IT201900001135A1 - GEOLOCALIZATION AND / OR TIMING VALIDATION BASED ON INSTANTS OF DIFFUSION OF AIRCRAFT TRACKING SIGNALS - Google Patents

Description

DESCRIPTION

Technical field

The present invention relates to geolocation and / or timing. More specifically, this invention relates to the validation of geolocation and / or timing.

Technological context

The background of the present invention is introduced hereinafter with the discussion of techniques relating to its context. However, even when this discussion concerns documents, deeds, artifacts and the like, it does not suggest or recognize that the techniques discussed are part of the known art or are general knowledge in the relevant sector for the present invention.

The geolocation of entities of various types (ie, the determination of their position in the real world) is commonly used in many applications, for example, to trace a place of origin of products. For this purpose, it is possible to associate with terminal entities capable of using widely used geolocation services (for example, based on geolocation satellites, such as GPS); this makes it possible to dynamically determine the position of the terminals (and therefore of the entities associated with them) on the basis of corresponding geolocation signals (broadcast by the geolocation satellites in the case in question). Such geolocation services also provide a very accurate synchronization mechanism of the terminals' internal clocks. This makes it possible to use the internal clocks to time events associated with the same entities (for example, by determining their occurrence instants).

However, the geolocation of the terminals (and the synchronization of their internal clocks) can be subject to accidental or intentional malfunctions (including for criminal purposes). For example, geolocation signals can undergo degradation due to interference phenomena with other radio signals (with a technique known with the English term “jamming” in the case of their intentional generation). Furthermore, since the configuration of the geolocation signals is known in advance, it is possible to provide false geolocation signals to the terminals, both by modifying the (actual) geolocation signals and by shielding them and replacing them with different geolocation signals created specifically (technique known by the English term " spoofing "); it is also possible to record (actual) geolocation signals in one place and replicate them in a different place by shielding the actual ones (technique known by the English term “meaconing”). In any case, this involves the determination of positions of the terminals (and instants of occurrence) which are incorrect (ie, different from the actual ones).

In some applications, it is important to guarantee (with a sufficient level of confidence) the correctness of the geolocation of the terminals (and of the instants of occurrence). This is particularly relevant whenever it is necessary to certify the position of the corresponding entities, for example, for security, contractual, commercial reasons and so on. For example, in the case of tracing the place of origin of products, this makes it possible to ensure that the products actually come from that place of origin. In this way, it is possible to guarantee the authenticity of the products and therefore their quality standard; consequently, the risk of distribution of counterfeit products (which could also be dangerous for consumers, as in the case of harmful raw materials, treatments and / or preservation) is avoided (or at least substantially reduced).

For this purpose, the Italian patent n.102016000110784 describes a technique to validate the geolocation of terminals based on tracking signals transmitted by aircraft that provide information relating to the same useful for air traffic management (for example, identification code, position, altitude , speed, and so on). In short, each terminal is equipped with two receivers for geolocation signals and for tracking signals. The terminal receives at the same time of validation the geolocation signals and the tracking signals from satellites and aircraft, respectively, which are visible from its position. The tracking signals vary continuously over time (according to the aircraft that are flying over the position at the instant of validation) and in a non-repetitive way (according to countless contingent factors not known a priori); therefore, the tracking signals represent a sort of signature of the position at the instant of validation. The terminal transmits the geolocation signals and the tracking signals to a service center. The service center also collects aircraft-related information which is freely provided by various services on the Internet. The service center compares the tracking signals provided by the terminal with the information collected for the same position and at the same validation instant; this allows you to determine if the tracking signals were actually received in that position at that instant, and therefore if the terminal was actually located where it was indicated. Since the tracking signals are not predictable a priori, the aforementioned technique makes it difficult to simulate terminal positions other than the actual ones.

Summary

A simplified summary of the present invention is presented herein in order to provide a basic understanding thereof; however, the sole purpose of this summary is to introduce some concepts of the invention in simplified form as a prelude to its following more detailed description, and it is not to be interpreted as an identification of its key elements or as a delimitation of its scope.

In general terms, the present invention is based on the idea of verifying the instants of transmission of the tracking signals.

In particular, one aspect provides a method for validating a geolocation and / or timing of a terminal. For this purpose, tracking signals broadcast by one or more aircraft visible from a terminal position are received by the terminal at corresponding reception instants. The position and / or timing of the terminal is validated in accordance with a comparison between the tracking information of the terminal (based on the tracking signals and indicative of corresponding instants of diffusion from the aircraft of the tracking signals, each estimated in accordance with the corresponding instant reception, the position of the corresponding aircraft indicated in the tracking signal and the position of the terminal) and reference information (representative of actual values of the tracking signals and the corresponding broadcast instants).

A further aspect provides a computer program (software) for implementing the method.

A further aspect provides a corresponding software program product. A further aspect provides a corresponding system.

More specifically, one or more aspects of the present invention are indicated in the independent claims and advantageous features thereof are indicated in the dependent claims, with the text of all claims being incorporated herein by reference (with any advantageous features provided by reference to each specific aspect that applies mutatis mutandis to any other aspect).

Brief description of the figures

The solution of the present invention, as well as further characteristics and relative advantages, will be better understood with reference to the following detailed description, provided purely by way of non-limiting indication, to be read in conjunction with the attached figures (in which, for simplicity, corresponding elements are indicated with the same or similar references and their explanation is not repeated, and the name of each entity is generally used to indicate both its type and its attributes, such as value, content and representation). In this regard, it is expressly understood that the figures are not necessarily to scale (with some details that may be exaggerated and / or simplified) and that, unless otherwise indicated, they are simply used to conceptually illustrate the structures and procedures described. . In particular:

FIG.1A-FIG.1C show the general principles of the solution according to an embodiment of the present invention,

FIG. 2 shows the general principles of the solution in accordance with another embodiment of the present invention,

FIG. 3 shows the general principles of the solution in accordance with another embodiment of the present invention,

FIG.4 shows a basic block diagram of a processing infrastructure that can be used to put the solution into practice in accordance with an embodiment of the present invention,

FIG. 5 shows the main software components that can be used to implement the solution according to an embodiment of the present invention, and

FIG.6A-FIG.6D show an activity diagram that describes the flow of activities related to an implementation of the solution in accordance with an embodiment of the present invention.

Detailed description

With reference in particular to FIG.1A-FIG.1C, the general principles of the solution are shown in accordance with an embodiment of the present invention.

Starting from FIG.1A, a plurality of terminals 105 are used to geolocate corresponding entities (not shown in the figure), for example, a place of origin of products, and / or to time corresponding events, for example, commercial transactions. Terminals 105 are present in a geographical area that is flown over by one or more aircraft 110 (only one shown in the figure); this means that the aircraft 110 are visible from the terminals 105, that is, they are capable of receiving tracking signals continuously diffused (broadcast) by the aircraft 110 as they fall within their transmission range (for example, of the order of a few hundred of Km). The tracking signals include information relating to aircraft 110 (for air traffic management), including an indication of their position. The tracking signals are diffused by the aircraft 110 in a pseudo-random way (to reduce collision phenomena of the tracking signals during their reception), so it is not known a priori when this occurs; moreover, even the content of the tracking signals is not known a priori (as it depends on innumerable contingent factors, such as advances / delays, trajectories, speeds / altitudes and so on of the aircraft 110).

The terminals 105 receive the tracking signals (received tracking signals) at corresponding reception instants, determined by an internal clock of the terminal 105. In the solution according to an embodiment of the present invention, for each terminal 105 a corresponding diffusion instant from the aircraft 110 of each received tracking signal (estimated diffusion instant). The estimated diffusion instant is determined in accordance with the position of the aircraft 100 (extracted from the tracking signal received) and a position of the terminal 105 (for example, determined based on geolocation signals received from geolocation satellites, not shown in the figure). In particular, starting from the reception instant it is possible to trace the estimated diffusion instant by subtracting a transmission time of the tracking signal from the aircraft 110 to the terminal 105, determined on the basis of their distance defined by the position of the aircraft 110 and from the terminal location 105.

Turning to FIG.1B, each of the terminals 105 transmits to a central processor, for example, a central server 115 of a provider of a geolocation and / or timing service, tracking information corresponding to one or more reception instants; for each instant of reception, the tracking information is based on the tracking signals received (at the moment of reception) and are indicative of the corresponding estimated diffusion instants. The central server 115 possesses reference information; the reference information represents (with a sufficient level of reliability) the actual tracking signals broadcast by the aircraft 110 (actual tracking signals) and the actual values of their diffusion instants (effective diffusion instants). For example, the reference information is determined based on the tracking information provided by the terminals 105. A majority mechanism can be used for this purpose. Furthermore, one or more of the terminals 105 can be reference terminals which are managed by the provider of the geolocation / timing service; this ensures that the reference terminals are not subject to intentional malfunctions (with a sufficient degree of confidence), so that the tracking information provided by them can be considered substantially correct.

Moving on to FIG.1C, a generic terminal 105 submits to the central server 115 a request for validation of its position (for example, determined by the same through the geolocation signals) at a validation instant (determined by its internal clock) and / or a validation instant. In response to this, the central server 115 compares the tracking information of the terminal 105 corresponding to the validation instant with the reference information. The central server 115 can certify the position of the terminal 105 as correct if the tracking information is consistent with the reference information (for example, if the tracking signals received by the terminal 105 at the validation instant correspond to the tracking signals which have been diffused by the aircraft 110 around the position of the terminal 105 and if their estimated diffusion instants match the corresponding actual diffusion instants within a certain tolerance); in fact, if the estimated diffusion instant of a received tracking signal matches the actual diffusion instant of the same actual tracking signal, this means that the terminal 105 is at a distance from the corresponding aircraft 110 equal to that of its position to be validated (used to calculate the estimated scattering instant), and therefore on a corresponding spherical surface (defined by the locus of the points at this distance from the aircraft 110). Having at least three received / actual tracking signals available, it is therefore possible to determine that the terminal 105 is in a specific position defined by the intersection of the corresponding spherical surfaces. At the same time, the central server 115 can certify the validation instant as correct if the tracking information is consistent with the reference information; in fact, if the estimated diffusion instant of a received tracking signal matches the actual diffusion instant of the same actual tracking signal within a certain tolerance, this also means that the internal clock of the terminal 105 is substantially correct.

The validation of the position of the terminal 105 and / or of the validation instant is subject to an uncertainty (of validation) depending on the tolerances of the corresponding information. In particular, the validation uncertainty is mainly defined by the tolerance of the internal clock of the terminal 105 (for example, a fraction of a microsecond if synchronized via reference terminals as described below) and by the tolerance of the position of the aircraft 110 (e.g. example, which can be corrected up to a few meters as described below), while in the absence of intentional malfunctions the tolerance of the position of the terminal 105 can be considered negligible (for example, a few meters if determined by the geolocation signals). This creates a corresponding area of uncertainty for the distance of the terminal 105 from the aircraft 110 (with a radius of a few tens of meters in the case in question) and for the instant of validation (of a fraction of a microsecond in the case in question).

The solution described above makes it possible to guarantee (with a sufficient level of confidence) the correctness of the geolocation of the terminals, and therefore of the entities associated with them. In addition or alternatively, the same solution allows to guarantee (with a sufficient level of confidence) the correctness of the timing of the terminals, and therefore of the validation instants associated with them. In particular, it is impossible (or at least very difficult) to carry out “spoofing” attacks by generating false tracking signals to be provided to the terminals; in fact, neither the contents nor the diffusion instants of the tracing signals are known a priori.

Furthermore, it is impossible (or at least very difficult) to implement “meaconing” attacks by recording the tracking signals in one place to supply them to terminals in another place; in fact, the delay introduced by the transfer of the tracing signals would cause the calculation of incorrect diffusion instants of the tracing signals.

This is particularly advantageous whenever it is necessary to certify the position of the entities associated with the terminals, for example, for security, contractual, commercial reasons and so on (for example, in the case of tracing the place of origin of products, this allows to guarantee the authenticity of the products and therefore their quality standard, substantially reducing the risk of distribution of counterfeit products). In addition or alternatively, this is particularly advantageous whenever it is necessary to certify the instant of occurrence of events associated with the terminals, for example, commercial transactions, IT documents, photographs, creations and so on.

With reference now to FIG.2, the general principles of the solution are shown in accordance with another embodiment of the present invention.

Also in this case, a generic terminal 105 (whose position and / or instant of occurrence is to be validated) receives the tracking signals broadcast by one or more aircraft 110 (only one shown in the figure). However, in certain situations it is possible that the aircraft 110 are also visible from other terminals sufficient to determine the corresponding reference information as indicated above; for example, this can happen when the terminal 105 is located in a remote geographical area, where the solution described above is not very common, in general during the night and / or holidays and so on.

In the solution according to an embodiment of the present invention, one or more repeaters are used for this purpose, for example, satellites 205 such as telecommunications satellites (only one shown in the figure). The satellites 205 function as repeaters (transponders) which forward the aircraft tracking signals; for this purpose, the satellites 205 receive the aircraft tracking signals which are visible by them and re-transmit them (for example, on a different frequency). The forwarding of tracking signals is being studied for use in air traffic management to allow tracking signals to be received even from aircraft located in areas where they are not directly visible from any receiving station to land (for example, when flying over the oceans). In the specific case, the aircraft 110 is visible from the satellite 205, so the satellite 205 receives the tracking signals of the aircraft 110 and re-transmits them. In turn, one or more other (remote) terminals, only one shown in the figure where it is differentiated with the reference 105 ', are able to receive signals transmitted by the satellite 205 (for example, directly as they fall within its range of transmission, typically of the order of tens of thousands of km, or via a ground receiving station, not shown in the figure); for example, the remote terminals 105 'include one or more reference terminals. Therefore, the terminal 105 'receives the tracking signals of the aircraft 110 (not visible from the same) which are forwarded by the satellite 205 (tracking signals forwarded). In addition, one or more (further) aircraft are visible from terminal 105 ', only one shown in the figure, where it is differentiated with the reference 110'. Therefore, the terminal 105 'receives the tracking signals transmitted by the aircraft 110' both directly from them and forwarded by the satellites 205. In particular, a generic tracking signal of each aircraft 110 '(received directly by the terminal 105' at the corresponding instant of reception) is forwarded by each satellite 205 and received again by the terminal 105 'at a delayed reception instant, subsequent to the reception instant due to the longer time taken for its forwarding.

Terminal 105 'uses the information relating to the tracking signals received / forwarded by aircraft 110' to determine the estimated diffusion instants of the tracking signals forwarded by the aircraft 110.

In fact, a time necessary to receive by the terminal 105 'each tracking signal forwarded by each aircraft 110,110' through the satellite 205 (forwarding time) is given by the sum of a time spent to propagate the tracking signal from the aircraft 110,110 'to satellite 205 (aircraft / satellite propagation time), a time spent to propagate the tracking signal inside the satellite (internal propagation time) and a time spent to propagate the tracking signal from satellite 205 to terminal 105' (satellite / terminal propagation time). The tracking signals forwarded by all 110,110 ’aircraft have the same internal propagation time and the same satellite / terminal propagation time (collectively referred to as common propagation time). The aircraft / satellite propagation time of each tracking signal forwarded varies with the position of the corresponding aircraft 110.110 '. In particular, the aircraft / satellite propagation time depends mainly on the distance of the aircraft 110.110 'from the satellite 205, defined by the position of the aircraft 110.110' and the position of the satellite 205. Furthermore, the aircraft / satellite propagation time is affected by a propagation delay due to the passage of the tracking signal through the ionosphere / troposphere. The propagation delay depends on the position of the aircraft 110.110 'with respect to the satellite 205, and in particular on the corresponding elevation angle (the lower the elevation angle, the greater the path through the ionosphere / troposphere and therefore the greater the propagation delay); the effect of passage through the ionosphere / troposphere is highly variable according to countless contingent factors, such as time of day, season, geographical area, solar activity, geomagnetic activity, and so on, but can be estimated through a propagation model (for example, based on information provided in the geolocation signals).

For each forwarded tracking signal of the aircraft 110 ', it is possible to calculate the forwarding time as the difference between its delayed reception instant and the estimated diffusion instant (calculated as indicated above for the tracking signal received directly from the aircraft 110 '). Furthermore, it is also possible to estimate the aircraft / satellite propagation time based on the position of the aircraft 110 '(extracted from the received / forwarded tracking signal) and the position of the satellite 205 (for example, publicly known or estimated by the central server, not shown in the figure), taking into account the propagation delay estimated using the propagation model. Starting from the forwarding time, the common propagation delay can then be determined by subtracting the aircraft / satellite propagation time.

Consequently, also for each forwarded tracking signal of the aircraft 110 it is possible to determine the estimated diffusion instant by subtracting from the corresponding delayed reception instant the aircraft / satellite propagation time (estimated on the basis of the position of the aircraft 110 extracted from the signal and the position of the satellite 205, taking into account the propagation delay estimated by the propagation model) and the common propagation delay (for example, equal to an average of the values obtained for all forwarded tracking signals of the aircraft 110 'visible from terminal 105').

This allows to validate the positions of the terminal 105 and / or the instants of validation as above, by comparing the tracking information of the terminal 105 (defined by the tracking signals received directly from the aircraft 110 and their estimated diffusion instants) with the corresponding information reference, defined by the tracking signals forwarded to the terminals 105 '(through the satellites 205) and their estimated diffusion instants (calculated as indicated above).

This allows to considerably increase the coverage of the proposed solution, up to the possibility of carrying out validations for terminals practically in any position in the world with the use of a few satellites.Moreover, in this way the reference information of any aircraft can almost always be determined (at least in part) through one or more reference terminals, thereby considerably improving the accuracy of the results obtained.

With reference now to FIG.3, the general principles of the solution are shown in accordance with another embodiment of the present invention.

In this case, a generic terminal 105 (the positions of which it is desired to validate) measures a frequency variation of each tracking signal received (measured frequency variation) with respect to its nominal value; in particular, the figure shows the tracking signals received by the same aircraft 110 in different positions assumed during an entire flyby of the terminal 105, during which the aircraft 110 is visible from the terminal 105 (typically, 1-5 minutes for 3-50 Km). The measured frequency change is due to the Doppler effect, with typical values from 0 Hz (when a component of the speed of the aircraft 110 along a direction of propagation of the tracking signal from the aircraft 110 to the terminal 105 is zero, that is, a speed vector of the aircraft 110 is perpendicular to a distance vector from the position of the aircraft 100 to the position of the terminal 105) up to approximately ± 1 KHz (increasing in absolute value with the component of the speed of the aircraft 110 along the direction of propagation of the tracking signal, i.e., with the angle between the velocity vector and the distance vector). Furthermore, the terminal 105 determines the speed of the aircraft 110 (for example, indicated in the corresponding tracking signals received), and possibly its relative value with respect to a speed of the terminal 105 (for example, determined on the basis of its positions in time ); the terminal 105 can thus calculate the theoretical value due to the Doppler effect of the frequency variation of each tracking signal based on the corresponding speed of the aircraft 110 (calculated frequency variation). Terminal 105 validates its position (and its speed) in accordance with such information. In particular, the terminal 105 certifies its position as correct if the measured frequency variation of each tracking signal is consistent with its calculated frequency variation, for example, if a difference between them is compatible with the local oscillator tolerances of the aircraft 110 and terminal 105. This evaluation can be performed for several aircraft 110, and for each of them on a sequence of tracking signals received at the overflight of terminal 105 by aircraft 110, in which the frequency variation measured / calculated takes a broad spectrum of positive values (when aircraft 110 approaches terminal 105), negative values (when aircraft 110 moves away from terminal 105) and possibly a null value (if aircraft 110 passes over terminal 105). In this way, it is possible to check whether the measured frequency variations of all tracking signals of all 110 aircraft are compatible with the tolerance of the local oscillator of terminal 105 (common for them) and whether the measured frequency variations of all the tracking signals of each aircraft 110 are compatible with the tolerance of the local oscillator of the aircraft 110 (common for them).

Again, the validation uncertainty depends on the tolerances of the corresponding information. In particular, the validation uncertainty is mainly defined by the drifts of the local oscillators of the aircraft 110 and of the terminal 105 (of the order of a few Hz during the overflight of the terminal 105), while the tolerances of the position of the terminal 105, of the speed of the aircraft 110 and the movement of the aircraft 110 during the reception of the tracking signal can be neglected in a first approximation. This creates a corresponding area of uncertainty for the distance of the terminal 105 from the aircraft 110. For the overflight of each aircraft 110, the area of uncertainty presents privileged directions in terms of uncertainty. Therefore, the areas of uncertainty relating to the overflights of the various aircraft 110 intersect to define an area of uncertainty around the position of the terminal 105 which decreases as the number of aircraft overflights increases (generally, with a radius of some kilometres).

In this way, each terminal can certify its position even autonomously. Also in this case, it is very difficult (if not impossible) to implement "spoofing" or "meaconing" attacks (as it would be necessary to simulate the same frequency variation of the tracking signals corresponding to the Doppler effect due to the speed of the aircraft, also keeping account of the intrinsic characteristics of the local oscillators of the terminal and aircraft).

Referring now to FIG.4, a basic block diagram of a processing infrastructure 400 is shown that can be used to put the solution into practice in accordance with an embodiment of the present invention.

The processing infrastructure 400 comprises the terminals 105 (comprising one or more reference terminals, only one shown in the figure where it is differentiated with the reference 105r) and the central server 115, which are connected to a telecommunication network 405 (e.g. example, Internet-based global type). For this purpose, a secure connection between the central server 115 and each terminal 105 is implemented on the telecommunication network 405 (for example, through a virtual private network); the secure connection guarantees (with a sufficient degree of reliability) the authenticity and integrity of the information exchanged (ie, that the information has actually been sent by the central server 110 or by the terminal 105 and that it has not been corrupted). The reference terminals 105r are arranged in stations 410 which ensure (with a sufficient degree of confidence) that they are not subject to intentional malfunctions. For this purpose, the 410 stations are equipped with security measures that prevent (or at least make it extremely difficult) to provide false signals (of geolocation and tracking) to the reference terminals 105r, for example, by installing them in protected places equipped with controls. access. In this way, it is possible to ensure that the positions of the 105r reference terminals (preset or determined via the geolocation satellites) and their internal clocks (for example, synchronized with those of the geolocation satellites) are very safe and accurate (for example, with a tolerance of a few centimeters for the position and a fraction of a microsecond for the internal clocks).

Each of the aforementioned processing devices (i.e., terminals 105, both reference and non-reference, and central server 115) comprises various units which are connected to each other via a bus structure 415 with one or more levels (with an architecture that is suitably scaled in accordance with the type of processing device 105,115). In particular, one or more microprocessors (µP) 420 control the operation of the processing device 105, 115; a non-volatile memory (ROM) 425 contains basic code for starting the processing device 105.115 and a volatile memory (RAM) 430 is used as working memory by the microprocessors 420. The processing device 105.115 is equipped with a memory mass 435 to store programs and data (for example, a flash memory E <2> PROM for each terminal 105 and storage devices of a data processing center in which the central server 115 is implemented). Further, the processing device 105,115 comprises various peripheral controllers, or input / output (I / O) units, 440; for example, the peripherals 440 of each terminal 105 comprise an aerial receiver for receiving the tracking signals (for example, operating at a frequency of 1,090 MHz to receive ADS-B tracking signals), a satellite receiver for receiving the tracking signals geolocation (for example, operating at two frequencies of 1.575.42MHz and 1.227.60MHz to receive GNSS type geolocation signals, and in particular GPS type), a telecommunications receiver to receive the tracking signals forwarded by telecommunications satellites (for example, operating at a frequency of 0.2-40 GHz), a network card (wireless, wireless, or wired, wired) to connect to the 405 telecommunication network (for example, cellular / Wi-Fi type or Ethernet, respectively), one or more anti-tampering devices (to prevent, or at least substantially hinder, any unauthorized modification of the operation of the 105 terminal) and any environmental sensors ( such as temperature sensors, pressure sensors, a digital compass, motion and shock sensors, a mini camera, a mini camera and so on), while the central server 115 peripherals 440 include a network card to connect to the communication network 405 and a reader / writer of removable storage units, such as DVD, implemented by a data center console.

With reference now to FIG.5, the main software components that can be used to implement the solution in accordance with an embodiment of the present invention are shown.

In particular, all the software components (programs and data) are indicated as a whole with the reference 500. The software components are typically stored on the mass memory and loaded (at least in part) into the working memory of each processing device 105, 115 when the programs are running (in addition to an operating system not shown in the figure). Programs are initially installed on mass storage, for example, from removable storage drives or from the telecommunication network. In this regard, each program can represent a module, segment or portion of code, which comprises one or more executable instructions to implement the specified logic function.

Starting from a generic terminal 105 (only one shown in the figure), to which an identification code (pre-set) is associated, it comprises the following software components.

An aerial pilot module (driver) 503, a satellite pilot module 506 and a telecommunications pilot module (telco) 507 pilot the aerial receiver, the satellite receiver and the telecommunications receiver, respectively, possibly also contributing to their implementation in technology Software Defined Radio (SDR). A 509 network driver module drives the network card. An internal clock 512 provides a clock signal which is used to synchronize the operation of the terminal 105 (using a local oscillator, for example, with an accuracy of 0.05-0.5 ppm). A synchronization agent 515 synchronizes the internal clock 512 with respect to a universal time; for this purpose, the synchronization agent 515 interacts with the network driver module 509. A frequency analyzer 518 determines the measured frequency variations and the calculated frequency variations of the tracking signals received by the terminal 105. frequency 518 uses the 503 airborne pilot module. A collector 521 collects, together with the 518 frequency analyzer, validation information used to validate the positions of the 105 terminals. 521 collector uses the 503 airborne pilot module , the satellite driving module 506, the telecommunications driving module 507 and the internal clock 512, and accesses (in reading / writing) a validation register 524, which is also accessed (in writing) by the frequency analyzer 518. The validation register 524 stores (temporarily) the validation information; for example, the validation register 524 includes a series of entries for the last moments of reception (such as 200-2,000), each of which stores the moment of reception, the geolocation signals received at the moment of reception, the position of the terminal at the moment of reception (if any), the tracking signals received / forwarded at the moment of reception each with a type indicator (i.e., received only directly from an aircraft, received only forwarded by a satellite or in both the modes), its delayed reception instant (if any), estimated diffusion instant, measured frequency variation and calculated frequency variation. An upload agent 527 uploads the tracking information to the central server 115; the tracking information comprises the received / forwarded tracking signals each with its estimated diffusion instant. The loading agent 527 accesses (reads) the validation register 524 and uses the network driving module 509. A validation agent 530 checks the validation of the position of the terminal 105 and / or of the validation instants. The validation agent 530 accesses (reads) the validation register 524, interacts with the network control module 509 and accesses (writes) a local validation history (log) 533. The local validation history 533 stores the results of the validations (position / instants) of the terminal 105; for example, the local validation history 533 includes a series of entries, each of which stores the validation instant, the position of the terminal at the validation instant (if any) and the result of the validation of the terminal 105 (positive / negative) .

Moving on to the central server 115, it includes the following software components.

A network driver module 536 drives the network card (in particular, to communicate with the network driver modules 509 of all the terminals 105). A collection manager 539 collects the tracking information received from the terminals 105. The collection manager 539 takes advantage of the network driver module 536 and accesses (writes) a tracking register 542. The tracking register 542 stores (temporarily) the tracking information received from the terminals 105; for example, the tracing register 542 comprises a series of entries, each of which stores a tracing signal received / forwarded, the identification code of the terminal 105 from which it was received and its estimated broadcast instant. A synchronization manager 545 manages the synchronization of the internal clocks of the terminals 105. The synchronization manager 545 accesses (reads) the tracking register 542 and interacts with the network driver module 536. A consolidation engine 548 generates the reference information ( for validation of terminals 105). The consolidation engine 548 accesses (reads) the trace register 542 and accesses (writes) a reference register 551. The reference register 551 stores (temporarily) the reference information; for example, the reference register 551 comprises a series of entries corresponding to the received / forwarded tracking signals included in the tracking register 542, each of which stores the actual tracking signal and its actual diffusion instant. A validation manager 554 manages the validations of the terminals 105. The validation manager 554 interacts with the network driving module 536, accesses (reads) the reference register 551 and accesses (writes) a global validation history 557. It global validation history 557 stores the results of the validations of the terminals 105; for example, the global validation history 557 includes a series of items, each of which stores the identification code of the terminal 105 which was validated, the corresponding validation instant, the position of the terminal 105 at the validation instant ( if any) and the result of the validation of the terminal 105.

With reference now to FIG.6A-FIG.6D, an activity diagram is shown that describes the flow of activities related to an implementation of the solution in accordance with an embodiment of the present invention.

In particular, the diagram represents an exemplary process that can be used to validate the terminals with a method 600. In this regard, each block can correspond to one or more executable instructions to implement the specified logic function on the relevant processing devices.

Starting from the lane of a generic terminal, a cycle is performed continuously to synchronize the internal clock of the terminal. For this purpose, the process passes from block 601 to block 602 at the end of a synchronization period (for example, every 0.2-5 s). At this point, the flow of activities is divided according to the type of synchronization implemented.

In particular, in the case of synchronization based on a network synchronization service (for example, of the NTP type), the synchronization agent at block 603 submits a synchronization request to one or more processors, for example, synchronization servers ( not shown in the figure) and receives corresponding responses (via the network control module). The synchronization agent at block 604 calculates an internal clock synchronization error (with respect to those of the synchronization servers) based on the transmission times from the terminal to the synchronization servers and vice versa (for example, equal to their average) .

With reference again to block 602, in the case of synchronization based on the reference terminals, the synchronization agent at block 605 submits (via the network control module) a synchronization request to the central server. By passing to the lane of the central server, the synchronization manager at block 606 receives (through the network driving module) this synchronization request. In response to this, the synchronization manager at block 607 calculates the synchronization error of the internal clock of the terminal (compared to those of the reference terminals). For this purpose, the synchronization manager (via the tracing register) determines the tracing signals received both by the terminal and by one or more of the reference terminals after submitting a previous synchronization request from the same terminal (for example, determined by a pre-defined period or indicated in the synchronization request); for each of these tracking signals, the synchronization manager calculates a difference between the broadcast instant estimated by the terminal and the broadcast instant estimated by each of the reference terminals. At this point, the synchronization manager calculates the synchronization error based on these differences (for example, equal to their average). The synchronization manager at block 608 returns (via the network driving module) the synchronization error to the terminal. The process then returns to block 606 awaiting a new synchronization request. With reference again to the terminal lane, the synchronization agent at block 609 receives (via the network control module) the synchronization error from the central server.

The flow of activity rejoins block 610 from block 604 or block 609. At this point, the synchronization agent corrects the terminal's internal clock in accordance with the synchronization error (for example, incrementally with a feedback control). The process then returns to block 601 to repeat the same operations periodically.

The synchronization based on the network synchronization service allows to synchronize the internal clock in a safe and economic way (albeit with an acceptable tolerance at least initially, for example, of the order of a millisecond currently and prospectively of the order of a fraction of a microsecond with the advent of 5G mobile phone technology). The synchronization based on the reference terminals allows to synchronize the internal clock in a safe and precise way (for example, with a tolerance determined in practice only by that of the internal oscillator of the terminal between successive synchronizations, for example, of the order of one fraction of a microsecond). In particular, it is possible to use synchronization based on the network synchronization service initially and then switch to synchronization based on reference terminals once enough tracking information has been collected for this purpose.

Completely independently, a cycle is performed continuously to collect the validation information of the terminal 105. For this purpose, the process passes from block 611 to block 612 at the end of a collection period (for example, every 1-10 ms ). At this point, the collection agent adds a new entry to the validation register, containing the instant of receipt equal to the current time provided by the internal clock. The flow of activities is then divided into three branches which are performed in parallel and in synchrony.

In a first branch, the satellite driving module at block 613 records the geolocation signals that are available at the moment (from at least 4 geolocation satellites to ensure a high accuracy of the geolocation) and supplies them to the collection agent, who adds to the new entry; in this way, the instant of receipt of the voice determined above substantially represents the instant of receipt of the geolocation signals. For example, each geolocation signal indicates an instant of transmission (determined by atomic clocks on board the corresponding geolocation satellite, with a tolerance of a few nanoseconds) and the position of the geolocation satellite defined by its ephemeris (determined by control stations terrestrial, with a tolerance of a few meters or fractions of a meter). In addition, the satellite driving module at block 614 determines the position of the terminal (through the geolocation signals received) and provides it to the collection agent, who adds it to the new item.

At the same time, the aircraft piloting module at block 615 records the tracking signals received (directly) by the aircraft that are available at the moment (in almost perfect synchronization with the geolocation signals thanks to the multiple receiver of the terminal) and supplies them to the agent of collection; in this way, the instant of receipt of the item determined above substantially represents the instant of receipt of the tracking signals received. For example, each tracking signal broadcast by aircraft includes the position (such as latitude, longitude and altitude), speed and an identification code of the corresponding aircraft. The aircraft determines its position and speed precisely (for example, through geolocation signals); moreover, this is done safely (for example, through verification with information provided by an aircraft inertial navigation system equipped with very accurate accelerometers and gyroscopes). However, since the tracking signals are broadcast from the aircraft in a pseudo-random way (while the position and speed are determined periodically), the position and speed indicated in each tracking signal were generally determined at an earlier instant; this introduces a corresponding error in the position of the aircraft due to its displacement in the meantime (for example, of the order of a hundred meters) and a possible error in the speed of the aircraft due to its variation in the meantime (for example, of the order of a few percentage units in module and a few degrees in direction). A cycle is started at block 616, in which the collector takes into account one (current) of the tracking signals received (starting from a first in any order). The collection agent at block 617 adds the tracking signal received to the new entry in the validation register, setting the corresponding signal type indicator received only directly from the aircraft. The frequency analyzer at block 618 determines the measured frequency variation of the received tracing signal with respect to its nominal value (1.090 MHz in the example in question) by analyzing the entire tracing signal (for example, with a duration of 120µs) ; the frequency analyzer adds the measured frequency variation (for example, represented by a polynomial on the phase over time) to the new entry in the validation register. Continuing to block 619, the collection agent checks if all the tracking signals received have been considered. If not, the process returns to block 616 to perform the same operations on a subsequent track signal received.

At the same time, the telecommunications control module at block 620 records the tracking signals forwarded by the satellites at the moment (in almost perfect synchronization with the geolocation signals thanks to the multiple receiver of the terminal), and supplies them to the collection agent; in this way, the current time used to define the instant of receipt of the new voice substantially represents the instant of delayed reception of the forwarded tracking signals. A cycle started at block 621, in which the collection agent takes into account one (current) of the tracking signals sent (starting from a first in any order). The collection agent at block 622 looks for the tracking signal forwarded in the validation register. If the forwarded tracking signal is not present in the validation register, this means that it was received by an aircraft not visible from the terminal; in this case, the collection agent adds the tracking signal forwarded to the new entry in the validation register, setting the corresponding type indicator to signal received only forwarded by the satellite. Conversely, if the forwarded tracking signal is already present in a (previous) entry of the validation register, this means that it has been received again by an aircraft visible from the terminal (following its direct reception at the instant of receipt of the entry previous one); in this case, the collection agent associates the tracking signal (received) of the previous entry in the validation register with its delayed reception instant, setting the corresponding signal type indicator received both directly from the aircraft and forwarded by the satellite. Continuing to block 623, the collection agent checks if all the tracking signals forwarded have been considered. If not, the process returns to block 621 to perform the same operations on a subsequent trace signal forwarded.

The flow of activity rejoins from block 614 (directly), from block 619 (once all the tracking signals received have been taken into account) or from block 623 (once all the tracking signals forwarded have been taken into account), thus returning to block 611 to repeat the same operations periodically.

At the same time, a loop is continuously executed to process the terminal validation information. For this purpose, the process is waiting at block 624 for an event that triggers the processing of validation information. The processing is applied to one or more relevant entries in the validation register. In particular, in an implementation based solely on tracking signals received directly from the aircraft, each new entry in the validation register is processed directly after its creation as described above; on the contrary, in an implementation based also on the tracking signals sent by the satellites, the entries of the validation register are processed with a processing delay (for example, 1-2 s) such as to guarantee the possible subsequent reception of the same signals tracking already received directly from aircraft also as forwarded by satellites.

In response to this, the process continues to block 625 where the collector changes the positions and speeds of the aircraft indicated in the tracking signals received present in the validation register, applying a filter (e.g. Kalman or minimum squares) at the positions and speeds of each aircraft; this improves the accuracy of this information (for example, by obtaining a tolerance of a few meters for positions and a fraction of a unit in percentage for the module and a fraction of a degree in direction for speeds).

A cycle is started at block 626 to process one (current) of the relevant entries of the validation register (new entry or all entries whose instant of receipt precedes the time of at least the processing delay, starting from a first in any order) . Moving on to block 627, for each of the tracking signals (received and possibly also forwarded) of the relevant item that come from the aircraft visible from the terminal and therefore have been received directly by them (as indicated by the corresponding type indicator in the item), the collector determines its estimated dissemination instant as follows and adds it to the relevant entry in the validation register. For this purpose, the following relationship is used:

TSbro = Trec -Dat · c,

where TSbro is the estimated scattering instant (to be calculated), Trec is the receiving instant (known), Dat is the distance of the aircraft from the terminal (defined by their known positions) and c is the speed of light (known) , with the term c · Dat representing the transmission time of the tracking signal from the aircraft to the terminal.

Moving on to block 628, for each of the same tracking signals received (directly from the aircraft visible from the terminal), the collection agent determines the calculated frequency variation of the tracking signal received and adds it to the relevant entry in the validation register. For this purpose, the collector calculates the speed of the terminal based on the validation information (for example, equal to the movement of the terminal between two or more of its last positions indicated in corresponding entries in the validation register divided by the time elapsed between their instants of reception). The collection agent calculates a relative speed of the aircraft with respect to the terminal, as the difference (vector) between the speed of the aircraft (extracted from the tracking signal received) and the speed of the terminal (calculated above). The collection agent can thus determine the frequency variation calculated according to the Doppler effect for this relative speed.

Moving on to block 629, for each of the tracking signals (received and forwarded) of the relevant item that come from the aircraft visible from the terminal and that were both received directly by the aircraft and forwarded by the satellites (as indicated by the corresponding type indicator in the item) , the collector determines the common propagation time (internal propagation time plus satellite / terminal propagation time). For this purpose, the collection agent determines the forwarding time of the tracking signal forwarded (from the aircraft to the terminal through the corresponding telecommunications satellite) using the following relationship:

Trel = Tdel-TSbro

where Trel is the forwarding time (to be calculated), Tdel is the delayed reception instant (known) and TSbro is the estimated broadcast instant (calculated above). In the event that the positions of the telecommunications satellites are known with sufficient accuracy (for example, transmitted by the telecommunications satellites themselves), the collector determines the aircraft / satellite propagation time for the relayed tracking signal using the following relationship :

Tas = Das · c + ΔTas

where Tas is the aircraft / satellite propagation time (to be calculated), Das is the distance of the aircraft from the telecommunications satellite (defined by their known positions) and c is the speed of light (known), with the term Das c which represents an ideal transmission time from aircraft to telecommunications satellite, and ΔTas is the propagation delay due to passage through the ionosphere / troposphere; the propagation delay ΔTas is calculated by applying the propagation model (obtainable from geolocation satellites operating at frequencies similar to those of aircraft) to the positions of the aircraft and the telecommunications satellite (notes). At this point, the collector can determine the common propagation time for the tracking signal forwarded using the following relationship:

Tcom = Trel-Tas

where Tcom is the common propagation delay (to be calculated), Trel is the forward time (calculated above) and Tas is the aircraft / satellite propagation time (calculated above). The collector then determines the actual value of the common propagation delay for each telecommunications satellite based on the values calculated above for all forwarded tracking signals of the relevant item received by the aircraft visible from the terminal, both directly and forwarded by the satellite ( for example, equal to their average). If, on the other hand, the position of the telecommunications satellites is not known with sufficient precision, it is possible to use the above relations for the same tracking signals received of the relevant item to calculate the unknowns of the common propagation delay Tcom (considered the same for all the reports of each telecommunication satellite) and the positions of the telecommunication satellites (on which the distances of the aircraft from the Das telecommunication satellites and the aircraft / Tas satellite propagation delays depend).

Moving on to block 630, for each of the tracking signals (forwarded) of the relevant item that come from the aircraft not visible from the terminal and therefore were received only forwarded by the satellite (as indicated by the corresponding type indicator in the relevant item) the agent of collection determines its estimated dissemination instant as follows and adds it to the relevant entry in the tracking log. For this purpose, the collection agent determines the aircraft / satellite propagation time Tas as above (Tas = Das · c + ΔTas). At this point, the collection agent determines the estimated dissemination instant using the following relationship:

TSbro = Tdel-Tas-Tcom

where TSbro is the estimated diffusion instant (to be calculated), Tdel is the delayed reception instant (known), Tas is the aircraft / satellite propagation time (calculated above) and Tcom is the common propagation time of the corresponding satellite telecommunications (calculated above).

The collection agent at block 631 checks if all the relevant items have been processed. If not, the process returns to block 626 to process a subsequent relevant item. On the contrary, the flow of activities descends to block 632, in which the upload agent extracts the tracking information from the relevant items thus processed (i.e., their tracking signals received / forwarded each with the corresponding estimated and eventual diffusion instant calculated frequency variation) and transmits them (via the network control module) to the central server in association with the terminal identification code. The process then returns to block 624 to repeat the same operations periodically.

Processing the validation information locally by the terminal allows the central server not to be overloaded; furthermore, this makes the solution easily scalable.

By switching to the central server lane, the collection manager at block 633 receives (via the network driving module) the tracking information provided by the terminal. In response to this, the collection manager at block 634 saves the tracking information in the tracking register, adding the identification code of the terminal from which it was received (with the activity stream returning to block 633 awaiting new tracking information. tracing).

Quite independently, a loop is performed continuously to consolidate the tracking information into the reference information. For this purpose, the process passes from block 635 to block 636 at the end of a consolidation period (for example, every 1-2 s). At this point, a cycle is started to process each (current) of the relevant received / forwarded tracking signals, whose entry has been collected in the tracking log for at least a minimum time (e.g. 1-2 s) to ensure that the information relating to the same received / forwarded tracing signal has been collected from all the corresponding terminals. Moving on to block 637, the consolidation engine checks whether the entries collected for the relevant trace (received / forwarded) signal are significant. For example, the items collected are considered meaning if they are at least equal to a minimum number (such as 4-5 or even less, such as 1-2, if at least one of them comes from a reference terminal). If not, the relevant tracking signal is discarded (removing all entries containing it from the tracking register) and the process returns directly to block 636 to process a subsequent relevant tracking signal. On the contrary, in the positive case the consolidation engine at block 638 adds a new entry to the reference register, setting its actual tracking signal equal to the relevant tracking signal. The consolidation engine at block 639 determines the corresponding effective diffusion instant. For example, the actual diffusion instant is set equal to a weighted average of the estimated reception instants of all relevant entries in the tracing log that contain the tracing signal. For this purpose, a weight of the corresponding terminal is applied to each estimated diffusion instant; the weights are predefined to give much greater importance to the reference terminals than the other (non-reference) terminals, for example, with the weights of the reference terminals 10-100 times greater than the weights of the non-reference terminals. In this way, the actual reference instant is mainly defined by the reference terminals (safe and accurate) and in any case through a majority or voting mechanism (valid even in the absence of reference terminals); this allows to obtain a good level of confidence in any situation. The consolidation engine adds the actual diffusion instant to the new reference register entry (thus removing the entries that contain the relevant tracking signal from the tracking register). The consolidation engine at block 640 checks whether all relevant trace signals have been processed. If not, the process returns to block 636 to process a subsequent relevant tracking signal. On the contrary, the process returns to block 635 to repeat the same operations periodically. At this stage (not shown in the figure), the consolidation engine can also consolidate the measured frequency changes (when included in the tracking information). In particular, through the reference terminals or a similar majority mechanism it is possible to estimate, based on the measured frequency variations of the various tracking signals received by each aircraft, one or more drift characteristics of the aircraft oscillator, for example , its value, rate (rate) and so on (which define a sort of its "fingerprint" which is saved in a corresponding aircraft register). In addition or alternatively, it is also possible to estimate and save in a terminal register similar drift characteristics of the terminal oscillator, for example, based on the measured frequency variations of the various tracking signals received by the terminal, the more relevant the more the corresponding aircraft pass close to the terminal, at the limit with the Doppler effect zero when the aircraft pass over the terminal.

Considering again the terminal lane, the process passes from block 641 to block 642 whenever a validation of the terminal is required, that is, of its position at a validation instant and / or a validation instant. For example, this can occur periodically (such as every 10-120 s), either automatically or at the request of the central server, or in response to a request from an operator (entered manually as on the central server, on the terminal or through an associated personal computer at the same). In response to this, the validation agent checks (via the network control module) if the (secure) connection with the central server is available. If so, the validation agent at block 643 checks whether tracking signals received directly from the aircraft visible from the terminal (that is, to which the instant of reception is associated) are available for the instant of validation in one or more entries relevant; for example, for this purpose a last entry in the validation register is taken into consideration (whose reception instant is therefore the closest to the validation instant, if not coincident with it) or several last entries of the validation register (such as 2-5, with their content being appropriately mediated). If the relevant items contain at least a minimum number of tracking signals received coming directly from the aircraft visible from the terminal (such as 1-2), the process continues at block 644 to validate the terminal according to the estimated diffusion instants of these signals. tracking received. In particular, the validation agent determines the position of the terminal at the time of validation of the terminal (if necessary for its validation). For example, when the terminal is in motion, the validation agent sets the position of the terminal in accordance with those indicated in the relevant items. Conversely, when the terminal is fixed, the validation agent retrieves the position of the terminal from a registration in which it has been pre-set or does not perform any operation (when the position of the terminal is already known to the central server). The validation agent at block 644 extracts the tracking information (ie, tracking signals received and corresponding estimated broadcast instants) from the relevant items. The validation agent at block 646 submits (via the network control module) a request for terminal validation to the central server; the validation request includes the identification code of the terminal, the time of validation, the tracking information and possibly the location of the terminal.

Passing to the lane of the central server, the validation manager at block 647 receives (through the network control module) the validation request from the terminal. In response to this, the validation manager validates the position of the terminal (extracted from the validation request or from the terminal register through its identification code) and / or the validation instant by comparing the tracing information of the validation request with the information of the reference register, possibly after a preliminary consistency check (for example, presence of the identification code in the terminal register, position consistent with that expected for fixed terminals or route / speed consistent with those expected for mobile terminals according to the corresponding uncertainties such as indicated in the terminal register). For this purpose, a cycle is initiated at block 648 in which the validation manager checks one (current) of the received tracking signals of the validation request. The validation manager at block 649 determines whether a corresponding effective validation signal (with the same content) is available in the reference register. If not, the tracing signal received is not usable and the process returns directly to block 648 to perform the same operations on a subsequent tracing signal of the validation request. On the contrary, the received tracing signal can be used and therefore the validation manager at block 650 verifies it. For example, the validation manager calculates a difference between the estimated diffusion instant (of the tracing signal received in the validation request) and the actual diffusion instant (of the same actual tracing signal in the reference register); the tracking signal received is considered correct if this difference is lower (possibly in the strict sense) than a corresponding (diffusion) threshold depending on the corresponding validation uncertainty (mainly function of the tolerance of the terminal's internal clock as indicated above). As a further improvement, it is also possible to verify that the measured frequency variation of the received tracking signal (if included in the tracking information of the validation request) is consistent with the drift characteristics of the corresponding aircraft oscillator (indicated in the aircraft register) and / or the terminal (indicated in the terminal register). The validation manager at block 651 checks whether all the tracking signals received of the validation request have been verified. If not, the process returns to block 648 to verify a subsequent tracking signal received of the validation request. On the contrary, the flow of activities descends to block 652, where the validation manager determines the result of the validation of the terminal. For example, the position of the terminal and / or the instant of validation are considered correct if the tracing signals received usable reach a minimum threshold (such as 70-80% and at least 2-5) and if the correct ones of them reach a ' other minimum threshold (such as 90-100%). The validation manager then adds a corresponding new item to the global validation history (possibly also adding one or more values measured by the environmental sensors of the terminal if included in the validation request). The validation manager at block 653 returns the result of the validation to the terminal. The process then returns to block 647 awaiting a new validation request. With reference again to the terminal lane, the validation agent at block 654 receives the validation result from the central server. In response to this, the validation agent at block 655 adds a corresponding new entry to the local validation history.

Returning to block 642, if the connection with the central server is not available, the validation agent at block 654 checks whether the same minimum number of tracking signals received from the aircraft visible from the terminal (that is, to which the instant reception) are available in one or more relevant items as above. If so, the process continues at block 657 to validate the position of the terminal (locally) in accordance with the frequency variations (measured / calculated) of the tracking signals received directly from the aircraft of the relevant items. In particular, a cycle has begun in which the validation agent verifies one (current) of these tracking signals received (starting from a first in any order). The validation agent at block 658 calculates a difference between the measured frequency variation and the calculated frequency variation of the tracking signal received; the tracking signal received is considered correct if this difference is lower (possibly in the strict sense) than a corresponding (frequency) threshold depending on the corresponding validation uncertainty (mainly a function of the tolerance of the terminal and aircraft oscillators as indicated above) . The frequency threshold can be reduced (by increasing the accuracy of the validation) taking into account the drift characteristics of the aircraft and / or terminal oscillator (determined locally in the same way as indicated above or downloaded from the central server). The validation agent at block 659 checks if all the tracking signals received of the relevant items have been verified. If not, the process returns to block 657 to verify a subsequent tracking signal received of the relevant entries. On the contrary, the flow of activities descends to block 660, in which the validation agent determines the result of the validation of the position of the terminal. For example, the terminal position is considered correct if the received tracking signals of relevant items that are correct reach a minimum threshold (such as 90-100%). For this purpose, it is also possible to weight the tracking signals received of the relevant items in accordance with the drifts of the oscillators of the corresponding aircraft, so as to give greater importance to the aircraft whose oscillators are more precise. The validation agent then adds a corresponding new entry to the local validation history (with a possible indicator of the fact that the validation was carried out locally).

The process continues instead from block 642, if the (secure) connection with the central server is not available, or from blocks 643 or 656, if the minimum number of tracking signals received coming directly from aircraft visible from the terminal are not available in the entries relevant, in block 661 to validate the terminal (locally) in accordance with the instants of diffusion of the geolocation signals. For this purpose, a cycle has begun in which the validation agent checks one (current) of the geolocation signals of the relevant items (starting from a first in any order). The validation manager at block 662 estimates the instant of diffusion from the geolocation satellite of the geolocation signal (estimated diffusion instant). In particular, the validation agent calculates a transmission time of the geolocation signal from the geolocation satellite to the terminal, equal to the product of a distance of the geolocation satellite from the terminal (defined by the position of the terminal and the position of the geolocation satellite indicated in the geolocation signal) for the speed of light; the validation agent then calculates the estimated diffusion instant by subtracting the transmission time from the instant of receipt of the geolocation signal. The validation agent at block 663 calculates a difference between the estimated diffusion instant and an actual value of the geolocation signal diffusion instant (actual diffusion instant) indicated in the same; the geolocation signal is considered correct if this difference is lower (possibly in the strict sense) than a corresponding (geolocation) threshold depending on a corresponding validation uncertainty (mainly depending on the tolerance of the terminal's internal clock). The validation agent at block 664 checks if all the geolocation signals of the relevant items have been verified. If not, the process returns to block 661 to verify a subsequent geolocation signal of the relevant items. On the contrary, the flow of activities descends to block 665, in which the validation agent determines the result of the validation of the terminal. For example, the position of the terminal and / or the validation instant are considered correct if the geolocation signals that are correct reach a minimum threshold (such as 90-100%). The validation agent then adds a corresponding new entry to the local validation history (with a possible indicator of the fact that the validation was carried out locally). In this way, each terminal can validate its position and / or its timing (even autonomously) in any condition. Also in this case, it is very difficult (if not impossible) to implement "meaconing" attacks by recording the geolocation signals in one place to supply them to terminals in another place, as the delay introduced by their transfer would cause the calculation of instants of diffusion incorrect (although the possibility is not excluded that false geolocation signals are created and substituted for the actual ones since their contents and instants of diffusion are known a priori).

In both cases in which the terminal has been validated locally, not shown in the figure, it is possible to transmit the corresponding entries of the local validation history to the central server for further verification (as soon as the corresponding connection is available).

The process then returns from block 655, from block 660 or from block 665 to block 641 awaiting a new terminal validation request.

Terminal validations can be used in a variety of applications. For example, the terminal is installed at a place of origin of specific products (such as a place of cultivation, breeding, manufacturing, packaging, and so on). Terminal position validation is required for each output product; in response to this, the central server generates a verification code which is returned to a personal computer associated with the terminal, which prints it in association with the product, for example, in the form of a two-dimensional code (QRcode) on one of its packaging . This allows a consumer of the product to verify its origin, for example, through an app installed on a smart phone (smartphone); for this purpose, the app reads the verification code, transmits it to the central server, receives the result of the corresponding position validation and displays it.

Changes

Naturally, in order to satisfy contingent and specific needs, a person skilled in the art can make numerous logical and / or physical modifications and variations to the present invention. More specifically, although this invention has been described in some level of detail with reference to one or more embodiments thereof, it is clear that various omissions, substitutions and changes in form and detail as well as other embodiments are possible. In particular, various embodiments of the present invention can be put into practice even without the specific details (such as numerical values) set out in the previous description to provide a more complete understanding of them; on the contrary, well-known features may have been omitted or simplified in order not to obscure the description with unnecessary details. Furthermore, it is expressly understood that specific elements and / or method steps described in connection with each embodiment of the present invention may be incorporated into any other embodiment as a normal design choice. Furthermore, elements presented in the same group and different embodiments, examples or alternatives should not be interpreted as de facto equivalents of each other (but they are separate and autonomous entities). In any case, any numeric value should be read as modified by the term about (if not already done) and any range of numeric values should be understood as expressly specifying any possible number along the continuum within the range (including its extremes ). Furthermore, ordinal or other qualifiers are used merely as labels to distinguish elements with the same name but do not connote by themselves any priority, precedence or order. Furthermore, the terms include, understand, have, contain, involve and the like should be understood with an open and non-exhaustive meaning (i.e., not limited to the recited elements), the terms based on, dependent on, in accordance with, second, in function of and the like should be understood as a non-exclusive relationship (i.e., with any additional variables involved), the term one / a should be understood as one or more elements (unless expressly indicated otherwise), and the term means for ( or any functional formulation) should be understood as any structure suitable or configured to perform the relevant function.

For example, one embodiment provides a method for validating a geolocation and / or timing of a terminal. However, the method can be applied to any terminal (see below) to validate any geolocation (for example, of things, people, events and so on associated with both fixed and mobile terminals), timing (for example, of events, documents and so on) or their combination in any application (for example, to guarantee the origin of products, track vehicles, implement an alarm, perform an investigative service and / or to ensure the occurrence of commercial transactions, the creation of documents, respectively , and so on).

In one embodiment, the method comprises receiving (from the terminal) tracking signals. However, the tracking signals can be in any number and of any type (for example, ADS-B, Mode-S, and so on), and they can be received in any way (for example, at any sampling rate).

In one embodiment, the tracking signals are broadcast from one or more aircraft visible from the terminal. However, the tracking signals can be broadcast in any way (e.g., at any frequency, pseudo-random or even deterministically but not publicly known, and so on) by any number and type of aircraft (e.g., line, private, military and so on).

In one embodiment, the tracking signals are received at corresponding reception instants which are determined by an internal clock of the terminal. However, the internal clock can be of any type (for example, synchronized via network service, reference terminals, geolocation signals and so on).

In one embodiment, the tracking signals include an indication of a position of the corresponding aircraft. However, the position of each aircraft can be indicated in any way (for example, both explicitly, as through geographical coordinates, navigation such as GPS or Galileo, and the like, or implicitly, as through an identifier from which it is possible to trace it) ; moreover, it is possible to install additional terminals on the aircraft and use them as above to determine their position (and therefore also that of the aircraft), in order to increase their confidence.

In one embodiment, the method comprises providing (by the terminal) an indication of a position of the terminal and / or an instant of validation at the receiving instants and tracking information of the terminal. However, such information can be provided in any way (for example, transmitted to any central processor in any way, such as individually or in blocks, in real or deferred time, in push or pull mode, and so on, distributed to other terminals in peer mode. -to-peer or any combination thereof). Furthermore, the location of the terminal can be determined in any way (for example, dynamically by the terminal or pre-set in the case of a fixed terminal) and indicated in any way (for example, both explicitly when the terminal is mobile, such as via geographic coordinates. , navigation such as GPS or Galileo and the like, both implicitly when the terminal is fixed, as through its identification code). The position of the terminal and / or the time of validation can correspond to the time of receipt in any way (for example, in synchrony or not with the collection of tracking information, with a single survey or as an average of multiple surveys).

In one embodiment, the tracking information is based on the tracking signals and is indicative of corresponding instants of diffusion from aircraft of the tracking signals. However, the tracking information can be based on the tracking signals in any way (for example, including all of their content or only part of it, either directly or processed in any way) and can be indicative of the instants of diffusion in any way. (for example, both explicitly and implicitly through information for their calculation, such as corresponding positions of the aircraft and instants of reception).

In one embodiment, the spreading instants of the tracking signals are each estimated in accordance with the corresponding receiving instant, the position of the corresponding aircraft and the position of the terminal. However, the spread instants of the tracking signals can be estimated in any position (e.g., terminal, central processor, or combination thereof) and in any way (e.g., simply taking into account the distance calculated based on the positions or even others factors, such as the movement of the aircraft during the transmission of the tracking signal, and so on).

In one embodiment, the method comprises validating the position of the terminal and / or the instant of validation in accordance with a comparison between the tracking information of the terminal and reference information. However, only the position, only the time of validation or both can be validated in any position (for example, central processor, terminal or their combination) and in any way (for example, requiring that any percentage (up to all) of the tracking signals received are included in the reference information and / or any percentage (up to all) of the actual tracking signals broadcast by the aircraft within a certain radius of the location of the terminal are included in the tracking information, that every instant of diffusion estimated differs from the corresponding actual diffusion instant within any diffusion threshold and so on).

In one embodiment, the reference information is representative of actual values of the tracking signals and the corresponding diffusion instants. However, the reference information can be of any type (for example, indicating all the content of the tracking signals or only part of it, either directly or processed in any way, the point value of the diffusion instants or corresponding acceptable intervals, and so on) and can be obtained in any way (for example, determined in accordance with the tracking information collected from multiple terminals, also taking into account information downloaded from external processors, such as on the Internet, and so on).

In one embodiment, the method comprises receiving the tracking signals from a plurality of terminals. However, the terminals may be in any number, of any type (for example, all non-reference, with reference terminals in any number and of any type, both indistinct and separate for visible aircraft and non-visible aircraft) and in any location (for example, protected and / or public places).

In one embodiment, the method comprises collecting the corresponding tracking information of the terminals. However, tracking information can be collected in any location (e.g., host, terminal, or combination thereof) and in any way (see above).

In one embodiment, the method comprises determining the reference information in accordance with the tracking information of the terminals. However, the reference information can be determined in any location (e.g., central processor, terminal or combination thereof) and in any way (e.g., by majority and / or via reference terminals).

In one embodiment, the method comprises determining the reference information in accordance with a majority of the terminal tracking information. However, for this purpose it is possible to use any criterion (for example, requiring or not a minimum number of terminals, comparing the tracking signals received with those downloaded from official sources, calculating the actual diffusion instants as average, median or other function of all estimated diffusion instants, discarding their outliers, outliers, and so on).

In one embodiment, the method comprises determining the reference information in accordance with the tracking information of one or more reference terminals of said terminals. However, the reference terminals can be in any number, in any position and of any type (for example, more precise or even the same as the other terminals, installed in protected places with any access control or simply difficult to access, supervised and so on. ).

In one embodiment, the method comprises receiving (from each of one or more remote terminals of the terminals) the tracking signals broadcast by one or more of the aircraft not visible from the location of the remote terminal and which are forwarded by one or more repeaters. However, such tracking signals can be received in any number (even zero) by any number of terminals (from all to none); moreover, the same tracking signals can be broadcast by any number of non-visible aircraft and relayed by repeaters in any number and of any type (for example, telecommunications, geolocation satellites, other aircraft, and so on) in any way ( for example, at any frequency even equal to that of broadcasting from aircraft, directly and / or through ground stations and so on). In any case, a simplified embodiment based only on the aircraft visible from the terminals is contemplated.

In one embodiment, the method comprises providing (by each of the remote terminals) the non-visible aircraft tracking information. However, the tracking information can be provided in any way (both the same or different than above, with the tracking information of visible aircraft and non-visible aircraft that can be both indistinguishable and separate from each other).

In one embodiment, the instants of diffusion of the tracking signals of each of the non-visible aircraft are each estimated in accordance with the corresponding instant of reception, the position of the non-visible aircraft and a position of the corresponding repeater. However, the spread instants of the invisible aircraft tracking signals can be estimated at any position (both the same and different from that of the visible aircraft tracking signals) and in any way (for example, by estimating the repeater propagation time. / aircraft and adding the common propagation time or an estimate of the repeater / terminal propagation time based on their positions, with the estimated propagation times either simply based on the positions or also taking into account other factors, such as the propagation delay due to one or more causes, such as the passage in the ionosphere and / or troposphere, and so on); moreover, the position of the repeaters can be determined in any way (for example, extracted from signals diffused by them, downloaded from external processing, estimated together with the instants of diffusion of the tracking signals of the invisible aircraft and so on).

In one embodiment, the method comprises receiving (from each of the remote terminals) additional tracking signals. However, the additional tracking signals can be in any number and of any type, and can be received in any way (either the same or different as above).

In one embodiment, the further tracking signals are broadcast by one or more further aircraft visible from the remote terminal. However, the additional tracking signals may be broadcast in any way by any number and type of additional aircraft (either the same or different as above).

In one embodiment, the further tracking signals are received at corresponding further reception instants which are determined by the internal clock of the terminal. However, the further reception instants can be determined in any way (see above).

In one embodiment, the further tracking signals include an indication of a position of the corresponding further aircraft. However, the position of any additional aircraft may be indicated in any way (either the same or different from above).

In one embodiment, the method comprises receiving (from each of the remote terminals) the tracking signals further as forwarded by the repeaters. However, the additional tracking signals can also be received forwarded by any number of the repeaters in any way (see above).

In one embodiment, the additional tracking signals forwarded by the repeaters are received at corresponding delayed reception instants determined by the internal clock of the remote terminal. However, delayed reception times can be determined in any way (see above).

In one embodiment, the method comprises estimating corresponding forwarding times of the further tracking signals through the corresponding repeaters, each in accordance with the corresponding delayed reception instant and the corresponding diffusion instant. However, forwarding times can be estimated at any location (for example, terminal, central processor, or a combination thereof) and at any time (for example, either explicitly or implicitly during other calculations).

In one embodiment, the method comprises estimating corresponding aircraft / repeater propagation times of the further tracking signals each in accordance with the position of the corresponding further aircraft and the position of the corresponding repeater. However, aircraft / repeater propagation times can be estimated at any location (e.g., terminal, central processor, or combination thereof), in any way (e.g., simply taking into account distances calculated based on positions or even other factors , such as the propagation delay caused by the passage in the ionosphere and / or troposphere through any propagation pattern, as obtained from geolocation signals or downloaded from external computers, or simply as an average value, the movement of the aircraft during the transmission of the tracking and so on) and at any time (for example, either explicitly or implicitly during other calculations).

In one embodiment, the method comprises estimating corresponding common propagation times of the further tracking signals from the corresponding repeaters each in accordance with the corresponding forwarding time and the corresponding aircraft / repeater transmission time. However, common propagation times can be estimated at any location (e.g., terminal, central processor, or combination thereof) and at any time (e.g., either explicitly or implicitly during other calculations).

In one embodiment, the method comprises estimating corresponding common propagation times of the repeaters each in accordance with the common propagation times of the further tracking signals forwarded by the repeater. However, common propagation times can be estimated at any location (e.g., terminal, central processor, or combination thereof), in any way (e.g., as average, weighted average, median, and so on of the common propagation times of the corresponding tracking signals) and at any time (for example, either explicitly or implicitly during other calculations).

In one embodiment, the method comprises estimating the spread instants of the tracking signals further in accordance with the common propagation delay of the corresponding repeater. However, the spread instants of the tracking signals can be estimated in any position and in any way (either the same or different from above).

In one embodiment, the method comprises estimating the positions of the repeaters by said estimating the common propagation times of the further tracking signals. However, repeater positions can be estimated in any position (e.g., terminal, central processor, or combination thereof) and in any way (e.g., by solving a system of equations, fuzzy logic techniques, and so on). In any case, this feature can also be used on its own to trace repeaters (regardless of the terminal validation described above).

In one embodiment, the method comprises synchronizing (by each of the terminals) the corresponding internal clock via a network synchronization service. However, the network synchronization service can be of any type (for example, public or private, global or dedicated network-based, and so on) and the internal clock can be synchronized in any way (for example, by gradually correcting the synchronization error, correcting it completely, and so on).

In one embodiment, the method comprises receiving (from each of the terminals) synchronization information based on the estimated broadcast instants for one or more synchronization terminals of said terminals having corresponding internal reference clocks. However, the synchronization information can be of any type (for example, synchronization error, estimated diffusion instants of one or more received tracking signals, and so on); moreover, the synchronization information can be received in any way (for example, from the central processor, directly from the synchronization terminals or their combination, in push or pull mode) and can be based on any number and type of synchronization terminals ( for example, the same as the reference terminals, including the reference terminals or a part thereof, made up of dedicated terminals and so on).

In one embodiment, the method comprises synchronizing (by each of the terminals) the corresponding internal clock in accordance with a comparison between the estimated broadcast instants for the terminal and the synchronization information. However, the internal clock can be synchronized in any way (for example, by gradually correcting the synchronization error, correcting it completely and so on).

In one embodiment, the method comprises determining (by said terminal) corresponding aircraft speeds visible from the terminal. However, the speeds can be determined in any way (e.g., extracted from the tracking signals, calculated based on the positions extracted from the tracking signals and their receiving instants, with or without applying any filter, and so on).

In one embodiment, the method comprises validating the position of the terminal in accordance with corresponding frequency variations of the tracking signals and the speeds of the corresponding aircraft. However, such an operation can be performed in any position (e.g., terminal, central processor or combination thereof) and in any way (e.g., in continuous form, in discrete form, and so on). In any case, the validation based on the frequency variation can be independent (even without the validation based on the tracking signals), in addition to the validation based on the tracking signals (to increase its accuracy) or be completely omitted.

In one embodiment, the method comprises receiving (from said terminal) the tracking signals, each further comprising an indication of the speed of the corresponding aircraft. However, the speed of the aircraft can be indicated in any way (for example, both explicitly and implicitly, such as through the positions and their detection period).

In one embodiment, the method comprises determining (by said terminal) a speed of the terminal. However, the speed of the terminal can be determined in any way (for example, by varying its time position, by means of a dedicated sensor, and so on).

In one embodiment, the method comprises validating the position of the terminal in accordance with the frequency changes of the tracking signals, the speeds of the corresponding aircraft and the speed of the terminal. However, the speed of the terminal can also be neglected in a first approximation (especially when much lower than that of aircraft).

In one embodiment, the method comprises determining (by said terminal) the position of the terminal at the instant of reception of the tracking signals. However, the location of the terminal can be determined in any way (for example, via geolocation satellites, mobile phone networks, Wi-Fi access points, and so on).

In an embodiment, the method comprises receiving (by said terminal) at the instant of reception corresponding geolocation signals broadcast by one or more satellites visible from the position of the terminal. However, the satellites can be in any number and of any type (for example, GPS, Galileo, Glonass, and so on), coinciding or not with the satellites used to relay the tracking signals.

In one embodiment, the method comprises determining (by said terminal) the location of the terminal in accordance with the geolocation signals. However, the location of the terminal can be determined in any way (for example, autonomously, assisted, and so on).

In one embodiment, the method comprises estimating corresponding instants of diffusion from the satellites of the geolocation signals, each in accordance with the corresponding instant of reception, the position of the corresponding satellite indicated in the geolocation signal and the position of the terminal. However, the instants of diffusion of the geolocation signals can be estimated in any position (for example, terminal, central processor or their combination) and in any way (for example, simply taking into account the distance calculated based on the positions or even others factors, such as a corresponding propagation delay and so on).

In one embodiment, the method comprises validating the position of the terminal and / or the validation instant in accordance with a comparison between the estimated diffusion instants and actual values of the diffusion instants indicated in the geolocation signals. However, this operation can be performed in any position (for example, terminal, central computer or their combination, after transmission of the geolocation information from the terminal to the central computer where necessary) and in any way (both the same and different to that used for tracking information). In any case, validation based on geolocation signals can be stand-alone (even without validation based on tracking signals), in addition to validation based on tracking signals (to increase accuracy) or be completely omitted.

More generally, all the systems for validating the position and / or timing of the terminal described above (i.e., based on the instants of diffusion of the direct and / or forwarded tracing signals, on the frequency variations and on the instants of diffusion of the geolocation) can each be the only one available, two or more available to be used alternatively or in any combination (selectable both automatically and manually).

In general, similar considerations apply if the same solution is implemented with an equivalent method (using similar steps with the same functions of several steps or their portions, removing some non-essential steps or adding additional optional steps); moreover, the steps can be performed in different order, in parallel or overlapping (at least in part).

One embodiment provides a computer program configured to cause a corresponding processing system to perform each of the above methods when the computer program is executed on the processing system. One embodiment provides a computer program product comprising a computer readable storage medium that embeds a computer program, the computer program being loadable into a working memory of the same processing system thereby configuring the processing system to realize each of the same methods. However, similar considerations apply if the software program is structured differently, or if additional modules or functions are provided; similarly, the memory structures can be of another type, or they can be replaced with equivalent entities (not necessarily consisting of physical storage media). The program can take any form suitable for use by any processing system (see below), thereby configuring the processing system to perform the desired operations; in particular, the program can be in the form of external or resident software, firmware, or microcode (both in object code and in source code, for example, to be compiled or interpreted). Furthermore, it is possible to provide the program on any computer readable storage medium; the storage medium is any tangible medium (other than transient signals per se) that can maintain and store instructions for use by the processing system. For example, the storage medium can be of the electronic, magnetic, optical, electromagnetic, infrared, or semiconductor type; examples of such storage media are hard disks (where the program can be preloaded), removable disks, memory sticks (for example, USB), and the like. The program can be downloaded to the computer system from the storage medium or via a network (for example, the Internet, a geographic network and / or a local network including transmission cables, optical fibers, wireless connections, network devices); one or more network adapters of the processing system receives the program from the network and forwards it for storage in one or more storage devices of the processing system. In any case, the solution according to an embodiment of the present invention lends itself to being implemented also with an application having a different architecture (for example, distributing the various operations in any way between the terminal and the central processor) , with a hardware structure (for example, by electronic circuits integrated in one or more chips of semiconductor material), or with a combination of suitably programmed or otherwise configured software and hardware.

One embodiment provides a system comprising means configured to perform the steps of the above method. However, the system can be of any type (for example, any terminal, central computer or central computer with any number of terminals communicating with each other via any telecommunications network, such as a global, local, geographic network. , which uses any type of wireless connection, such as cellular or satellite type); furthermore, the system can be any entity capable of performing code processing, computation or execution operations (for example, a dedicated structure or embedded in a mobile phone for the terminal, a physical machine, a virtual machine or a static combination thereof or dynamic as in a cloud computing environment (cloud) for the central computer).

In general, similar considerations apply if the system has a different structure or includes equivalent components or has other operating characteristics. In any case, any of its components can be separated into several elements, or two or more components can be combined into a single element; moreover, each component can be replicated to support the execution of the corresponding operations in parallel. Furthermore, unless otherwise indicated, any interaction between different components generally does not need to be continuous, and can be either direct or indirect through one or more intermediaries.

Claims (10)

CLAIMS 1. A method (600) for validating a geolocation and / or timing of a terminal (105), where the method comprises: receiving (611-623) from the terminal (105) at corresponding reception instants, determined by means of an internal clock of the terminal (105), tracking signals broadcast by one or more aircraft (110) visible from the terminal (105), tracking signals including an indication of a position of the corresponding aircraft (110), provide (624-632) by the terminal (105) an indication of a position of the terminal (105) and / or an instant of validation at the receiving instants and tracking information of the terminal (105) based on the signals tracing and indicative of corresponding instants of diffusion from the aircraft (110) of the tracing signals, the instants of diffusion of the tracing signals being estimated (625-628) each in accordance with the corresponding instant of reception, the position of the corresponding aircraft ( 110) and the location of the terminal (105), e validate (647-653) the position of the terminal (105) and / or the time of validation in accordance with a comparison between the tracking information of the terminal (105) and reference information representative of actual values of the tracking signals and corresponding instants of diffusion. The method (600) according to claim 1, wherein the method comprises: receiving (611-623) the tracking signals from a plurality of terminals (105), collecting (624-632) the corresponding tracking information of the terminals (105), e determining (633-640) the reference information in accordance with the tracking information of the terminals (105). The method (600) according to claim 1 or 2, wherein the method comprises: determining (633-640) the reference information in accordance with a majority of the tracking information of the terminals (105) and / or with the tracking information of one or more reference terminals (105r) of said terminals (105). The method (600) according to claim 2 or 3, wherein the method comprises: receive (611-623) from each of one or more remote terminals (105 ') of the terminals (105) the tracking signals broadcast by one or more of the aircraft (110) not visible from the position of the remote terminal (105') which are forwarded by one or more repeaters (205), e provide (624-632) by each of the remote terminals (105 ') the tracking information of the non-visible aircraft (110), the instants of diffusion of the tracking signals (105) of each of the non-visible aircraft (110) being estimated (630) each in accordance with the corresponding instant of reception, the position of the non-visible aircraft (110) and a position of the corresponding repeater (205). The method (600) according to claim 4, wherein the method comprises: receiving (615-619) by each of the remote terminals (105 ') at corresponding further receiving instants, determined by the internal clock of the terminal remote (105 '), further tracking signals broadcast by one or more further aircraft (110') visible from the remote terminal (105 '), the further tracking signals including an indication of a position of the corresponding further aircraft (110') , receive (620-623) from each of the remote terminals (105 ') at corresponding delayed reception instants, determined by the internal clock of the remote terminal (105'), the further tracing signals further as forwarded by the repeaters (205 ), estimate (629) corresponding forwarding times of the further tracking signals through the corresponding repeaters (205) each in accordance with the corresponding delayed reception instant and the corresponding diffusion instant, estimate (629) corresponding aircraft / repeater propagation times of the further tracking signals each in accordance with the position of the corresponding further aircraft (110 ') and the position of the corresponding repeater (205), estimate (629) corresponding common propagation times of the further tracking signals from the corresponding repeaters (205) each in accordance with the corresponding forwarding time and the corresponding aircraft / repeater transmission time, estimate (629) corresponding common propagation times of the repeaters (205) each in accordance with the common propagation times of the further tracking signals forwarded by the repeater (205), and estimating (630) the spreading instants of the tracking signals (105) further in accordance with the common propagation delay of the corresponding repeater (205). The method (600) according to claim 4 or 5, wherein the method comprises: estimating (629) the positions of the repeaters (205) by means of said estimating the common propagation times of the further tracking signals. The method (600) according to any one of claims 1 to 6, wherein the method comprises: synchronize (601-610) by each of the terminals (105) the corresponding internal clock via a network synchronization service, and / or receive (606-608) from each of the terminals (105) synchronization information based on the estimated diffusion instants for one or more synchronization terminals (105r) of said terminals (105) having corresponding internal reference clocks and synchronizing (609-610) by each of the terminals (105) the corresponding internal clock in accordance with a comparison between the estimated diffusion instants for the terminal (105) and the synchronization information. The method (600) according to any one of claims 1 to 7, wherein the method comprises: determine (616) by said terminal (105) corresponding speeds of the aircraft (110) visible from the terminal (105), and validating (656-660) the position of the terminal (105) in accordance with corresponding frequency variations of the tracking signals and the speeds of the corresponding aircraft (110). The method (600) according to any one of claims 1 to 8, wherein the method (600) comprises: receive (613) from said terminal (105) at the instant of reception corresponding geolocation signals broadcast by one or more satellites visible from the position of the terminal (105), and determining (614) by said terminal (105) the position of the terminal (105) is in accordance with the geolocation signals. The method (600) according to claim 9, wherein the method comprises: estimating (661-662) corresponding instants of diffusion from the satellites of the geolocation signals each in accordance with the corresponding reception instant, the position of the corresponding satellite indicated in the geolocation signal and the location of the terminal (105), e validate (663-665) the position of the terminal (105) and / or the validation instant in accordance with a comparison between the estimated diffusion instants and actual values of the diffusion instants indicated in the geolocation signals.