Method for estimating the distance between an authentication device and a motor vehicle

Abstract

The object of the invention is a method for estimating the distance between a vehicle (10), in particular a motor vehicle, and an authentication device (20), the vehicle (10) comprising a computer and a plurality of communication modules, each communication module being able to communicate with the device (20) by exchanging signals on a wireless communication link (L1), each communication module comprising an electronic clock defining a sampling frequency for sampling signals received from the device (20). The method comprises a plurality of measurement phases, each measurement phase comprising determining, by the computer, the distance between the vehicle (10) and the device (20), and stopping and restarting the electronic clock, the method also comprising estimating the actual distance between the vehicle (10) and the device (20) based on the plurality of distances determined during the measurement phases.

Description

Technical Field

[0001] The invention relates to a detection system for a motor vehicle and more particularly to a method and a computer for estimating the distance between an authentication device and a vehicle, in order to activate a function of said vehicle, in particular at a distance. Background Art

[0002] Today, some motor vehicles are equipped with detection systems that make it possible to remotely authenticate a device carried by the user, such as a badge or an electronic ignition key, in order to implement certain functions from outside the vehicle. For example, such a detection system can be used to unlock the openings of the vehicle, in particular the doors or the luggage compartment, or to activate hospitality functions such as ambient lighting or seat adjustment, for example.

[0003] For safety reasons, it is known to parameterize the system so that these functions are activated only when the user is at a distance less than a predetermined distance, called the "detection distance", depending on the function to be activated. For example, the function of unlocking the opening means can be activated only when the user is within two meters of the vehicle. For another example, the reception lighting function can be activated only when the user is within five meters of the vehicle, or the request to maneuver the vehicle can be activated only when the user is within six meters of the vehicle, usually called "remote parking".

[0004] In a known solution, the vehicle and the device communicate via a wireless communication link of the LF / RF (Low Frequency / Radio Frequency) type. In this solution, the vehicle periodically sends a detection signal via the LF communication link. When the device receives this detection signal, it responds to the vehicle via the RF communication link for authentication. To determine the distance between the user and the vehicle, the vehicle measures the power of the signal received from the authentication device during these exchanges and deduces the distance therefrom. The advantage of this type of technology is that the propagation of the signal is not affected by mechanical elements such as the vehicle body.

[0005] For practical reasons, it is known today to use a smartphone to authenticate the vehicle. However, most smartphones in use today do not have a LF / RF communication interface. To compensate for this drawback, it is known to use a RFID reader that is available on most current smartphones. Communication interfaces, especially BLE ( The exchange over such an interface is achieved by means of frames encoded in signals called "BLE signals".

[0006] In order to determine the distance between the device and the vehicle, the vehicle receives the BLE signal sent by the smartphone and determines its power, for example by measuring the received signal strength indication (RSSI or Received Signal Strength Indication), in order to infer the distance therefrom. However, it is well known and often happens that the RSSI measurement may be erroneous when the signal sent by the smartphone is decomposed into a signal received in a straight line and one or more signals that bounce off one or more obstacles before reaching the vehicle (signals called "multipath signals"). In this case, the power of the combined signal received by the vehicle may be greater or less than the actual value of the signal received in a straight line, making the estimate of the distance erroneous.

[0007] In order to compensate for this drawback, it is known to determine the distance between the vehicle and the device by evaluating the signal transmission time between the vehicle and the device. To this end, it is known to have the vehicle send a signal called a "request signal", to which the device responds in a known manner after a predetermined period of 150 microseconds using a signal called a "response signal" using the BLE protocol. Knowing the moment of sending the request signal, the period between the reception of the request signal by the device and the sending of the response signal, and the moment of reception of the response signal, the vehicle then deduces therefrom the average travel time of the signals and the distance separating the vehicle from the device.

[0008] As is known, the BLE communication module of the vehicle filters and samples each received signal and detects that the signal is a BLE signal when a predetermined signal power detection threshold is exceeded, and the exceeding of the threshold is detected only when the signal is sampled. Figure 1 The following signals are shown superimposed: A an example of an unfiltered and noise-free response signal, and B the same response signal filtered as a comparison and C said response signal filtered and sampled, the power P of these signals being shown as a function of time t. C the filtered and sampled response signal RESP is detected when one of the samples c1 exceeds a predetermined detection threshold Sd.

[0009] Therefore, the time interval between two samples determines the maximum possible error in the distance measurement. For example, sampling a BLE signal using a quartz with a rhythm of 24MHz will result in an error of plus or minus 6.25 meters, which will show a significant drawback, even in situations where it is necessary to detect a user within 2 meters, 5 meters or 6 meters of the vehicle to activate some of its functions.

[0010] In addition, since the signal sent by the transmitter may bounce off obstacles during its propagation, thereby generating multiple components of the same signal, the receiver may receive multiple signals for the same signal sent by the transmitter. In this case, one of the received signals is detected - the first signal for which a threshold value is detected on a sample - which may again lead to an error in the estimation of the actual distance between the transmitter and the receiver. Therefore, this type of detection system has obvious technical limitations that may sometimes make it ineffective. Summary of the invention

[0011] The object of the present invention is therefore to at least partially remedy these drawbacks by proposing a simple and reliable solution for estimating the distance between the vehicle and an authentication device and for effectively activating a function of the vehicle remotely.

[0012] To this end, the object of the present invention is a method for estimating the distance separating a vehicle, in particular a motor vehicle, from an authentication device, said vehicle comprising a computer and a plurality of communication modules, each capable of communicating with said device by using signals exchanged on a wireless communication link, each communication module comprising an electronic clock defining a sampling frequency for sampling the signals received from the device, said method being notable in that it comprises:

[0013] -Multiple measurement phases, each measurement phase includes:

[0014] oThe distance between the vehicle and the device is determined by the computer,

[0015] o Stopping and restarting the electronic clock, preferably at random moments,

[0016] - estimating the actual distance of the vehicle from the device based on the plurality of distances determined during the measurement phase.

[0017] The term “actual distance” is understood to mean a refined distance resulting from an estimate based on a plurality of determined distances.

[0018] The method according to the invention makes it possible to effectively estimate the actual distance between the vehicle and the device by restarting the electronic clock. Restarting the electronic clock makes it possible to change the sampling moment for sampling the signal received from the authentication device in a random manner, thereby reducing the error in the distance estimation, in particular by diluting the error over the number of measurements.

[0019] Preferably, estimating the actual distance comprises calculating an average or median of the distances determined in the measuring phase.

[0020] According to one aspect of the invention, the method is repeated at least 10 times, preferably at least 30 times, and more preferably at least 100 times, in order to refine the estimate of the actual distance as the measurement phase progresses. Such iterations make it possible to refine the estimate of the distance so that it is relatively accurate, and for example reduce the error to within two meters after thirty iterations, or even reduce the error to within 50 centimeters after several hundred iterations.

[0021] Preferably, the step of resetting the electronic clock of the method is performed at the end of a predetermined delay period after determining the distance.

[0022] In one embodiment, the step of determining the distance in the measurement phase includes:

[0023] At least one of the communication modules sends a request signal to the device at a first moment,

[0024] receiving the request signal by the device,

[0025] sending, by the device, a response signal to at least one of the communication modules of the vehicle,

[0026] receiving the response signal by at least one of the communication modules at a second time, the second time being defined according to a sampling frequency of the electronic clock,

[0027] determining, by a computer, the time elapsed between the first moment and the second moment,

[0028] The distance is determined by a computer based on the calculated time elapsed between the first moment and the second moment.

[0029] Preferably, the measurement phase is performed on a series of signals received successively by the communication module.

[0030] In one embodiment, the electronic clock is a piezoelectric element. However, of course any type of clock suitable for the application can be used.

[0031] Advantageously, the sampling frequency of each communication module is less than 50 MHz, preferably about 24 MHz, which is a frequency usually used in piezoelectric elements of detection systems.

[0032] Advantageously, the method comprises, between two measuring phases, a step of saving the values ​​of the determined distances in a memory area of ​​the computer, so that the actual distance can be estimated based on the saved value or values ​​of the determined distances.

[0033] Preferably, each measurement phase comprises a step of sending a detection signal by the device to the vehicle before the step of sending a request signal by at least one of the communication modules to the device.

[0034] Preferably, the method comprises, after the step of estimating the actual distance, a step of activating, by the computer, at least one function of the vehicle when the estimated actual distance is less than a predetermined distance (eg, 2 meters, 5 meters or 6 meters).

[0035] Preferably, the wireless communication link enables the exchange of signals in the UHF (Ultra High Frequency) band between 300 and 3000 MHz. Still preferably, the wireless communication link is based on BLE ( Low energy consumption) standards.

[0036] The invention also relates to a vehicle computer, in particular a computer of a motor vehicle, making it possible to estimate the distance separating the vehicle from an authentication device, the vehicle comprising a plurality of communication modules, each communication module being able to communicate with the device by exchanging signals on a wireless communication link, each communication module comprising an electronic clock defining a sampling frequency for sampling signals received from the device, the computer being configured to:

[0037] - In multiple measurement phases:

[0038] oDetermine the distance between the vehicle and the device,

[0039] o preferably control stopping and restarting of the electronic clock at random moments,

[0040] - estimating the actual distance of the vehicle from the device based on the plurality of distances determined during the measurement phase.

[0041] According to one aspect of the invention, the computer is configured to estimate the actual distance by calculating the average or median of the distances determined during the measurement phase.

[0042] Preferably, the computer is configured to restart the electronic clock at the end of a predetermined delay period after determining the distance.

[0043] In one embodiment, the computer is configured to: determine the time elapsed between a first moment and a second moment, the first moment being the moment when at least one of the communication modules sends a request signal to the device, and the second moment being the moment when at least one of the communication modules receives a response signal, the second moment being defined according to a sampling frequency of an electronic clock; and determine the distance between the vehicle and the device based on the calculated time elapsed between the first moment and the second moment.

[0044] In one embodiment, the electronic clock is a piezoelectric element. However, of course any type of clock suitable for the application can be used.

[0045] The invention also relates to a vehicle comprising at least one computer and a plurality of communication modules, each communication module being able to communicate with said device.

[0046] According to one aspect of the present invention, the sampling frequency of each communication module of the vehicle is less than 50 MHz, preferably about 24 MHz.

[0047] The present invention also relates to a detection system, which comprises a vehicle as described above and an authentication device capable of communicating with a plurality of communication modules of the vehicle.

[0048] Preferably, where the authentication device comprises a communication unit configured to exchange signals with the communication module, the communication module and the communication unit are configured to communicate over a communication interface operating in a UHF (Ultra High Frequency) frequency band between 300 and 3000 MHz. Still preferably, the communication interface uses BLE ( Low energy consumption) technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Other characteristics and advantages of the invention will become apparent in the following description, which is made with reference to the accompanying drawings, given by way of non-limiting examples, and in which similar objects are given the same references.

[0050] Figure 1 The diagram shows the detection of the signal received by the communication module in the prior art.

[0051] Figure 2 A detection system according to the invention is schematically shown.

[0052] Figure 3 A vehicle according to the invention is shown schematically.

[0053] Figure 4 An embodiment of the communication module according to the present invention is schematically shown.

[0054] Figure 5 The signal exchange between a vehicle and a device according to the invention is schematically shown.

[0055] Figure 6 The graph shows the variation of the power of two signals received by the communication module according to the present invention over time.

[0056] Figure 7 The comparison of the restart time of the electronic clock of the communication module in the prior art and the communication module according to the present invention is schematically shown.

[0057] Figure 8 A test example of the method according to the invention is shown, which depicts the evolution of the distance error as a function of the number of method iterations.

[0058] Fig. 9A test example of the method according to the invention is shown, which plots the evolution of the cumulative probability with the distance error. DETAILED DESCRIPTION

[0059] The detection system according to the invention is intended to be installed in a vehicle, in particular a motor vehicle, in order to detect an authentication device carried by a user of said vehicle.

[0060] Such an authentication device may, for example, take the form of a badge, an electronic ignition key, or a smartphone, so as to enable a user to authenticate to the vehicle to perform certain functions. For example, such a detection system may be used to perform a vehicle lighting function or to perform a function of unlocking an opening component of the vehicle (e.g., a door or a trunk).

[0061] For safety reasons, it is known to parameterize the system so that these functions are activated only when the user is at a distance less than a predetermined distance, called the "detection distance", which depends on the function to be activated. For example, the unlocking function can only be activated when the user is within two meters of the vehicle.

[0062] Figure 2 A detection system 1 according to the present invention is schematically shown. The detection system 1 comprises a vehicle 10 and an authentication device 20. Figure 3 The vehicle 10 includes a computer 110 (eg, an ECU (Electronic Control Unit) type computer) and a plurality of communication modules 120 .

[0063] Reference again Figure 2 , the authentication device 20 includes a management module 210 and a communication unit 220. Preferably, the authentication device 20 is a smart phone, but this does not limit the scope of the present invention.

[0064] Preferably, the communication module 120 and the communication unit 220 are configured to communicate over a communication interface operating in the UHF (Ultra High Frequency) band between 300 and 3000 MHz. Still preferably, the communication interface uses BLE ( BLE technology in particular enables low energy communication and is advantageously integrated in most current smartphones. Since BLE technology itself is known, it will not be described in further detail here.

[0065] The present invention will be described below in the context of applying the present invention to unlocking of an opening member of the vehicle 10 , but this does not limit the scope of the present invention.

[0066] In the case of unlocking the vehicle 10 by manually activating the handle of the opening part of the vehicle 10, the number of communication modules 120 is advantageously equal to the number of the handle of the opening part of the vehicle 10. Figure 2 The vehicle 10 includes five opening components, four doors and a trunk door, which have handles PG1, PG2, PG3, PG4 and PG5 respectively, and each handle PG1, PG2, PG3, PG4, PG5 is simultaneously connected to the dedicated communication module 120 and to the computer 110.

[0067] refer to Figure 4 Each communication module 120 installed in the vehicle 1 includes an antenna 121, an amplifier 122, a baseband circuit 123 and an electronic clock, which in this example is in the form of a piezoelectric element 124.

[0068] The antenna 121 makes it possible to receive signals sent by the authentication device 20 or to send signals to the authentication device 20 via the wireless communication link L1 .

[0069] The amplifier 122 enables amplification of received signals having attenuated power due to their propagation in the air. For example, the amplifier 122 may be a low noise amplifier commonly referred to as “LNA” (“Low Noise Amplifier” in English) by those skilled in the art.

[0070] The baseband circuit 123 makes it possible to sample the received signals, that is to say to digitize them so that they can be used by the computer 110 .

[0071] The piezoelectric element 124 includes quartz that is rhythmic at a predetermined frequency (eg, 24 MHz) to enable the baseband circuit 123 to sample a signal at that frequency.

[0072] refer to Figure 5 The baseband circuit 123 is also configured to detect the noisy and delayed response signal RESP at a second time T2 when the amplitude of the noisy and delayed response signal RESP exceeds a predetermined detection threshold Sd, which is sent in response to the request signal REQ sent in advance by the antenna 121 at the first time T1. After receiving the detection signal AD sent by the communication unit 220 of the authentication device 20, the antenna 121 sends the request signal REQ. The baseband circuit 123 is also configured to send the detected value at the second time T2 to the computer 110 so that the computer 110 estimates the distance between the vehicle 10 and the authentication device 20.

[0073] For this reason, still refer to Figure 5The computer 110 of the vehicle 10 is configured to control at least one of the communication modules 120 to send a request signal REQ to the authentication device 20 at a first moment T1, receive a value of a second moment T2 detected by the at least one communication module 120 from the at least one communication module 120, calculate the time elapsed between the first moment T1 and the second moment T2, and estimate the distance between the vehicle 10 and the authentication device 20 based on the calculated time.

[0074] In a preferred embodiment, the computer 110 is configured to store the values ​​of the determined distances in a storage area, and to calculate a distance called "actual distance" based on the stored multiple determined distances, for example by calculating the median or average value of the estimated distances.

[0075] Preferably, the computer 110 is configured to calculate the actual distance once the number of distances determined exceeds a threshold value called the "acquisition threshold". The acquisition threshold is preferably greater than 10, 30 or even 100, so as to refine the estimate of the actual distance as the measurement phase progresses. Such iterations make it possible to refine the estimate of the distance so that it is relatively accurate and the value of the error is preferably reduced to within 50 centimeters.

[0076] Finally, the computer 110 is configured to activate at least one function of the vehicle 10 when the estimated distance is less than a predetermined distance (eg, 2 meters, 5 meters, or 6 meters).

[0077] The present invention will now be described in its embodiments.

[0078] First, refer to Figure 5 When the opening parts of the vehicle 10 are locked and the engine is stopped, especially when the vehicle 10 is parked, the management module 210 of the authentication device 20 controls the communication unit 220 so that the communication unit 220 periodically (for example, with a period between 20 milliseconds and 10.24 seconds) sends a detection signal AD, which is referred to as a "broadcast signal" by those skilled in the art.

[0079] When at least one of the communication modules 120 is within the radio coverage of the authentication device 20 and receives the detection signal AD, the computer 110 responds to the authentication device 20 and controls at least one of the communication modules 120 to send a request signal REQ at a first time T1 to request an identifier of the authentication device 20 for authentication. The computer 110 records the value of the first time T1 and waits for a response from the authentication device 20.

[0080] At the end of a predefined period of 150 μs after receiving the request signal REQ, the management module 210 of the authentication device 20 controls the sending of a response signal RESP comprising in particular an identifier of the authentication device 20 in order for the vehicle 10 to authenticate it.

[0081] When the computer 110 receives the response signal RESP via at least one of the communication modules 120 at the second moment T2, the computer 110 records the second moment T2 and calculates the average flight time of the signal, which corresponds to the period between the first moment T1 and the second moment T2 minus 150 μs and divided by two.

[0082] Then, the computer 110 determines the distance d between the vehicle 10 and the authentication device 20 between the two moments according to the following formula: Figure 2 ):

[0083]

Mathematical formula 1

[0084]

[0085] Where "d" is the distance in meters, "c" is the speed of light, "T1" and "T2" are given in seconds, and 0.00015 seconds (150 microseconds) corresponds to the predefined period between receiving the request signal REQ and sending the response signal RESP.

[0086] According to the present invention, when the computer 110 determines the distance d, the computer 110 controls the piezoelectric elements 124 of one or more communication modules 120 (or all communication modules 120) that have received the signal to stop and restart.

[0087] The signal exchange and the resetting of the piezoelectric element 124 which enable the distance d to be determined constitute a sequence, called a measuring phase, which is regularly repeated at the periodic transmission frequency of the detection signal AD.

[0088] The computer 110 estimates the actual distance of the vehicle 10 from the authentication device 20 based on the distance d determined in each measurement phase. This actual distance estimated in advance is preferably the average or median of the distances determined during previous measurement phases, preferably at least 10 or 100 previous measurement phases.

[0089] Of course, computer 110 may calculate the actual distance after each measurement phase, that is, based on the actual distance calculated in the previous measurement phase and the distance determined in the current measurement phase, rather than storing all distances determined during multiple consecutive measurement phases and then calculating the actual distance.

[0090] For each measurement phase, the baseband circuit 123 samples the response signal RESP and determines a second instant T2 when the power value of one of the samples of the response signal RESP exceeds a predetermined detection threshold Sd. The baseband circuit 123 stops and restarts the piezoelectric element 124 in a random manner between two signal exchange sequences, so that the sampling instant of the latter sequence is different from the sampling instant of the previous sequence. As a result, the detection of exceeding the detection threshold Sd will vary in a random manner between the sequences, so that when the number of measurement phases increases, the estimation error of the actual distance tends to zero, thereby significantly improving the accuracy of the detection system 1.

[0091] If the estimated distance is less than the detection distance, this will trigger one or more functions of the vehicle 10 to be remotely implemented, for example, unlocking the opening components of the vehicle 1 when the estimated distance is less than two meters. In the opposite case, if the estimated distance is greater than the detection distance, one or more related functions of the vehicle 10 remain inactive.

[0092] For example, refer to Figure 6 , which graphically shows the variation of the power P of a first received signal S1 and a second received response signal S2 sampled by the computer 110 over time t. It should be noted that these two signals are received for two consecutive measurement phases, but the sampled received signals are superimposed on the same time scale in order to show the offset caused by stopping and restarting the piezoelectric element 124.

[0093] In this example, it can be observed that the first sample of the first signal S1 exceeding the detection threshold Sd of the signal reception occurs at the end of the first waiting time tl1 which occurs at the instant t corresponding to said detection threshold Sd. H after.

[0094] Randomly stopping and restarting the piezoelectric element 124 enables the detection of the second signal S2 exceeding the detection threshold Sd to be moved to a second waiting time tl2 different from the first waiting time tl1. It should be noted that restarting the piezoelectric element 124 at random moments is performed between the authentication device 20 receiving the two signals.

[0095] Furthermore, when the computer 110 takes the average or median of the distances determined at these two different moments, it generates a refined estimate of the actual distance between the vehicle 10 and the authentication device 20. This value will become increasingly refined as the number of measurement phases (ie the number of stops and restarts) increases.

[0096] In addition, reference Figure 7In the case of the BLE protocol, it is known to use three channels with different frequencies numbered 37, 38 and 39 alternately. In the prior art solutions, the signal detection is statically between two values ​​of the sampled received signal ( Figure 7 The left part of the sampled received signal is “off”), that is, it is performed at the same detection time Ir for each measurement phase, while with the present invention, the piezoelectric element 124 is randomly restarted so that the detection time Ir (between two values ​​of the sampled received signal) can be changed. Figure 7 ” on the right side of ), which makes it possible to reduce the error in the estimation of the distance between the vehicle 10 and the authentication device 20, especially as the number of random restarts (ie the number of iterations of the method according to the invention) increases.

[0097] Figure 8 A test example of the method according to the invention is shown, which depicts the evolution of the distance error Err (in meters) with the number of iterations Nb of the method. In this example, it can be observed that after about 35 iterations, the error gradually becomes within 2 meters.

[0098] Fig. 9 A test example of the method according to the invention is shown, which depicts the evolution of the cumulative probability CP with the distance error Err (in meters). Five curves are shown, respectively implemented with 1, 10, 100, 1000 and 10000 iterations. In this example, it can be observed that after 100 iterations, the median value of the positioning error is about 20 cm (ie, on the curve of 100 iterations, the cumulative probability is equal to 0.5), which is a great advantage compared to known solutions.

[0099] The method according to the invention therefore advantageously makes it possible to reduce errors in the estimation of the actual distance between the vehicle 10 and the authentication device 20 by simply restarting the electronic clock after each reception of a signal sent by the device, that is, without changing the hardware structure of the vehicle, in particular the communication module.

Claims

1. A method for estimating a distance between a vehicle (10) and an authentication device (20), the vehicle (10) comprising a computer (110) and a plurality of communication modules (120), each communication module (120) being able to communicate with the authentication device (20) by exchanging signals over a wireless communication link (L1), each communication module (120) comprising an electronic clock (124), the electronic clock (124) defining a sampling frequency for sampling signals received from the authentication device (20), the method being characterized in that it comprises: a) a plurality of measurement phases, each measurement phase comprising determining, by the computer (110), a distance (d) separating the vehicle (10) from the authentication device (20) based on the time at which a signal sample of a signal exchanged between at least one of the communication modules (120) and the authentication device (20) exceeds a detection threshold, b) as a result of determining the distance, stopping and restarting an electronic clock (124) in a random manner between each of a plurality of measurement phases to add a random time offset to the samples for each of the plurality of measurement phases, the random time offset resulting in a random distance offset of the distance calculated during each of the plurality of measurement phases, c) estimating the actual distance between the vehicle (10) and the authentication device (20) based on the plurality of distances (d) determined during each of the plurality of measurement phases.

2. The method according to claim 1, wherein: Estimating the actual distance includes calculating the average or median of the distances (d) determined during the measurement phase.

3. The method according to any one of claims 1 and 2, wherein: This method was repeated at least 10 times.

4. The method according to any one of claims 1 and 2, wherein: Restarting the electronic clock (124) is performed at the end of a predetermined delay period after determining the distance (d).

5. The method according to any one of claims 1 and 2, wherein: Determining the distance (d) during the measurement phase includes the following steps: - at least one of the communication modules (120) sends a request signal (REQ) to the authentication device (20) at a first moment (T1), - receiving said request signal (REQ) by the authentication device (20), - sending a response signal (RESP) by the authentication device (20) to at least one of the communication modules (120) of the vehicle (10), - receiving the response signal (RESP) at a second time (T2) by at least one of the communication modules (120), the second time (T2) being defined according to a sampling frequency of the electronic clock (124), - determining, by a computer (110), the time elapsed between a first moment (T1) and a second moment (T2), - The distance (d) between the vehicle (10) and the authentication device (20) is determined by the computer (110) based on the calculated time elapsed between the first moment (T1) and the second moment (T2).

6. A vehicle (10) computer (110) enabling estimation of the distance between the vehicle (10) and an authentication device (20), the vehicle (10) comprising a plurality of communication modules (120), each communication module (120) being able to communicate with the authentication device (20) by exchanging signals over a wireless communication link (L1), each communication module (120) comprising an electronic clock (124), the electronic clock (124) defining a sampling frequency for sampling signals received from the authentication device (20), the computer (110) being characterized in that it is configured to: a) determining a distance (d) between the vehicle (10) and the authentication device (20) based on the time at which signal samples of a signal exchanged between at least one of the communication modules (120) and the authentication device (20) exceed a detection threshold in a plurality of measurement phases, b) as a result of determining the distance, controlling between each of a plurality of measurement phases to stop and restart an electronic clock (124) in a random manner to add a random time offset to the sample for each of the plurality of measurement phases, the random time offset resulting in a random distance offset of the distance calculated during each of the plurality of measurement phases, c) estimating the actual distance between the vehicle (10) and the authentication device (20) based on the plurality of distances (d) determined during each of the plurality of measurement phases.

7. Computer (110) according to the preceding claim, configured to estimate the actual distance by calculating the average or median of the distances (d) determined in the measurement phase.

8. The computer (110) according to any one of claims 6 and 7, the computer (110) being configured to restart the electronic clock (124) at the end of a predetermined delay period after determining the distance (d).

9. A vehicle (10) comprising at least one computer (110) according to any one of claims 6 to 8 and a plurality of communication modules (120), each communication module (120) being capable of communicating with the authentication device (20).

10. A detection system (1) comprising a vehicle (10) according to the preceding claim and an authentication device (20) capable of communicating with a plurality of communication modules (120) of the vehicle (10).

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