GNSS interference detection method and system based on DDM

Abstract

The invention provides a DDM-based GNSS interference detection method and system. The method comprises the steps of obtaining a DDM generated by a satellite-borne GNSS-R remote sensing detector; determining the position of a specular reflection point in the DDM; determining a noise part in the DDM; calculating a noise spectrum of the DDM according to the noise part in the DDM; determining a noise spectrum of the DDM under the condition of no GNSS interference; calculating the average noise spectrum of the DDM under the condition of no GNSS interference; calculating a mean value and a standard deviation of an average noise spectrum of the DDM under the condition of no GNSS interference, and an interference threshold value for interference detection; and performing GNSS interference detection by using the interference threshold. The method has the advantages that the GNSS interference can be successfully detected from the DDM influenced by the GNSS interference, and the method is simple, feasible and convenient to implement.

Description

Technical Field

[0001] The present application relates to the fields of GNSS remote sensing technology and applications and GNSS interference monitoring technology and applications, and specifically to a GNSS interference detection method and system based on DDM. Background Art

[0002] Space-based GNSS reflection (GNSS-R) remote sensing detection technology is a new type of earth remote sensing detection technology based on the Global Navigation Satellite System (GNSS). It has been widely used in the inversion of physical parameters of the earth's surface, such as sea surface wind speed and soil moisture. At present, the space-borne GNSS-R remote sensing detector is a special payload for space-based GNSS-R remote sensing detection. The space-borne GNSS-R remote sensing detector first receives the GNSS signal reflected by the earth's surface (called the GNSS reflection signal), then performs local correlation processing on the GNSS reflection signal, and finally generates a "Delay-Doppler Map (DDM)", namely DDM.

[0003] In addition, the current frequent occurrence of GNSS interference, especially malicious GNSS interference, has greatly endangered the security of GNSS-based applications and systems, and has attracted widespread attention from all over the world. Therefore, GNSS interference monitoring technology has become one of the current research hotspots. GNSS interference space-based monitoring has the significant advantages of all-weather and global coverage, and has attracted great attention from researchers.

[0004] While receiving GNSS reflected signals, satellite-borne GNSS-R receivers often receive GNSS interference from the earth's surface. These GNSS interferences are usually malicious interferences, which have greater power than GNSS reflected signals, thus forming obvious interference features in DDM. For this reason, GNSS interference detection based on DDM has become a hot issue. Summary of the invention

[0005] The purpose of this application is to propose a GNSS interference detection method and system based on DDM. The method and system can successfully detect GNSS interference from DDM affected by GNSS interference, thereby providing a simple and feasible technical solution to the current hot issue - GNSS interference detection based on DDM.

[0006] In order to achieve the above objectives, the present application proposes a GNSS interference detection method based on DDM, comprising:

[0007] Step S101) obtaining a DDM generated by a satellite-borne GNSS-R remote sensing detector;

[0008] Step S102) determining the position of the mirror reflection point in the DDM;

[0009] Step S103) determining the noise portion in the DDM;

[0010] Step S104) calculating the noise spectrum of the DDM according to the noise part in the DDM;

[0011] Step S105) determining the noise spectrum of the DDM without GNSS interference;

[0012] Step S106) calculating the average noise spectrum of the DDM without GNSS interference;

[0013] Step S107) calculating the mean and standard deviation of the average noise spectrum of the DDM under the condition of no GNSS interference, and the interference threshold for interference detection;

[0014] Step S108) GNSS interference detection is performed using the interference threshold.

[0015] As an improvement of the above method, the step S102) includes:

[0016] Determine the maximum value of DDM and its corresponding pseudo code delay:

[0017] [U,P]=max(D(n,m))

[0018] Where D(n,m) represents the element in the lower n rows and m columns of DDM; U represents the maximum value of DDM; P represents the pseudo code delay corresponding to the maximum value of DDM; max(·) represents the maximum value function;

[0019] Based on the pseudo code delay corresponding to the maximum value of DDM, determine the pseudo code delay corresponding to the mirror reflection point:

[0020] S=P-1

[0021] Among them, S represents the pseudo code delay corresponding to the mirror reflection point, 1 <S<N。

[0022] As an improvement of the above method, the step S103) includes:

[0023] The noise part in DDM is the DDM part whose pseudo code delay is less than the pseudo code delay corresponding to the mirror reflection point, that is, D(n,m), n∈[1,S-1] and m∈[1,M]; M represents the number of Doppler frequency units.

[0024] As an improvement of the above method, the step S104) includes:

[0025] The noise spectrum of DDM is expressed as:

[0026]

[0027] Wherein, F represents the noise spectrum of DDM; F(m) represents the mth spectrum line in the noise spectrum of DDM.

[0028] As an improvement of the above method, the step S105) includes:

[0029] The DDM generated by the GNSS reflection event in the South Pacific region is used as the DDM under the condition of no GNSS interference;

[0030] The noise spectrum of the DDM calculated based on the DDM under the condition of no GNSS interference is used as the noise spectrum of the DDM under the condition of no GNSS interference.

[0031] As an improvement of the above method, the step S106) includes:

[0032] The noise spectra of all DDMs without GNSS interference are averaged and expressed as:

[0033]

[0034] in, represents the mth spectral line in the noise spectrum of the jth DDM under the condition of no GNSS interference; represents the average noise spectrum of DDM without GNSS interference; represents the mth spectral line in the average noise spectrum of the DDM without GNSS interference; K represents the total number of noise spectra of the DDM without GNSS interference.

[0035] As an improvement of the above method, the step S107) includes:

[0036] Based on the calculated average noise spectrum of DDM under the condition of no GNSS interference The calculation results are:

[0037]

[0038] Wherein, M represents the number of Doppler frequency units; Ave represents the mean of the average noise spectrum of DDM without GNSS interference; Std represents the standard deviation of the average noise spectrum of DDM without GNSS interference;

[0039] Calculate the interference threshold Th for GNSS interference detection:

[0040] Th=Ave+2Std.

[0041] As an improvement of the above method, step S108) includes:

[0042] Based on the noise spectrum F(m) of any one DDM, calculate its maximum value:

[0043] V = max(F(m))

[0044] where V represents the maximum value of F(m);

[0045] When V ≥ Th, it is determined that there is GNSS interference; when V < Th, it is determined that there is no GNSS interference.

[0046] This application also provides a GNSS interference detection system based on DDM, which is implemented based on the above method. The system includes:

[0047] An acquisition DDM module, configured to acquire the DDM generated by the spaceborne GNSS-R remote sensor;

[0048] A mirror reflection point position determination module, configured to determine the position of the mirror reflection point in the DDM;

[0049] A noise determination module, configured to determine the noise part in the DDM;

[0050] A noise spectrum calculation module, configured to calculate the noise spectrum of the DDM according to the noise part in the DDM;

[0051] A non-interference noise spectrum determination module, configured to determine the noise spectrum of the DDM under the condition of no GNSS interference;

[0052] A non-interference average noise spectrum calculation module, configured to calculate the average noise spectrum of the DDM under the condition of no GNSS interference;

[0053] An interference threshold calculation module, configured to calculate the mean and standard deviation of the average noise spectrum of the DDM under the condition of no GNSS interference, and the interference threshold for interference detection;

[0054] An interference detection module, configured to perform GNSS interference detection using the interference threshold.

[0055] Compared with the prior art, the advantages of this application are as follows:

[0056] 1. The method proposed by the present invention can successfully detect GNSS interference from the DDM affected by GNSS interference.

[0057] 2. The method proposed by the present invention is simple and feasible and easy to implement. Brief Description of the Drawings

[0058] Figure 1Shown is a flow chart of a GNSS interference detection method based on DDM;

[0059] Figure 2 Shown is the structural block diagram of the GNSS interference detection system based on DDM. DETAILED DESCRIPTION

[0060] The technical solution of the present application is described in detail below with reference to the accompanying drawings.

[0061] like Figure 1 As shown, the present invention proposes a GNSS interference detection method based on DDM, comprising:

[0062] Step S101) Obtaining the DDM generated by the onboard GNSS-R remote sensing detector.

[0063] The DDM generated by the satellite-borne GNSS-R remote sensing detector is an N×M two-dimensional matrix. N represents the number of pseudo-code delay units, and M represents the number of Doppler frequency units. Generally, D is used to represent the DDM, and D(n,m) represents the element in the nth row and mth column of the DDM. n represents the code delay unit ordinal number, and n∈[1,N]; m represents the Doppler frequency unit ordinal number, and m∈[1,M]. When a GNSS reflection event occurs, the satellite-borne GNSS-R remote sensing detector continuously generates a series of DDMs at fixed time intervals. In the present invention, the series of DDMs are obtained for GNSS interference detection.

[0064] Step S102) Determine the position of the mirror reflection point in the DDM.

[0065] According to the geometric structure of space-based GNSS-R observations and the electromagnetic wave scattering model, the maximum value of DDM and its corresponding pseudo code delay are first determined:

[0066] [U,P]=max(D(n,m)) (1)

[0067] Wherein, U represents the maximum value of DDM; P represents the pseudo code delay corresponding to the maximum value of DDM; max(·) represents the maximum value function.

[0068] Based on the pseudo code delay corresponding to the maximum value of DDM, the pseudo code delay corresponding to the mirror reflection point can be determined:

[0069] S=P-1 (2)

[0070] Among them, S represents the pseudo code delay corresponding to the mirror reflection point, and 1 <S<N。

[0071] Step S103) Determine the noise portion in the DDM.

[0072] According to the geometric structure of space-based GNSS-R observations, the noise part in the DDM is the DDM part where the pseudo code delay is less than the pseudo code delay corresponding to the mirror reflection point, that is, D(n,m), where n∈[1,S-1] and m∈[1,M]. This part of the DDM does not contain the GNSS reflection signal power component.

[0073] Step S104) Calculate the noise spectrum of the DDM.

[0074] Based on the noise part in DDM, the noise spectrum of DDM can be calculated and expressed as:

[0075]

[0076] Wherein, F represents the noise spectrum of DDM; F(m) represents the mth spectrum line in the noise spectrum of DDM.

[0077] Step S105) Determine the noise spectrum of the DDM without GNSS interference.

[0078] Generally, the South Pacific region (170°W to 90°W, 60°S to 10°S) is far from the mainland, sparsely populated, and GNSS interference rarely occurs. Therefore, the South Pacific region is regarded as a GNSS interference-free region. The DDM generated by the GNSS reflection event in this region is regarded as the DDM under the condition of no GNSS interference. The noise spectrum of the DDM calculated based on the DDM under the condition of no GNSS interference is called the noise spectrum of the DDM under the condition of no GNSS interference. represents the noise spectrum of the kth DDM without GNSS interference.

[0079] Step S106) Calculate the average noise spectrum of the DDM without GNSS interference.

[0080] The noise spectra of all DDMs without GNSS interference are averaged and expressed as:

[0081]

[0082] in, represents the average noise spectrum of DDM without GNSS interference; represents the mth spectrum line in the average noise spectrum of DDM without GNSS interference. K represents the total number of noise spectra of DDM without GNSS interference.

[0083] Step S107) Calculate the mean and standard deviation of the average noise spectrum of the DDM under the condition of no GNSS interference.

[0084] Based on the calculated average noise spectrum of DDM under the condition of no GNSS interference It can be calculated that:

[0085]

[0086] Among them, Ave represents the mean value of the average noise spectrum of the DDM under the condition of no GNSS interference; Std represents the standard deviation of the average noise spectrum of the DDM under the condition of no GNSS interference. Th represents the threshold for GNSS interference detection, and Th = Ave + 2Std.

[0087] Step S108) GNSS interference detection

[0088] Based on the noise spectrum F(m) of any one DDM, first calculate its maximum value:

[0089] V = max(F(m)) (6)

[0090] Among them, V represents the maximum value of F(m).

[0091] When V ≥ Th, it is determined that there is GNSS interference. When V < Th, it is determined that there is no GNSS interference.

[0092] As Figure 2 shown, the present application also provides a GNSS interference detection system based on DDM, which is implemented based on the above method. The system includes:

[0093] An acquisition DDM module, configured to acquire the DDM generated by the spaceborne GNSS-R remote sensing detector;

[0094] A mirror reflection point position determination module, configured to determine the position of the mirror reflection point in the DDM;

[0095] A noise determination module, configured to determine the noise part in the DDM;

[0096] A noise spectrum calculation module, configured to calculate the noise spectrum of the DDM according to the noise part in the DDM;

[0097] A noise spectrum determination module without interference, configured to determine the noise spectrum of the DDM under the condition of no GNSS interference;

[0098] An average noise spectrum calculation module without interference, configured to calculate the average noise spectrum of the DDM under the condition of no GNSS interference;

[0099] An interference threshold calculation module, configured to calculate the mean value and standard deviation of the average noise spectrum of the DDM under the condition of no GNSS interference, and the interference threshold for interference detection;

[0100] An interference detection module, configured to perform GNSS interference detection by using the interference threshold.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application is described in detail with reference to the embodiments, a person skilled in the art should understand that any modification or equivalent replacement of the technical solution of the present application does not depart from the spirit and scope of the technical solution of the present application and should be included in the scope of the claims of the present application.

Claims

1. A DDM-based GNSS interference detection method, comprising: Step S101) Obtain the DDM generated by the spaceborne GNSS-R remote sensing detector; Step S102) Determine the position of the specular reflection point in the DDM; Step S103) Determine the noise part in the DDM; Step S104) Calculate the noise spectrum of the DDM according to the noise part in the DDM; Step S105) Determine the noise spectrum of the DDM under the condition of no GNSS interference; Step S106) Calculate the average noise spectrum of the DDM under the condition of no GNSS interference; Step S107) Calculate the mean and standard deviation of the average noise spectrum of the DDM under the condition of no GNSS interference, and the interference threshold for interference detection; Step S108) Perform GNSS interference detection using the interference threshold.

2. The GNSS interference detection method based on DDM according to claim 1, characterized in that: The said step S102) includes: Determine the maximum value of the DDM and its corresponding pseudo-code delay: [U, P]=max(D(n, m)) where D(n, m) represents the element in the low n rows and the mth column of the DDM; U represents the maximum value of the DDM; P represents the pseudo-code delay corresponding to the maximum value of the DDM; max(·) represents the maximum value function; Based on the pseudo-code delay corresponding to the maximum value of the DDM, determine the pseudo-code delay corresponding to the specular reflection point: S = P - 1 where S represents the pseudo-code delay corresponding to the specular reflection point, and 1 < S < N.

3. The GNSS interference detection method based on DDM according to claim 2, characterized in that: The said step S103) includes: The noise part in the DDM is the part of the DDM where the pseudo-code delay is less than the pseudo-code delay corresponding to the specular reflection point, that is, D(n, m), n ∈ [1, S - 1] and m ∈ [1, M]; M represents the number of Doppler frequency units.

4. The GNSS interference detection method based on DDM according to claim 3, characterized in that: The said step S104) includes: The noise spectrum of the DDM is expressed as: where F represents the noise spectrum of the DDM; F(m) represents the mth spectral line in the noise spectrum of the DDM.

5. The GNSS interference detection method based on DDM according to claim 4, characterized in that: The said step S105) includes: Take the DDM generated by the occurrence of GNSS reflection events in the South Pacific region as the DDM under the condition of no GNSS interference; The noise spectrum of the DDM calculated based on the DDM under the condition of no GNSS interference is used as the noise spectrum of the DDM under the condition of no GNSS interference.

6. The GNSS interference detection method based on DDM according to claim 1, characterized in that: The said step S106) includes: Average all the noise spectra of the DDM under the condition of no GNSS interference, expressed as: in, represents the mth spectral line in the noise spectrum of the kth DDM without GNSS interference; represents the average noise spectrum of DDM without GNSS interference; represents the mth spectral line in the average noise spectrum of the DDM without GNSS interference; K represents the total number of noise spectra of the DDM without GNSS interference.

7. The GNSS interference detection method based on DDM according to claim 6, characterized in that: The said step S107) includes: Based on the calculated average noise spectrum of DDM under the condition of no GNSS interference The calculation results are: where M represents the number of Doppler frequency units; Ave represents the mean of the average noise spectrum of the DDM under the condition of no GNSS interference; Std represents the standard deviation of the average noise spectrum of the DDM under the condition of no GNSS interference; Calculate the interference threshold Th for GNSS interference detection: Th = Ave + 2Std.

8. The GNSS interference detection method based on DDM according to claim 7, characterized in that: The said step S108) includes: Based on the noise spectrum F(m) of any one DDM, calculate its maximum value: V = max(F(m)) where V represents the maximum value of F(m); When V ≥ Th, it is determined that there is GNSS interference; when V < Th, it is determined that there is no GNSS interference.

9. A GNSS interference detection system based on DDM, implemented based on the method according to any one of claims 1 to 8, characterized in that: The said system includes: A DDM acquisition module, used to acquire the DDM generated by the spaceborne GNSS-R remote sensing detector; A module for determining the position of a mirror reflection point is used to determine the position of the mirror reflection point in the DDM; A noise determination module is used to determine the noise portion in the DDM; A noise spectrum calculation module is used to calculate the noise spectrum of the DDM according to the noise part in the DDM; A module for determining the noise spectrum without interference is used to determine the noise spectrum of DDM without GNSS interference; The module for calculating the average noise spectrum without interference is used to calculate the average noise spectrum of DDM without GNSS interference; an interference threshold calculation module, used to calculate the mean and standard deviation of the average noise spectrum of the DDM under the condition of no GNSS interference, and the interference threshold for interference detection; and The interference detection module is used to perform GNSS interference detection using an interference threshold.

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