Method for detecting at least one persistent interfering effect on GNSS reception in the vicinity of a GNSS receiver of a vehicle - Patent Application 20070122999

Abstract

The present invention relates to a method for detecting at least one persistent interfering effect (1) on GNSS reception in the vicinity of a GNSS receiver (2) of a vehicle (3). [Solution] The method comprises at least the following steps: a) determining a first time series of data describing the signal-to-noise ratio of at least one GNSS signal (4) received using the GNSS receiver (2) during a first observation time frame; b) determining at least one second time series of data describing the signal-to-noise ratio of at least one GNSS signal (4) received using the GNSS receiver (2) during at least one second observation time frame, the first observation time frame and the second observation time frame partially overlapping in time; and c) analyzing whether persistent interfering effects (1) in the vicinity of the GNSS receiver (2) can be inferred from the time series of data describing the signal-to-noise ratio.

Description

[Technical Field]

[0001] The present invention relates to a method for detecting at least one persistent interfering effect on GNSS reception in the vicinity of a GNSS receiver of a vehicle, which is moved relative to the Earth's surface by the vehicle. Furthermore, a computer program, a localization system, and the use of GNSS reflectometry are described. The present invention can be used in particular in GNSS-based localization systems for at least partially automated, autonomous, or semi-autonomous driving. [Background technology]

[0002] Conventional technology Global Navigation Satellite Systems (GNSS) allow geographical spatial positioning of any point on Earth. GNSS satellites orbit the Earth and transmit coded signals. Using these signals, a GNSS receiver calculates the distance or separation from the receiver to the satellites by estimating the time difference between when the signal is received and when it is transmitted. The estimated distance to the satellites can be converted by a GNSS sensor into an estimate of the receiver's position, for example, if a sufficient number of satellites (typically more than five) are being tracked. Currently, there are over 130 GNSS satellites orbiting the Earth, which means that typically up to 65 of them are visible above the local horizon.

[0003] Satellite-aided positioning has undergone rapid development in recent years. In the early days of satellite navigation, GNSS receivers had to rely on a single constellation of satellites in orbit—either the American GPS system or the Russian GLONASS system—to determine their position. Currently, there are a variety of operational systems, such as the European Galileo system and the Chinese Beidou system, as well as a variety of localized augmentation systems that can be attached to these two original systems. Multi-constellation GNSS receivers, capable of simultaneously receiving signals from all GNSS constellations in orbit, are now the norm. This allows the receiver to track a greater number of satellites, even in situations where large portions of the sky are obscured, such as urban (or actual) street canyons, thereby improving accuracy and reducing positioning time. Summary of the Invention [Problem to be solved by the invention]

[0004] Multipath effects are a significant error source for GNSS (Global Navigation Satellite System) receivers. This phenomenon is related to the combination of a line-of-sight (LOS) signal and a series of non-line-of-sight (NLOS) signals that are reflected one or more times from nearby obstacles before reaching the receiving antenna. Multipath signals differ from LOS signals in power, code delay, carrier phase, and frequency, all of which distort the correlation curve between the received signal and the simulation generated by the receiver, which can lead to pseudorange errors (code phases) on the order of tens of meters. Multipath interference occurs when signals reach the antenna via various paths. This is primarily due to the proximity of the antenna to reflective structures, which becomes important when signals arrive from satellites with low elevation angles. This error is different for different frequencies. It affects both phase and code measurements. For codes, the theoretical value can reach 1.5 wavelengths ("chips"). This means, for example, that multipath in the GPS-C1 code can be up to 450 m, while values ​​above 15 m are difficult to observe. Usually it is less than 2-3 meters. The theoretical maximum value of the phase is one-quarter of a wavelength. For GPS L1 or L2 signals, this means about 5 centimeters, but usually it is less than 1 centimeter.

[0005] Many techniques have been developed in the literature to attenuate the effects of multipath. Among the approaches investigated to reduce the effects of multipath, receiver-level monitoring of signal quality and integrity has received much attention because these techniques do not require major hardware modifications. A typical GNSS receiver consists of an HF front end that downconverts and samples the HF signal, a signal processing module where signals are acquired, tracked, and measurements are generated, and a navigation means. Integrity monitoring can be performed in each of these modules. Multipath errors can be minimized by improving the quality of the antenna, i.e., by attenuating signals arriving from specific directions with low elevation angles, and by moving the antenna away from reflective objects (if possible). [Means for solving the problem]

[0006] Disclosure of the Invention Herein, according to claim 1, a method is proposed for detecting at least one persistent interfering influence on GNSS reception in the vicinity of a GNSS receiver of a vehicle, which is movable or moving relative to the Earth's surface by a vehicle, said method comprising at least the following steps: a) determining a first time series of data describing a signal-to-noise ratio of at least one GNSS signal received using the GNSS receiver during a first observation time window; b) determining at least one second time series of data describing a signal-to-noise ratio of at least one GNSS signal received with the GNSS receiver during at least one second observation time period, the first observation time period and the second observation time period partially (but incompletely) overlapping in time; c) analyzing whether persistent interfering effects in the vicinity of the GNSS receiver can be inferred from the time series of data describing the signal-to-noise ratio; Includes.

[0007] It is particularly preferred if the GNSS receiver is moved relative to the Earth's surface by the vehicle during at least the first and second observation time periods.

[0008] Steps a), b) and c) can be performed at least once and / or repeatedly, for example in the order presented, to implement the method. Furthermore, steps a), b) and c), in particular steps a) and b), can be performed at least partly in parallel or simultaneously.

[0009] The method is used to identify long-lasting multipath sources in dynamic situations by analyzing GNSS signals, among other things. The method provides for the first time an approach to identify long-lasting multipath sources in dynamic situations by analyzing the time series of GNSS signals reflected from the surroundings.

[0010] According to the present invention, a method for identifying long-lasting multipath sources in dynamic scenarios, i.e., especially when the GNSS receiver is moving, is presented for the first time. Current algorithms for multipath reception suppression are based on residuals of GNSS signals. In the case of long-lasting multipath sources, such as those on the roof of a car, residual-dependent methods are unable to identify the situation because anomalous residual behavior is treated as normal.

[0011] Current algorithms for mitigating multipath errors are based on GNSS measurements for individual epochs and the resulting residuals. To identify multipath measurements, such algorithms attempt to identify measurements with specific behavior or large residuals. According to this principle, current error limiting algorithms are not in a position to identify long-lasting multipath sources, because they generate distorted residuals for many satellite measurements. If many measurements are distorted, the solution may also be distorted, which leads to small residuals.

[0012] A persistent interfering influence is understood to mean, in particular, an interfering influence that remains static or constant, especially in dynamic situations, such as when the GNSS receiver is moving relative to the Earth's surface, especially over the Earth's surface. The vehicle may be, for example, a motor vehicle, such as an automobile. The vehicle may be configured for an at least partially automated or autonomous driving mode.

[0013] In particular, persistent interfering influences are those that cause multipath propagation of GNSS signals. Such interfering influences can be, for example, objects in the vicinity of the GNSS receiver. In particular, the interfering influences are objects that are fixedly or detachably connected to the vehicle. These objects can be located in the area of ​​the GNSS receiver and / or can impair signal reception of the GNSS receiver. The objects can be, for example, bicycles, roof boxes, etc. that are located in or on the vehicle.

[0014] According to an advantageous embodiment, it is proposed that the time series represent signal-to-noise ratio data determined over the elevation angles of the GNSS satellites transmitting the GNSS signals. The determined signal-to-noise ratio data can be, for example, the signal-to-noise ratio of each of the reflected GNSS signals. These signals can be plotted over the elevation angles to form the time series.

[0015] According to a further advantageous embodiment, it is proposed that the variations in the signal-to-noise ratio are analyzed in order to recognize reflected GNSS signals. In particular, it is proposed herein to use the variations in the signal-to-noise ratio (SNR for short) in GNSS signals in order to identify long-lasting multipath sources. In other words, it can also be stated herein that the variations in the signal-to-noise ratio, which are observable in the case of persistent multipath interfering effects, are used in order to recognize the reception of reflected GNSS signals.

[0016] For example, within a time window, the long-term behavior of the signal-to-noise ratio (SNR) for each satellite can be removed. This means, for example, that the signal-to-noise ratio (SNR) of the reflected GNSS signal can be Reflexion ) can be obtained through the application of a first order polynomial (SNR - long-term behavior). Reflexion The values ​​for can be analyzed along with the elevation angles of the individual satellites.

[0017] According to a further advantageous embodiment, it is proposed that in step c) a spectral analysis is carried out. The spectral analysis can be, for example, a Fourier analysis. Preferably, the spectral analysis is a Lomb-Scargle analysis. The spectral analysis can be carried out, for example, with the aim of identifying multipath reflection heights.

[0018] For example, in the context of spectral analysis, a periodogram with a relatively strong output (e.g., greater than twice the median output) can identify a long-lasting multipath source. A low reflection height output (e.g., less than one meter) can be evaluated as a long-lasting multipath source, such as one attached to a vehicle. A high reflection height can be evaluated as a long-lived multipath source due to the environment.

[0019] According to a further advantageous embodiment, it is proposed to check whether there are periodic fluctuations in the analyzed data when looking in the time domain, or whether there are dominant frequencies in the analyzed data when looking in the spectral domain, from which persistent interfering influences in the vicinity of the GNSS receiver can be inferred.

[0020] In particular, if at least one dominant frequency is present in the same region for the first time series or first observation time frame and for the second time series or second observation time frame, it is particularly advantageous to be able to infer persistent interfering effects (in dynamic cases).

[0021] According to a further advantageous embodiment, it is proposed that an object located on the vehicle is identified as an interfering influence if the reflection height determined within the framework of the analysis is below a predefined limit value. For example, the reflection height can be determined from at least one signal-to-noise ratio of the reflected GNSS signal. In particular, a spectral analysis can be performed to determine the reflection height. Furthermore, for example, an object located on the vehicle can be identified as an interfering influence if the reflection height is below a predefined limit value.

[0022] According to a further advantageous embodiment, it is proposed that the detected persistent interference effects are taken into account when determining at least one integrity parameter for the integrity of a GNSS-based localization result for localizing a vehicle. The integrity parameter can, for example, describe a confidence interval within which a localization result actually exists with a predefinable minimum probability. The integrity parameter can, for example, be a so-called protection level. The integrity parameter can, for example, be used to weight the GNSS influence on the localization as needed. For example, the GNSS influence, in particular the weight of the GNSS signal, can be reduced if persistent interference effects are detected. In this case, localization can, for example, be achieved primarily using inertial navigation or other alternative means.

[0023] In particular, identified long-lasting multipath sources can be used, for example, as monitors to improve location capabilities and / or to improve the integrity of GNSS-based systems.

[0024] According to a further aspect, a localization system for a vehicle is proposed, the localization system comprising at least one GNSS receiver arranged in the vehicle, a localization device and a module for detecting at least one persistent interfering effect on GNSS reception in the vicinity of the GNSS receiver, the localization system being configured to implement the method described herein.

[0025] The module for detecting at least one persistent interfering effect may include, for example, a computer and / or a controller capable of executing instructions for implementing the method. To this end, the computer or controller may execute, for example, a computer program as also presented herein. For example, the computer or controller may access a storage medium as also described herein to enable it to execute the computer program.

[0026] According to a further aspect, a computer program is proposed, which comprises instructions for causing a location system to carry out the method described herein, in other words, a computer program (product) comprising instructions for causing a computer to carry out the method described herein when the program is executed by the computer.

[0027] Furthermore, a machine-readable storage medium on which the computer program proposed herein is stored or stored can also be presented. Typically, the machine-readable storage medium is a computer-readable data carrier.

[0028] According to a further aspect, the use of GNSS reflectometry (SNR method) for detecting at least one persistent interfering effect on GNSS reception in the vicinity of a GNSS receiver of a vehicle, where the GNSS receiver is moved relative to the Earth's surface by the vehicle, is presented.

[0029] The details, features and advantageous embodiments described in relation to the method can likewise be implemented in the location system and / or computer program and / or use presented herein, and vice versa, and to that extent full reference is made to the embodiments described therein for a more detailed characterization of the features.

[0030] The solutions presented in this specification and their technical environments will be described in more detail below with reference to the drawings. Please note that the present invention should not be limited by the illustrated embodiments. In particular, unless otherwise explicitly indicated, some aspects of the matters described in the drawings may be extracted and combined with other components and / or findings from other drawings and / or this specification. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a schematic diagram showing an exemplary procedure of the method presented herein. [Figure 2] 1 is a schematic diagram illustrating an exemplary structure of a location system presented herein. [Figure 3] FIG. 1 is a schematic diagram showing an exemplary visualization of the application of the methods described herein. DETAILED DESCRIPTION OF THE INVENTION

[0032] 1 shows a schematic diagram of an exemplary procedure of the method presented herein, which is used to detect at least one persistent interfering effect 1 on GNSS reception in the vicinity of a GNSS receiver 2 of a vehicle 3, which is moved relative to the Earth's surface by the vehicle 3. The procedure of steps a), b) and c) shown using blocks 110, 120 and 130 is exemplary and can, for example, be performed at least once in the illustrated sequence to implement the method.

[0033] In block 110, according to step a), a first time series of data describing the signal-to-noise ratio of at least one GNSS signal 4 received with the GNSS receiver 2 during a first observation time window is determined. In block 120, according to step b), at least one second time series of data describing the signal-to-noise ratio of at least one GNSS signal 4 received with the GNSS receiver 2 during at least a second observation time window is determined, where the first and second observation time windows partially overlap in time. In block 130, according to step c), an analysis is made of whether persistent interfering effects 1 in the vicinity of the GNSS receiver 2 can be inferred from the time series of data describing the signal-to-noise ratio.

[0034] The method is particularly characterized in that the GNSS receiver 2 is moved relative to the Earth's surface by the vehicle 3 during at least a first observation time period and a second observation time period.

[0035] Figure 2 shows a schematic diagram of an exemplary structure of a localization system 6 for a vehicle 3 presented herein. The localization system 6 comprises at least one GNSS receiver 2 arranged on the vehicle 3, a localization device 7, and a module 8 for detecting at least one persistent interfering influence 1 on GNSS reception in the vicinity of the GNSS receiver 2, wherein the localization system 6 is configured to implement a method according to any one of claims 1 to 8. Furthermore, Figure 2 also shows a module 9 for determining integrity information, such as a protection level, via the results of the localization device 7. This localization device 7 may comprise a localization filter.

[0036] 3 shows a schematic representation of an exemplary visualization of the application of the method described herein. The interfering influence 1 is here exemplarily a bicycle fixed on a vehicle 3, causing reflections and multipath signal propagation of GNSS signals 4 in the direct vicinity of the GNSS receiver 2. The bicycle represents a persistent or constant interfering influence even in dynamic riding situations, i.e., when riding along the ground surface and thus in situations where the reception conditions change. The method advantageously contributes to making it possible to advantageously easily and reliably detect such an interfering influence 1.

[0037] The time series may represent signal-to-noise ratio data determined over an elevation angle ε of a GNSS satellite 5 transmitting a GNSS signal 4. In particular, during the first observation time period and the second observation time period, respectively, at least one time series of signal-to-noise ratio data may be determined over an elevation angle ε relative to the data and stored, for example, as a value pair.

[0038] In particular, based on the data so determined, the variations in the signal-to-noise ratio can be analyzed in order to recognize the reflected GNSS signals 4. For this purpose, for example, a spectral analysis can be carried out, which can preferably be a Romskargle analysis.

[0039] For the analysis of the fluctuations in the signal-to-noise ratio, it is possible to check, for example, whether there are periodic fluctuations in the analyzed data when looking in the time domain, or whether there are dominant frequencies in the analyzed data when looking in the spectral domain that can infer persistent interfering effects in the vicinity of the GNSS receiver.

[0040] In the dynamic case, i.e. when the GNSS receiver 2 is moving, interference-free signal reception will not typically lead to the estimation of periodic fluctuations. Rather, if a periodic structure is present in the dynamic case, a constant interference source can be inferred.

[0041] Each of these time series can be subjected to spectral analysis. By using spectral analysis, periodic signal structures can be recognized, identified, or highlighted in a particularly advantageous manner. For example, in the spectral domain, dominant frequencies (e.g., f=2Hr / Lambda; where Hr here refers to the reflection height) can be recognized. If dominant frequencies are present, they can be used to infer multipath sources.

[0042] In particular, it is particularly advantageous to be able to infer persistent interfering effects (in the dynamic case) if at least one dominant frequency is present in the same region for the first time series or first observation time frame and for the second time series or second observation time frame, which can be stated in other words as being able to infer persistent interfering effects in the dynamic case, especially if a coincidence / consistency in dominant frequencies can be observed in temporally spaced examination time frames / time series (which at least partially overlap).

[0043] In the following, the mathematical relationship will be described exemplarily based on the depiction in Fig. 3, where x, y, and z represent an exemplary coordinate system, Pr, Pr', and Pi represent spatial distances, respectively, ε represents the elevation angle, h represents the reflection height, and R represents an exemplary reflection point.

[0044] According to the sketch in Figure 3, the residual path δ=P_i+P_r of the reflected GNSS signal is given by the following equation: δ=2hcos((π / 2)-ε)=2hsinε It can be calculated as follows:

[0045] Here, ε is the elevation angle of the satellite, and h is the reflection height. According to this relationship, the reflection height can be calculated by the following formula: h=δ / 2sinε This can be obtained by knowledge of redundant routes, as shown below.

[0046] The above formulation is a geometric view. Considering the wave description of the direct and reflected signals, we can formulate the following two equations for the signal-to-noise ratio of the direct signal: SNR dir =Vcos(φ)

[0047] where V is the amplitude and φ is the phase of the received SNR. The amplitude of the reflected signal is attenuated, so an attenuation factor β can be considered. The reflected signal arrives with a time delay, so the reflected SNR (SNR ref ) is depicted using the following formula: SNR ref =βVcos(φ+Δφ) The phase shift ΔΦ can be considered as follows:

[0048] where ΔΦ is a function of the excess path and also of the height angle as considered above. Hence, the following equation: Δφ=(2π / λ)δ=(2π / λ)2hsinε=(4πh / λ)sinε It can be written as follows:

[0049] Substituting into the above equation and writing βV as A for the amplitude of the reflected SNR, we get: SNR ref =Acos((4πh / λ)sinε+φ) It can be written as follows:

[0050] The formula described advantageously converts the reflection height h into the SNR _ It can be obtained by spectral analysis of Ref. In particular, for each satellite, first, SNR _ ref can be obtained. For this purpose, the long-term behavior of the SNR of the GNSS signal can first be removed as a function of the elevation angle of the corresponding satellite. After removing the long-term behavior and obtaining SNR_Ref, a Romskargle analysis can be performed to obtain the power spectral density for various height reflections. The height reflection with the dominant power spectrum can be identified as the height of reflection point R.

[0051] The described technique is an advantageous approach for GNSS reflectivity measurements. Here, for the first time, such an approach is used for application in dynamic situations, in particular during the travel period of the vehicle 3. In particular, it is proposed for the first time to use a GNSS reflectivity measurement approach in a travel scenario in order to recognize long-lasting multipath sources, which may be present, for example, when the driver fixes an object (bicycle, trunk) on the roof of the car.

[0052] Therefore, an example is given of whether and possibly how an object (here, a bicycle) placed on the vehicle 3 can be identified as an interfering effect 1. This can be advantageously identified, for example, if the reflection height h determined within the framework of the analysis lies below a predefinable limit value.

[0053] In a further advantageous embodiment, the detected persistent interfering effects 1 can be taken into account when determining at least one integrity parameter via the integrity of the GNSS-based localization result for locating the vehicle 3. The integrity parameter can be, for example, a protection level.

[0054] For example, within the scope of the present invention, the GNSS reflectometry method (SNR method) can be used to detect at least one persistent interfering influence 1 on the GNSS reception in the vicinity of the GNSS receiver 2 of a vehicle 3, where the GNSS receiver 2 is moved relative to the Earth's surface by the vehicle 3.

Claims

1. A method for detecting at least one persistent interfering effect (1) on GNSS reception in the vicinity of a GNSS receiver (2) of a vehicle (3), comprising: At least the following steps: a) determining a first time series of data describing a signal-to-noise ratio of at least one GNSS signal (4) received using said GNSS receiver (2) during a first observation time frame; b) determining at least one second time series of data describing a signal-to-noise ratio of at least one GNSS signal (4) received with said GNSS receiver (2) during at least one second observation time frame, said first observation time frame and said second observation time frame partially overlapping in time; c) analyzing whether persistent interfering influences (1) in the vicinity of the GNSS receiver (2) can be inferred from the time series of data describing the signal-to-noise ratio; A method comprising:

2. 2. The method of claim 1, wherein the GNSS receiver (2) is moved relative to the Earth's surface by the vehicle (3) during at least the first observation time period and the second observation time period.

3. 3. The method of claim 1 or 2, wherein the time series represents signal-to-noise ratio data determined over an elevation angle (ε) of a GNSS satellite (5) transmitting the GNSS signal (4).

4. 4. The method according to any one of claims 1 to 3, wherein the variations in the signal-to-noise ratio are analyzed to recognize reflected GNSS signals (4).

5. 5. The method according to claim 1, wherein in step c) a spectral analysis is performed.

6. 6. The method according to claim 1, wherein the presence of periodic fluctuations in the analyzed data is checked when observed in the time domain, or when observed in the spectral domain, whether there are dominant frequencies in the analyzed data from which persistent interfering influences (1) in the vicinity of the GNSS receiver (2) can be inferred.

7. 7. The method according to claim 1, wherein an object arranged on the vehicle is identified as an interference influence if a reflection height determined within the framework of the analysis is below a predefinable limit value.

8. 8. The method according to claim 1, wherein the detected persistent interference effects (1) are taken into account when determining at least one integrity parameter related to the integrity of a GNSS-based localization result for locating the vehicle (3).

9. A location system (6) for a vehicle (3), comprising: At least one GNSS receiver (2) arranged on the vehicle (3); a location determination device (7); a module (8) for detecting at least one persistent interfering effect (1) on GNSS reception in the vicinity of said GNSS receiver (2); Including, A location system (6), wherein the location system (6) is configured to implement the method according to any one of claims 1 to 8.

10. A computer program comprising instructions for causing a location system (6) according to claim 9 to carry out the method according to any one of claims 1 to 8.

11. Use of GNSS reflectometry to detect at least one persistent interfering effect (1) on GNSS reception in the vicinity of a GNSS receiver (2) of a vehicle (3), where the GNSS receiver (2) is moved relative to the Earth's surface by the vehicle (3).

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