Method and apparatus for providing signal information and security

Abstract

A method for providing signal intelligence and security by obtaining legality information of a remote source is described. The method includes receiving, at a receiver, a signal from a remote source in a first direction; providing a local signal; determining a movement of the receiver; providing a correlation signal by correlating the local signal with the received signal; providing motion compensation for at least one of the local signal, the received signal, and the correlated signal based on the determined movement in the first direction to provide a preferential gain for the signal received along the first direction; based on the correlation, identifying a remote source vector corresponding to a portion of the propagation path of the received signal, the portion coinciding with the remote source; and generating legality information of the remote source from the remote source vector of the received signal. Systems and computer program products for providing signal intelligence and security are also described.

Description

Technical Field

[0001] Embodiments of the present invention relate generally to radio communications, and more particularly to methods and systems for providing legitimacy information regarding a source of a signal. Background Art

[0002] Radio transmissions are used in a variety of communication and positioning systems. WiFi, Bluetooth, and cellular communication transceivers are ubiquitous. Global Navigation Satellite System (GNSS) receivers are used in nearly every mobile device, and reliable satellite radio transmissions are required to accurately determine the position of the GNSS receiver. Systems using these technologies are becoming critical to the future of functional infrastructure, communications, and transportation. For example, these systems help provide functionality for self-driving cars. Accurate position and communication to and from self-driving cars are essential for vehicle operation.

[0003] Unfortunately, some people aim to disrupt the reliable functioning of systems that rely on radio transmissions by using spoofed transmitters. This spoofing poses a huge cybersecurity threat. Illegal transmitters such as jammers (aka spoofers) can transmit signals that mimic legitimate signals so that a receiver can receive and process the spoofed signal as if it were legitimate. For example, in a GNSS receiver, a spoofer may generate a signal that causes the receiver to provide inaccurate position information. This spoofing of a GNSS receiver can be an annoyance to a person using the signal for guidance, or lead to disaster for an autonomous vehicle that uses the signal for guidance.

[0004] Therefore, there is a need for methods and apparatus for obtaining information regarding the legality of radio transmissions and providing signal intelligence and security. Summary of the invention

[0005] According to a first aspect of the present invention, a method for obtaining legitimacy information for a remote source is provided, the method comprising: receiving a signal from a remote source in a first direction at a receiver; providing a local signal; determining the movement of the receiver; providing a correlated signal by correlating the local signal with the received signal; based on the determined movement in the first direction, providing motion compensation for at least one of the local signal, the received signal and the correlated signal to provide preferential gain for the signal received along the first direction; based on the correlation, identifying a remote source vector corresponding to a portion of the propagation path of the received signal, the portion coinciding with the remote source; and generating legitimacy information for the remote source based on the remote source vector of the received signal.

[0006] It has been found that the problem of obtaining legitimacy information for remote sources can be solved by means of a motion compensated correlation process applied to signals received by a moving receiver. The inventors have appreciated that the results of the motion compensated correlation (which can provide angle of arrival information for signals received from remote sources) can be advantageously used to obtain accurate determinations about the legitimacy of these sources.

[0007] The legitimacy information may alternatively be referred to as validity information, security information, or signal intelligence, in the sense that it may include information that may relate to a spoofer, a cybersecurity threat, or other illegitimate signal source. The legitimacy information typically includes information indicating whether the source of the signal is a legitimate source or transmitter, or whether it is illegitimate. Thus, the method may alternatively be viewed as a method of verifying or assessing the legitimacy of a remote source.

[0008] Once the legitimacy information is acquired, and optionally improved by further verification as will be described later in the present disclosure, appropriate action can be taken with respect to sources indicated by the information as illegal or potentially illegal. In some cases, such action may be taken by authorities, and may include investigating, blocking or disabling illegal transmitters. In some cases, the action may be taken by a receiver, which may be the aforementioned receiver, or may be a further receiver that can access the legitimacy information, such as a data set to which one or more receivers or devices coupled to them can contribute. Therefore, the action may include suppressing or discarding signals received from illegal sources or from sources whose legitimacy score parameter values ​​are below a predetermined threshold. In such a manner, a receiver or a device including or physically and / or communicatively coupled to a receiver may be configured so that any signal from a source indicated by the legitimacy information as illegal is excluded from any processing that the device is configured to perform on a legitimate signal in other ways. For example, any additional signal received from a GNSS signal source that has been identified as a possible spoofer in the legitimacy information may be excluded from a positioning calculation based on the received GNSS signal.

[0009] Optionally, the data may be used by the receiver or further receiver to perform additional evaluation or verification of the allegedly illegal source, and may do so by performing the above-mentioned steps based on motion compensation correlation, or using any of the secondary verification techniques described later in this disclosure. Thus, the method may additionally include, prior to any one or more of the above-mentioned steps, obtaining preliminary legitimacy information for the remote source, and if the preliminary information indicates that the source is illegal, performing the step of obtaining legitimacy information.

[0010] In some embodiments, preliminary legitimacy information can be obtained from a legitimacy data set (such as a remotely hosted database), and the data therein can be obtained by any one or more of the following: the method for obtaining legitimacy information as described above and any alternative method. In some embodiments, preliminary legitimacy information can be generated based on the type, characteristics or identifier of the received signal, and can be generated based on the known location of the receiver. For example, a mismatch between the type of received signal and data indicating one or more signal types that are expected to exist at the location of the receiver (estimated or otherwise) or the area where the receiver is located or that are expected to be receivable at it can be used to generate a preliminary indication of illegality. Similarly, if the receiver has not previously received a signal of that type and / or a signal from a claimed transmitter, the signal or its transmitter can be preliminarily indicated as illegal. In this way, unnecessary verification of established signals and transmitters can be avoided while continuing to evaluate the validity of newly received transmissions.

[0011] Generating legitimacy information based on the remote source vector can be understood as determining, evaluating, estimating or inferring the legitimacy of the remote source and / or received signal based on the remote source vector. In other words, such generation can be regarded as performing legitimacy verification or legitimacy checking, i.e. verifying or checking the legitimacy of the source or signal.

[0012] The identification of vectors or directions, as described in the present disclosure, can generally be considered to be the calculation or generation of vectors. The correlation can be understood as the correlation of the respective local signals with the received signal. In some embodiments, the preferential gain provided can be understood as a gain compared to a signal received in a corresponding second direction. In some cases, the first direction is a line-of-sight direction between the receiver and the remote source, while the second direction is not. However, in some embodiments, motion compensation is performed in such a way that preferential gain is provided for signals received along a first direction that is not a line-of-sight direction, particularly in the case where additional information is available to enable the remote source vector to be identified from such non-line-of-sight signals.

[0013] The remote source vector corresponding to a portion of a propagation path can be understood as a remote source vector preferably colinear with the portion. However, due to the probabilistic nature of the determined signal direction, the correspondence typically means that the remote source vector represents or indicates a portion of the propagation path, or is an estimate of a portion of the propagation path. For the line-of-sight direction between the receiver and the remote source, the remote source vector is typically along the direction of arrival (DoA) vector, i.e., the direction from which the receiver receives the signal. However, when a given first direction corresponds to a reflected signal (the reflected signal changes its propagation direction by reflecting away from some objects after being transmitted by the remote source), suitable techniques can be used to calculate the portion of the propagation path between the remote source and the reflective structure based on the DoA from which the reflected signal is received. For example, when the modeling and ray tracing of the reflective structure can be used to enable the use of reflected signals in calculating the remote source vector, this can be used. The propagation path of the received signal can be specifically understood as the propagation path between the remote source and the receiver.

[0014] Motion compensation may be applied to the received signal, the local signal, or a combination thereof before the signals are correlated. Motion compensation may also be applied to the correlated signal after correlation. By providing motion compensation in a first direction extending between the receiver and the remote source, preferential gain for signals received along that direction may be achieved. Thus, line-of-sight signals between the receiver and the remote source will receive gain in preference to reflected signals received in a different direction. In a GNSS receiver, this may result in a significant improvement in the accuracy of calculations based on the received signal, since non-line-of-sight signals (e.g., reflected signals) are significantly suppressed. The highest correlation may be achieved for line-of-sight signals, even if the absolute power of the signal is less than that of the non-line-of-sight signals.

[0015] The received signal may include any known or unknown transmitted information pattern, digital or analog, which may be found in the broadcast signal by a cross-correlation process using a local copy of the same pattern. The received signal may be encoded with a chipping code that may be used for ranging. Examples of such received signals include GPS signals, which include Gold codes encoded within radio transmissions. Another example is the extended training sequence used in GSM cellular transmissions.

[0016] Conventionally, phase changes in the received signal caused by changes in the line-of-sight path between the receiver and the remote source are viewed as nuisances that reduce positioning accuracy. The counter-intuitive approach of the present invention can actually exploit these phase changes to improve the identification of line-of-sight signals from remote sources.

[0017] The motion compensation unit may provide motion compensation to the local signal so that it more closely matches the received signal. In another arrangement, motion compensation may be applied to the received signal to reduce the effect of the received signal on the motion of the receiver. Similar results may be achieved by providing partial motion compensation to the local signal and the received signal. These techniques allow relative motion compensation to be applied between the local signal and the received signal. In some embodiments, motion compensation may be performed in parallel with correlation. Motion compensation may also be applied directly to the correlated signal.

[0018] In practice, the received signal may be processed as a complex signal, comprising an in-phase and a quadrature component. The local signal may similarly be complex. The correlation unit may be arranged to provide a correlation signal, which may also be complex and may be used as a measure of the correlation between these complex signals.

[0019] High accuracy can be achieved by providing motion compensation for at least one of the local signal and the received signal based on a measured or assumed movement in a first direction. In practice, the local signal and the received signal can be encoded with a periodically repeated code when applied to a GNSS signal. For example, for the GPS L1C / A code, the local signal and the received signal can include 1023 pseudo-random digital chips. The local signal and the received signal can be analog waveforms that can be digitized to provide values ​​at the radio sampling rate, which means that there may be millions of values ​​in a 1ms time period. The correlation between the local signal digital value and the received signal digital value can be calculated, first correcting any set of values ​​using the motion compensation vector for the relevant time period. Then, these data points can be summed over the time period. In practice, this can produce accurate results because it works at the radio sampling frequency, although it may be computationally intensive.

[0020] Lower accuracy can be achieved by providing motion compensation of the correlated signals. In the above example, when applied to the GPS L1 C / A code, correlation can be performed independently on each of the ~1000 pseudo-random digital chips to produce ~1000 complex correlator signal outputs. Then, the motion compensation vector can be applied to these ~1000 correlated signal components. Finally, the motion compensated correlated signals can be summed to produce a measure of correlation. Therefore, motion compensation of the correlated signals can produce an approximation of the results that can be achieved by motion compensation of the local signal and the received signal. However, for some applications, the loss of accuracy can be negligible and acceptable because it enables a reduction in computational load.

[0021] The remote source vector can be used to obtain various legitimacy indicators, as will be described later in this disclosure. Any one or more of these types of information (which can be related to the altitude, movement, and geographic location of the source) can be used alone or in combination, and in some embodiments, can be used in cooperation with reference data to generate legitimacy information.

[0022] In some embodiments, legitimacy information is generated according to the signal type of the received signal. Knowledge of the signal type (e.g., GNSS, cellular, WiFi, or Bluetooth) can help determine whether the signal source is legitimate, especially because the angle or azimuth information collected from the remote source vector can be compared with the expected attributes or angle or azimuth information of the legitimate source of a given type of signal or evaluated according to it. The method may be useful for verifying that the signal is expected to originate from a specific height or from a given azimuth. For example, the method can be applied to GNSS signals, which should be transmitted from a higher source in the sky, and therefore should have a DoA and / or remote source vector with a steeper inclination. For example, a ground-based deception source can be identified by having a transmission path that is less steeply inclined than expected. Therefore, the method may include, when the angle formed by the remote source vector and the horizontal direction, or alternatively or additionally the angle between the horizontal and the direction of arrival is less than a predefined threshold angle, generating legitimacy information to indicate or make it indicate that the remote source is an illegal source. That is, if the angle that can be calculated based on the remote source vector identified is less than the expectation of the legitimate source, then legitimacy information can be generated so that it indicates that the source is illegal. This may be in the form of, for example, a flag or any suitable form of data to indicate an invalid or potentially suspicious source.

[0023] The predetermined threshold angle may be 5 degrees in some embodiments, or 10 degrees, 20 degrees, 30 degrees or 40 degrees in some cases, depending on the selected discrimination level to be applied. The horizontal direction may be understood as a direction orthogonal to the vertical direction and located in the same vertical plane as the remote source or arrival direction vector forming an angle therewith. The horizontal direction may also be considered as a direction or vector parallel to the horizontal plane and located in the same vertical plane as the vector. In some embodiments, such horizontal and vertical reference vectors or directions may be defined relative to the orientation of the receiver, such as when receiving a signal, or at a position incident on the earth's surface by a vector collinear with the remote source vector. The vertical reference direction may be defined as a direction parallel to the direction of gravity experienced at the point on the earth's surface or at the position of the receiver.

[0024] For certain signal types, the determination of legitimacy or illegitimacy may be aided by determining whether the angle at which the signal is transmitted from the source is as steep as expected, in addition to or as an alternative to the above method. Thus, in some embodiments, the method may include generating legitimacy information to indicate that the remote source is a legitimate source when the angle formed by the remote source vector and the horizontal direction is greater than a predetermined threshold angle. In addition, for signals originating from earth-orbiting satellites, for example, a positive determination of the legitimacy of the signal source may be made when the azimuth angle of the transmission is sufficiently large.

[0025] In the embodiment that uses threshold angle to determine that source is illegal, as mentioned above, the threshold angle for any one of these determinations can be identical, but preferably different.The first threshold angle (the source below the threshold angle can be considered as illegal) is preferably less than the second threshold angle (the source above the threshold angle can be considered as legal).The difference between two threshold angles can be, for example, 5 degree, 10 degree or 15 degree.In this way, three azimuth ranges can be defined above, below and between these two threshold angles, and the acquisition of legitimacy information can be performed by comparing the remote source vector with these ranges.In certain embodiments, particularly if the signal ostensibly originates from a satellite, the remote source vector in the shallowest of the three ranges may be an indicator that the source is illegal, the remote source vector in the highest of the three angle ranges may cause the source to be considered as legal, and the third, middle range can correspond to being classified or indicated as a potential legal source, for example, marked as such, so that further investigation about the source can be performed.

[0026] As described above, in addition to or alternatively to using the angle information in this way, the azimuth information based on the identified remote source vector can also be used to verify the source. The location information of the remote source can be found based on receiving and identifying the remote source vector of more than one signal from the source. In some embodiments, the method also includes: for each of the multiple signals received from the remote source at the receiver, where each of the signals is received in a corresponding first direction: providing a corresponding local signal; determining the corresponding movement of the receiver; providing a corresponding correlation signal by correlating the corresponding local signal with the received signal; based on the determined corresponding movement in the corresponding first direction, providing motion compensation for at least one of the corresponding local signal, the received signal and the corresponding correlation signal to provide preferential gain for the signal received along the corresponding first direction; and based on the correlation, identifying a corresponding remote source vector corresponding to a portion of the propagation path of the received signal, which portion coincides with the remote source. The multiple received signals will be understood to include the previously described received signals. Therefore, such embodiments of the method include the steps of providing a local signal, determining a corresponding movement and providing a corresponding correlation signal for at least a second received signal received from the remote source in the second direction. However, preferably, in such an embodiment, further signals are received at the receiver from the source and corresponding steps are performed on these signals as well. In this way, a greater number of remote source vectors can be obtained, which can improve the accuracy of the information about the source. The corresponding local signal, corresponding movement and corresponding correlation signal corresponding to the first received signal can be understood to be the same as the above-mentioned local signal, movement and correlation signal.

[0027] It may be considered that, in embodiments involving multiple signals, the multiple signals, or at least a subset thereof, are transmitted by a remote source as part of a single transmission. That is, the distinction between different signals in the multiple signals may be arbitrary, since these different signals, while for the purposes of the method, are considered separate or distinct when identifying their corresponding remote source vectors, are typically part of a given transmission made by a remote source.

[0028] For example, separate signals may typically be defined by differences in the time or period during which a given transmission or portion of a transmission is received by a receiver, and / or by the orientation and / or orientation change of the receiver at the time of its reception. Thus, the distinction between signals will be understood to be generally independent of the content of the signals. Any two or more of the plurality of signals may include or consist of different or identical information. Thus, typically, each of the plurality of signals is a portion of a transmission from a remote source received by a receiver during a corresponding one of the plurality of time periods.

[0029] In addition to providing improvements to the determination of legitimacy by increasing the number of remote source vectors identified, this embodiment can also, as described above, further improve this determination by providing location information of the source. In the context of the present disclosure, location information can be understood as data indicating an orientation, absolute or relative (e.g., for a receiver), or, for example, a geographic location. In some embodiments, the location information includes the geographic location of the remote source, and it will be understood that the location information can be related to the remote source transmitter antenna. Therefore, the method can be considered to include the step of locating the remote source. In some embodiments, the method also includes: generating the location information of the remote source by identifying one or more locations of two or more intercepts in the corresponding remote source vectors of multiple received signals. Then, legitimacy information can be generated based on the location information. In this way, the signal intelligence of the source can be obtained based on the calculated location of the source. Knowledge of the location of the source, whether it includes an indication of a geographic location such as geographic coordinates, an indication of the height of the source such as altitude, or an indication of the position in the sky or an indication of the orbital orientation can be used to determine the authenticity of the source.

[0030] With respect to the position and / or orientation of the receiver, in particular its receiving antenna, two, preferably more than two, and more preferably all of the received plurality of signals may be received along different respective first directions. In some embodiments, the directions in which the signals are received differ, during the time the method is performed, due to movement of the receiver relative to or near the remote source during that time. In this case, the movement of the receiver may include one or two components orthogonal to the direction of arrival or reception of the signals.

[0031] However, it will be understood that the aforementioned movement of the receiver near the source only needs to be sufficient for performing the described motion compensation correlation. That is, the movement generally includes a component oriented in the direction parallel to the direction of the arrival vector of the signal, and in the space and / or time range that allows compensation calculation. However, for the generation of the described position information, the movement of no receiver (except for the movement that can perform motion compensation correlation) must be realized. Therefore, the degree of any receiver movement or any component thereof transverse to the arrival direction and / or the straight line between the receiver and the source does not need to be large enough to allow or facilitate the calculation of the position information based on two remote source vectors by making the angle of the movement or component at the remote source and / or the position where the signal is reflected to the receiver large enough. On the contrary, in some cases, the movement of the receiver may not be enough to achieve a purpose like this, therefore, alternatively or additionally, any cross position is calculated based on the arrival direction vector difference attributable to the difference on the signal propagation path.

[0032] Thus, differences in the signal reception directions of any two or more signals received during the execution of the method may, in some embodiments, be caused by the propagation path of one or more of these signals including one or more changes in direction, i.e., from one or more of these signals having been reflected. In this way, two sufficiently different remote source vectors corresponding to two different transmission angles can be obtained and the intersection position of these vectors calculated, regardless of whether the receiver has moved to an extent that the line-of-sight vector of the source can be triangulated. In other words, by including one or more reflected signals in the basis of the calculation, the position of the remote source can still be identified even if the receiver has not moved sufficiently to achieve sufficiently accurate triangulation based on the two line-of-sight signal vectors.

[0033] For example, the generation of the position information may be performed such that the position information comprises a point corresponding to an average of a plurality of positions at each of which two or more of the identified remote source vectors intersect, in particular an average position. The generation of the position information may also be understood to be based on the one or more intersection positions. Each intersection position may correspond to a point or a one-, two- or three-dimensional region defined by the intersection between two remote source vectors and typically also defined by any degree of uncertainty in the identified vectors. Typically, at least two, preferably more than two, identified remote source vectors intersect at each of the one or more intersection positions.

[0034] The method facilitates accurate calculation of the position of the remote source relative to the receiver. By positioning the receiver in the coordinate system, the absolute position of the remote source, such as geographic location data, can be found relative to the established coordinate system. Therefore, in some embodiments, the method also includes obtaining the position information of the receiver. The position information of the remote source can be generated based on the position information of the receiver, for example, based on one or more intersections or intersection areas between the remote source vectors relative to the receiver. The receiver position is typically obtained for at least one of the multiple received signals, that is, it can include information indicating the position of the receiver when receiving at least one of the multiple received signals or during the reception thereof. The receiver position can be obtained using GNSS (Global Navigation Satellite System) and / or IMU (Inertial Measurement Unit) data, and can be obtained based on the determined movement of the receiver (such as the corresponding determined movement corresponding to any one or more of the received signals) in addition.

[0035] As previously described in the present disclosure, in some embodiments, additional information about the received signal may be used to enable the method to take into account signals that may be non-line-of-sight signals. Thus, identifying the remote source vector of the signal may include obtaining corresponding line-of-sight information about the received signal. In particular, the additional line-of-sight information may indicate whether the received signal is a line-of-sight signal. Advantageously, the indication may be used to determine whether to use, discard, or perform additional processing or calculations on the arrival direction vector for the purpose of identifying the intersection position. The additional information may indicate whether the propagation path from the source to the receiver is direct, i.e., along the line-of-sight between them. Conversely, for some signals, the line-of-sight information may indicate that the received signal is a non-line-of-sight signal, such as a reflected signal.

[0036] By using this information, a greater number of signals that may be received during a given time period or during the movement of the receiver along a given path portion can be utilized because non-line-of-sight signals can be identified as such signals. Therefore, despite the indirect propagation path of these signals, these signals can be used to more quickly and accurately locate the intersection between remote source vectors, and thereby locate the remote source. Therefore, identifying the remote source vector of the received signal can also include: identifying the corresponding direction of arrival based on the correlation, and identifying the remote source vector according to the corresponding direction of arrival and the corresponding line-of-sight information. The direction of arrival can be considered to correspond to or represent the direction or vector from which the signal is received at the receiver, and / or the direction of travel of the signal when it is received at the receiver. It will be understood that, in general, the method typically includes estimating the direction of arrival (DoA) of the signal using the super-correlation technique discussed in more detail later in this disclosure.

[0037] For line-of-sight signals, the DoA and the remote source vector typically correspond to the same direction, i.e., they can be considered to be parallel and typically have collinear vectors. Line-of-sight information can be used to enhance the method so that for non-line-of-sight signals, a hyper-correlation technique is applied to obtain the DoA. These DoAs can then be used in conjunction with knowledge of nearby reflecting structures, such as any one or more of the position, orientation, shape of one or more reflecting surfaces or objects, to calculate the remote source vector. Therefore, by using additional remote source vectors, additional data can be obtained, and therefore improved position accuracy, even if they are based on DoA calculations that do not directly correspond to the direction in which the signal is received from the source. For example, these additional remote source vectors may also be useful if the line-of-sight signals from a given transmitter are obscured or attenuated to the point where they cannot be used to obtain position information.

[0038] Identifying the remote source vector based on the direction of arrival and line-of-sight information typically includes a modification to the motion compensation correlation technique that results in preferential gain being achieved for signals received along these non-line-of-sight directions, particularly on the basis that they can still be used. Alternatively, in some embodiments, one or more signals indicated as reflected signals may be excluded from the plurality of signals based on which the calculations for obtaining the position information are performed.

[0039] In embodiments involving the use of non-line-of-sight signals regardless of their indirect propagation paths, the method may also include obtaining reflection model data, which includes a geometric model of a set of structures capable of reflecting signals. Such a model (which can enable the calculation of a remote source vector based on the DoA of the reflected signal) may be particularly useful in an urban environment. For example, a method utilizing a predetermined 3D building model may be beneficial, which represents a structure that may hinder and / or reflect transmissions such as those including received signals. Using techniques such as ray tracing, the propagation path through such an environment can be modeled in such a way that, even when, for example, the only signal received for a given orientation along the receiver's path of movement is a signal that has been reflected by one or more structures, useful remote source vector information can be inferred. It will be understood that the geometric model may include a set of one or more structures, which may be natural or artificial, such as buildings, landscapes, and terrain features. Those structures capable of reflecting signals can be understood as being particularly capable of reflecting, that is, reflecting to signals of the same or similar type as one or more of the multiple signals. For example, near a receiver, a model of a structure within a predetermined radius of an estimated or obtained position of a receiver at a given time or within an area containing the position can be obtained and used to model the propagation path. Typically, the model data comprises three-dimensional geometric data representing the reflecting structures and contains sufficient information about their position and / or orientation to allow calculation of propagation paths including one or more reflections from them.

[0040] Identifying the remote source vector based on the corresponding direction of arrival and the corresponding line-of-sight information may include: if the corresponding line-of-sight information indicates that the received signal is not a line-of-sight signal, calculating the corresponding remote source vector based on the reflection model data and the corresponding direction of arrival. Typically, the aforementioned use of the estimated non-line-of-sight direction of arrival requires geometric information that allows the transmission direction or the remote source vector to be calculated or estimated. In embodiments involving reflection model data, compensation may be applied to take into account the fact that reflections are present, which may otherwise result in positioning errors, or the reflected signal may be used in other ways to improve positioning accuracy.

[0041] In various embodiments, the reflection model data and the line-of-sight information may be separate, or they may be related, or the same. For example, a set of line-of-sight information may indicate that the direction of arrival is that of a non-line-of-sight signal by virtue of indicating that the direction-of-arrival vector intersects or coincides with a reflection structure modeled in the reflection model data.

[0042] The method may also include obtaining time of arrival data or time difference of arrival data for one or more of the plurality of received signals, and line of sight information may be obtained based on the time of arrival data. For example, the anomalous time of arrival data may be used to make a determination that the received signal is a line of sight signal, and vice versa. This may then be used to exclude non-line of sight signals from one or more calculations when obtaining position information of the remote source. This may also be used to perform additional processing, such as using reflection model data.

[0043] In some embodiments, generating legitimacy information based on location information includes obtaining reference location data indicating one or more legitimate signal sources (which may also be referred to as reference source location data), and generating legitimacy information based on a comparison between the generated location information and the reference location data. For example, the reference location data may include one or more areas in which legitimate sources are known to be located, or indications thereof. Thus, determining that a remote source is illegitimate may be based on location information generated thereby, which indicates that the source is outside of the one or more areas.

[0044] Whether or not reference location data is available to allow comparison of the determined source location with known emitter locations or areas containing them, the generated location information may also be used to determine legitimacy based on whether the signal source should be in a particular area. Thus, in some embodiments, the method further comprises: obtaining reference geographic data corresponding to or containing information about one or more geographic areas and including information indicating the expected presence of one or more legitimate sources therein, and generating legitimacy information based on the generated location information and the reference geographic data.

[0045] The reference geographic data may define: any of the boundaries of a geographic region and the extent or area of ​​a geographic region, or indeed any information sufficient to determine whether a given location is located within that region. A geographic region may be understood as a specific area on and / or above the surface of the Earth. One or more geographic regions may contain a location, in particular a geographic location, which may be indicated by the location information, or coincide with that location. Expected presence may be understood as the level of presence or degree of presence of legitimate sources, and may be expressed in terms of an absolute or relative quantity, number or density or spatial distribution of legitimate sources. For example, it may indicate an expected level, and may therefore be considered as an expected presence or absence of legitimate sources from a region.

[0046] In such an embodiment, the location information can be used to identify a geographic region corresponding to the reference geographic data, in which the source is located. Therefore, an assessment of the validity of the source can be made based on the expected existence of a legitimate source here. For example, in general, if the expected existence in the area from which the signal has been determined to have been transmitted is zero, the method may include determining that the source is illegal. The method may also involve: calculating or otherwise determining the number of sources within the area, such as by obtaining location information indicating that they are located therein for multiple sources, and comparing the number with the expected existence. For example, if an excessive number of sources (compared to the amount of reference data) is found in an area, one or each of the sources identified as being in the area can be determined to be illegal, or may be illegal. In addition, the method may involve additional checks on these sources, as will be described in more detail later in this disclosure.

[0047] The reference geographic data may include expected source type information. This information may correspond to one or more geographic regions, and legitimacy information may be generated based on a comparison between the source type and the type of one or more of the identified multiple received signals. The expected source type, as may be indicated by the expected source type information, may refer to an expectation based on some knowledge of what type of source should exist in the region and / or what source is known or may be transmitted from the region. The source type may include or be indicated by or inferred from any one or more of the following: signal wavelength, signal content, time and / or date of signal transmission or reception. The expected source type information may indicate any one or more of one or more source types expected to exist in the region; one or more source types not expected to exist in the region. For example, the method may include: if the content of the source or different indications of the source type are not expected within a given type of terrain, water body, or geopolitically defined area, the illegality of the source is inferred. The method may include: identifying or determining the signal type so as to obtain the identified type of one or more of the multiple received signals.

[0048] In an embodiment involving the use of multiple received signals, the method may further include: generating source movement information indicating the movement state of the remote source based on multiple remote source vectors, i.e., corresponding remote source vectors of the multiple received signals (including the first remote source vector as described above). Then, the legitimacy information may be generated based on the source movement information.

[0049] Acquiring multiple remote source vectors of signals transmitted at different times can reveal clues to the legitimacy of the source. In particular, obtaining an accurate indication of whether the source is moving or stationary, together with knowledge of whether a legitimate source of that type will move, is valuable for obtaining legitimacy information. Therefore, the mobile state referred to above can be understood as information about whether the source is moving and how the source is moving. The generation of source movement information can include calculating movement or its components. For example, it may involve calculating the coordinates, orientation, rate, velocity, acceleration or its components of the source. For example, in some components, the information may simply indicate whether the first and second remote source vectors of multiple remote source vectors are different, or whether they are the same, or whether they differ by more than a threshold angle. Remote source vectors that remain the same over a given period of time can indicate no movement, for example, while conversely, the difference between them can indicate movement of the source.

[0050] The method may also include obtaining reference source mobility data indicating the expected mobility state of a legitimate remote source. The reference source mobility data may indicate, for example, whether the source should move. This may be based on the type of signal, for example, for a signal reportedly transmitted by a cellular network base station, the reference data may indicate that the source should not move. The indication within the data may include an explicit flag, or may be implicit, for example within the type of source and / or signal. The data may include expected mobility states for a variety of signal and source types. The method may include generating legitimacy information based on the generated source mobility information and the reference source mobility data. This typically includes a comparison between the source mobility information and the reference source mobility data. If the generated mobility information is different or inconsistent with the reference data, legitimacy information may be generated to indicate that the source is illegal. For example, for a cellular base station, if the generated source mobility information indicates movement of the source, contrary to an implicit or explicit indication to the contrary of the reference data, the source may be marked as illegal.

[0051] It will be appreciated that in some embodiments, assessing source legitimacy based on the determination of its movement does not require the calculation of the position of the source or changes therein. On the contrary, in some cases, the movement of the source can be inferred from the change of the remote source vector identified. However, preferably, a sufficient number of remote source vectors are calculated for the source, and if a sufficient number is obtained, then the data can be used to calculate two or more intersection positions of those remote source vectors, each corresponding to signals transmitted at different times, so that two or more positions of the sources at those different times can be found.

[0052] However, in some embodiments, the remote source vector can be used to infer source movement independently of any calculated position. That is, at least the angular change or angular / lateral component of movement over a given time period can be inferred from the remote source vector itself, and this does not necessarily need to include calculating the radial component of movement, i.e., the component of movement in the remote source vector direction or direction of arrival. However, by calculating two or more positions based on the obtained remote source vector, the assessment of legitimacy can be improved, as described above.

[0053] Therefore, the method may also include: generating first position information of a remote source by identifying one or more intersecting positions of a first group of two or more of a plurality of remote source vectors, generating second position information of a remote source by identifying one or more intersecting positions of a second group of two or more of a plurality of remote source vectors that are different from the first group, and generating source movement information based on the first position information and the second position information. The second group of remote source vectors may be different from the first group because they correspond to signals received or transmitted at different times. That is, preferably, each of the remote source vectors of the second group corresponds to a signal transmitted after one or all of the signals of the first group. Preferably, the reception and / or transmission times corresponding to the two groups are separated by a sufficiently long duration to assess the movement of the source. For example, the duration may be on the order of seconds, tens of seconds, minutes or hours.

[0054] The generation of source movement information can involve comparing the first position information and the second position information, or calculating the difference between them. In addition, the method can include using the third, fourth and any number of other groups of remote source vectors corresponding to the corresponding different signal transmission times to calculate the corresponding further position. The estimated moving path of the remote source can be defined using multiple identified positions. Comparing the moving path with the expected movement mode or type of the legal source may help to obtain legitimacy information. Therefore, in some embodiments, the generated source movement information includes the generated source movement path based on the first position information and the second position information (i.e., calculated based on the first position information and the first position information). In fact, this can be based on any additional position information. In some preferred embodiments, a detailed path can be generated, tracking the estimated movement of the source with the remote source vectors of enough groups and the corresponding calculated positions.

[0055] The reference source movement data may include an expected legitimate source movement path, and legitimacy information may be generated based on a comparison between the generated source movement path and the expected source movement path. That is, if the comparison operation returns a difference or inconsistency between the paths that is greater than a predetermined threshold, such as a displacement or deviation from the path expected for a legitimate source, legitimacy information may be generated to indicate that the source is illegitimate. Similarly, if the difference between the calculated paths is less than a predetermined tolerance, or if no difference or substantially no difference is identified, the legitimacy information may indicate that the source is legitimate.

[0056] Preferably, the method includes storing the legitimacy information of the remote source in a remote source legitimacy data set. In this way, a receiver, or preferably a plurality of receivers operating simultaneously or at different times in a region, can establish a data store that can be used to confirm the legitimacy of a transmitting source therein and / or to flag, notify or alert any party that an illegal source exists in the region so that appropriate action can be taken. Such a data set is preferably stored in a database, which is typically implemented on one or more servers or other computer devices, which are preferably remote from the receiver and are preferably accessible directly or indirectly by the receiver via one or more wired or wireless communication links or any other mode of transferring data.

[0057] For each source in which information is recorded, the source legitimacy data set may indicate any of the following: a legitimacy status, a legitimacy flag, a legitimacy score, and any other form of legitimacy indicator. Preferably, for one or more sources, the data set additionally includes location information of the source. More preferably, the stored location information indicates or represents the geographical location of the source, for example in the form of geographical coordinates.

[0058] The source location information to be stored in the data set can be obtained in various ways, including as part of the method, such as by receiving and identifying a remote source vector of more than one signal from the source, and for example identifying a crossover location, as previously described in this disclosure. In some embodiments, the location information of the source is obtained by other techniques or using additional data. For example, satellite or aerial images representing the geographic area where the source is located can be used to intuitively infer the location of the transmitter, and in some embodiments can be used for a secondary legitimacy check of the source.

[0059] In some embodiments, the position information includes a relative position, for example indicating the orientation of the source relative to the receiver when the signal is received. Such relative position information may additionally or alternatively include angle or direction information, and may in particular include an indication of the direction in which the source is located relative to the receiver. The information may include an indication of a remote source vector together with position information derived from the position information of the receiver. In this way, for embodiments in which the orientation of the source is not necessarily obtained during the method, a range of positions along the remote source vector, and therefore including the true or at least approximate position of the source, may be obtained. Such information may be used in conjunction with similar information obtained by performing the method multiple times using the receiver and preferably one or more additional receivers.

[0060] By providing or updating a data set with information about the locations of illegal transmitters, any receiver that may enter or pass through the broadcast range of those transmitters or may receive transmissions from those locations can be provided with a preliminary indication or warning about the potential presence, direction and / or orientation of the identified transmitter. This may be the case even if no location or no precise location is known for the receiver arriving or approaching the vicinity. The data set may be used by the receiver to establish, for example, a directional range relative to its own known or estimated location, where illegal or potentially illegal transmitters are indicated by previously acquired legitimacy information as being within, or based on this information, where transmissions from these sources are expected. Using this knowledge, the receiver can utilize the data set itself in order to take appropriate action with respect to signals received from directions or areas where legitimacy information indicates that illegal transmissions may originate. Such actions may include selectively processing or excluding certain signals, as previously described in this disclosure, and it may include these receivers performing their own primary and / or secondary legitimacy verification on the signals by any of the techniques described herein. Therefore, the legitimacy information that can be added to the data set can itself constitute preliminary legitimacy information for subsequent use by any receiver.

[0061] It will be appreciated that in some cases, the legitimacy or illegality of a source may not be explicitly determined by the method, and the legitimacy information generated may indicate that a source may be illegal, without being explicitly so. Therefore, in some embodiments, it may be useful to perform a further legitimacy assessment based on a certainty level or parameter associated with the information, or in circumstances where an assessment based on the remote source vector indicates that the source is not necessarily legal. Therefore, some embodiments also include, if the legitimacy information indicates that the remote source is an illegal source: performing a legitimacy verification on the remote source using or based on the received signal. Therefore, the method may also include updating the legitimacy information based on the results and / or certainty parameters of the legitimacy verification.

[0062] The legitimacy verification may be considered a secondary legitimacy check or second legitimacy verification, taking into account the initial generation of legitimacy information which may be considered a first check or first verification step. It may be useful to perform one or more of these secondary checks. However, the efficiency of the process of verifying sources and identifying illegal sources is typically improved by conditionally performing these additional checks (first identifying potential illegal sources based on remote source vectors accurately determined using motion compensated correlation techniques).

[0063] Preferably, additional verification is performed based on one or more signal features in addition to directional information. That is, these features may exclude the direction of arrival, the remote source vector, or other information generally associated with or derived from the propagation path of the signal or any portion thereof. In some embodiments, the updating of the legitimacy information may be an optional step, or may itself be performed conditionally. For example, the legitimacy information may remain unchanged if it is consistent with or confirmed by a secondary check. For example, if the check returns a result confirming the illegality of the source, an update may be performed so that the legitimacy of the indication in the data remains unchanged, although preferably the data may be updated to indicate that a secondary check has been performed.

[0064] In some embodiments, the update may include modifying or adding to the legitimacy information, such as modifying the source / signal legitimacy or illegality indication included by the data. In some cases, the update may confirm the initial indication that the source is valid or invalid. For example, in certain other cases, if further inspection concludes that the potential illegal source is actually valid, the information may be updated to reflect the modified illegality indication. Similarly, after any number of secondary inspections, the update may include marking the signal or source for further investigation, for example, if those further inspections are inconclusive as to legitimacy.

[0065] This information may also be updated to include further details of the source, such as the source's monitored properties, technical information, test results, recorded signal content and characteristics.

[0066] In general, the result of an illegality verification may include any data generated as a result of a verification step. Typically, this indicates the legality of the source as assessed by the verification process.

[0067] An example of a scenario in which a secondary verification step would be valuable involves receiving a signal that has been reflected, particularly a signal whose propagation path involves reflections from moving objects. For example, a signal such as a cellular base station transmission may be reflected by a moving vehicle such as a bus or heavy goods vehicle for a period of time and received by a receiver. In this case, the receiver will calculate the remote source vector without knowing that the signal has been reflected by the vehicle, typically because any geometric data by which an indirect propagation path can be modeled will generally omit transient reflecting structures and surfaces such as vehicles. In that case, calculating multiple remote source vectors assuming that the signal is a line-of-sight signal, and determining the movement state or movement path of the source based on this, will indicate that the source is moving. Comparison with the expected movement state of a transmitter such as a cellular base station can then result in the originally generated legitimacy information indicating that the source is illegitimate. Therefore, in order to maintain that the legitimacy information is accurate, a secondary verification of the legitimacy of the source may be advantageous.

[0068] For example, secondary verification may involve obtaining additional signals from the source, which may include signals for which a remote source vector can be found to be truly coincident with the source's emitter (whether a line-of-sight signal or an indirect signal where the reflected propagation path can be accurately modeled). In this way, the legitimacy of the source can be verified, and in addition, the information obtained can be updated in this way to indicate, for example, that a mobile signal received therefrom is likely to be reflected and should be discarded.

[0069] One way of performing a secondary check, which is particularly advantageous when the potentially illegal received signal is a positioning broadcast (such as a GNSS signal), may involve evaluating the effect of the signal on the positioning calculation result. Thus, in some embodiments, particularly where the signal is a positioning signal, which may be enumerated as a first positioning signal, the legitimacy verification may include: performing a first positioning calculation based on a plurality of received positioning signals including the first positioning signal to obtain first position information of the receiver, performing a second positioning calculation based on a plurality of received positioning signals other than the first positioning signal to obtain second position information of the receiver, and obtaining a comparison between the first position information and the second position signal. In other words, the additional verification may be based at least in part on comparing two calculated receiver positions, one of which is based on one or more suspected illegal broadcasts and the other is based on positioning broadcasts that exclude the one or more suspected illegal broadcasts. If the comparison between the two positioning results indicates an inconsistency between the calculated positions, such as an orientation difference, preferably defined as a difference exceeding a predetermined distance or difference threshold, the verification may confirm that the source and / or signal is illegal.

[0070] Typically, illegal transmitters include components of lower quality than legal transmitters. In particular, illegal sources often use less stable and / or accurate frequency standards. This common shortcoming can be used as an indicator of illegality, and the presence of these components can be inferred from signal characteristics, and therefore used as a secondary check for those sources that the initial legality information may have indicated as possibly illegal. Therefore, legality verification can include obtaining a source quality parameter of a remote source using a received signal. The parameter can indicate an assessed quality level of a component of the remote source. Obtaining the parameter can include analyzing the stability, accuracy and / or phase noise of the carrier frequency. If the source quality parameter or its value is lower than or indicates that the component quality is lower than a predetermined threshold, such as less than that expected for a legal source corresponding to an ostensibly legal source, the legality information can, and in some embodiments, be updated to confirm or reiterate illegality.

[0071] As mentioned above, the component of the remote source can be a frequency standard component. In such an embodiment, the source quality parameter is typically obtained by calculating the quality of the frequency standard component of the remote source based on the received signal. Quality is typically defined as the frequency stability of the frequency standard used by the transmitting source, or a measure or indication thereof. For example, a measure such as the Allan variance can be used.

[0072] A further method for performing secondary verification may involve the polarization state of the radiation carrying the signal. In other words, in some embodiments, the legitimacy verification may be based on the monitored polarization state of the received signal. Thus, the signal may be received using an antenna, by which the polarization state of the radiation carrying the signal may be monitored. The method may include comparing the state with an expected polarization state, for example, as expected for a legitimate signal of the same type and / or from the same type of source and / or from the same location.

[0073] In some embodiments, a mixed-mode signal evaluation may be performed during either or both of the secondary verification step and the step of obtaining preliminary legitimacy information (as previously described in the present disclosure). Checking different kinds of signals in addition to the signal being verified for legitimacy may advantageously improve the efficiency of the method and the quality of the signal intelligence obtained. Thus, such an evaluation may produce a preliminary and / or secondary indication of the legitimacy of the signal source. For one or more further received signals that are different from the first received signal and preferably have a different signal type or mode than the first received signal, the evaluation typically includes performing a comparison between one or more signal features and a set of corresponding one or more signal features. Features may include any one or more of the direction of arrival of the transmitter, the signal type or mode, the intensity, the duration, and the content. The expected features may be obtained by reference data, which is typically associated with and acquired with respect to one or more given geographical areas in which the receiver may operate. For example, in the case where a received GNSS signal is to be verified, i.e., legitimacy information is obtained about it by the method, an additional mixed-mode signal evaluation may involve monitoring a set of additional signals, and typically their reception direction and type, and comparing the monitored signals with the signals expected to be present in the area at least in these respects. For example, an inconsistency between a monitored signal and an expected signal may indicate the presence of an invalid source, and conversely, a confirmed similarity between the measurement and the expectation can be used to confirm or indicate to the receiver the area or location in which it is operating, which can therefore be used to identify erroneous positions calculated using positioning broadcasts such as GNSS signals, and thereby indicate the illegality of those broadcasts.

[0074] According to a second aspect of the present invention, a system is provided, comprising: a local signal generator configured to provide a local signal; a receiver configured to receive a signal from a remote source in a first direction; a motion module configured to provide a determined movement of the receiver; a correlation unit configured to provide a correlated signal by correlating the local signal with the received signal; a motion compensation unit configured to provide motion compensation for at least one of the local signal, the received signal and the correlated signal based on the determined movement in the first direction; a source vector unit configured to identify a remote source vector corresponding to a portion of a propagation path of the received signal based on the correlation, wherein the portion coincides with the remote source, and a legitimacy information unit configured to generate legitimacy information based on the remote source vector of the received signal.

[0075] Typically, any one or more of the local signal generator, the motion module, the correlation unit, the motion compensation unit, the source vector unit, and the legitimacy information unit are provided as part of a single device. In some embodiments, the device also includes a receiver. Typically, the device including the receiver is a user equipment (UE) in a communication network. Any one or more of the modules and units can be provided separately from the receiver or the device including it, so that the system is distributed. For example, certain calculations, such as those performed by the motion compensation unit and / or the correlation unit, can be performed by a processor in the network or a processor that otherwise communicates data with the device including the receiver. In this way, for the purpose of efficiency and user device battery use, the UE can offload calculations to a remote or distributed process where appropriate. In some embodiments, the system, and preferably the device including the receiver, includes a GNSS positioning device. The output of the positioning device and / or the output of the inertial measurement unit (which can also be specifically included by the system or the user device, or the device including the receiver) can be used to provide the determined movement of the receiver and provide one or more position information of the receiver (so that the absolute position and / or movement path of the remote source can be determined based on the relative position information relative to the receiver).

[0076] According to a third aspect of the present invention, there is provided a computer program product comprising executable instructions which, when executed by a processor, cause the processor to perform steps including: receiving a signal from a remote source in a first direction at a receiver; providing a local signal; determining the movement of the receiver; providing a correlated signal by correlating the local signal with the received signal; providing motion compensation for at least one of the local signal, the received signal and the correlated signal based on the determined movement in the corresponding first direction to provide preferential gain for the signal received along the corresponding first direction; identifying a remote source vector corresponding to a portion of a propagation path of the received signal based on the correlation, wherein the portion coincides with the remote source; and generating legitimacy information of the remote source based on the remote source vector of the received signal.

[0077] Any attributes, features, and steps described in the present disclosure with respect to the foregoing and following embodiments may be related to the method of the first aspect, the system of the second aspect, the computer program product of the third aspect, or the aspects described below.

[0078] According to a fourth aspect of the present invention, there is provided a method for locating a cellular transmitter using a receiver, comprising: performing motion compensated correlation on at least one received signal to generate at least one motion compensated correlation result; using at least one motion compensated correlation result to identify a direction of arrival of at least one received signal; and determining the position of the cellular transmitter from the direction of arrival of at least one received signal.

[0079] In any aspect of the present invention provided in the present disclosure, the method may include any one or more of the following: determining the arrival time of at least one received signal; and using the arrival time to remove the direction of arrival of the received signal associated with a non-line-of-sight signal; and determining whether the transmitter is legal or illegal; and if the transmitter is illegal, taking action to mitigate interference generated by the illegal transmitter.

[0080] According to a further aspect of the present invention, there is provided an apparatus for performing signal correlation within a signal processing system, comprising at least one processor and at least one non-transitory computer-readable medium for storing instructions which, when executed by the at least one processor, cause the apparatus to perform operations including: performing motion compensated correlation on at least one received signal to generate at least one motion compensated correlation result; using at least one motion compensated correlation result to identify a direction of arrival of at least one received signal; and determining a position of a cellular transmitter from the direction of arrival of at least one received signal.

[0081] Embodiments of the present invention are generally directed to methods and apparatus for providing signal intelligence and security as shown in at least one of the figures and / or described in connection therewith.

[0082] These and other features and advantages of the present disclosure may be understood from a review of the following detailed description of the disclosure, taken in conjunction with the accompanying drawings, in which like reference numerals refer to like parts throughout. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] In order that the above-described features of the present invention can be understood in detail, a specific description of the present invention may be provided by reference to embodiments, some of which are shown in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only typical embodiments of the present invention and are therefore not to be considered limiting of its scope, as the present invention may admit of other equally effective embodiments.

[0084] Figure 1 A block diagram depicting a scenario with a receiver for providing signal intelligence according to at least one embodiment of the present invention;

[0085] Figure 2 According to at least one embodiment of the present invention Figure 1 A block diagram of a receiver;

[0086] Figure 3 Describes at least one embodiment of the present invention. Figure 1 and Figure 2 The operating scenario of the receiver;

[0087] Figure 4 is a flowchart of a method of operating signal processing software according to at least one embodiment of the present invention; and

[0088] Figure 5 is a flow chart of a method of operation of transmitter location software in accordance with at least one embodiment of the present invention. DETAILED DESCRIPTION

[0089] Embodiments of the present invention include apparatus and methods for providing signal intelligence and security. Digital communication systems such as cellular, Bluetooth, or WiFi utilize coded digital signals to improve communication throughput and security. Most of these systems utilize some form of deterministic digital code to facilitate signal acquisition, such as Gold codes, training sequences, synchronization words, channel characteristic sequences, or other forms of acquisition codes. GNSS transmissions also utilize repeatedly transmitted acquisition codes. This digital code is determined by the receiver and repeatedly broadcast by the transmitter to enable the receiver to acquire and receive the transmitted signal. Using this deterministic code in combination with an accurate motion model of the receiver, embodiments of the present invention are useful for identifying the direction of arrival (DoA) of the propagation path between the receiver and the transmitter. The technique of performing this DoA determination using receiver motion information is called SUPERCORRELATION TM , and described in commonly assigned U.S. Patents 9,780,829 issued on October 3, 2017; 10,321,430 issued on June 11, 2019; 10,816,672 issued on October 27, 2020; U.S. Patent Publication 2020 / 0264317 published on August 20, 2020; and U.S. Patent Publication 2020 / 0319347 published on October 8, 2020, which are hereby incorporated by reference in their entirety herein. A receiver can use this DoA data to determine information about one or more transmitters near the receiver. For example, the DoA data can be used to identify the location of spoofed transmitters and the location of legitimate transmitters. These locations can be used to create a map of legitimate transmitters so that, in the future, transmitters that are not on the map may be considered illegal transmitters and require further investigation. Based on the DoA data, a user receiver (e.g., a mobile device or a GNSS receiver) can be operated to avoid or suppress signals from spoofed transmitters so that these illegal transmitters no longer pose a threat. Using the illegal transmitter locations, government authorities can identify and disable these transmitters.

[0090] In an exemplary embodiment, a receiver can be transported through an area containing various transmitters and can identify the signal propagation path and location of each nearby transmitter. These transmitters can be GNSS satellites, cellular signal transceivers, WiFi transceivers, Bluetooth transceivers, and the like. The receiver can be carried by pedestrians and functionalized via application software to map the transmitters in a local area. Alternatively, the receiver can be moved by using a car on a ground path to perform transmitter location and mapping. In other embodiments, the receiver can be carried by an aircraft-manned or unmanned (e.g., drones, helicopters, airplanes, etc.). The functionality of embodiments of the present invention can be embedded in cellular phones, Internet of Things (IoT) devices, mobile computers, tablet computers, control systems of self-driving cars, and the like. Embodiments find use on any mobile platform that receives signals that can be related to locally generated signals.

[0091] As a receiver passes through an area, it collects DoA data for transmitters that are nearby (i.e., within range of the transmitter). The receiver knows its position using a Global Navigation Satellite System (GNSS) receiver and / or an inertial guidance system. Based on the receiver position and multiple DoA vectors (representing the direction from the receiver to the transmitter) to a particular transmitter, embodiments of the present invention calculate the position of the transmitter relative to the receiver. The relative position can then be converted to geographic coordinates. When the transmitter position is calculated, a geographic coordinate map showing the location of the transmitter is generated.

[0092] In some embodiments, multiple receivers may be used to receive signals in a coordinated manner. In further embodiments, one or more receivers may receive signals from multiple types of transmitters operating in various frequency bands to facilitate the collection of information related to many systems, thereby generating a signal profile for a given area. Some embodiments may perform signal processing locally on a mobile platform. In other embodiments, transmitter information, receiver motion information, and receiver location information may be collected at the mobile platform and communicated (wired or wireless) to a server for remote processing in real time or at a later time. In some embodiments, data is stored and processed when demand arises, such as when law enforcement requires the path of travel of a specific mobile phone or other transmitter.

[0093] Figure 1A block diagram of a scenario 100 with at least one receiver 102 for receiving signals from transmitters 106, 108, and 110 is depicted in accordance with at least one embodiment of the present invention. In other embodiments, multiple receivers 102 may be deployed to collect transmitter information. Transmitters 106, 108, 110 may be legitimate transmitters (communication or positioning transmitters) or illegitimate transmitters (jammers or spoofers). Transmitters 106, 108, 110 may be stationary or mobile. Each of the at least one receiver 102 includes a transmitter locator 104 configured to receive and process signals transmitted by transmitters 106, 108, 110 (three transmitters are depicted, but receivers 102 may process signals from any number of transmitters). Signals from legitimate transmitters 106 and 110 may be intended to communicate with, for example, a mobile device 114 (e.g., a cellular phone, a laptop, a tablet, an Internet of Things (IoT) device, an autonomous vehicle, etc.). The mobile device may communicate with the transmitters 106, 110 using cellular signals (e.g., CDMA, GSM, and the like) supporting cellular standards such as, but not limited to, 3G, 4G, LTE, and / or 5G standards. Alternatively or in addition, the legitimate transmitters 106, 110 may be WiFi or Bluetooth or other communication devices that communicate between themselves or with the mobile device 114. Furthermore, the legitimate transmitters 106, 110 may be satellite-based transmitters of GNSS signals.

[0094] Scenario 100 includes at least one illegal transmitter 108, such as a jammer or spoofer, which may target a mobile device (e.g., device 114). The intention of the jammer is to interfere with the reception of transmissions of the legitimate transmitters 106, 108. The jammer may transmit a signal similar to the legitimate transmitter signal to overwhelm or confuse the signal processing capabilities of the target receiver. On the other hand, a spoofer transmits a signal similar to the legitimate transmitter signal so that the target receiver can pick up the spoofer signal and even process the signal as if it were legitimate.

[0095] Receiver 102 includes a transmitter locator 104 in accordance with at least one embodiment of the present invention that operates to accurately locate transmitters 106, 108, 110. Transmitter locator 104 may locate both legitimate and illegitimate transmitters, or locator 104 may locate only illegitimate transmitters. As will be apparent from this description, the goal of a transmitter locator is to provide signal intelligence for transmissions occurring in its vicinity. Using signal intelligence, actions may be taken to improve the signal security of transmissions for users, e.g., avoiding or suppressing reception of illegitimate transmissions, disabling illegitimate transmitters, and the like.

[0096] In one embodiment, the transmitter locator 104 in at least one receiver 102 receives and processes the transmitter transmission locally within the receiver. In other embodiments, the receiver-based transmitter locator 104 can collect data about the transmitter transmission and receiver parameters (e.g., receiver motion, orientation, etc.). The transmitter data can be communicated immediately or stored for later communication to the server 112 via the communication network 114. The server 112 includes the transmitter locator 104 for processing the transmitter data to determine the transmitter location. The transmitter data can be processed in real time or at a later time. In other embodiments, the transmitter data can be processed partially in the receiver 102 and partially in the server 112.

[0097] As described in detail below, the transmitter locator 104 (whether receiver-based or server-based) uses SUPERCORRELATION TM Techniques, such as those described in commonly assigned U.S. Patents 9,780,829, issued on October 3, 2017; 10,321,430, issued on June 11, 2019; 10,816,672, issued on October 27, 2020; U.S. Patent Publication 2020 / 0264317, published on August 20, 2020; and U.S. Patent Publication 2020 / 0319347, published on October 8, 2020, are hereby incorporated by reference in their entirety herein. The technique determines the direction of arrival (DoA) of a signal received at a receiver from a transmitter 106, 108, 110 (i.e., a received signal). When the receiver 102 moves (indicated by arrow 118), the transmitter locator 104 calculates motion information representing the motion of the receiver 102. The motion information is used to perform motion compensated correlation of the received signal. Based on the motion compensated correlation process, the transmitter locator 104 estimates the DoA of the received signal. The transmitter locator 104 uses the receiver position along with the DoA data to determine the locations of the transmitters 106, 108, 110. The intersection of multiple DoA vectors generated as the receiver moves along the path 118 identifies the locations of the transmitters 106, 108, 110, as described in detail below.

[0098] Based on the signal DoA data, the receiver 102 or server 112 can create a map of the transmitter locations. In one embodiment, the location information can be accumulated within the receiver and downloaded to a mapping application at a later time. In an alternative embodiment, the transmitter locations can be continuously, periodically, or intermittently transmitted via cellular or WiFi communications to the server 112, where the mapping application creates a map of the transmitter locations.

[0099] In an alternative embodiment, the received signal may be processed to determine the time of arrival (TOA) or time difference of arrival (TDOA) information of the signal. As is known in the art, TOA and TDOA information may be used for the calculation of the position of the transmitter. Such calculations may be used to enhance DoA vector processing to increase the speed of obtaining a position solution. In addition, TOA and / or TDOA information may be used to identify delayed received signals indicating a non-line-of-sight (NLOS) signal path. The DoA vector associated with the NLOS signal may be removed from the transmitter position calculation to reduce the amount of calculation and / or remove a source of position error.

[0100] Figure 2 2 is a block diagram of a receiver 102 according to at least one embodiment of the present invention. Receiver 102 includes mobile platform 206, antenna 202, receiver front end 204, signal processor 206, and motion module 228. Receiver 102 may form part of a laptop computer, a mobile phone, a tablet computer, an Internet of Things (IoT) device, a drone, a mobile computing system in an autonomous vehicle, a human-operated car, etc.

[0101] In the receiver 102, the mobile platform 200 and the antenna 202 are an inseparable unit, wherein the antenna 202 moves together with the mobile platform 200. SUPERCORRELATION TM The operation of the technique is based on determining the motion of the signal receiving antenna. Any reference to motion herein refers to the motion of the antenna 202. In some embodiments, the antenna 202 may be separate from the mobile platform 200. In this case, the motion estimate used in the motion compensation related process is the motion of the antenna 202. In most scenarios, the motion of the mobile platform 200 is the same as the motion of the antenna 202, and therefore, the following description will assume that the motion of the platform 200 and the antenna 202 are the same.

[0102] The mobile platform 200 includes a receiver front end 204, a signal processor 206, and a motion module 228. The receiver front end 204 down-converts, filters, and samples (digitizes) the received signal in a manner known to those skilled in the art. The output of the receiver front end 204 is a digital signal containing data. The data of interest is a deterministic training or acquisition code, such as a Gold code, which is used by the transmitter to synchronize transmissions to the transceiver.

[0103] Signal processor 206 includes at least one processor 210, support circuits 212, and memory 214. At least one processor 210 may be any form of processor or combination of processors, including but not limited to a central processing unit, a microprocessor, a microcontroller, a field programmable gate array, a graphics processing unit, a digital signal processor, and the like. Support circuits 212 may include well-known circuits and devices that facilitate the functions of one or more processors. Support circuits 212 may include one or more of a power supply, a clock circuit, an analog-to-digital converter, a communication circuit, a cache, a display, and / or the like, or a combination thereof.

[0104] The memory 214 includes one or more forms of non-transitory computer readable media, including one or more of read-only memory or random access memory or any combination thereof. The memory 214 stores software and data, including, for example, signal processing software 216, transmitter position software 208, and data 218. The data 218 includes receiver positions 220, direction of arrival (DOA) vectors 222 (collectively referred to as DOA data), transmitter positions 224, and data for performing SUPERCORRELATION. TM The signal processing software 216, when executed by one or more processors 210, performs motion compensated correlation on the received signal to estimate the DoA vector of the received signal. The motion compensated correlation process is described in detail below. The operation of the signal processing software 216 is used to Figure 1 The transmitter locator 104.

[0105] As described in detail below, DoA vectors 222 and receiver positions 220 are used by transmitter position software 208 to determine the position of each transmitter. Data 218 stored in memory 214 may also include signal estimates, correlation results, motion compensation information, motion information, motion and other parameter assumptions, orientation information, and the like.

[0106] The motion module 228 generates a motion estimate for the receiver 102. The motion module 228 may include an inertial navigation system (INS) 230 and a global navigation satellite system (GNSS) receiver 226, such as GPS, GLONASS, GALILEO, BEIDOU, etc. INS230 may include one or more of the following, but not limited to: a gyroscope, a magnetometer, an accelerometer, and the like. In order to facilitate motion compensation correlation, the motion module 222 generates motion information (sometimes referred to as a motion model), which includes at least the speed of the antenna 202 in the direction of the transmitter of interest (i.e., the estimated direction of the received signal source). In some embodiments, the motion information may also include an estimate of the platform orientation or heading, including but not limited to the pitch, roll, and yaw of the platform 200 / antenna 202. Typically, the receiver 102 can test each direction and iteratively narrow the search to one or more directions of interest.

[0107] Figure 3 Describes at least one embodiment of the present invention. Figure 1 and Figure 2 Scenario 300 of the operation of the receiver 102 of FIG. Scenario 300 includes moving the receiver 102 from position 1 along path 302 to position 2, and then moving along path 304 to position 3. As the receiver 102 traverses the area, the receiver 102 calculates DoA vectors 306 at position 1, 308 at position 2, and 310 at position 3. The three DoA vectors 306, 308, and 310 intersect at the location 312 of the transmitter 106. Although three discrete positions are described as the locations where the DoA vectors are calculated, in other embodiments, the DoA vectors may be calculated periodically, intermittently, or continuously as the receiver moves. Additional vectors may be used to converge the solution to the precise transmitter location. In addition, the transmitter 106 may move so that the convergence point moves and can be tracked. The receiver 102 may be a single receiver or multiple different receivers that coordinate their data collection efforts. The DoA vectors may be processed at a remotely located server to determine the location of the transmitter using vectors from different receivers.

[0108] In an urban environment, some of the DoA vectors 302, 304, 306 are line-of-sight (LOS), and some of the DoA vectors 314 are non-line-of-sight (NLOS), i.e., the LOS vectors represent signals transmitted directly from the transmitter 106 to the receiver 102, while the NLOS vectors may be reflected from structures 316 near the receiver 102. In one embodiment, received signals (e.g., undesired signals) that may result in NLOS vectors may be ignored in the DoA and position calculations. In another embodiment, as more and more DoA vectors are collected and processed, the LOS vectors converge on a particular location, such as location 312. In addition, if TOA or TDOA information is available, this information may be used to remove DoA vectors for NLOS paths, because for NLOS signals, the arrival time will be abnormal (delayed) compared to the LOS signal, i.e., the time information of the NLOS signal will contain a delay compared to the LOS signal.

[0109] In other embodiments, structure 316 may be modeled in a building model. The building model in conjunction with ray tracing techniques may be used to determine the DoA of the reflected signal. Thus, the path of the reflected transmitter signal is estimated and the reflected signal may be used in the transmitter location calculation.

[0110] In other embodiments, one or more receivers 102 may collect all transmitter signals, LOS and NLOS, over a period of time as the receiver traverses an area. These collected signals may be processed using the transmitter location techniques described herein to create a signal profile for the area. The signal formula will contain a DoA vector cross-region identifying the transmitter location. In some embodiments, a Bayesian estimator may be used to compare various hypotheses about the transmitter location using information provided by available measurements.

[0111] Typically, the vector intersection position 312 is not a point, but a region or area, due to the probabilistic nature of the DoA vectors, i.e., the determined direction of each vector has uncertainty caused by measurement errors, and the intersection forms a region rather than a point. The intersection region will form the maximum amount of the position of the transmitter 106.

[0112] Since the receiver 102 knows its position through GNSS and / or INS calculations, the geolocation coordinates of the receiver 102 can be converted to the geolocation coordinates of the transmitter locations 312. Therefore, a geolocation map of the transmitter locations can be generated. Although this scenario depicts the receiver 102 calculating the location 312 of a single transmitter 106, in various other embodiments, the receiver 102 can generate the locations of many nearby transmitters sequentially and / or simultaneously.

[0113] The foregoing embodiments perform transmitter vector and position determination within the receiver 102. In other embodiments, the data used to generate the DoA vector (i.e., transmitter data), the DoA vector itself, the position information, etc. may be transmitted from the receiver to a server ( Figure 1 112) for processing to produce the transmitter position.

[0114] Figure 4 4 is a flow chart of a method 400 of operation of the signal processing software 216 according to at least one embodiment of the present invention. The method 400 may be implemented in software, hardware, or a combination of both (e.g., using Figure 2 signal processor 206).

[0115] Method 400 begins at 402 and proceeds to 404, where a signal is transmitted as described above. Figure 1 The described method receives at a receiver at least one remote source (e.g., such as Figure 1 Each received signal includes a synchronization or acquisition code, such as a Gold code, extracted from a radio frequency (RF) signal received at an antenna. The process of down-converting the RF signal and extracting the digital code is well known in the art. At 406, method 400 performs the following steps: Figure 2 The motion module 228 receives the motion information. The motion information includes Figure 1 An estimate of the motion of the receiver 102, such as one or more of speed, heading, orientation, etc.

[0116] In some embodiments, the receiver uses a single local oscillator to receive the transmitter signal and receive the GNSS signal. Therefore, before processing the transmitter signal, the SUPERCORRELATION TM Techniques are applied to GNSS signals to facilitate improved position accuracy and to correct local oscillator instabilities. As a result, the receiver position is very precise and the local oscillator is stable over long periods of time, allowing very long coherent integration times (e.g., 1 second) to be used to process GNSS and transmitter signals.

[0117] At 408, method 400 generates a plurality of phasor sequence hypotheses associated with the directions of interest of the received signal. Each phasor sequence hypothesis includes a time series of phase offset estimates that vary with parameters such as receiver motion, frequency, DoA of the received signal, and the like. Signal processing correlates a local code encoded in the local signal with the same code encoded in the received RF signal. In one embodiment, the phasor sequence hypothesis is used to adjust the carrier phase of the local signal with sub-wavelength accuracy. In some embodiments, such adjustment or compensation can be performed by adjusting a local oscillator signal, one or more received signals, or a correlation result to produce a phase compensated correlation result. The signal and / or correlation result is a complex signal including an in-phase (I) and a quadrature-phase (Q) component. The method applies each phase offset in the phasor sequence to a corresponding complex sample in the signal or correlation result. If the phase adjustment includes an adjustment of a component of the receiver motion in the estimated direction of the transmitter, the result is a motion compensated correlation result. For each received signal, at 410, method 400 correlates the received signal with a set of (multiple) directional hypotheses containing estimates of the sequence of phase offsets required to accurately correlate received signals arriving from a particular direction over a long coherent integration period (e.g., 1 second). There is a set of hypotheses representing a search space for each received signal and each parameter of interest (e.g., receiver motion and / or signal DoA).

[0118] Motion estimation is typically a motion hypothesis in a direction of interest, such as in the direction of an interested transmitter transmitting a received signal, i.e., if an illegal transmitter is the interested transmitter, a hypothetical search space containing a component of the motion of the receiver in the direction of the illegal transmitter is generated. At initialization, the direction of interest may be unknown or inaccurately estimated. Therefore, a brute force search technique may be used to identify one or more directions of interest by searching in all directions and correlating the signals received in all directions. Comparison of the correlation results in all directions enables method 400 to narrow the search space. There is a very strong correlation between the true values ​​of these hypotheses between code repetitions, so that the initial search may be intensive, but subsequent processing only requires tracking the receiver motion and signal DoA in the receiver as these parameters evolve. Therefore, subsequent compensation is performed on a narrow search space.

[0119] In one embodiment, if a signal from a given transmitter was previously received, the hypothesis set for the newly received signal includes a set of phasor sequence hypotheses (using the expected frequency and frequency rate and / or the last frequency and last frequency rate used when the previous signal was received from that particular transmitter). These values ​​can be centered around the last used value, or the last used value can be additionally offset by a prediction of further offset based on the expected receiver motion. At 410, the method 400 correlates each received signal with the hypothesis set for that signal. These hypotheses are used as parameters to form a phase compensation phasor to phase compensate the correlation process. Thus, phase compensation can be applied to the received signal, the local frequency source (e.g., an oscillator signal), or the correlation result value. In addition to searching on the DoA space, the method 400 can also apply hypotheses related to other variables (parameters), such as oscillator frequency, to correct for frequency and / or phase drift, or heading, to ensure that the correct motion compensation is applied. The number of hypotheses may be different for each variable. For example, the search space may contain ten hypotheses for searching DoA, and have two hypotheses for searching receiver motion parameters (such as speed) - that is, a total of twenty hypotheses (ten times two). The result of the correlation process is a plurality of phase compensated correlation results - one phase compensated correlation result value for each hypothesis of each received signal.

[0120] At 412, method 400 processes the correlation results to find a "best" or optimal result for each received signal. The correlation output may be a single value representing a parameter hypothesis (preferred hypothesis) that provides an optimal or best correlation output. Typically, a cost function is applied to the correlation values ​​for each received signal to find the optimal correlation output corresponding to one or more preferred hypotheses, e.g., the maximum correlation value is associated with a preferred hypothesis of the correct signal DoA.

[0121] At 414, method 400 identifies the DoA vector for each received signal based on the best correlation results for the signal. Received signals along the DoA vector typically have the strongest signal-to-noise ratio and represent line-of-sight (LOS) reception between the transmitter and the receiver. Thus, using motion compensated correlation enables receiver 102 to identify the DoA vector for one or more received signals. Method 400 ends at 416.

[0122] In other embodiments, rather than using the maximum magnitude correlation value, other testing criteria may be used. For example, method 400 may monitor the progress of the correlation as hypotheses are tested and apply a cost function indicating the best hypothesis when the cost function reaches a minimum (e.g., a small Hamming distance between peaks in the correlation graph). In other embodiments, additional hypotheses may be tested in addition to the DoA hypothesis, for example to ensure that motion compensation (i.e., velocity and heading) is correct.

[0123] Figure 55 is a flow chart of a method 500 of operation of the location software 288 according to at least one embodiment of the present invention. The method 500 may be performed locally within the receiver, or may be performed remotely on a server. If performed remotely, the DoA vector or data generating the DoA vector is transmitted from the receiver to the remote server for processing according to the method 500.

[0124] Method 500 begins at 502 and proceeds to 504, where method 500 receives a DoA vector for a particular transmitter. At 506, method 500 determines a location where the DoA vectors intersect. The transmitter location is relative to the receiver position. This process can be iterative as additional DoA vectors are generated, or can be calculated when a predefined number (e.g., three, five, ten, etc.) of DoA vectors have been determined. In some embodiments, TOA or TDOA information can be used to enhance the position calculation. For example, time information related to the time at which the signal is received at various receiver positions can be used to identify LOS signals from NLOS signals, for example, as the NLOS signal has a delayed reception time compared to the LOS signal. The DoA vector associated with the NLOS signal can then be removed from the set of vectors used to determine the transmitter location.

[0125] At 508, the method 500 calculates the geolocation coordinates of the transmitter location by converting the known geolocation coordinates of the receiver to the transmitter location determined at 506. At 510, the method updates a map or database with the transmitter geolocation so that a comprehensive list of transmitter locations is created. At 512, the method queries whether another set of DoA vectors for another transmitter is available for processing. If the query is answered affirmatively, the method 500 returns to 504 to process additional DoA vectors. If the query is answered negatively, the method 500 ends at 514.

[0126] Embodiments of the present invention may be used to collect transmitter data over time without processing the data, i.e., the transmitter and receiver data is stored for subsequent processing as needed. For example, an autonomous vehicle may collect and store transmitter and receiver data that is processed after a traffic incident occurs. The processing may indicate that a GNSS spoofing transmitter may have caused the car's GNSS receiver to malfunction and follow an incorrect path.

[0127] Embodiments of the present invention may be used to process collected cell phone data where a cell phone is the transmitter of interest and a police vehicle having an embodiment of the above receiver collects the transmitter data for subsequent processing. When the need arises, transmitter data from a receiver known to be in a crime area may be processed to determine the movement of a particular cell phone over a particular period of time. Such movement evidence may form useful evidence in an investigation.

[0128] The transmitter locator 104 can be a feature of the mobile device so that once an illegal transmitter is discovered, the mobile device can use the location of the transmitter to take action to suppress the signals arriving from the DoA of the transmitter. Such action can involve changing the antenna pattern of the mobile device, or can involve using SUPERCORRELATION TM Techniques are used to suppress reception of signals from locations of transmitters and / or to enhance reception of signals from legitimate transmitters.

[0129] A plurality of examples are given here to illustrate various features, and are not intended to be so limited. Any one or more features may not be limited to the specific examples presented herein, regardless of any order, combination or connection described. In fact, it should be understood that any combination of features and / or elements described above by way of example is contemplated, including any variation or modification that is not listed but can achieve the same. Unless otherwise stated, any one or more features may be combined in any order.

[0130] As mentioned above, the drawings are presented herein for illustrative purposes and are not meant to impose any structural limitations unless otherwise specified. Various modifications to any structure shown in the drawings are considered to be within the scope of the invention presented herein. The present invention is not intended to be limited to any scope of the claim language.

[0131] Where "coupled" or "connected" is used, unless otherwise stated no limitation is implied and coupling or connection is limited to physical coupling or connection and should be understood to include communicative coupling, including wireless transmissions and protocols.

[0132] Any block, step, module or other means described herein may represent one or more instructions, which may be stored as software on a non-transitory computer-readable medium and / or executed by hardware. Any such block, module, step or other means may be executed in an automated manner by various software and / or hardware combinations, including using dedicated hardware designed to achieve such purposes. As described above, any number of blocks, steps or modules may be executed in any order, or not at all, including substantially simultaneously, i.e. within the tolerance range of the system executing the blocks, steps, or modules.

[0133] Where conditional language is used, including but not limited to "can," "could," "may," or "might," it should be understood that the associated features or elements are not required. Thus, where conditional language is used, elements and / or features should be understood to be optionally present in at least some examples, and not necessarily conditional on anything, unless otherwise specified.

[0134] Where a list is listed with alternatives or conjunctions (e.g., one or more of A, B, and / or C), unless otherwise specified, it should be understood to include one or more of each element, including any one or more combinations of any number of the listed elements (e.g., A, AB, AC, ABC, ABB, etc.). When "and / or" is used, it should be understood that the elements can be connected with alternatives or conjunctions.

[0135] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the following claims.

Claims

1. A method for obtaining legitimacy information for a remote source, the method comprising: At a receiver, receiving a signal from the remote source in a first direction; Provide local signals; determining movement of the receiver; providing a correlation signal by correlating the local signal with a received signal; providing motion compensation for at least one of the local signal, the received signal, and the correlation signal based on the determined movement in the first direction to provide preferential gain for signals received along the first direction; Based on the correlation, identifying a remote source vector corresponding to a portion of a propagation path of the received signal, wherein the portion coincides with the remote source; and Legitimacy information for the remote source is generated based on the remote source vector of the received signal.

2. The method according to claim 1, wherein: The validity information is generated according to a signal type of the received signal.

3. A method according to any one of the preceding claims, comprising: When the angle formed by the remote source vector and the horizontal direction is less than a predetermined threshold angle, the legitimacy information is generated to indicate that the remote source is an illegal source.

4. A method according to any one of the preceding claims, comprising generating the legitimacy information to indicate that the remote source is a legitimate source when the angle formed by the remote source vector and the horizontal direction is greater than a predetermined threshold angle.

5. The method according to any one of the preceding claims, further comprising: For each of a plurality of signals received at the receiver from the remote source, wherein each of the signals is received in a respective first direction: Provide corresponding local signals; determining a corresponding movement of the receiver; providing a corresponding correlated signal by correlating the corresponding local signal with a received signal; providing motion compensation for at least one of the corresponding local signal, the received signal, and the corresponding correlation signal based on the determined corresponding movement in the corresponding first direction to provide preferential gain for signals received along the corresponding first direction; and Based on the correlation, a corresponding remote source vector is identified corresponding to a portion of a propagation path of the received signal, the portion coinciding with the remote source.

6. The method according to claim 5, further comprising: generating position information of the remote source by identifying one or more locations where two or more of the respective remote source vectors of the plurality of received signals intersect, Wherein, the legitimacy information is generated according to the location information.

7. The method according to claim 6, wherein: Generating the legitimacy information based on the position information includes obtaining reference position data indicating one or more legitimate signal sources and generating the legitimacy information based on a comparison between the generated position information and the reference position data.

8. The method according to claim 6 or claim 7, further comprising: obtaining reference geographic data corresponding to one or more geographic regions and including information indicating an expected presence of a legitimate source therein, and The legitimacy information is generated based on the generated location information and the reference geographic data.

9. The method according to claim 8, wherein: The reference geographic data includes expected source type information corresponding to the one or more geographic regions, and wherein the legitimacy information is generated based on a comparison between the source type information and the identified types of one or more of the plurality of received signals.

10. The method according to any one of claims 5 to 9, further comprising: generating source movement information indicating a movement state of the remote source based on a plurality of remote source vectors, and Wherein, the legitimacy information is generated according to the source movement information.

11. The method according to claim 10, further comprising: obtaining reference source movement data indicative of expected movement states of legitimate remote sources, and The legitimacy information is generated based on the generated source movement information and the reference source movement data.

12. The method according to any one of claims 10 and 11, further comprising: generating first position information of the remote source by identifying one or more positions where a first set of two or more remote source vectors of the plurality of remote source vectors intersect, generating second position information of the remote source by identifying one or more positions where a second set of two or more remote source vectors from the plurality of remote source vectors, different from the first set, intersect, and The source motion information is generated based on the first position information and the second position information.

13. The method according to claim 12, wherein: The generated source movement information includes: a generated source movement path based on the first position information and the second position information, and wherein the reference source movement data includes an expected legitimate source movement path, and wherein the legitimacy information is generated based on a comparison between the generated source movement path and the expected source movement path.

14. The method according to any one of the preceding claims, further comprising: The legitimacy information for the remote source is stored in a remote source legitimacy data set.

15. A method according to any preceding claim, further comprising, if the legitimacy information indicates that the remote source is an illegal source, then: Performing legitimacy verification on the remote source using the received signal; and The legitimacy information is updated according to the result of the legitimacy verification.

16. The method according to claim 15, wherein: The signal is a first positioning signal, and wherein the legitimacy verification comprises: performing a first positioning calculation based on a plurality of received positioning signals including the first positioning signal to obtain first position information of the receiver, performing a second positioning calculation based on a plurality of received positioning signals excluding the first positioning signal to obtain second position information of the receiver, and A comparison between the first position information and the second position information is obtained.

17. The method according to claim 15 or claim 16, wherein: The legitimacy verification includes obtaining a source quality parameter of the remote source using the received signal.

18. The method according to claim 17, wherein: The source quality parameter is obtained by calculating the quality of a frequency standard component of the remote source based on the received signal.

19. The method according to any one of claims 15 to 18, wherein: The legitimacy verification is based on a monitored polarization state of the received signal.

20. A system comprising: a local signal generator configured to provide a local signal; a receiver configured to receive a signal in a first direction from a remote source; a motion module configured to provide a determined movement of the receiver; a correlation unit configured to provide a correlation signal by correlating the local signal with a received signal; a motion compensation unit configured to provide motion compensation for at least one of the local signal, the received signal, and the correlation signal based on the determined movement in the first direction; a source vector unit configured to identify, based on the correlation, a remote source vector corresponding to a portion of a propagation path of the received signal, the portion coinciding with the remote source, and The legitimacy information unit is configured to generate legitimacy information according to the remote source vector of the received signal.

21. A computer program product comprising executable instructions which, when executed by a processor, cause the processor to perform steps comprising: At a receiver, receiving a signal from a remote source in a first direction; Provide local signals; determining movement of the receiver; providing a correlation signal by correlating the local signal with a received signal; providing motion compensation for at least one of the local signal, the received signal, and the correlation signal based on the determined movement in the first direction to provide preferential gain for signals received along the first direction; Based on the correlation, identifying a remote source vector corresponding to a portion of a propagation path of the received signal, the portion coinciding with the remote source; and The legitimacy information of the remote source is generated according to the remote source vector of the received signal.

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