 5%, and the overall detection probability is 97.75%.
Considering that the position of the spoofing source may affect the determination of the ADS-B signal source, four sets of spoofing source groups including 200 spoofing sources are respectively arranged in four directions of the track group, i.e. south, east, west and north, as shown in a simulation scenario B of fig. 4, and the results of the simulation verification are shown in table 2:
table 2 verification results
Table 2 gives the effect of changing the location of the spoof source on the verification performance. As can be seen from table 2: 1) Changing the position of the spoofing source does not affect the size of the false alarm probability; 2) Changing the position of the deception source slightly affects the false alarm probability, the false alarm probability is lower than 3.5%, and the detection probability reaches more than 98.25%, so that the verification result shows that the deception source has robustness.
As shown in fig. 6, the influence of the frequency estimation error on the verification performance is given (the horizontal position errors of simulation scenes a and ADS-B are 4m, the vertical position error of ADS-B is 6.6m, and the satellite orbit determination error is 10 m); simulation results show that: 1) The false alarm probability is reduced along with the reduction of the frequency estimation error, and after the frequency is reduced to 9hz, the false alarm probability is close to 0 percent; 2) The false-alarm-missing probability is reduced along with the reduction of the frequency estimation error, and after the frequency estimation error is reduced to 1hz, the false-alarm-missing probability is about 5 percent; 3) The detection probability increases with decreasing frequency estimation error, and when the frequency estimation error decreases to 1hz, the detection probability is more than 97%.
Therefore, the frequency estimation error of the ADS-B signal reaches 10 -1 And in the hz condition, the method has better verification performance.
The influence of the horizontal position error of the ADS-B on the verification performance is shown in FIG. 7 (simulation scene A, frequency estimation error of 1hz, vertical position error of the ADS-B of 6.6m, and satellite orbit determination error of 10 m); wherein, the abscissa represents the horizontal position error of ADS-B, the ordinate represents the probability, the asterisk represents the false alarm probability, the circle represents the false alarm probability, and the square represents the detection probability. The simulation result shows that: 1) The false alarm probability is always maintained at about 0% along with the increase of the horizontal position error of the ADS-B from 5m to 40 m; 2) The false-missing probability is always maintained at about 5 percent; 3) The detection probability is always more than 97%; the three curves show that: the method provided herein is insensitive to ADS-B horizontal position errors.
As shown in fig. 8, the influence of the vertical position error of ADS-B on the verification performance is given (simulation scene a, frequency estimation error of 1hz, horizontal position error of ADS-B of 4m, satellite orbit determination error of 10 m); the horizontal coordinate represents the ADS-B vertical position error, the vertical coordinate represents the probability, the asterisk represents the false alarm probability, the circle represents the false alarm probability, and the square represents the detection probability. Simulation results show that: 1) The false alarm probability is always maintained at about 0% along with the increase of the vertical position error of the ADS-B from 5m to 40 m; 2) The false-missing probability is always maintained at about 5 percent; 3) The detection probability is always greater than 97%. The three curves show that: the method proposed herein is insensitive to ADS-B vertical position errors.
The influence of the satellite orbit determination error on the verification performance is given as the graph in FIG. 9 (simulation scene A, frequency estimation error of 1hz, ADS-B horizontal position error of 4m, ADS-B vertical position error of 6.6 m); wherein, the abscissa represents the satellite orbit determination error, the ordinate represents the probability, the asterisk represents the false alarm probability, the circle represents the false alarm probability, and the square represents the detection probability. Simulation results show that: 1) As the orbit determination error of the satellite is increased from 10m to 100m, the false alarm probability is always maintained at about 0 percent; 2) The false-alarm-missing probability is slightly increased from 5% to about 7%; 3) The detection probability is slightly reduced and is always greater than 96%. The three curves show that: the method provided by the invention is less sensitive to the satellite orbit determination error, and has better verification performance under the condition that the satellite orbit determination error reaches the accuracy of several meters at present.
As shown in fig. 10, the influence of different data comparison methods on the verification performance is given (the horizontal position errors of simulation scenes a and ADS-B are 4m, the vertical position error of ADS-B is 6.6m, and the satellite orbit determination error is 10 m); wherein the abscissa represents frequency estimation error, the ordinate represents detection probability, the square represents Kolmogorov-Smimov test, the asterisk represents wilcoxon symbol rank sum test of a matched sample, the circle represents symbol test, the rhombus represents Pearson correlation coefficient, the plus sign represents Kendall correlation coefficient, and the triangle represents Spearman correlation coefficient. The influence of a common nonparametric hypothesis test method and a correlation coefficient method on the verification performance is analyzed, and a simulation result shows that: 1) The highest detection probability is achieved by using a Kolmogorov-Smimov test, and is about 97 percent or more; 2) The detection probability using the three nonparametric hypothesis tests is greater than the detection probability using the correlation coefficient method. Comparison of several curves shows that: the use of the Kolmogorov-Smimov test is more applicable to the star-based ADS-B system described herein.
The reason of the result 2) is that, for the satellite-based ADS-B system, the satellite has a larger speed and height compared with the deception source and the aircraft, so the influence of the satellite on the link doppler shift is larger, when the deception source is closer to the aircraft to be forged, the change trends of the two groups of doppler shift change amounts are approximately consistent, and the correlation coefficient mainly detects the data change trend, so the verification performance using the correlation coefficient method is poor; the nonparametric hypothesis test can test two groups of data from the aspects of median number, distribution function and the like, and makes full use of the statistical characteristics of the data, so that the method has better verification performance.
The beneficial effects of the above technical scheme are that: the method can effectively solve the problem of false target interference of the satellite-based ADS-B system, does not need to carry out space direction finding on the received signals, and has simpler receiving equipment; the time synchronization problem among base stations does not need to be considered; the influence of carrier frequency offset of a transmitter and a receiver is eliminated; the existing ADS-B system protocol architecture does not need to be changed, and the method is easy to fuse with the existing aircraft monitoring system; only a single low orbit satellite carrying the ADS-B receiver is needed for monitoring, and the time synchronization problem among the satellites does not need to be considered.
Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.
Claims (10)
1. An aircraft independent position verification method based on Doppler frequency shift change quantity is characterized by comprising the following steps:
s1: establishing a satellite-based ADS-B verification system, and determining the Doppler frequency shift of an aerospace link of an aircraft and a satellite-borne ADS-B receiver in the verification system;
s2: analyzing the change amount of Doppler frequency shift in two ways based on the position information of the aircraft and the carrier frequency of the signal;
s3: and judging whether the distribution of the change amount of the Doppler frequency shift obeying the total is obviously different or not under the two approaches, if not, judging that the ADS-B signal source is an aircraft flying normally, and if so, judging that the ADS-B signal source is a deception source.
2. The method of claim 1, wherein the method comprises: in step S1, the Doppler shift f d Through the following disclosureCalculating the formula:
in the formula (f) ot The carrier frequency of a transmitting signal of an ADS-B transmitter of an aircraft, c is the speed of light, X, Y and Z respectively represent an X axis, a Y axis and a Z axis of a geocentric geostationary coordinate system, and v sp Is the velocity vector v of the satellite s Velocity vector v with aircraft p Velocity difference vector of r sp Is a position difference vector between a vector OS from a satellite position S to a coordinate system origin O under a geocentric geostationary coordinate system and a vector Op from an aircraft position p to the coordinate system origin O, and theta is a position difference vector r sp And velocity difference vector v sp The included angle of (a).
3. The method of claim 1, wherein the method comprises: in step S2, the change Δ f in the Doppler shift is determined on the basis of the aircraft position information d (i) Calculated by the following formula:
{Δf d (i)＝ d (i+1)- d (i)，i＝1,2...-1}
wherein I is the number of samples.
4. The method of claim 1, wherein the method comprises: in step S2, the change amount of Doppler shift in the signal carrier frequency-based path
Extracting carrier frequency estimation values of corresponding signals of the ADS-B position information through the satellite-based ADS-B verification system to calculate:
where σ is the error in the carrier frequency estimation.
5. The method of claim 1, wherein the method comprises: in step S3, the step of determining whether the distribution of the change amount of the doppler shift obeys the population has a significant difference includes:
a1, respectively calculating delta f d (i) And
empirical distribution function of (2):
A2, calculating a test statistic D according to the following formula Observation of ：
A3, according to the test statistic D Observation of And Δ f d (i) And
the number of samples of (1) is obtained by examining a critical value table by a Chargomorgolov-Smirnov (k-s) test or by using a p-value approximation formula to obtain p ks ；
A4, comparison of p ks And the significance level alpha is calculated according to the proportion that alpha =0.05 and p is equal to ks >At α, Δ f d (i) And
there was no significant difference in the overall distribution obeyed when p ks <At α, Δ f d (i) And with
The overall distribution obeyed has significant differences.
6. The method of claim 1, wherein the method comprises: in step S1, the ADS-B signal received by the satellite-borne ADS-B receiver is represented as:
in the formula, P is the received signal power, d (t) is the ADS-B baseband signal, f is the carrier frequency, phi is the initial phase of the carrier, and n (t) is the channel input white Gaussian noise.
7. The method of claim 6, wherein the carrier frequency f is determined by the following equation:
f＝f 0 +Δf t + d +Δf r
in the formula (f) 0 Is the nominal frequency, f, of the ADS-B system 0 ＝1090，Δf t Carrier frequency offset, f, for aircraft ADS-B transmitter d Doppler shift, Δ f, for relative motion of an aircraft and a satellite-borne ADS-B receiver r The carrier frequency offset is the carrier frequency offset of the satellite-borne ADS-B receiver.
8. The aircraft independent location verification based on doppler shift change amount of claim 6Method, characterized in that the estimated value of the ADS-B signal carrier frequency f
Calculated by the following formula:
where σ is the error in the carrier frequency estimation.
9. The method of claim 3, wherein the change in Doppler shift Δ f is calculated based on a location message of the aircraft d (i) The method comprises the following steps:
b1: determining, by the verification system, a reception time t of an ADS-B location message p (i) Corresponding ADS-B location message m p (i) Velocity message m v (i) Wherein, i =1,2,;
b2: for ADS-B location message m p (i) Decoding and transforming coordinates to obtain the position coordinates { x ] of the aircraft in the geocentric geostationary coordinate system p (i)，y p (i)，z p (i)，i＝1,2,...,}；
B3: for velocity message m v (i) Decoding and transforming coordinates to obtain a velocity vector { v } of the aircraft in a geocentric geostationary coordinate system p (i)＝v px (i)，v py (i)，v pz (i))，i＝1,2...I}；
B4: obtaining the position coordinates of the satellite at the corresponding moment under the geocentric geostationary coordinate system through the verification system
B5: using { x p (i)，y p (i)，z p (i) I =1,2,. 1, I } and { x } s (i)，y s (i)，z s (i) I =1,2., } results in a set of position difference vectors { r } sp (i) I =1,2, ·, }; using { v p (i) I =1,2.. 1., I } and { v } s (i) I =1,2., } results in a set of velocity difference vectors { v } sp (i)，i＝1,2,...,}；
B6: position difference vector r sp (i) I =1,2.. I } and a velocity difference vector { v } sp (i) I =1,2.. I } is substituted into the Doppler shift f of the aircraft and satellite-borne ADS-B receiver chain d To obtain { f d (i) I =1,2.. 1, I } and { Δ f d (i)＝fdi+1-，i＝1,2,...,-1。
10. The method of claim 1, wherein the verification system comprises: the system comprises an aircraft, a satellite-borne ADS-B receiver, a ground gateway station, a ground verification terminal and a ground application subsystem, wherein the aircraft acquires the spatial position and speed information of the aircraft through a GNSS system and broadcasts an ADS-B signal in a plaintext broadcasting mode through a 1090 data link, the satellite-borne ADS-B receiver is used for receiving the ADS-B signal broadcasted by the aircraft to acquire the position, speed and identification information of the aircraft and can record the receiving time and carrier frequency of the ADS-B signal, the received information is transmitted to the ground gateway station through an inter-satellite link, the satellite-borne ADS-B receiver acquires the spatial position, speed and corresponding time information of a satellite through the GNSS system and transmits the information to the ground gateway station through the inter-satellite data link, the ground gateway station transmits the received information to the ground verification terminal and verifies the position information of the aircraft at the ground verification terminal, and the ground application subsystem is used for monitoring the position information of the aircraft.
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