Detection of an interfering signal in a radio navigation receiver

Abstract

Detection of an interfering signal in a radio navigation receiver is characterized by the fact that the statement about interference detection is obtained by comparing, on the basis of common physical quantities, information from the pseudorange measurement and the statistical characteristics of this feature, calculated on the basis of measuring the travel time of the radio signal from the transmitter to navigation receiver, with information obtained through measurements from the inertial sensor regarding the movement of the receiver antenna, calculated on the basis of acceleration and rotation measurements.

Description

[0001] Detection of an interfering signal in a radio navigation receiver

[0002] The subject of the invention is the detection of an interfering signal of the jamming or spoofing type in a radio navigation receiver, including GNSS.

[0003] Radio and satellite navigation signals (e.g. GNSS) are transmitted through a medium in which protection against interference cannot be ensured. Radio signals travel thousands and tens of thousands of kilometers between transmitting and receiving antennas, and the space they fill must be shared with signals from other sources. To some extent, such radio transmission systems assume correct functioning in an environment not physically protected against interference and sharing the bandwidth with incompatible signals.

[0004] Preventive actions are taken from the legal side. The occupation of the radio band for radio navigation purposes is regulated by the International Telecommunication Union (ITU-R), whose Radio Regulations (https: / / www.itu.int / pub / R-REG-RR / en, WRC-2000) define the current frequency allocations for navigation services, while classifying interference with definitions No. 1.166 to 1.168, dividing it into interference that does not violate the regulatory criteria, interference that violates ITU-R regulations but is allowed with the consent of band users, and harmful and safety-threatening interference, (https: / / insidegnss.com / rnss-and-the- itu -radio-regulations / ) .

[0005] Corrective or reactive actions are also used, which focus on handling the radio signal with harmful interference. In radio navigation applications, no signal quality improvement system is provided or possible, and the only effective way to respond to interference present in the navigation signal is to filter it out, preceded by correct detection. The effectiveness of such action depends on the power and type of interference, the effectiveness and accuracy of interference detection, and the filtering method.

[0006] The purpose of the invention is a method for effective and accurate interference detection, based on the combination of pairs of information which, after analysis and comparison, enable a quantitative assessment of the occurrence of interference, and a qualitative assessment, i.e. a description of the interference.

[0007] An additional assumption of this detection method is to use it at the earliest possible stage of processing the received data, preceding the calculation and formation of navigation information.

[0008] The essence of the method is that the statement about interference detection is obtained by comparing, on the basis of common physical quantities, information from the pseudorange measurement and the statistical characteristics of this feature, calculated on the basis of the measurement of the travel time of the radio signal from the transmitter to the navigation receiver, with the information obtained using measurements from an inertial sensor regarding the movement of the receiver antenna, calculated on the basis of acceleration and rotation measurements.

[0009] Preferably, the source of interference information is a pseudorange measurement, and by analyzing the pseudorange measurements between the transmitter and the navigation receiver, information about the delay caused by interference is extracted.

[0010] Advantageously, each radio channel connecting the transmitter with the navigation receiver is a separate source of pseudorange measurements, and the analysis of pseudorange measurements of each channel extracts separate information about the delay caused by interference, assigned to the appropriate channels.

[0011] Preferably, the current values of physical quantities describing the movement of the navigation receiver antenna, measured and calculated in the inertial system, constitute the basis for determining the expected pseudo-ranges and their statistical characteristics for each of the radio navigation channels, based on an independent propagation model, estimation and known locations of radio transmitters, between the transmitters and the navigation receiver, which in turn are considered as reference values in the comparison method described according to claim 1.

[0012] Advantageously, short and long-term dynamics of changes in the specified parameters are calculated based on the comparison of predicted and measured pseudoranges and their statistical characteristics.

[0013] Preferably, the quantitative and qualitative analysis of the calculated parameters of the dynamics of changes is used to assess the occurrence of interference detection in a radio channel, radio band or in the entire frequency range of the navigation system, and is also used to classify interference and locate its source, while providing statistical parameters describing the analysis results.

[0014] The first information to be compared in the interference detection algorithm is the pseudorange measurement and the statistical characteristics of this feature. It is calculated based on the measurement of the travel time of the radio signal from the transmitter to the navigation receiver. This measurement takes into account radio signal propagation models. The information therefore includes components such as the propagation delay estimation residual and transmitter and receiver clock errors, as well as delay caused by interference such as jamming or spoofing. The second piece of information compared in the interference detection algorithm is the speed and acceleration measured using an inertial sensor. Inertial measurements involve the movement of the antenna, are not dependent on the radio navigation system and are not subject to radio interference. Inertial measurements and the information obtained from them are recognized in the algorithm as a reference base against which information from radio navigation can be evaluated.

[0015] Both pieces of information are reduced to common physical quantities in the algorithm so that they can be compared directly. The set of common physical quantities includes: distance, for the pseudorange calculated in the radio navigation system and inertial counting system, speed relative to each transmitter, as a derivative of the pseudorange determined in the radio system and integration of accelerations in the inertial counting system, acceleration, as a double derivative of the pseudorange determined in the system radio navigation and inertial system measurements. This set also includes all applicable statistical values, for example variances, means, standard deviations and others.

[0016] The operation of the algorithm begins with obtaining information about the pseudorange, i.e. after recognizing the radio navigation signal, tuning the frequency and phase of the signal, demodulating and decoding the information, and calculating the pseudorange taking into account the propagation model and the position of the transmitter. As many pseudorange measurement results are generated in parallel as the number of signals the radio receiver can handle during the measurement. Each measurement is assigned to the appropriate transmitter, and further processing of this information is applied to each transmitter, service and band separately.

[0017] The next step is to calculate the current values from the inertial system: acceleration, speed, position, distances to individual transmitters, based on an independent estimation propagation model and known locations of radio transmitters.

[0018] The next element of the algorithm is the short- and long-term determination of the dynamics of changes in the specified parameters and their statistical descriptions, for each radio transmitter separately. At this stage, a quantitative analysis is performed, which involves observing the intensity of occurrences of the measured values of selected characteristics.

[0019] The key step of the algorithm is to determine, based on the analysis of the obtained parameter dynamics comparison results, which of the radio measurements contain interference or are suspected of being interfered with in a harmful way. At this stage, a qualitative analysis of the results is performed, supported by monitoring measurement trends and adjusting the interference detection sensitivity, as well as the decision to detect interference and the classification of interference and its location.

[0020] A special case of the analysis of the obtained results is the classification of interference into a jamming signal, i.e. jamming a signal transmitted by a specific transmitter and on a specific band, or a spoofing signal, i.e. imitating a specific transmitter and service.

[0021] The final step of the algorithm is assigning an appropriate flag as information to be used when deciding, for example, to exclude the signal or attempt to regenerate it in the radio navigation receiver.

Claims

Patent claims1. Detection of an interfering signal in a radio navigation receiver, characterized in that the statement on interference detection is obtained by comparing, on the basis of common physical quantities, information from the pseudorange measurement and the statistical characteristics of this feature, calculated on the basis of the measurement of the travel time of the radio signal from the transmitter to the navigation receiver, with information obtained through measurements from the inertial sensor regarding the movement of the receiver's antenna, calculated on the basis of acceleration and rotation measurements.

2. Detection of an interfering signal according to claim 1, characterized in that the source of information about interference is a pseudorange measurement and by analyzing the pseudorange measurements between the transmitter and the navigation receiver, information about the delay caused by interference is extracted.

3. Detection of an interference signal according to claim 1, characterized in that each radio channel connecting the transmitter with the navigation receiver is a separate source of pseudorange measurements, and the analysis of pseudorange measurements of each channel extracts separate information about the delay caused by interference, assigned to the appropriate channels.

4. Detection of an interference signal according to claim 1, characterized in that the current values of physical quantities measuring and calculated in the inertial system, describing the movement of the navigation receiver antenna, constitute the basis for determining, based on an independent propagation model, estimation and known locations of radio transmitters, predicted pseudoranges and their statistical characteristics for each of the radio navigation channels between the transmitters and the navigation receiver, which in turn are considered as reference values in the comparison method described according to claim 1.

5. Detection of a disturbance signal according to claim 1, characterized in that short and long-term dynamics of changes in the specified parameters are calculated based on the comparison of predicted and measured pseudoranges and their statistical characteristics.

6. Detection of an interference signal according to claim 1, characterized in that the quantitative and qualitative analysis of the calculated parameters of the dynamics of changes is used to assess the occurrence of interference detection in a radio channel, radio band or in the entire frequency range of the navigation system, and is also used to classify interference and localization, its sources, while providing statistical parameters describing the analysis results.

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