A method for constructing a GNSS performance evaluation index system for ionospheric scintillation processes

Abstract

The present invention relates to the technical field of evaluation system construction methods, and in particular to a method for constructing a GNSS performance evaluation index system for ionospheric scintillation processes. The method comprises: utilizing historical GNOS observation data from ground-based GNSS, China's FY-3C / D, and the United States COSMIC to invert high-resolution ionospheric TEC over land and sea and extract its rate of change standard deviation (ROTI) as an evaluation index for ionospheric scintillation; extracting the spatiotemporal characteristics of ionospheric scintillation obtained by inversion S1; simulating the spatiotemporal characteristics of ionospheric scintillation extracted by S2; modulating the spatiotemporal characteristics of ionospheric scintillation simulated by S3 into a normal signal for transmission to a receiver; evaluating the spatiotemporal characteristics of ionospheric scintillation obtained by S4; and statistically analyzing the correlation between the spatiotemporal characteristics of ionospheric scintillation and performance indicators in S2 to construct a GNSS performance index system for ionospheric scintillation correlation. The present invention can provide a basis for correcting positioning errors of GNSS-disturbed satellites during ionospheric scintillation processes by accurately determining the spatiotemporal characteristics of ionospheric scintillation and the GNSS performance attenuation index system.

Description

Technical Field

[0001] The present invention relates to the technical field of evaluation system construction methods, and in particular to a method for constructing a GNSS performance evaluation index system for an ionospheric scintillation process. Background Art

[0002] The ionosphere is a significant factor impacting GNSS service performance, particularly in the presence of anomalous ionospheric activity. Providing stable, real-time, and reliable ionospheric delay correction information is a key challenge facing GNSS. Anomalous ionospheric activity can have a destabilizing effect on radio signals. When radio signals pass through an anomalous ionosphere, they experience fluctuations in both signal amplitude and phase, known as ionospheric scintillation. This ionospheric scintillation can have severe, even destructive, impacts on GNSS. Currently, research on ionospheric scintillation in my country primarily focuses on scintillation monitoring and prediction, as well as statistical analysis of regional characteristics. However, in-depth research on the impact of ionospheric scintillation on GNSS performance has been lacking. Therefore, as my country's Beidou system enters the era of global service, there is an urgent need for large-scale, long-timescale research on the impact of ionospheric scintillation on GNSS performance, including a systematic and comprehensive performance evaluation index system, particularly one specifically focused on evaluating the impact of ionospheric scintillation on Beidou performance. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a method for constructing a GNSS performance evaluation index system for ionospheric scintillation process.

[0004] To solve the above technical problems, the present invention provides the following technical solution: a method for constructing a GNSS performance evaluation index system for ionospheric scintillation process, comprising the following steps:

[0005] S1: Using historical GNOS observation data from ground-based GNSS, China's FY-3C / D satellites, and the US COSMIC satellites, we invert high-resolution ionospheric TEC over land and sea and extract its rate of change standard deviation (ROTI) as an ionospheric scintillation assessment index.

[0006] S2: Extract the spatiotemporal characteristics of ionospheric scintillation obtained by inversion of S1;

[0007] S3: simulate the spatiotemporal characteristics of ionospheric scintillation extracted by S2;

[0008] S4: Modulate the spatiotemporal characteristics of ionospheric scintillation simulated in S3 into a normal signal and transmit it to the receiver;

[0009] S5: Perform performance evaluation on the temporal and spatial characteristic indicators of ionospheric scintillation obtained in S4;

[0010] S6: Statistically analyze the correlation between the spatiotemporal characteristics of ionospheric scintillation and performance indicators in S2, and construct a GNSS performance indicator system related to ionospheric scintillation.

[0011] As a preferred technical solution of the present invention, the S1 uses the historical GNOS observation data of ground-based GNSS, China's FY-3C / D and the United States COSMIC to invert the high-resolution ionospheric TEC of land and sea and extract its rate of change standard deviation (ROTI) as an evaluation index of ionospheric scintillation. The S2 extracts the spatiotemporal characteristics of ionospheric scintillation by using the ROTI inverted by S1 and the amplitude scintillation index S4, phase scintillation index and carrier-to-noise ratio C / N0 obtained by the GNSS ionospheric scintillometer. The S3 uses the spatiotemporal characteristics of ionospheric scintillation of S2 to simulate scintillation of different intensities based on the Nakagami-n fading channel.

[0012] As a preferred technical solution of the present invention, the simulation of scintillation of different intensities can obtain ionospheric scintillation sequences of different intensities. S4 modulates the simulated ionospheric scintillation sequence obtained by S3 into a normal positioning signal and transmits it to the receiver. The receiver calculates the carrier loop tracking error, code loop error, GDOP value degradation value, positioning accuracy, positioning availability, and time-space positioning badness function indicators.

[0013] As a preferred technical solution of the present invention, S5 evaluates the impact of ionospheric scintillation on Beidou positioning performance based on the indicators obtained in S4, and S6 statistically analyzes the correlation between ionospheric scintillation intensity and performance indicators based on the spatiotemporal characteristics of ionospheric scintillation in S2. S6 constructs a GNSS performance indicator system associated with ionospheric scintillation.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The present invention effectively solves the problem that my country currently lacks a systematic and complete GNSS performance evaluation system under the influence of ionospheric scintillation by providing a method for constructing an evaluation index system for GNSS performance degradation during the ionospheric scintillation process.

[0016] 2. This method for constructing an evaluation index system for GNSS performance degradation during ionospheric scintillation can accurately determine the spatiotemporal characteristics of ionospheric scintillation and the GNSS performance degradation index system, and can provide a basis for correcting positioning errors caused by GNSS interference during ionospheric scintillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the implementation process of the present invention;

[0018] Figure 2 It is the ionospheric scintillation intensity correlation index and GNSS performance index of the present invention. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, purpose and efficacy of the present invention easy to understand, the present invention is further described below in conjunction with specific examples, but the following examples are only preferred embodiments of the present invention, not all. Based on the examples in the embodiments, other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention. The experimental methods in the following examples, unless otherwise specified, are conventional methods, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0020] Example: Figure 1 and Figure 2 As shown, a method for constructing an ionospheric scintillation process GNSS performance evaluation index system includes the following steps:

[0021] S1: Using historical GNOS observation data from ground-based GNSS, China's FY-3C / D satellites, and the US COSMIC satellites, we invert high-resolution ionospheric TEC over land and sea and extract its rate of change standard deviation (ROTI) as an ionospheric scintillation assessment index.

[0022] S2: Extract the spatiotemporal characteristics of ionospheric scintillation obtained by inversion of S1;

[0023] S3: simulate the spatiotemporal characteristics of ionospheric scintillation extracted by S2;

[0024] S4: Modulate the spatiotemporal characteristics of ionospheric scintillation simulated in S3 into a normal signal and transmit it to the receiver;

[0025] S5: Perform performance evaluation on the temporal and spatial characteristic indicators of ionospheric scintillation obtained in S4;

[0026] S6: Statistically analyze the correlation between the spatiotemporal characteristics of ionospheric scintillation and performance indicators in S2, and construct a GNSS performance indicator system related to ionospheric scintillation.

[0027] S1 uses historical GNOS observation data from ground-based GNSS, China's FY-3C / D, and the United States COSMIC to invert high-resolution ionospheric TEC over land and sea and extract its rate of change standard deviation (ROTI) as an evaluation index for ionospheric scintillation. S2 uses the ROTI inverted by S1 and the amplitude scintillation index S4, phase scintillation index, and carrier-to-noise ratio C / N0 obtained by the GNSS ionospheric scintillometer to extract the spatiotemporal characteristics of ionospheric scintillation. S3 uses the spatiotemporal characteristics of ionospheric scintillation obtained by S2 to simulate scintillation of different intensities based on the Nakagami-n fading channel.

[0028] The simulation of scintillation with different intensities can obtain ionospheric scintillation sequences with different intensities. S4 modulates the simulated ionospheric scintillation sequence obtained by S3 into the normal positioning signal and transmits it to the receiver. The receiver will calculate the carrier loop tracking error, code loop error, GDOP value degradation value, positioning accuracy, positioning availability, and time-space positioning badness function indicators.

[0029] S5 evaluates the impact of ionospheric scintillation on Beidou positioning performance based on the indicators obtained in S4. S6 uses the spatiotemporal characteristics of ionospheric scintillation in S2 as the background to statistically analyze the correlation between ionospheric scintillation intensity and performance indicators. S6 constructs a GNSS performance indicator system related to ionospheric scintillation.

[0030] Working principle:

[0031] 1. GNSS / GNOS inverted ionospheric TEC rate of change standard deviation ROTI and GNSS ionospheric scintillometer obtained amplitude scintillation index S4, phase scintillation index The effects of carrier-to-noise ratio (C / N0) on the temporal and spatial characteristics of ionospheric scintillation are studied.

[0032] ① Standard deviation of TEC change rate:

[0033] Where <> represents the average value over a period of time; ROT is the rate of change of TEC, which can be calculated as follows:

[0034] Where i is the number of the observed satellite, k is the epoch, and t is the GPS time.

[0035] ② Ionospheric amplitude scintillation index:

[0036] Where I is the strength of the satellite signal, It is the average value of the satellite L1 frequency band signal-to-noise ratio during an observation period.

[0037] ③ Ionospheric phase scintillation index:

[0038] in, is the carrier phase after detrending.

[0039] ④ Satellite signal carrier-to-noise ratio: C / N0 = C+B+G a +L-(N0+I)

[0040] Among them, C is the minimum signal strength received by the receiver antenna end, B is the difference between the actual measurement value and C, which can generally be taken as 3dB, G a is the antenna gain, L is the signal loss in receiver channel processing, N0 is the noise power, and I is the interference power.

[0041] 2. Based on the simulation method of statistical model, the impact of ionospheric scintillation is equivalent to the satellite signal processed by Nakagami-n fading channel, and the ionospheric scintillation sequence with the characteristics of regional ionospheric scintillation is generated.

[0042] ①Nakagami-n fading channel model, the channel response function is: In the formula is the direct component, is a complex constant, and ∈(t) is the time-varying multipath component.

[0043] ②Statistically significant static scintillation sequences can be used to effectively evaluate the impact of ionospheric scintillation on the tracking loop. The model is driven by a zero-mean white noise process and passed through a second-order low-pass filter with an amplitude response function of the following form: In the formula β = 1.24; ζ0 is the decorrelation time.

[0044] ③The signal after the filter is recorded as ε(t), and its variance From the characteristics of Nakagami-n distribution, the direct component can be obtained as in

[0045] Direct component By adding ∈(t) and then performing normalization, the ionospheric scintillation sequence can be obtained.

[0046] 3. This method uses indicators such as carrier loop tracking error, code loop error, GDOP degradation value, positioning accuracy, positioning availability, and spatiotemporal positioning badness function to evaluate the impact of ionospheric scintillation on Beidou positioning performance. Then, based on the ionospheric scintillation characteristics in the Asian and Australian sectors, the correlation between ionospheric scintillation intensity and performance indicators is statistically analyzed. Finally, a GNSS performance indicator system related to ionospheric scintillation is constructed.

[0047] ①Carrier loop tracking error under the influence of amplitude flicker: in,

[0048] B n is the bandwidth of the PLL loop or DLL loop, and η is the receiver pre-detection integration time.

[0049] ②Carrier loop tracking error under the influence of phase flicker: Where k is the receiver PLL loop order, f n is the natural frequency of the loop, and p is the spectral index of the phase scintillation spectrum.

[0050] ③Code loop error model under the influence of amplitude flicker: in,

[0051] d is the correlator spacing.

[0052] ④GNSS positioning error

[0053] GNSS positioning error can be measured by the observed satellite geometric precision factor and the user equivalent distance error. Assume that the observation value matrix is:

[0054] where the first three coefficients in each row are the three components of the Earth-fixed, geocentric rectangular coordinate system pointing to the uniform vector of the nth satellite, and N is the number of available satellites. G describes the geometry of the GNSS satellite constellation and has a direct impact on the estimation results.

[0055] GNSS satellite geometric dilution of precision GDOP:

[0056] Where Tr(·) is the trace operator, G T G is the sum of the diagonal elements of the square matrix.

[0057] Assume that the measurement residual between the GNSS receiver and the satellite satisfies the variance The standard Gaussian normal distribution of :

[0058] Assume that the estimated position vector at a given time t is Then the related error covariance matrix is ​​defined as:

[0059]

[0060] Therefore, the standard deviation of GNSS positioning error can be calculated as follows:

[0061]

[0062] ⑤ The GDOP degradation value is the increase in the user's GDOP after the satellite is unavailable due to ionospheric scintillation compared to the GDOP value when there is no ionospheric scintillation.

[0063] Among them, GDOP ion-sci is the GDOP value with ionospheric scintillation, GDOP un is the GDOP value without ionospheric scintillation.

[0064] ⑥ Positioning availability refers to the percentage of time that GNSS positioning services can be used. Positioning is considered unavailable when the number of available satellites is less than 4 or the GDOP value is greater than 10. It can be calculated by the following formula:

[0065]

[0066] where T is the total number of observation epochs, and PVT k (i) is a logical variable indicating whether the positioning service is available at the k-th grid point in the i-th observation epoch. If the number of available satellites is greater than or equal to 4, then PVT k (i) is 1, indicating that the positioning service is available; otherwise it is 0, indicating that the positioning service is unavailable.

[0067] ⑦ The spatial positioning severity function refers to the percentage of the non-positionable area under the ionospheric scintillation center. The larger this percentage, the more severe the impact. Its expression is:

[0068] ⑧ The time positioning severity function is the percentage of the locatable time of the target point during the entire observation period under different ionospheric scintillation centers. The smaller this percentage, the more severe the impact. Its expression is:

[0069]

[0070] Generally, the ionospheric scintillation intensity can be divided into four levels according to the S4 index: S4 ≤ 0.2, no scintillation; 0.2 < S4 ≤ 0.4, weak scintillation; 0.4 < S4 ≤ 0.6, medium-intensity scintillation; S4 ≥ 0.6, strong scintillation. Therefore, this project will first use the S4 index as a reference benchmark, combine with ROTI, and the c / N0 index to determine the indication data of ionospheric scintillation at each intensity level; then, based on the spatio-temporal characteristics of ionospheric scintillation in the Asia-Australia sector and the grid maps of diurnal, quarterly, and interannual variations as background data, use the conditional correlation analysis method to statistically analyze the GNSS performance during the ionospheric scintillation processes of different levels in the Asia-Australia sector from 2000 to 2020, and obtain the GNSS performance indicators associated with different intensity ionospheric scintillation indices as the basis for correcting the GNSS performance attenuation during ionospheric scintillation.

[0071] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to this. Various changes can be made without departing from the gist of the present invention within the knowledge scope of those skilled in the art.

Claims

1. A method for constructing an ionospheric scintillation process GNSS performance evaluation index system, characterized in that: The following steps are involved: S1: Using historical GNOS observation data from ground-based GNSS, China's FY-3C / D satellites, and the US COSMIC satellites, we invert high-resolution ionospheric TEC over land and sea and extract its rate of change standard deviation (ROTI) as an ionospheric scintillation assessment index. S2: Extract the spatiotemporal characteristics of ionospheric scintillation obtained by inversion of S1; S3: simulate the spatiotemporal characteristics of ionospheric scintillation extracted by S2; S4: Modulate the spatiotemporal characteristics of ionospheric scintillation simulated in S3 into a normal signal and transmit it to the receiver; S5: Perform performance evaluation on the temporal and spatial characteristic indicators of ionospheric scintillation obtained in S4; S6: Statistically analyze the correlation between the spatiotemporal characteristics of ionospheric scintillation and performance indicators in S2, and construct a GNSS performance indicator system related to ionospheric scintillation.

2. The method for constructing an ionospheric scintillation process GNSS performance evaluation index system according to claim 1, characterized in that: The S1 uses historical GNOS observation data from ground-based GNSS, China's FY-3C / D and the United States COSMIC to invert high-resolution ionospheric TEC over land and sea and extracts its rate of change standard deviation ROTI as an evaluation index for ionospheric scintillation.

3. The method for constructing an ionospheric scintillation process GNSS performance evaluation index system according to claim 2, characterized in that: The S2 extracts the spatiotemporal characteristics of ionospheric scintillation by using the ROTI inverted by S1 and the amplitude scintillation index S4, phase scintillation index and carrier-to-noise ratio C / N0 obtained by the GNSS ionospheric scintillometer.

4. The method for constructing an ionospheric scintillation process GNSS performance evaluation index system according to claim 3 is characterized in that: The S3 utilizes the spatiotemporal characteristics of the ionospheric scintillation of S2 to simulate scintillation of different intensities based on the Nakagami-n fading channel.

5. The method for constructing an ionospheric scintillation process GNSS performance evaluation index system according to claim 4, characterized in that: The simulation of scintillation with different intensities can obtain ionospheric scintillation sequences with different intensities.

6. The method for constructing an ionospheric scintillation process GNSS performance evaluation index system according to claim 5, characterized in that: The S4 modulates the simulated ionospheric scintillation sequence obtained in S3 into a normal positioning signal and transmits it to the receiver.

7. The method for constructing an ionospheric scintillation process GNSS performance evaluation index system according to claim 6, characterized in that: The receiver will calculate carrier loop tracking error, code loop error, GDOP value degradation value, positioning accuracy, positioning availability, and spatiotemporal positioning badness function indicators.

8. The method for constructing an ionospheric scintillation process GNSS performance evaluation index system according to claim 7, characterized in that: The S5 evaluates the impact of ionospheric scintillation on Beidou positioning performance based on the indicators obtained in S4.

9. The method for constructing an ionospheric scintillation process GNSS performance evaluation index system according to claim 8, characterized in that: The S6 statistically analyzes the correlation between the ionospheric scintillation intensity and the performance indicators based on the spatiotemporal characteristics of the ionospheric scintillation in S2.

10. The method for constructing an ionospheric scintillation process GNSS performance evaluation index system according to claim 9, characterized in that: The S6 constructs a GNSS performance indicator system associated with ionospheric scintillation.

Images