Method of detecting fraud in a receiver, receiver device and computer program product

Abstract

Embodiments of the present disclosure relate to methods, receiver devices, and computer program products of detecting spoofing in a receiver. A satellite tracking channel has a frequency loop that tracks a carrier frequency of a satellite signal. A first indication of a spoofing signal is generated based on a determined satellite signal noise floor value associated with the satellite tracking channel and a tracking channel signal noise threshold associated with the satellite tracking channel. A second indication of a spoofing signal is generated based on a determined satellite tracking phase noise associated with the satellite tracking channel and a tracking channel phase noise threshold associated with the satellite tracking channel. A reception of a spoofing signal on the satellite tracking channel is detected based on the generated first indication of a spoofing signal and the generated second indication of a spoofing signal.

Description

Technical Field

[0001] Embodiments of this disclosure relate to solutions for detecting spoofing signals in GNSS (Global Navigation Satellite System) receivers, and related receiver devices.

[0002] This invention relates in particular to techniques for detecting tracking channels affected by spoofing signals in GNSS multi-frequency multi-constellation receivers. Background Technology

[0003] Integrity is a key feature in the transportation race, and increasing the availability of low-cost "(deceptive interference) meaconing" / "spoofing" systems is a critical issue.

[0004] A so-called "spoofer" can intentionally mislead a receiver to estimate a false location and cause incorrect decisions.

[0005] Autonomous and assisted driving applications place higher demands on airborne GNSS receivers and require robust anti-spoofing systems to operate with such receivers.

[0006] Specifically, spoofing jamming equipment involves intercepting and replaying GNSS navigation signals. These signals are typically rebroadcast on the received carrier at a higher power than the original signal to confuse enemy navigation. As a result, aircraft, UAVs, or ground stations are given inaccurate bearings. This spoofing jamming can also be used in transport environments to provide inaccurate bearings to land vehicles such as automobiles in assisted and autonomous driving scenarios.

[0007] Anti-spoofing methods are known to combat spoofing interference. For example, known solutions envision using more constellation charts independently to perform location identification and check for consistency among them. This relies on the assumption that spoofing does not affect all tracked constellation charts / bandwidths (Hyp).

[0008] This solution only works after the decoy has acquired the tracking channel and multi-frequency / parallel positioning is required.

[0009] Furthermore, it can be used for navigation message authentication, which is a Galileo PRS service.

[0010] The Galileo Public Control Service (PRS) is an encrypted navigation service for government-authorized users. Signal ephemeris is "encrypted," and key management is employed between the satellite and the PRS receiver.

[0011] Of course, it requires PRS Galileo tracking and use, so it cannot be applied to other systems.

[0012] Other methods for detecting GPS spoofing use multi-antenna arrays. Therefore, this solution requires additional hardware. Summary of the Invention

[0013] In one embodiment, a method includes: determining a satellite signal noise floor associated with a satellite tracking channel having a frequency loop at a carrier frequency for tracking a satellite signal; comparing the determined satellite signal noise floor with the tracking channel signal noise threshold associated with the satellite tracking channel; determining satellite tracking phase noise associated with the satellite tracking channel; comparing the determined satellite tracking phase noise with the tracking channel phase noise threshold associated with the satellite tracking channel; detecting reception of a spoofing signal on the satellite tracking channel based on the comparison of the determined satellite signal noise floor with the tracking channel signal noise threshold and the comparison of the determined satellite tracking phase noise with the tracking channel phase noise threshold; and generating a signal indicating that a spoofing signal has been detected on the satellite tracking channel in response to the comparison of the determined satellite signal noise floor with the tracking channel signal noise threshold indicating that the determined satellite signal noise floor exceeds the tracking channel signal noise threshold and the comparison of the determined satellite tracking phase noise with the tracking channel phase noise threshold indicating that the determined satellite tracking phase noise exceeds the tracking channel phase noise threshold.

[0014] In one embodiment, a device includes: a memory; and a signal processing circuitry coupled to the memory. The signal processing circuitry, in operation,: implements a satellite tracking channel having a frequency loop having a tracking satellite signal carrier frequency; determines a satellite signal noise floor associated with the satellite tracking channel; generates a first indication of a spoofing signal based on the determined satellite signal noise floor and a tracking channel signal noise threshold associated with the satellite tracking channel; determines a satellite tracking phase noise associated with the satellite tracking channel; generates a second indication of the spoofing signal based on the determined satellite tracking phase noise and the tracking channel phase noise threshold associated with the satellite tracking channel; and detects reception of the spoofing signal on the satellite tracking channel based on the first indication and the second indication of the generated spoofing signal.

[0015] In one embodiment, a system includes: a host processor; and signal processing circuitry coupled to the host processor. The signal processing circuitry, in operation: implements a satellite tracking channel having a frequency loop having a tracking satellite signal carrier frequency; determines a satellite signal noise floor associated with the satellite tracking channel; generates a first indication of a spoofing signal based on the determined satellite signal noise floor and a tracking channel signal noise threshold associated with the satellite tracking channel; determines a satellite tracking phase noise associated with the satellite tracking channel; generates a second indication of the spoofing signal based on the determined satellite tracking phase noise and the tracking channel phase noise threshold associated with the satellite tracking channel; and detects reception of the spoofing signal on the satellite tracking channel based on the first indication and the second indication of the generated spoofing signal.

[0016] In one embodiment, the content of a non-transitory computer-readable medium causes a signal processing system to perform a method comprising: implementing a satellite tracking channel having a frequency loop having a tracking satellite signal carrier frequency; determining a satellite signal noise floor associated with the satellite tracking channel; generating a first indication of a spoofing signal based on the determined satellite signal noise floor and a tracking channel signal noise threshold associated with the satellite tracking channel; determining satellite tracking phase noise associated with the satellite tracking channel; generating a second indication of the spoofing signal based on the determined satellite tracking phase noise and the tracking channel phase noise threshold associated with the satellite tracking channel; and detecting reception of the spoofing signal on the satellite tracking channel based on the first indication and the second indication of the generated spoofing signal. In one embodiment, the content comprises instructions executed by a processor of the signal processing system. Attached Figure Description

[0017] Embodiments of this disclosure will now be described with reference to the accompanying drawings, which are provided by way of non-limiting example only, in which:

[0018] Figure 1 This is a schematic diagram illustrating a GNSS (Global Navigation Satellite System) system;

[0019] Figure 2 Is Figure 1 A schematic diagram of the tracking channel used in the system;

[0020] Figure 3 This is a flowchart of the method according to the embodiments; and

[0021] Figures 4A to 4C This is a diagram illustrating the operation of an embodiment. Detailed Implementation

[0022] In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. The embodiments may be practiced without one or more of these specific details, or using other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments.

[0023] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0024] The titles provided in this document are for convenience only and do not explain the scope or meaning of the embodiments.

[0025] Navigation receivers operate by down-converting the input signal received from satellites to quasi-baseband, which is typically transmitted in the L-band (1-2 GHz). They use a local oscillator to reduce the input frequency and allow for baseband digital management of satellite information.

[0026] refer to Figure 1 This schematically illustrates a GNSS global navigation satellite system 1000 (e.g., Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), Galileo system, or other types of satellite-based positioning systems, such a GNSS global navigation satellite system 1000 comprising (multiple) NS satellites S0-S1000). NS－1 The constellation and at least one receiver 100. Satellite signals used in GNSS (Global Navigation Satellite System) are typically of the CDMA (Code Division Multiple Access) type. Satellite signal reception at receiver 100 is typically achieved through standard steps performed in the following sequence: analog filtering, frequency conversion and digitization, acquisition, tracking, decoding, and positioning.

[0027] The receiver 100 includes: an antenna 1, an analog receiver module AFE (analog front end) equipped with a radio frequency (RF) stage 2, and an analog-to-digital converter 3 (ADC) that can be implemented by a hardware module.

[0028] In addition, the receiver 100 includes a digital processing module DFE (digital front end), which includes an acquisition module 4 (ACQ) and a tracking module 5 (TRK).

[0029] In addition, the receiver 100 has a subframe recovery module (SBF-REC) 6, an ephemeris processing and pseudorange calculation module (EPH-PSR) 7, a satellite orbit prediction module (ORB-PRE) 8, a satellite type detection module (MOD-DET) 9, a satellite position calculation module (SAT-POS) 10, and a user position calculation module (USR-POS).

[0030] In the example embodiment, the acquisition module 4 and the tracking module 5 can be implemented in hardware (e.g., using discrete circuit 26), while the remaining modules 6-11 can be implemented in software (e.g., software stored in memory 24 and executed on processor 22). Furthermore, it can be seen that the acquisition module 4 and the tracking module 5 can also be implemented through various combinations of hardware and software.

[0031] The receiving device 100 is equipped with a central processing unit 22, a memory 24 (mass memory and / or working memory) and corresponding interfaces (not shown), including a microprocessor or microcontroller for running software residing therein.

[0032] The following embodiments are described in a non-limiting manner with reference to GPS technology; however, the teachings of the present invention can also be applied to other satellite positioning systems.

[0033] When the receiver 100 is operational, the antenna 1 receives signals from one or more satellites S0-S1 of a satellite constellation operating in system 1000. NS－1 Receive multiple signals S0, ..., S NS－1 For example, these signals can be modulated on a carrier wave with a frequency of approximately 1.5 GHz. Each received signal transmits a pseudo-random code and a message for data communication.

[0034] A pseudo-random code, called a CA code, is used, for example, at 1 MHz, to distinguish one satellite from another and to enable receiver 100 to measure the time when a signal is transmitted by the corresponding satellite. The pseudo-random code is implemented using a sequence of pulses called chips.

[0035] Radio frequency stage 2 operates on signals received by (analog type) antenna 1 and converts them to baseband or intermediate frequency (IF). Analog-to-digital converter 3 converts the IF signals into corresponding digital signals. Radio frequency stage 2 uses the frequency of the local signal LS, which can be provided by temperature-compensated crystal oscillator (TCXO) 2a, for IF conversion.

[0036] Acquisition module 4 identifies visible satellites in the digital signal generated by analog-to-digital converter 3, tests their presence by attempting to match their transmitted PRN (pseudo-random noise) code sequences, CA codes, and corresponding local copies, and provides initial GNSS information and code / frequency information to the basic intermediate frequency tracking correlation block when a peak confirmation is found. Furthermore, acquisition module 4 detects multiple parameters associated with the satellites and used for time tracking of the satellites.

[0037] Data navigation messages transmit data (e.g., at a bit rate of 50 Hz) and are specifically modulated using binary phase shift keying (BPSK) technology. Furthermore, data navigation messages are hierarchically divided into frames and subframes, and transmit several pieces of information, including multiple parameters used to determine the orbit and thus the satellite's position.

[0038] Tracking module 5 has multiple tracking channels, represented by channel indices i from 0 to NS-1, specifically TRK0…TRK NS－1 Each tracking channel is assigned to a different satellite in the constellation. Specifically, tracking module 5 is configured to operate as a carrier tracking loop, which can be designed to use a phase-locked loop (PLL) to track the phase of the input signal, or a frequency-locked loop (FLL) to track the Doppler frequency of the input signal. Phase noise (residual fluctuations in the tracking process) is intended as a quality metric, and it is used to identify the quality of the tracking itself at a given carrier pair noise Cn0.

[0039] Tracking module 5 is configured to provide data as a time series of sample pairs denoted as {I, Q} to subframe recovery module 6. Each sample {I, Q} is, for example, the result of a 20ms bit coherent integration (step-by-step and quadrature, respectively) performed by a correlator based on the modulation technique binary phase shift keying (BPSK), and each sample pair {I, Q} represents the transmitted bits.

[0040] As is known in the field of digital communication theory, each sample {I, Q} can be further interpreted as a phasor by treating the values ​​I and Q as the real and imaginary parts of a two-dimensional vector in a complex Cartesian plane.

[0041] Furthermore, for each satellite, in tracking module 5, the location of satellites S0-S1 is determined. NS－1 The Doppler frequency and transmission time of the transmitted GPS signal.

[0042] exist Figure 2 In the diagram, the i-th satellite S belonging to the general system is shown. i Tracking channel TRK i A schematic diagram of 50.

[0043] Hardware correlator circuit 51 receives the sampled received signal from block 4x(k) and provides the correlation signal:

[0044] x(k)=s(k)+w(k)=Ip(k)+jQp(k)

[0045] For example, every millisecond (which is the period of index k of the samples of the correlated signal x(k)) to the carrier / Cn0 estimation loop block or circuit 52, which outputs the frequency drift Δf(n) = atan(Qave / Iave) at iteration n to the numerically controlled oscillator hardware block NCO or circuit 53. The signal component is s(k), and w(k) is the noise component of the correlated signal, Ip, Qp are synchronous or in phase, and the quadrature components Iave and Qave of the correlated signal are the corresponding values ​​averaged over one or more bits (the iteration index n is updated, for example, every 20 or 200 samples / milliseconds (interval of index k = 1ms)) to estimate the residual frequency drift Δf and match the i-th satellite S. i The Doppler is used to strip and optimize peak tracking at subsequent correlations. NCO 53 provides a fine-tuning frequency Doppler reference NCO(n+1) = NCO(n) + Δf(n). Therefore, starting from the peak code phase position and using the fine-tuning frequency Doppler reference NCO(n) updated through carrier loop 52 and NCO 53, for the tracked satellite S i The relevant operation is executed once every millisecond.

[0046] The signal model used for satellite locking can be written as follows:

[0047] x(k)=s(k)+w(k)

[0048]

[0049] w I，Q (k)~N(0,σ)

[0050] Where σ is the background noise of the I and Q noise components (the standard deviation of one component), assumed to be AWGN (additive white Gaussian noise). This is the initial stage. α D This energy attenuation is due to residual Doppler error (between the programmed carrier NCO frequency F and the true SV Doppler). C A is the chip duration, and A is the amplitude.

[0051] For can be by Figure 2 The carrier noise ratio Cn0 of the output of block 52 can be estimated by starting from the synchronous and quadrature sampling Ip and Qp available per millisecond on the Prompt signal, and by accumulating the wideband power PW and the narrowband power PN (at 1 kHz and 50 Hz, respectively).

[0052] Each bit (e.g., every 20ms in the case of GPS) is written as

[0053]

[0054]

[0055] Broadband power P W and narrowband power P N The number of consecutive times / periods N dc The average is typically 10, for example, 10 times the bit length of 20ms.

[0056]

[0057] Then, they are filtered for stability.

[0058]

[0059]

[0060] Using the following formula, the filtered quantity P WS，FILT P NS，FILT The carrier-to-noise ratio Cn0 of the locked channel involved in deriving the synchronous and orthogonal samples Ip and Qp:

[0061]

[0062] The denominator of the Cn0 formula is called the satellite noise floor N0, which is the broadband power minus the narrowband power divided by the bit length Nb.

[0063] Its value, averaged across all locked satellites, is known as the channel noise floor.

[0064] The satellite's phase Ip and orthogonal phase Qp correlation samples are also incoherently accumulated over the bit length, starting from the effective bit edge phase, to establish the corresponding accumulation amount Qsum20. k And Isum20 k k is the bit index, and they are then mixed between consecutive bits, such as k and k-1, to produce a quantity corresponding to the beat frequency information (Imix). k Qmix k This beat frequency information is used to detect incremental phase or equivalent frequency offset relative to the already tracked phase and update the frequency value of the satellite being tracked.

[0065] Referring to GPS, with a bit length of 20ms, without loss of generality, the rules for frequency updates can be derived sequentially by applying the equations reported below:

[0066] Imix k =Isum20 k *Isum20 k-1 +Qsum20 k *Qsum20 k-1

[0067] Qmix k =Isum20 k *Qsum20 k-1 -Qsum20 k *Isum20 k-1

[0068]

[0069]

[0070] Where L is the phase rate quantity Δtan2(Qmixk, Imixk) averaged for the decision interval (e.g., 10 bits).

[0071] The quality metric used for the frequency loop is the tracking phase noise Ph, which is the residual between the phase rate obtained from the phase difference measurement and its average value [desired value]. It is expressed in milliequivalents, and under nominal conditions, in a steady state, it should stably become zero to indicate the achievement of fully locked frequency tracking.

[0072] Therefore, for each i-th tracking channel TRK i In a manner known per se, a frequency-locked loop and a carrier-to-noise ratio meter are included, which estimate the carrier-to-noise ratio C / No of the frequency loop of the tracking channel, for example every N (e.g., 10) cumulative cycles, wherein the fundamental coherent channel is defined by the bit length of the signal under consideration (e.g., 20 ms for the GPS L1 / CA case) and aligned with the first millisecond of the bit.

[0073] The subframe recovery module 6 decodes the different received subframes that form the navigation data message using an appropriate algorithm. The ephemeris processing and pseudorange calculation module 7 stores the satellite orbit as ephemeris data and calculates the distance between the satellite and the receiver 100: this distance is called the pseudorange. Using these calculated values ​​and the time used to transmit the GPS signal, the satellite position calculation module 10 calculates the satellite's position in 3D coordinates at the time of transmission.

[0074] The satellite orbit prediction module 8 can be activated to assist the ephemeris processing and pseudorange calculation module 7 and / or the satellite position calculation module 10 when ephemeris data is not available at the receiving device 100.

[0075] Satellite type detection module 9 is configured to determine the type of the tracked satellite based on a pattern described below as an example, and through this, to determine the solar radiation pressure model to be used in the orbit prediction of satellite orbit prediction module 8. Satellite type detection module 9 is able to determine the type of satellite in order to select a solar radiation pressure model that better provides information about the satellite's shape, mass, and size.

[0076] In this embodiment, the satellite position calculation module 10 operates on the time for transmitting GPS signals and the reception time (known due to the clock within the receiver device 100). The satellite position calculation module 10 operates to estimate how long it takes for signals from each satellite to reach the receiver device 100, thereby assessing the distance (pseudorange) to the corresponding satellite.

[0077] Using a triangulation algorithm, the user location calculation module 11 calculates the location of the receiver 100 based on the distances of the receiver 100 (for example) to at least four satellites and based on the locations of the same satellites known at this processing stage. In the following text, the location of the receiver 100 (which is actually consistent with the user location) will be referred to as “fixed”.

[0078] As described above, tracking module 5 includes multiple channels and tracking correlation blocks, which typically allow parallel operation. Each tracking correlation block is tuned to a different satellite PRN code and frequency from those previously identified by acquisition block 4, with the aim of confirming or ultimately discarding the reception hypothesis for each of them. For confirmed satellites, after initial refinement of the codes and frequencies provided by the acquisition module, stable lock-on tracking phase begins. This includes following the frequency offset (velocity) and code phase (range) of the analyzed satellite vehicle and demodulating the position and time information embedded in its bit stream. This information is then provided to a Kalman filter for triangulation of the receiver position.

[0079] The tracking channel described above includes a correlator, which comprises a PRN (pseudo-random noise) delay sequence generator. The GNSS signal received at the receiver includes ranging codes modulated into the carrier, also known as pseudo-random noise (PRN) codes, which spread the spectrum and allow for the retrieval of ranging information. Therefore, the tracking channel includes a PRN delay sequence generator that generates PRN sequences that are ahead, on time, or delayed relative to each other to perform correlation with the ranging codes.

[0080] The embodiments briefly described herein relate to a method for detecting spoofing in a GNSS (Global Navigation Satellite System) receiver that monitors data from one or more satellites S0-S1. NS－1 Received satellite signals (e.g., S0, ..., S) NS－1The solution describes a method to detect spoofing attacks as soon as it begins monitoring the statistical properties of satellite signals and comparing them to expected statistical properties, particularly with defined thresholds.

[0081] The method includes examining the statistical characteristics of satellite signals relative to expected characteristics, and performing joint checks on quantities derived from these statistical characteristics so that a spoofing attack is revealed once these quantities are simultaneously different from the expected characteristics.

[0082] Specifically, the method includes:

[0083] By updating the carrier noise ratio of each satellite The moving average filter is used to evaluate all tracked satellites S0-S1. NS－1 This average noise To check the satellite's background noise value, i.e., the i-th tracked satellite / signal S1, N0 i carrier noise ratio The denominator N0 of the quality factor is relative to the average channel noise available on the communication channel. The ratio. In other words, take, for example, the carrier noise ratio quality factor (e.g., S0, ..., S) of each satellite signal over a given accumulation period. NS－1 Find the value of the denominator N0 of the fraction, and calculate the denominators N0, N00, ..., N0 NS－1 The moving average filter is the average of these values. The moving average filter can be a filter that performs smoothing, which converges to the denominators N0, N00, ..., N0 under normal conditions aligned in any way. NS－1 The average value in;

[0084] For a carrier-to-noise ratio of interest in the application, such as the phase noise threshold, check the tracking phase noise Ph against a quality factor that indicates good operation of the tracking channel for different carrier-to-noise ratios. The phase noise threshold can be different.

[0085] Then, these quantities, the satellite background noise value, and the tracking phase noise Ph are jointly examined, especially at a given carrier noise ratio. This allows for the detection of deceptive attacks when they are separated from anticipated deceptive attacks.

[0086] This embodiment is based on the immediate observation of both real and spoofed signals in the received data when a spoofing attack occurs. Upon attack, the satellite tracking loop shifts to the spoofed signal while keeping the real signal within the tracking noise bandwidth.

[0087] This makes the denominator noise N0 (carrier noise ratio) The signal is increased by a molecular carrier signal C (a part of the true signal), which exists due to the spoofed signal tracked by the corresponding tracking channel, but is no longer tracked by its tracking channel. Therefore, when the spoofing attack begins, the real satellite signal is treated as noise N0 in the formula, resulting in an increase in noise N0.

[0088] Furthermore, the frequency loop noise is affected by the unexpected presence of two carriers (the real satellite signal carrier and the spoofing signal carrier) and by the fact that the frequency loop suddenly shifts to the spoofing frequency of the spoofing signal, while the real signal is treated as an unrecovered random fluctuation that increases frequency noise. Under nominal conditions, such as in the absence of spoofing, strong satellite signals do not exhibit significant frequency noise compared to what occurs during a spoofing attack in the transition phase from the real signal to the spoofing signal loop.

[0089] Refer to the signal model of the received signal x(k) and the equation for the carrier-to-noise ratio Cn0:

[0090]

[0091] The noise floor and satellite noise under nominal conditions are aligned because the former is a filtered version of the latter.

[0092] Under a spoofing attack, the signal models reported to date no longer hold true because the spoofed signal overlaps with the real signal.

[0093] The following two factors can be considered simultaneously to update the received signal model:

[0094] x(k)=s(k)+g(k)+w

[0095] The deception signal is s(k) and is

[0096]

[0097] The actual signal g(k) is

[0098]

[0099] And noise is

[0100] w I，Q (k)~N(0,σ)

[0101] A1 and A2 are the amplitudes of the deceptive signal and the real signal, respectively, and f1 and f2 are their respective frequencies.

[0102] Deception attacks rely on sequential steps:

[0103] Initial silent synchronization is true (A1 << A2, f1 = f2). Although present, the spoofers are not yet active;

[0104] Power increase for capturing channel control (A2 >> A1, f1 = f2). There is a typical 6 dB (4-fold amplitude) separation;

[0105] Trajectory divergence by frequency, moving the position away (A2 >> A1 f1!= f2).

[0106] When the trajectory divergence is occurring, the tracking channel is locked on the frequency f1!= f2 (true) but at least within the capture range of the cn0 formula |f1 - f2| during the first second of the attack (broadband power of 1 KHz).

[0107] Therefore, the embodiments described herein provide: in a receiver, during the tracking process of a tracking channel, periodically performing the steps of the method described herein for detecting spoofing in a GNSS (Global Navigation Satellite System) receiver, in an embodiment, the GNSS receiver may include:

[0108] Receiving at least one satellite signal S i ,

[0109] Obtaining the satellite signal S i as a received signal,

[0110] Receiving the received signal in at least one tracking channel TRK i where the tracking channel TRK i includes a frequency loop for tracking the carrier frequency of the satellite signal S i where the method includes, during the tracking,

[0111] obtaining the satellite background noise N0 value as the noise of the tracking channel TRK1,

[0112] obtaining the average channel noise calculated on all satellite signals S0,..., S

[0113] tracked in the receiver 100, NS－1 obtaining the ratio R of the satellite background noise N0 value to the average channel noise

[0114] comparing the ratio R with a ratio threshold R ,

[0115] obtaining the satellite tracking phase noise Ph, th comparing the satellite tracking phase noise Ph with a phase noise threshold Ph

[0116] obtaining the satellite tracking phase noise Ph,

[0117] comparing the satellite tracking phase noise Ph with a phase noise threshold Phth Compare;

[0118] If both the ratio R and the satellite tracking phase noise Ph are higher than their respective thresholds R th Ph th For example, a signal can be sent to notify the TRK tracking channel by setting a detection flag SD. i A spoofing signal was detected.

[0119] For example, in an embodiment, the steps of periodically executing a method for detecting spoofing in GNSS in the receiver during the tracking process of the tracking channel may include: executing a method step at the end of every N tracking cycles, specifically updating the carrier-to-noise ratio, for example, N = 10 × 20 ms = 200 ms is the period of executing the method steps.

[0120] The method described here has the advantage of being applicable to every RF channel and signal type (traditional L1, L2, and L5). This provides a complete anti-spoofing parallel detection mechanism "on all channels and paths".

[0121] exist Figure 3 The diagram shows a flowchart of an embodiment of the inspection process 300 of the method described herein, which includes obtaining the channel average noise floor in step 110. Noise floor is a measure of the signal produced by the sum of all noise sources and unwanted signals within a measurement system, where noise is defined as any signal other than the signal being monitored. Channel average noise floor value. It is a parameter evaluated by the moving average filter across all tracked satellites when updating the carrier-to-noise ratio of each satellite.

[0122] In step 120, which can be performed simultaneously before or after step 110, the satellite background noise N0 is obtained, which is the denominator of the carrier noise ratio C / N0 measured in the tracking channel within a defined time period.

[0123] In step 130, the satellite noise floor N0 and the channel average noise floor are calculated. The ratio R between them As mentioned, such as in the tracking channel TRK i In this context, background noise refers to any signal other than the signal tracked by its frequency loop. Under normal circumstances, the tracked signal is the i-th satellite signal S being tracked. i During the attack, the tracked signal becomes a deceptive signal, therefore the satellite signal S is calculated from the satellite background noise N0. i Therefore, in the event of an attack, this determines the satellite noise floor N0 and the channel average noise floor. The increase in the ratio R between them.

[0124] Therefore, in step 140, it is checked whether the ratio R is greater than the threshold ratio R. th For example, check whether the increase in ratio R due to the increase in satellite background noise N0 is higher than the level expected to correspond to the presence of a spoofing signal when passing through.

[0125] As mentioned above, the satellite noise floor N0 and the channel average noise floor For example, it can be obtained from the carrier-to-noise ratio table available in each tracking channel, where the satellite noise floor value N0 is the average noise floor value. The common input, the average noise floor value, is, for example, a filtered version of the satellite noise floor value, which is performed by averaging the noise provided by all tracked and unspoofed satellites.

[0126] In step 150, the satellite tracking phase noise Ph is obtained, which is in the tracking channel TRK. i The measurement is performed at the frequency loop. This step can be performed simultaneously with, during, before, or after steps 110-140.

[0127] In step 160, it is checked whether the satellite tracking phase noise Ph is greater than the phase noise threshold Ph. th As mentioned above, frequency loop noise is affected by the actual satellite signal carrier S. i The strong satellite signal does not exhibit significant frequency noise in the absence of deception, compared to what occurs during the transition phase of the loop from the real signal to the deception signal under a deception attack. Therefore, based on the tracking channel TRK... i The expected noise without deception is used to define the phase noise threshold Ph. th .

[0128] In step 170, a joint check of the measured quantities is performed; if both the ratio R and the satellite tracking phase noise Ph are higher than their respective thresholds R... th Ph th Then, check if steps 140 and 160 are both affirmative. If affirmative, issue a spoofing signal detection flag SD, for example, setting it from logic 0 to logic 1. This spoofing signal detection flag SD is set and forwarded to the upper integrity layer module controlling receiver operation, typically included within the receiver itself, such as a SIS (Signal Integrity System Layer) module or circuitry. Such a module is responsible for tracking the spoofed channel TRK. iPlaced in isolation, and generating general spoofing alarms, especially isolating such signals at predetermined time intervals. The isolation list avoids using spoofing signals for localization and prevents convergence to the wrong location.

[0129] When operating in the channel frequency domain, the solution described herein can be easily integrated with other spoofing detection mechanisms operating in the code domain, which monitors the correlation values ​​of the correlator group in the tracking channel.

[0130] exist Figure 4A -4C shows graphs representing the test results of the solution. In these graphs, a spoofing signal SS is applied in orbit, with a frequency jump of 200 Hz applied from the satellite signal frequency to the spoofing signal frequency, and a position of 2 km is applied.

[0131] Artificially moving code / frequency coordinates triggers satellite tracking loss and re-acquisition.

[0132] exist Figure 4A The figure shows the phase noise Ph on the vertical axis and the ratio R on the horizontal axis. Circles represent cheating. As shown in the figure, for a given value (threshold R) on each axis... th Ph th On the other hand, the joint detection of values ​​indicates deception.

[0133] exist Figure 4B The diagram shows the time plot, which illustrates the carrier noise ratio Cn0 as a function of the time quantity and the tracking period, and... Figure 4C The figure shows the lock-in time in seconds as a function of the tracking period. As shown, the circles representing deception indicate the time at which satellite tracking is lost and reacquired.

[0134] Therefore, the solution disclosed here has significant advantages over known solutions.

[0135] Advantageously, the solution described here by employing a software-implemented process relies solely on the statistical difference between the expected and spoofed quantities (noise and frequency loops of the signal C / N0). This solution extends spoofing detection capability to every RF channel (L1-L2-L5) without any limitations and allows matching customer expectations far exceeding available countermeasures.

[0136] Of course, without departing from the principles of this disclosure, the details of the construction and embodiments may vary extensively relative to what is described and shown herein by way of example only, without departing from the scope of this disclosure as defined by the appended claims.

[0137] The receiver device can send detection alerts to the host processor of an autonomous driving system or another navigation system that utilizes such a GNSS receiver device.

[0138] In different embodiments, instead of the average background noise obtained by averaging the background noise values ​​from other satellite tracking channels, the average channel noise is used. Reference average noise can be used Its channel tracking TRK i An additional correlator is used internally for estimation, which allows integration over chip length Tc and different Doppler frequencies (e.g., always at coordinates, although very far from the Doppler frequencies of the true signal). This correlation produces an autonomous “zero-value” carrier-to-noise ratio Cn0 (noise only), whose denominator represents the satellite noise floor N0 value used for this additional correlation, which can be used as an autonomous “clean reference” even under attack and enables a self-contained detection mode.

[0139] In one embodiment, a method for detecting spoofing in a GNSS receiver (100) can be summarized as including at least receiving satellite signals (S i ), to acquire the satellite signal (S i As a received signal, including tracking satellite signals (S i At least one tracking channel (TRK) of the frequency loop (51, 52, 53) of the carrier frequency of ) i The method includes receiving the received signal in the tracking channel (TRK) during the tracking process, wherein the method includes obtaining the satellite background noise value (No) as the tracking channel (TRK). i The noise is calculated by comparing the satellite's background noise value (No) with the noise threshold (N). th The satellite tracking phase noise (Ph) is compared with the phase noise threshold (Ph) to obtain the satellite tracking phase noise (Ph). th The comparison is performed; if both the satellite background noise value (N0) and the satellite tracking phase noise (Ph) are higher than their respective thresholds (N... th Ph th If the signaling (SD) on the tracking channel detects a spoofing signal, then the spoofing signal will be detected.

[0140] In one embodiment, the method includes, during the tracking, obtaining (110) as a tracking channel (TRK). i The satellite background noise value (No) is obtained from the noise of the satellite, and a reference background noise value (120) is obtained, for example, calculated as the noise of all tracked satellite signals (so, ..., S). NS－1 The average channel noise is the average value of the background noise on the average channel noise. Obtain the ratio (R) of the satellite noise floor (N0) to the reference noise floor, such as the average channel noise. The ratio (R) and the ratio threshold (R) thThe satellite tracking phase noise (Ph) is compared with the phase noise threshold (Ph) to obtain the satellite tracking phase noise (Ph). th The ratio (R) and satellite tracking phase noise (Ph) are compared; if both are higher than their respective thresholds (R0 and Ph), the comparison is performed. th Ph th If the signaling (SD) on the tracking channel detects a spoofing signal, then the spoofing signal will be detected.

[0141] In one embodiment, the reference noise floor value can be obtained in the tracking channel (TRK). i The calculation is performed using a correlator that integrates over the chip length (Tc) and over different Doppler frequencies relative to the frequency tracking loop.

[0142] In one embodiment, the signaling (SD) detection of spoofing signals on the tracking channel may include a module that sets a flag and forwards the flag to an upper integrity layer that controls the operation of the receiver, particularly isolating spoofing signals over predetermined time intervals.

[0143] In one embodiment, the module of the upper integrity layer that controls the operation of the receiver can send a detection alarm to the host processor of the autonomous driving system or another navigation system utilizing such a GNSS receiver device.

[0144] In one embodiment, the receiver device may be configured to perform an embodiment of the methods disclosed herein.

[0145] In one embodiment, a computer program product that can be directly loaded into the internal memory of a digital computer can be summarized as a software code portion that includes steps for performing embodiments of the methods disclosed herein.

[0146] In one embodiment, a method includes: determining a satellite signal noise floor associated with a satellite tracking channel having a frequency loop at a carrier frequency for tracking a satellite signal; comparing the determined satellite signal noise floor with a tracking channel signal noise threshold associated with the satellite tracking channel; determining satellite tracking phase noise associated with the satellite tracking channel; comparing the determined satellite tracking phase noise with a tracking channel phase noise threshold associated with the satellite tracking channel; detecting reception of a spoofing signal on the satellite tracking channel based on the comparison of the determined satellite signal noise floor with the tracking channel signal noise threshold and the comparison of the determined satellite tracking phase noise with the tracking channel phase noise threshold; and generating a signal indicating that a spoofing signal has been detected on the satellite tracking channel in response to the comparison of the determined satellite signal noise floor with the tracking channel signal noise threshold indicating that the determined satellite signal noise floor exceeds the tracking channel signal noise threshold and the comparison of the determined satellite tracking phase noise with the tracking channel phase noise threshold indicating that the determined satellite tracking phase noise exceeds the tracking channel phase noise threshold. In one embodiment, comparing a determined satellite signal noise floor value with a tracking channel signal noise threshold associated with the satellite tracking channel includes: determining a reference signal noise floor value; determining a ratio of the determined satellite signal noise floor value to the reference signal noise floor value; and comparing the determined ratio with the tracking channel signal noise threshold. In one embodiment, the reference signal noise floor value is the average channel noise over a plurality of tracked satellite signals. In one embodiment, a correlator is used in the tracking channel to calculate the reference signal noise floor value, the correlator integrating over the chip length and at different Doppler frequencies relative to the frequency tracking loop. In one embodiment, generating a signal indicating the detection of a spoofing signal on the satellite tracking channel includes setting a flag and isolating the spoofing signal over a defined time interval. In one embodiment, generating a signal indicating the detection of a spoofing signal on the satellite tracking channel includes sending a detection alert to the host processor of an autonomous driving system or another navigation system. In one embodiment, the satellite tracking channel is a tracking channel of a Global Navigation Satellite System (GNSS).

[0147] In one embodiment, a device includes: a memory; and signal processing circuitry coupled to the memory. The signal processing circuitry, in operation: implements a satellite tracking channel having a frequency loop having a tracking satellite signal carrier frequency; determines a satellite signal noise floor value associated with the satellite tracking channel; generates a first indication of a spoofing signal based on the determined satellite signal noise floor value and a tracking channel signal noise threshold associated with the satellite tracking channel; determines a satellite tracking phase noise associated with the satellite tracking channel; generates a second indication of the spoofing signal based on the determined satellite tracking phase noise and the tracking channel phase noise threshold associated with the satellite tracking channel; and detects reception of a spoofing signal on the satellite tracking channel based on the first indication and the second indication of the generated spoofing signal. In one embodiment, the signal processing circuitry, in operation, responds to the first indication and the second indication of the spoofing signal indicating the detection of a spoofing signal by generating a signal indicating the detection of a spoofing signal on the satellite tracking channel. In one embodiment, the signal processing circuitry generates a first indication of a spoofing signal by: determining a reference signal noise floor; determining a ratio of the determined satellite signal noise floor to the reference signal noise floor; and comparing the determined ratio to a tracking channel signal noise threshold. In one embodiment, the signal processing circuitry determines the reference signal noise floor by determining the average channel noise over multiple satellite signals being tracked. In one embodiment, a correlator is used in the tracking channel to calculate the reference signal noise floor, the correlator integrating over the chip length and at different Doppler frequencies relative to the frequency tracking loop. In one embodiment, generating a signal indicating that a spoofing signal has been detected on the satellite tracking channel includes setting a flag and isolating the spoofing signal over a defined time interval. In one embodiment, generating a signal indicating that a spoofing signal has been detected on the satellite tracking channel includes sending a detection alert to the host processor of an autonomous driving system or another navigation system. In one embodiment, the satellite tracking channel is a tracking channel of a Global Navigation Satellite System (GNSS).

[0148] In one embodiment, a system includes: a host processor; and signal processing circuitry coupled to the host processor. The signal processing circuitry, in operation: implements a satellite tracking channel having a frequency loop having a tracking satellite signal carrier frequency; determines a satellite signal noise floor associated with the satellite tracking channel; generates a first indication of a spoofing signal based on the determined satellite signal noise floor and a tracking channel signal noise threshold associated with the satellite tracking channel; determines a satellite tracking phase noise associated with the satellite tracking channel; generates a second indication of the spoofing signal based on the determined satellite tracking phase noise and the tracking channel phase noise threshold associated with the satellite tracking channel; and detects reception of a spoofing signal on the satellite tracking channel based on the first indication and the second indication of the generated spoofing signal. In one embodiment, the signal processing circuitry, in operation, responds to the first indication and the second indication of the spoofing signal indicating the detection of a spoofing signal by generating a signal indicating the detection of a spoofing signal on the satellite tracking channel. In one embodiment, the signal processing circuitry generates a first indication of a spoofing signal by: determining a reference signal noise floor; determining a ratio of the determined satellite signal noise floor to the reference signal noise floor; and comparing the determined ratio with a tracking channel signal noise threshold. In one embodiment, the signal processing circuitry determines the reference signal noise floor by determining the average channel noise over multiple tracked satellite signals. In one embodiment, the signal processing circuitry responds to the detection of a spoofing signal by sending a detection alarm to a host processor. In one embodiment, the host processor implements a navigation system, and the signal processing circuitry detects signals from a Global Navigation Satellite System (GNSS) during operation.

[0149] In one embodiment, the content of a non-transitory computer-readable medium causes a signal processing system to perform a method comprising: implementing a satellite tracking channel having a frequency loop having a tracking satellite signal carrier frequency; determining a satellite signal noise floor associated with the satellite tracking channel; generating a first indication of a spoofing signal based on the determined satellite signal noise floor and a tracking channel signal noise threshold associated with the satellite tracking channel; determining satellite tracking phase noise associated with the satellite tracking channel; generating a second indication of the spoofing signal based on the determined satellite tracking phase noise and the tracking channel phase noise threshold associated with the satellite tracking channel; and detecting reception of the spoofing signal on the satellite tracking channel based on the first indication and the second indication of the generated spoofing signal. In one embodiment, the method includes responding to the first indication and the second indication of the spoofing signal indicating the detection of the spoofing signal by generating a signal indicating the detection of the spoofing signal on the satellite tracking channel. In one embodiment, the content comprises instructions executed by a processor of the signal processing system.

[0150] Some embodiments may take the form of or include a computer program product. For example, according to one embodiment, a computer-readable medium is provided that includes a computer program adapted to perform one or more of the methods or functions described above. The medium may be a physical storage medium, such as a read-only memory (ROM) chip, or a disk, such as a digital multifunction disc (DVD-ROM), optical disc (CD-ROM), hard disk, memory, network, or a portable media article readable by a suitable drive or via a suitable connection, including one or more barcodes or other related codes encoded on one or more such computer-readable media and readable by a suitable reader device.

[0151] Furthermore, in some embodiments, some or all of these methods and / or functions may be implemented or provided in other ways, for example, at least in part in firmware and / or hardware, which includes, but is not limited to, one or more application-specific integrated circuits (ASICs). i C), digital signal processors, discrete circuits, logic gates, standard integrated circuits, controllers (e.g., by executing appropriate instructions, and including microcontrollers and / or embedded controllers), field-programmable gate arrays (FPGAs), complex programmable logic devices (CPLDs), and devices employing RFID technology and various combinations thereof.

[0152] The various embodiments described above can be combined to provide other embodiments. If desired, aspects of the embodiments can be modified to incorporate concepts from various patents, applications, and publications to provide other embodiments.

[0153] Based on the detailed description above, these and other changes can be made to the embodiments. Generally, the terminology used in the following claims should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted to include all possible embodiments and the full scope of the authorized equivalents of these claims. Therefore, the claims are not limited to this disclosure.

Claims

1. A method for detecting spoofing in a receiver of a global navigation satellite system, comprising: Determine the background noise value of the satellite signal associated with the satellite tracking channel, which has a frequency loop at the carrier frequency of the tracking satellite signal; The determined satellite signal background noise value is compared with the tracking channel signal noise threshold associated with the satellite tracking channel; Determine the satellite tracking phase noise associated with the satellite tracking channel; The determined satellite tracking phase noise is compared with the tracking channel phase noise threshold associated with the satellite tracking channel; The reception of spoofing signals on the satellite tracking channel is detected by comparing the determined satellite signal background noise value with the tracking channel signal noise threshold and the determined satellite tracking phase noise with the tracking channel phase noise threshold. as well as A signal indicating that a spoofing signal has been detected on the satellite tracking channel is generated in response to the following two factors: The comparison between the determined satellite signal noise floor value and the tracking channel signal noise threshold indicates that the determined satellite signal noise floor value exceeds the tracking channel signal noise threshold. The comparison between the determined satellite tracking phase noise and the tracking channel phase noise threshold indicates that the determined satellite tracking phase noise exceeds the tracking channel phase noise threshold.

2. The method of claim 1, wherein comparing the determined satellite signal background noise value with a tracking channel signal noise threshold associated with the satellite tracking channel comprises: Determine the background noise value of the reference signal; Determine the ratio of the determined satellite signal noise floor value to the reference signal noise floor value; as well as The determined ratio is compared with the tracking channel signal noise threshold.

3. The method according to claim 2, wherein the reference signal noise floor value is the average channel noise on the multiple satellite signals being tracked.

4. The method of claim 3, wherein a correlator integrating over the chip length and at different Doppler frequencies relative to the frequency loop is used to calculate the reference signal noise floor value in the tracking channel.

5. The method of claim 1, wherein the generation of the signal indicating that a spoofing signal has been detected on the satellite tracking channel includes setting a flag and isolating the spoofing signal over a defined time interval.

6. The method of claim 5, wherein the generation of the signal indicating that a spoofing signal has been detected on the satellite tracking channel comprises sending a detection alert to a host processor of an autonomous driving system or another navigation system.

7. The method of claim 1, wherein the satellite tracking channel is the tracking channel of the Global Navigation Satellite System (GNSS).

8. A device for detecting spoofing in a receiver of a global navigation satellite system, comprising: Memory; as well as Signal processing circuitry, coupled to the memory, wherein the signal processing circuitry is in operation: To realize a satellite tracking channel with a frequency loop that tracks the carrier frequency of the satellite signal; Determine the satellite signal background noise value associated with the satellite tracking channel; A first indication of a deception signal is generated based on the determined satellite signal background noise value and the tracking channel signal noise threshold associated with the satellite tracking channel. Determine the satellite tracking phase noise associated with the satellite tracking channel; A second indication of the deception signal is generated based on the determined satellite tracking phase noise and the tracking channel phase noise threshold associated with the satellite tracking channel; as well as The reception of the spoofing signal on the satellite tracking channel is detected based on both the first indication of the generated spoofing signal and the second indication of the generated spoofing signal.

9. The device of claim 8, wherein the signal processing circuit means, in operation, responds to the first indication indicating the detection of a spoofing signal and the second indication indicating the detection of a spoofing signal by generating a signal indicating that a spoofing signal has been detected on the satellite tracking channel.

10. The device of claim 8, wherein the signal processing circuitry generates the first indication of the deceptive signal during operation by means of the following steps: Determine the background noise value of the reference signal; Determine the ratio of the determined satellite signal noise floor value to the reference signal noise floor value; and The determined ratio is compared with the tracking channel signal noise threshold.

11. The device of claim 10, wherein the signal processing circuitry determines the reference signal noise floor value in operation by determining the average channel noise over the plurality of satellite signals being tracked.

12. The device of claim 11, wherein a correlator integrating over the chip length and at different Doppler frequencies relative to the frequency loop is used to calculate the reference signal noise floor value in the tracking channel.

13. The device of claim 9, wherein the generation of the signal indicating that a spoofing signal has been detected on the satellite tracking channel includes setting a flag and isolating the spoofing signal over a defined time interval.

14. The device of claim 13, wherein the generation of the signal indicating that a spoofing signal has been detected on the satellite tracking channel comprises sending a detection alert to a host processor of an autonomous driving system or another navigation system.

15. The device of claim 8, wherein the satellite tracking channel is the tracking channel of the Global Navigation Satellite System (GNSS).

16. A system for detecting spoofing in a receiver of a global navigation satellite system, comprising: Host processor; as well as Signal processing circuitry, coupled to the host processor, wherein the signal processing circuitry, in operation: To realize a satellite tracking channel with a frequency loop that tracks the carrier frequency of the satellite signal; Determine the satellite signal background noise value associated with the satellite tracking channel; A first indication of a deception signal is generated based on the determined satellite signal background noise value and the tracking channel signal noise threshold associated with the satellite tracking channel. Determine the satellite tracking phase noise associated with the satellite tracking channel; A second indication of the deception signal is generated based on the determined satellite tracking phase noise and the tracking channel phase noise threshold associated with the satellite tracking channel; as well as The reception of the spoofing signal on the satellite tracking channel is detected based on both the first indication of the generated spoofing signal and the second indication of the generated spoofing signal.

17. The system of claim 16, wherein the signal processing circuitry responds in operation to the first indication indicating the detection of a spoofing signal and the second indication indicating the detection of a spoofing signal by generating a signal indicating that a spoofing signal has been detected on the satellite tracking channel.

18. The system of claim 16, wherein the signal processing circuitry generates the first indication of the deception signal during operation by means of the following steps: Determine the background noise value of the reference signal; Determine the ratio of the determined satellite signal noise floor value to the reference signal noise floor value; and The determined ratio is compared with the tracking channel signal noise threshold.

19. The system of claim 18, wherein the signal processing circuitry determines the reference signal noise floor value by determining the average channel noise on the plurality of satellite signals being tracked during operation.

20. The system of claim 16, wherein the signal processing circuitry responds to the detection of a spoofing signal by sending a detection alarm to the host processor during operation.

21. The system of claim 20, wherein the host processor implements the navigation system in operation, and the signal processing circuitry detects signals of the Global Navigation Satellite System (GNSS) in operation.

22. A non-transitory computer-readable medium having content that causes a signal processing system to perform a method, the method comprising: To realize a satellite tracking channel with a frequency loop that tracks the carrier frequency of the satellite signal; Determine the satellite signal background noise value associated with the satellite tracking channel; A first indication of a deception signal is generated based on the determined satellite signal background noise value and the tracking channel signal noise threshold associated with the satellite tracking channel. Determine the satellite tracking phase noise associated with the satellite tracking channel; A second indication of the deception signal is generated based on the determined satellite tracking phase noise and the tracking channel phase noise threshold associated with the satellite tracking channel; as well as The reception of the spoofing signal on the satellite tracking channel is detected based on the first indication and the second indication of the generated spoofing signal.

23. The non-transitory computer-readable medium of claim 22, wherein the method comprises responding to a first indication indicating the detection of a spoofing signal and a second indication indicating the detection of a spoofing signal by generating a signal indicating that a spoofing signal has been detected on the satellite tracking channel.

24. The non-transitory computer-readable medium of claim 22, wherein the content comprises instructions executed by the processor of the signal processing system.

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