Validating navigational positioning

Abstract

And verifying navigation positioning. According to the present invention there is provided a method of determining verification of a PVT solution in a Global Navigation Satellite System (GNSS) system receiver, the method comprising: receiving a plurality of GNSS signals from a plurality of satellites, a first plurality of the signals having no trusted data and a second plurality of the signals having trusted data; estimating a PVT solution based on all the received GNSS signals; determining, for each received signal, a residual comprising a difference between the distance of the spacecraft to the estimated PVT solution and the pseudo-range of each signal; determining statistics from the residuals of the first plurality of signals; comparing the statistical magnitude with a first value; and in response to the comparison, determining the location as passing verification or not passing verification.

Description

Technical Field

[0001] The present invention relates to the field of Global Navigation Satellite Systems (GNSS). More specifically, the present invention relates to the field of verifying position, velocity and time determinations. Background Art

[0002] Methods for calculating vehicle position and velocity using a global navigation satellite system (GNSS), such as the Global Positioning System (GPS), are known. Traditionally, position calculations rely on multilateration, based on the time required for signals to arrive at a receiver from at least four different satellites. The information received from the satellites enables the receiver to calculate the positions of several satellites and thereby calculate its own position relative to the satellites via multilateration.

[0003] GNSS receivers are expected to avoid using incorrect signals to calculate the vehicle's position. Spoofing attacks that result in inaccurate position estimates are a known problem. In these attacks, an attacker broadcasts "fake" GNSS signals to intentionally mislead a GNSS receiver. The fake signals have the structure and information content that a legitimate / valid GNSS signal would have; therefore, it is easy for a GNSS receiver to accept them as valid GNSS signals. However, the content of the signals is intentionally constructed so that it results in a different (wrong) position fix. If a GNSS receiver treats the fake signals as legitimate signals and uses them to calculate its position / velocity, the attack is successful.

[0004] To help detect false signals, an authentication process can be performed. The receiver authenticates the signal to ensure that it comes from a trusted source. There are many different possible authentication techniques. Authentication can be based on characteristics at the carrier or subcarrier level, such as variable pulse shaping or frequency hopping. Alternatively, authentication can be based on authentication of the navigation message.

[0005] As an example, the navigation information authentication can be based on the Timed Efficient Stream Loss Tolerant Authentication (TESLA) protocol. In the TESLA system, the key used to authenticate the MAC (Message Authentication Code) in the first packet is sent in subsequent packets. The receiver uses the key sent in the subsequent packets to authenticate the MAC in the first packet. A false signal cannot use the key that has not yet been sent to generate the MAC of the first packet.

[0006] As an example, some GNSS systems use Open Service Navigation Message Authentication (OSNMA), where these signals are authenticated via the TESLA and MAC protocols as described above.

[0007] While some satellites transmit authentication data, not all do so. A navigation solution based only on a signal with authentication data (sometimes called a position velocity timing (PVT) solution) may be less accurate than a PVT solution based on both a signal with authentication data and a signal without authentication data. However, a solution based on both a signal with authentication data and a signal without authentication data may contain spurious signals and therefore be an incorrect or erroneous solution.

[0008] Therefore, there is a need to provide a method of verifying a navigation solution using both signals with and without trusted data. The trusted data may include authentication data and / or encryption data. Summary of the invention

[0009] All available signals can be used to generate a navigation solution, and for each individual signal, the difference between the solution and the pseudorange (e.g., distance) based on that individual signal is calculated: this is called the residual. False signals can cause the distribution of residual values ​​to be irregular. As an example, if the weight of the false signal is large, the residual from the trusted signal may be large. On the other hand, if the weight of the trusted signal is large, the false signal will have a large residual because the position indicated by the false signal is very different from the overall solution.

[0010] Some signals are authentic and some signals are untrustworthy. Examples of authentic signals include signals containing authentic data or some encrypted signals. Examples of untrustworthy signals are signals that do not contain authentic data and are not encrypted. It is known that signals containing authentic data are not false, but the authenticity of signals that do not contain authentic data is unknown. The residuals from signals without authentic data form a first distribution, while the residuals from signals with authentic data form a second distribution.

[0011] The characteristics of the first distribution may be analyzed to determine the authenticity of the signal that does not include credible data. One or more statistics may be determined and compared to a value. The value compared to the statistic may be an absolute value or a value derived from the second distribution. The first and second distributions may be compared.

[0012] If the characteristics of the first distribution meet the pre-specified criteria, then the navigation solution may be determined to be validated. If the characteristics do not meet the pre-specified criteria, then the navigation solution is not validated.

[0013] The invention is defined by the claims. According to a first aspect, there is provided a method of determining validation of a navigation solution in a Global Navigation Satellite System (GNSS) receiver, the method comprising the following steps:

[0014] receiving a plurality of GNSS signals from a plurality of satellites, a first plurality of the signals not having trusted data and a second plurality of the signals having trusted data;

[0015] Estimate a navigation solution based on all received GNSS signals;

[0016] determining, for each satellite from which a signal is received, an estimated measurement from the satellite based at least on the navigation solution;

[0017] determining a residual for each received signal, the residual comprising a difference between the estimated measurement from the satellite that transmitted the received signal and a pseudorange for the corresponding signal;

[0018] determining a statistic from residuals of the first plurality of signals;

[0019] comparing the statistic to a first value;

[0020] Responsive to the comparing, the navigation solution is determined to be validated or not validated.

[0021] Thus, if the statistic is below the first value, the navigation solution is determined to be validated. If the statistic is not below the first value, the navigation solution is determined to be unvalidated. However, different statistics may be used in different ways: for other statistics, if the statistic is above the first value, the navigation solution is determined to be validated, and if the statistic is not above the first value, the navigation solution is determined to be unvalidated.

[0022] Trusted data may include authenticated data or data from an encrypted signal or data from a signal that has been verified by an external method. Authenticated data or encrypted data.

[0023] The pseudorange can be either the detected distance to the satellite or the time of detection. The estimated measurement is based on the navigation solution and may also include corrections for transmission effects (e.g., signal propagation through the ionosphere and / or troposphere). If the pseudorange is the time of detection, the given position is used together with the navigation solution to determine the residual.

[0024] Therefore, the present invention provides a method for verifying a navigation solution based on signals containing trusted data and signals that do not contain trusted data. If only signals containing trusted data are used, it is likely that fewer signals are used, and therefore the solution may be less accurate. On the other hand, if all signals are used (without using the claimed verification method), there may be some false signals, which can lead to a wrong solution. Advantageously, the present invention enables all signals to be used if signals without trusted data can be verified. Therefore, as more signals are used, a more accurate navigation solution can be found.

[0025] The residuals of a false or forged signal may be larger than the true signal. Therefore, by considering the residuals, the likelihood of a false signal can be determined. For example, a very large residual can indicate a forged signal. On the other hand, a small residual can indicate that a forged signal is unlikely to exist. Therefore, by considering the distribution of the residuals of the signal without credible data (the first plurality of signals), the navigation solution can be verified.

[0026] The statistic is used to evaluate the distribution of the residuals. This can be the mean residual, the spread of the residuals, or the largest residual below a predetermined percentile. If the statistic is below the first value, it indicates that the residuals have a low mean, or a small spread, or that the largest residual below a predetermined percentile is relatively small. Therefore, the first plurality of signals can be considered reliable and the navigation solution is validated.

[0027] On the other hand, if the statistic is large and above the first value, the residual may be large, which may indicate one or more false or spurious signals. The navigation solution may then be determined to have failed validation.

[0028] The estimate of the initial navigation solution is based on both signals with trusted data and signals without trusted data, so only one navigation solution needs to be determined initially, thereby reducing the required processing.

[0029] The residuals form a residual distribution, and the step of comparing may include comparing a maximum residual of the first plurality of signals below a first predetermined percentile of the residual distribution to the first value; and in response to the maximum residual below the first predetermined percentile being below the first value, determining that the navigation solution is validated. The residual used is the absolute value of the residual.

[0030] Thus, if the maximum residual below the first predetermined percentile of the residual distribution is below the first value, the navigation solution is determined to be validated. If the maximum residual below the first predetermined percentile of the residual distribution is not below the first predetermined percentile, the navigation solution is determined to be unvalidated. Evaluating the maximum residuals below the predetermined percentile excludes only a minority of the largest residuals, thereby evaluating whether the majority of the residuals are affected by false signals.

[0031] The first plurality of signals may be ordered in increasing order of absolute magnitude in order to obtain a maximum residual below a predetermined percentile.

[0032] In addition to considering the first plurality of signals, a second plurality of signals may be evaluated. A statistic of residuals from the second plurality of signals may be determined, and the statistic may then be compared to a second value. In response to the comparison, the navigation solution may be determined to be validated or not validated.

[0033] Thus, if the statistic of the residuals from the second plurality of signals is below the second value, and the statistic of the residuals from the first plurality of signals is below the first value, the navigation solution is determined to be validated. If the statistic is not below the second value, the navigation solution is determined to be unvalidated. However, similar to the first plurality of signals, different statistics may be used in different ways: for other statistics, if the statistic is above the second value, the navigation solution is determined to be validated, and if the statistic is not above the second value, the navigation solution is determined to be unvalidated.

[0034] The second plurality of signals may be sorted in increasing order of magnitude to facilitate obtaining a maximum residual below a predetermined percentile.

[0035] A maximum residual of the second plurality of signals below a second predetermined percentile of a residual distribution may be compared to the second value. In response to the maximum residual of the second plurality of signals at the second predetermined percentile being below the second value and the maximum residual of the first plurality of signals at the first predetermined percentile being below the first value, determining the navigation solution as validated.

[0036] Thus, if the maximum residual below a first predetermined percentile of the residual distribution of the first plurality of signals is below a first value and the maximum residual of the residual distribution of the second plurality of signals is below a second value, the navigation solution is determined to be validated. If the maximum residual below a first predetermined percentile of the residual distribution of the first plurality of signals is not below a first value and / or the maximum residual of the residual distribution of the second plurality of signals is not below a second value, the navigation solution is determined to be unvalidated.

[0037] In some examples, the first predetermined percentile and the second predetermined percentile are the same. In some examples, the first value and the second value are the same.

[0038] In some embodiments, a maximum residual of the second plurality of signals below a second predetermined percentile of a distribution of residuals of the second plurality of signals may be determined, and the step of determining the statistic may include determining a maximum residual of the first plurality of signals below a third predetermined percentile of the first plurality of signals. The step of comparing may include determining whether the maximum residual of the first plurality of signals below the third predetermined percentile is greater than a maximum residual of the second plurality of signals below the second predetermined percentile by more than a predetermined percentage. In response to the maximum residual of the first plurality of signals below the third predetermined percentile being greater than a maximum residual of the second plurality of signals below the second predetermined percentile by more than a predetermined percentage, the navigation solution is determined to be validated.

[0039] Thus, if the maximum residual of the first plurality of signals below the third predetermined percentile is greater than the maximum residual of the second plurality of signals below the second predetermined percentile by more than a predetermined percentage, the navigation solution is determined to be validated. If the maximum residual of the first plurality of signals below the third predetermined percentile is greater than the maximum residual of the second plurality of signals below the second predetermined percentile by no less than a predetermined percentage, the navigation solution may be determined to be unvalidated.

[0040] This provides a way to compare two distributions of residuals: the residuals of the first plurality of signals and the residuals of the second plurality of signals. If the characteristics of the distributions are similar, it is unlikely that any false signals are present. In this embodiment, the largest residuals of each distribution are excluded and the largest residuals below a certain predetermined percentile are compared. If the residuals obtained from the first plurality of signals are within a range of the residuals obtained from the second plurality of signals, it is an indication that there is some consistency between the distributions, and therefore the PVT solution (based on both the signals with trusted data and the signals without trusted data) is determined to pass validation.

[0041] The second predetermined percentile and the third predetermined percentile may be the same.

[0042] In some embodiments, the number of signals in the second plurality of signals is determined, and in response to the number of signals in the second plurality of signals being greater than a first signal threshold, the method as described above is performed.

[0043] Therefore, if the number of signals in the second plurality of signals is greater than the first signal threshold, the method of the present invention is performed. If the number of signals is not greater than the first threshold, the method of the present invention is not performed.

[0044] If there are relatively few signals with credible data, the method of the present invention may not be suitable because there are insufficient signals with credible data.

[0045] The method may include determining a dilution of precision for the second plurality of signals, and in response to the dilution of precision being below a dilution of precision threshold, performing a method as described above.

[0046] Therefore, if the precision reduction factor is lower than the precision reduction factor threshold, the above method is performed. If the precision reduction factor is not lower than the precision reduction factor threshold, the method of the present invention is not performed.

[0047] If the second plurality of signals has a significant dilution of precision, it may not be suitable to implement the present invention, because the navigation solution based only on the second plurality of signals will have too large a dilution of precision. Therefore, in order to avoid the dilution of precision being too large, the first plurality of signals must always be used.

[0048] The invention may include comparing the maximum residual of the first plurality of signals below a fourth predetermined percentile to a fourth value, and in response to the maximum residual of the first plurality of signals below the fourth predetermined percentile being below the fourth value, determining an individual signal below the fourth predetermined percentile as being validated. This may be used in situations where the overall navigation solution has been determined to be unvalidated, and may be used to validate an individual signal.

[0049] Thus, if the largest residual of the first plurality of signals below a fourth predetermined percentile is below a fourth value, then the individual signals below a fourth predetermined percentile may be determined to have passed validation.

[0050] If individual signals of the first plurality of signals have been verified, a new navigation solution may be estimated based on the second plurality of signals and the verified signals from the first plurality of signals. Thus, the solution is based only on the verified signals.

[0051] Similarly, individual signals in the second plurality of signals may be verified by comparing a maximum residual of the second plurality of signals at a fifth predetermined percentile to a fifth value, and in response to the maximum residual at the fifth predetermined percentile being lower than the fifth value, the individual signal below the fifth predetermined percentile being determined to have passed verification.

[0052] A number of signals in the second plurality of signals may be determined, and in response to the number of signals in the second plurality of signals being above a signal number threshold, the method as described above may be performed.

[0053] The method may include determining a navigation solution based only on the second plurality of signals.For example, if the navigation solution is determined to have failed validation, the navigation solution may be determined based only on the second plurality of signals.

[0054] In some embodiments, in response to the navigation solution failing validation, estimating a first updated navigation solution based only on the second plurality of signals, and determining, for each of the first plurality of signals, an estimated measurement from the corresponding satellite based on at least the first updated navigation solution. An updated residual is determined, the updated residual comprising a difference between the estimated measurement from the satellite and a pseudorange for the corresponding signal. A maximum residual below a sixth predetermined percentile of the sorted first plurality of signals may be compared to a sixth value, and in response to the maximum residual below the sixth predetermined percentile being below the sixth value, determining the signal below the sixth predetermined percentile as passing validation.

[0055] The present invention may further include, in response to a maximum residual below the sixth predetermined percentile being below the sixth value, determining a second updated navigation solution based on the first plurality of signals and signals from the second plurality of signals below the sixth predetermined percentile.

[0056] In response to the navigation solution failing validation, a second updated navigation solution based only on the second plurality of signals and the validated signal from the first plurality of signals may be estimated. For each of the first plurality of signals, an estimated measurement from the corresponding satellite based on at least the second updated navigation solution is determined. An updated residual is determined, the updated residual comprising a difference between the estimated measurement from the corresponding satellite and a pseudorange for the signal. A maximum residual of the updated residual distribution of the first plurality of signals below a seventh predetermined percentile may be compared to a seventh value, and in response to the maximum residual below the seventh predetermined percentile being below the seventh value, the signal below the seventh predetermined percentile is determined to be validated. Thus, the individual signals may be validated based on the updated navigation solution.

[0057] In response to the maximum residual below a seventh predetermined percentile being below a seventh value, a second updated navigation solution based on the second plurality of signals and signals from the first plurality of signals below the seventh predetermined percentile may be estimated.

[0058] It will be apparent that the term "navigation solution" may refer to one or more of position, time and / or velocity.

[0059] According to the present invention, a GNSS receiver is provided, the GNSS receiver comprising an antenna and a processor, the antenna being configured to receive a plurality of GNSS signals from a plurality of satellites, a first plurality of signals among the signals not having trusted data, and a second plurality of signals among the signals having trusted data; the processor being configured to:

[0060] Estimate a navigation solution based on all received GNSS signals;

[0061] determining, for each satellite from which a signal is received, an estimated measurement from the satellite based at least on the navigation solution;

[0062] determining a residual for each received signal, the residual comprising a difference between the estimated measurement from the satellite that transmitted the received signal and a pseudorange for the corresponding signal;

[0063] determining a statistic from residuals of the first plurality of signals;

[0064] comparing the statistic to a first value; and

[0065] Responsive to the comparing, the navigation solution is determined to be validated or not validated.

[0066] According to the invention, there is provided a computer program comprising computer program code configured to, when running the computer program on one or more processors, cause the one or more processors to perform all the steps of the method according to any one of the preceding claims.

[0067] A GNSS receiver is also provided. The GNSS receiver may include an RF front end. The RF front end may be configured to receive GNSS signals via an antenna. The GNSS receiver may also include a signal processing unit. The signal processing unit may be configured to perform GNSS measurements (pseudorange measurements, and optionally carrier range measurements) on the GNSS signals received by the RF front end. The GNSS receiver may also include one or more processors. The one or more processors may be configured to implement the steps of the method for determining verification of a navigation solution in a GNSS system based on GNSS measurement results as claimed.

[0068] There is also provided a base station for a communication network, comprising the GNSS receiver as described above.

[0069] There is also provided a computer program comprising computer program code configured to, when executing the computer program on the one or more processors, cause the one or more processors to perform all the steps of the method as described above. The one or more processors may comprise or consist of one or more processors of a GNSS receiver. The computer program may be stored on a computer readable storage medium (optionally, non-transitory). BRIEF DESCRIPTION OF THE DRAWINGS

[0070] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0071] Figure 1 is a schematic block diagram of a GNSS receiver for verifying positioning according to an embodiment of the present invention;

[0072] Figure 2 is a flowchart of a method for verifying positioning according to an embodiment of the present invention;

[0073] Figure 3 is a plot depicting the residuals sorted by increasing magnitude;

[0074] Figure 4 is a flowchart of a method for verifying positioning according to an embodiment of the present invention;

[0075] Figure 5 is a flowchart of a method for verifying positioning according to an embodiment of the present invention;

[0076] Figure 6 is a flowchart of a method for verifying positioning according to an embodiment of the present invention; and

[0077] Figure 7 is a flowchart of a method for verifying positioning according to an embodiment of the present invention.

[0078] It should be noted that these figures are schematic only and are not drawn to scale. DETAILED DESCRIPTION

[0079] Reference will now be made in detail to examples according to the present disclosure illustrated in the accompanying drawings. The scope of the present disclosure should not be interpreted as limited to the description given in this section; other examples may have different forms. These and other features, aspects and advantages of the apparatus, system and method of the present disclosure will be better understood from the following description, the attached claims and the accompanying drawings. It should be understood that the same reference numerals are used throughout the drawings to indicate the same or similar parts.

[0080] The present invention provides a method for determining verification of positioning in a global navigation satellite system (GNSS). A GNSS receiver can be configured to perform the method for verifying positioning according to an embodiment of the present invention. Accordingly, the present invention also provides a GNSS receiver configured to determine verification of a PVT solution in a global navigation satellite system (GNSS).

[0081] There are currently four fully operational GNSS: the United States' Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), China's BeiDou Navigation Satellite System (BDS), and the European Union's Galileo. GNSS receivers that can simultaneously acquire and track two or more GNSS are called multi-GNSS receivers.

[0082] The GNSS satellites of these various systems typically transmit GNSS signals in more than one frequency band. As an example, the frequency bands currently available under GPS include the L1, L2, and L5 frequency bands. For the L1 signal frequency band, the signal carrier frequency is typically in the range of 1.559 GHz to 1.610 GHz. For the L2 signal frequency band, the signal carrier frequency is typically in the range of 1.18845 GHz to 1.258 GHz. And, for the L5 signal frequency band, the signal carrier frequency is typically in the range of 1.164 GHz to 1.189 GHz. Additional or different frequency bands may become available for GPS in the future.

[0083] Different signal bands have different characteristics. L1, L2, and L5 have different chip rates: L1 has a chip rate of 1.023MHz, L2 has a chip rate of 511.5kHz, and L5 has a faster chip rate of 10.23MHz. Since L5 has a faster chip rate, the peak of the correlation function becomes narrower than the peaks of L1 and L2. For example, the correlation peak of L1 corresponds to 293m, while the correlation peak of L5 corresponds to 29.3m. Due to the narrower correlation function, it is easier to distinguish L5 signals sent by different paths (for example, due to reflections in a multipath environment) than to distinguish L1 or L2 signals sent by different paths. Therefore, L5 signals are more adaptable than L1 signals in a multipath environment.

[0084] A GNSS receiver may operate in a single-band mode, where the GNSS receiver performs signal processing to determine navigation measurements on signals in only one frequency band (e.g., only the L1 band or, as another example, only the L5 band). Alternatively, a GNSS receiver may operate in a dual-band or multi-band mode, where it performs signal processing using signals in multiple frequency bands within a particular constellation, such as the L1 and L5 dual-band mode in GPS. As another example, a GNSS receiver may be configured to operate in a multi-band mode utilizing three or more signal frequency bands (e.g., L1, L2, and L5). It is generally expected that multi-band processing will achieve more accurate navigation measurements than single-band processing.

[0085] Figure 1 A schematic block diagram of a GNSS receiver 100 for determining verification of a PVT (navigation) solution in a global navigation satellite system according to an embodiment of the present invention is illustrated. Figure 1 As shown, the GNSS receiver 100 is configured to receive GNSS satellite signals from GNSS satellites via an antenna 101. The received signal is passed from the antenna 101 to an RF front end 102, which performs tasks such as amplification, down-conversion, filtering, and digitization of the captured satellite signals. The RF front end 102 may include additional functions, such as frequency synthesis (not shown).

[0086] Receiver 100 is further configured to process received signals using processor 104 to extract observables and navigation data from various channels of baseband processing unit 103 and generate navigation solution 106. Processor 104 may include internal or external memory 105 for storing and / or retrieving data associated with the processing.

[0087] The navigation solution 106 generated by the receiver 100 may include the calculated position and velocity of the receiver 100 and the determination of the precise GNSS time. The navigation solution may be derived from any one or more of the GNSS band signals received at the antenna 101, which may include GNSS signals from different GNSS constellations. The navigation solution may also take into account the discounting of any one or more of the GNSS band signals received at the antenna 101. More specifically, the receiver 100 receives satellite signals from one or more GNSS constellations, and the processor 104 processes these signals to provide GNSS measurements, such as pseudoranges, carrier phases, pseudorange rates, etc., to the navigation filter. The processor 104 may, for example, implement a filter, such as a Kalman filter or a least-squares (LSQ) filter, for determining the navigation solution 106 based on the GNSS measurements.

[0088] Processor 104 may also determine whether multipath interference may exist.

[0089] The processor 104 (which may include one or more processors) may also determine the validation of the PVT solution.

[0090] Figure 2 A flow chart illustrating a method according to an embodiment of the invention is shown. In a first step 201, GNSS signals are received from a plurality of satellites (via antenna 101). Some of the signals are authentic, for example including authentic data such as OSNMA, while some of the signals do not include any authentic data. A first plurality of satellites from which the signals are received have no authentic data and a second plurality have authentic data. From each signal a pseudorange may be determined, including the distance from the respective satellite to the receiver.

[0091] In a second step 202, the position (or navigation solution) is estimated based on all received GNSS signals (this includes signals with trusted data and signals without trusted data). Methods for estimating position based on GNSS signals are well known. However, they generally involve determining the distance to each satellite based on each signal. The best fit solution is then found, typically using a least squares solution.

[0092] For each received signal, an estimated measurement based on a navigation solution from each satellite is determined at step 203. The estimated measurement may take into account ionospheric and / or tropospheric delays at the satellite and the receiver and Helmert-Wolf blocking. Based on the estimated measurement, a residual is determined in step 204. The residual is the difference between the estimated measurement and the pseudorange of the signal. Thus, the residual represents the difference between the solution determined from all signals and the solution determined from that individual signal. Thus, a larger residual indicates that there is a large difference between the solution based on all signals and the distance based on only a single signal. Thus, a large residual may indicate that a signal is more likely to be falsified.

[0093] It is known that a signal containing trusted data cannot be forged, while a signal without trusted data may be forged. A large residual of the signal without trusted data (the first plurality of signals) may indicate that forgery has occurred. Similarly, a large difference in residuals between the signal without trusted data (the first plurality of signals) and the signal with trusted data (the second plurality of signals) may indicate that the signal without trusted data has been forged.

[0094] The residuals from the first plurality of signals (without credible data) are then grouped together and a statistic is determined in a fifth step 205. The statistic may be the mean residual, or the largest residual below a certain percentile when the residuals are sorted by size.

[0095] In step 206, the statistic is compared to a certain value. Based on the comparison result, the position is determined to have passed verification 207 or failed verification 208. Sometimes the value is a threshold, and if the statistic is below (or sometimes above) the threshold, the position is determined to have passed verification. As an example, a small average of all residuals of the first plurality of signals can indicate that the first plurality of signals has a good correlation with the overall position estimate and is unlikely to be falsified. Therefore, the overall position based on the second plurality of signals with credible data and the first plurality of signals that do not have credible data but are considered reliable based on the comparison of the statistic is determined to have passed verification. As a specific example, if the average residual is below a certain value, the position can be determined to have passed verification.

[0096] After the antenna receives the GNSS signal ( 201 ), the processor 104 performs steps 202 , 203 , 204 , 205 , 206 , 207 and 208 .

[0097] The above methods involve estimating measurements of the estimated position and pseudorange of the signal (i.e. these relate to distance / position). The same methods can be applied to velocity measurements. However, if the position is already known (provided by another source), this can be used to estimate the measurement, and only the time at the receiver is unknown and can be verified.

[0098] The statistic determined in the fifth step can take a variety of forms, and one implementation includes considering the distribution of the residual values. As an example, the residuals can be sorted in ascending order, such as Figure 3 As shown. A maximum residual below a predetermined percentile may be determined. If the maximum residual below a first predetermined percentile is below a first value, the position previously determined in the method may be determined to be validated.

[0099] The second plurality of signals may also be used to validate the PVT estimate. To this end, a statistic of the residuals from the second plurality of signals is determined. In some embodiments, this may be the same statistic as used for the first plurality of signals. However, in other embodiments, it may be a different statistic. The statistic may be compared to a certain value. Alternatively, statistics from the first plurality of signals and the second plurality of signals may be compared.

[0100] Figure 4 An embodiment using a second plurality of signals is shown. Steps 401, 402, 403, 404, 405 are similar to the corresponding steps 201, 202, 203, 204 and 205 described above. After step 405, a statistic is determined from the second plurality of signals. In this embodiment, it is the maximum residual below the second predetermined percentile. However, as described above, the statistic is not limited to this. In addition, steps 405 and 406 can be performed simultaneously, or step 406 can be performed before step 405. As Figure 2 As in step 206 of , at step 407, the statistic from the first plurality of signals is compared to the first value. If the statistic is not less than the first value, the PVT solution is determined to have failed validation. If the statistic is less than the first value, then at step 408, the statistic from the second plurality of signals is compared to the second value. If the statistic from the second plurality of signals is also less than the second value, the PVT solution is determined to have passed validation. Steps 407 and 408 may be performed simultaneously or in an alternate order. However, both comparisons must be satisfied for validation to occur. If either comparison fails or is not satisfied, the PVT solution is determined to have failed validation.

[0101] The first value and the second value may be the same. Similarly, the first predetermined percentile and the second predetermined percentile may be the same.

[0102] Figure 5 An alternative embodiment is shown in which statistics from a first plurality of signals are compared with statistics from a second plurality of signals. Steps 501, 502, 503 and 504 are similar to Figure 2The corresponding steps 201, 202, 203 and 204 in are the same. The statistic in this embodiment is the maximum residual of the first plurality of signals below the third predetermined percentile, which is determined at step 505. At step 506, the maximum residual of the second plurality of signals below the second predetermined percentile is determined. In this example, the second predetermined percentile and the third predetermined percentile are the same. Therefore, the maximum residual of the first plurality of signals below the predetermined percentile and the maximum residual of the second plurality of signals below the same predetermined percentile can be compared. In particular, at step 507, it is determined whether the maximum residual of the first plurality of signals below the third predetermined percentile is greater than the maximum residual of the second plurality of signals below the second predetermined percentile by more than a predetermined percentage. If so, the residuals are similar and therefore the PVT estimate is deemed to be validated. Advantageously, the method compares the distribution of the residuals.

[0103] The method of the present invention may be applicable only when there are enough signals. For example, it may be applicable only when the second plurality of signals is enough or the dilution of precision of the second plurality of signals is of suitable quality. Therefore, the number of signals in the second plurality of signals may be determined, and the method of the present invention may be performed only when the number of signals is above a first signal threshold. Alternatively or additionally, the dilution of precision of the second plurality of signals is determined, and the method of the present invention is performed only when it is below a dilution of precision threshold.

[0104] The present invention can be used to verify individual signals. This can be used in situations where the PVT estimate fails verification 208, such as Figure 6 As shown. At step 601, the maximum residual of the first plurality of signals below a fourth predetermined percentile may be compared to a fourth value. If the maximum residual is below the fourth value, then those signals whose residuals are below the fourth predetermined percentile may be determined to have passed verification. Alternatively, if the maximum residual is not below the fourth value, then the maximum residual at a different lower predetermined percentile may be compared to a value (which may be the same as the fourth value) at step 602. If the maximum residual is below the value, then the signals below the predetermined percentile are determined to have passed verification. This may continue and repeat until some individual signals pass verification or it is determined that no signal is below the value.

[0105] Alternatively, if signals below a fourth predetermined percentile pass validation, a greater number of signals may be evaluated using a different (higher) predetermined percentile.

[0106] Just as individual signals from the first plurality of signals may be authenticated, signals from the second plurality of signals may be authenticated in the same manner.

[0107] If the PVT estimate fails validation, then a PVT solution may be estimated based solely on the second plurality of signals (with trusted data).

[0108] exist Figure 7 Another embodiment is depicted in which the PVT solution has been determined to have failed validation 207. An updated position is estimated based only on the second plurality of signals 701. For each of the first plurality of signals, an estimated measurement result from the corresponding satellite to the updated position is determined at step 702. At step 703, for each of the first plurality of signals, an updated residual is determined based on the updated estimated position. In step 704, the maximum residual of the first plurality of signals below a sixth predetermined percentile is compared to a sixth value. If the maximum residual below the sixth predetermined percentile is less than the sixth value, the signal below the sixth predetermined percentile is considered to have passed validation 705. If the maximum residual at the sixth predetermined percentile is not less than the sixth value, the signal below the sixth predetermined percentile has failed validation. Although Figure 7 It is not shown in , but the process can be repeated for different values ​​and different percentiles.

[0109] Optionally, at step 706, only verified signals from the first plurality of signals and all of the second plurality of signals may be used to estimate the second updated position.

[0110] Figure 7 Step 701 of only uses the second plurality of signals. However, step 701 may also use a single verified signal from the first plurality of signals as well and repeat the process to determine a more accurate PVT estimate.

[0111] It should be understood that when the phrase "number of satellites" is used, it refers to the number of satellites from which signals are received at a given location at that point in time.

[0112] It should be understood that the scope of the present disclosure is not limited to the above examples. Based on the above description, many variations will be apparent to those skilled in the art.

[0113] Generally, in the flowcharts of the accompanying drawings, the arrows between the steps do not necessarily imply a causal relationship between the steps. They only indicate an exemplary order in which the steps can be performed. The method steps can be performed in an order different from the exemplary order shown in the accompanying drawings.

[0114] It should be understood that Figure 1 The various components shown in the figure can be implemented in hardware, software, or a mixture of the two. In addition, some components can be grouped together in a given implementation, or can be implemented separately. Other implementations are also possible, which divide and distribute various functions in different ways between hardware and software, or between different hardware components, software modules, and / or processors running the software.

[0115] It should be noted that for a particular threshold value, the term "above" may be equivalently replaced by "below".

[0116] In the claims, any reference numerals placed between brackets shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in the claim. However, where the word "comprising" is used, this also discloses as a special case the possibility that the listed elements or steps are exhaustive, i.e., the device or method may consist of only those elements or steps. The word "one" before an element does not exclude the presence of multiple such elements. The embodiment may be implemented by hardware comprising several different elements. In a device claim that lists several means, several of these means may be embodied by the same hardware item. The mere fact that certain measures are recorded in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. In addition, in the appended claims, a list comprising "at least one of A, B, and C" should be interpreted as (A and / or B) and / or C.

[0117] In flowcharts, summaries, claims, and descriptions related to methods, the order in which the steps are listed is generally not intended to limit the order in which they are performed. The steps may be performed in an order different from that indicated (except where specifically indicated or where subsequent steps depend on the results of previous steps). However, the order in which the steps are described may in some cases reflect a preferred order of operation.

[0118] In addition, in general, various embodiments may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be performed by a controller, microprocessor, or other computing device, although these are not limiting examples. Although various aspects described herein may be illustrated and described as block diagrams, flow charts, or using some other graphical representation, it is well understood that, as non-limiting examples, these blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general hardware or controllers or other computing devices, or some combination thereof.

[0119] The embodiments described herein may be implemented by computer software (e.g., in a processor entity) executable by a data processor of the device, or by hardware or by a combination of software and hardware. In addition, in this regard, it should be noted that any box of the logic flow as in the accompanying drawings may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on physical media such as memory chips or memory blocks implemented in a processor, magnetic media such as hard disks or floppy disks, and optical media such as DVDs and data variants thereof, or CDs.

[0120] The memory may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. As non-limiting examples, the data processor may be of any type suitable for the local technical environment and may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a gate-level circuit, and a processor based on a multi-core processor architecture.

[0121] The embodiments discussed herein can be practiced in various components such as integrated circuit modules. The design of integrated circuits is typically a highly automated process. Complex and powerful software tools are available to convert logic level designs into semiconductor circuit designs that are ready to be etched and formed on semiconductor substrates.

Claims

1. A method of determining validation of a navigation solution in a Global Navigation Satellite System (GNSS) receiver, the method comprising the following steps: receiving a plurality of GNSS signals from a plurality of satellites, a first plurality of the signals not having trusted data and a second plurality of the signals having trusted data; Estimate a navigation solution based on all received GNSS signals; determining, for each satellite from which a signal is received, an estimated measurement from the satellite based at least on the navigation solution; determining a residual for each received signal, the residual comprising a difference between the estimated measurement from the satellite that transmitted the received signal and a pseudorange for the corresponding signal; determining a statistic from residuals of the first plurality of signals; comparing the statistic to a first value; and Responsive to the comparing, the navigation solution is determined to be validated or not validated.

2. The method according to claim 1, wherein: The step of comparing comprises comparing a maximum residual of said first plurality of signals below a first predetermined percentile of a residual distribution to said first value; and In response to a maximum residual at the first predetermined percentile being below the first value, the navigation solution is determined to be validated.

3. The method according to claim 1 or 2, further comprising: determining a statistic from residuals of the second plurality of signals; comparing the statistic to a second value; Responsive to the comparing, the navigation solution is determined to be validated or not validated.

4. The method according to claim 3, further comprising: comparing a maximum residual of the second plurality of signals below a second predetermined percentile of the residual distribution to the second value; The navigation solution is determined to be validated in response to a maximum residual of the second plurality of signals below the second predetermined percentile being below the second value and a maximum residual of the first plurality of signals below the first predetermined percentile being below a first value.

5. The method according to claim 4, wherein: The first predetermined percentile and the second predetermined percentile are the same.

6. The method according to claim 4 or 5, wherein: The first value and the second value are the same.

7. The method according to claim 1 or 2, further comprising: determining a maximum residual of the second plurality of signals that is below a second predetermined percentile of a distribution of residuals of the second plurality of signals; wherein the step of determining the statistic comprises determining a maximum residual of the first plurality of signals that is below a third predetermined percentile of the first plurality of signals; wherein the step of comparing includes determining whether a maximum residual of the first plurality of signals below the third predetermined percentile is greater than a maximum residual of the second plurality of signals below the second predetermined percentile by more than a predetermined percentage; The navigation solution is determined to be validated in response to a maximum residual of the first plurality of signals below the third predetermined percentile being greater than a maximum residual of the second plurality of signals below the second predetermined percentile by more than a predetermined percentage.

8. The method according to claim 7, wherein: The second predetermined percentile and the third predetermined percentile are the same.

9. The method according to claim 1 or 2, further comprising: determining a number of signals in the second plurality of signals; In response to the number of signals in the second plurality of signals being greater than a first signal threshold, the method according to any one of claims 1 to 8 is performed.

10. The method according to claim 1 or 2, further comprising: determining a dilution of precision for the second plurality of signals; In response to the dilution of precision being lower than a dilution of precision threshold, the method according to any one of claims 1 to 9 is performed.

11. The method according to claim 1 or 2, further comprising: comparing a maximum residual of the first plurality of signals below a fourth predetermined percentile to a fourth value; In response to a maximum residual of the first plurality of signals below the fourth predetermined percentile being below the fourth value, individual signals below the fourth predetermined percentile are determined to have passed validation.

12. The method of claim 1 or 2, further comprising estimating a navigation solution based only on the second plurality of signals.

13. The method according to claim 1 or 2, further comprising: In response to the location not being validated: estimating a first updated navigation solution based only on the second plurality of signals; determining, for each of the first plurality of signals, an estimated measurement from a corresponding satellite based on at least the first updated navigation solution; determining, for each of the first plurality of signals, an updated residual, the updated residual comprising a difference between the estimated measurement from the satellite and a pseudorange for the corresponding signal; comparing a maximum residual below a sixth predetermined percentile of the first plurality of signals to a sixth value; In response to the maximum residual below the sixth predetermined percentile being below the sixth value, the signal below the sixth predetermined percentile is determined to pass verification.

14. The method of claim 13, further comprising, in response to a maximum residual below the sixth predetermined percentile being below the sixth value, determining a second updated position based on the second plurality of signals and a signal from the first plurality of signals below the sixth predetermined percentile.

15. A GNSS receiver, the GNSS receiver comprising an antenna and a processor, the antenna being configured to receive a plurality of GNSS signals from a plurality of satellites, a first plurality of signals of the signals not having trusted data, and a second plurality of signals of the signals having trusted data; the processor being configured to: Estimate a navigation solution based on all received GNSS signals; determining, for each satellite from which a signal is received, an estimated measurement from the satellite based at least on the navigation solution; determining a residual for each received signal, the residual comprising a difference between the estimated measurement from the satellite that transmitted the received signal and a pseudorange for the corresponding signal; determining a statistic from residuals of the first plurality of signals; comparing the statistic to a first value; and Responsive to the comparing, the navigation solution is determined to be validated or not validated.

16. A computer program product comprising a computer program, the computer program comprising computer program code configured to, when the computer program is run on one or more processors, cause the one or more processors to perform all the steps of the method according to any one of claims 1 to 14.

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