Transmitter And/Or Receiver Units

Abstract

The present disclosure relates to transmitter and/or receiver units (transceivers), such as in particular motor vehicle transceivers. The teachings thereof may be embodied in methods and devices for detecting changes in the positions of transceivers relative to each other. For example, a system may include: a distance determining device to measure a current distance value corresponding to a respective distance of two of the transceivers relative to each other; and a comparator to compare the at least one current distance value and with a stored reference distance value.

Claims

1. A system for detecting changes in the distances of transceivers on a device relative to each other, the system comprising: a distance determining device to measure a current distance value corresponding to a respective distance of two of the transceivers relative to each other; and a comparator to compare the at least one current distance value and with a stored reference distance value.

2. The system according to claim 1, wherein several current distance values relating to distances between a respective two of several transceivers are measured.

3. The system according to claim 1, wherein the comparator compares the measured current distance value and the stored reference distance value by comparing a correlation value (k) in the form of (k=Σ.sub.i,jv.sub.ij.sup.2) sum of squares of the differences for a respective current distance value relative to a stored reference distance value.

4. The system according to claim 1, wherein at least one of the stored reference distance values is stored during the production of the vehicle, or measured before the current current distance values.

5. The system according to claim 1, wherein the distance determining device measures a current distance value representing a distance of two device transceivers relative to each other periodically or at prescribed times or when a prescribed situation occurs.

6. The system according to claim 1, wherein the distance determining device measures at least one current distance value while checking the authorization for opening a vehicle door or trunk lid or for starting up a motor vehicle.

7. The system according to claim 1, wherein: the distance determining device comprises a runtime determining device for determining the runtime; and the distance values comprise runtime values or distance-indicating values.

8. The system according to claim 1, wherein the transceivers are fixed to a motor vehicle.

9. The system according to claim 1, further comprising two device-external transceivers; wherein the system measures a respective current distance value representing a respective distance between the two device-external transceiver.

10. A method for detecting changes in the distances of transceivers of associated with a system relative to each other, the method comprising: measuring a current distance value with a distance determining device, the current distance value representing a distance between two of the transceivers relative to each other; and comparing the current distance value to a stored reference distance value.

11. The system according to claim 1, wherein the comparator compares the measured current distance value and the stored reference distance value by comparing a correlation value (k=|{v.sub.ij|v.sub.ij>s}|) indicates the number of times a threshold for the ratio is exceeded or the difference between a respective current distance value and a stored reference distance value.

12. The system according to claim 1, wherein the comparator compares the measured current distance value and the stored reference distance value by comparing a correlation value $\left(k=\underset{i,j}{\max }.Math..Math.v_{\mathrm{ij}}\right)$ corresponding to the maximum number of times a threshold is exceeded for the ratio or the difference between a respective current distance value and the stored reference distance value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Additional features and advantages of several configurations of the present teachings may be gleaned from the following description of embodiments based on the drawings. Shown in a schematically simplified manner in order to illustrate several configurations:

[0016] FIG. 1 is the activation of a function of a device by radio from a terminal (in particular radio key and/or card) of a user,

[0017] FIG. 2 are device transceivers on a device installed with varying reference distance values relating to distances (here motor vehicle transceiver on a motor vehicle),

[0018] FIG. 3 is the motor vehicle transceiver on FIG. 2, where the position of a motor vehicle transceiver has changed by comparison to FIG. 2,

[0019] FIG. 4 are vehicle transceivers and additional components communicating with each other via different radio systems and busses in a motor vehicle,

[0020] FIG. 5 is the sequence of a test to determine whether access to a function, e.g., opening the door or starting an engine of a motor vehicle, is to be granted by radio.

DETAILED DESCRIPTION

[0021] Various embodiments may efficiently optimize a radio access function in particular of a motor vehicle. While the teachings can be implemented in particular in a motor vehicle, it is also suitable for other systems that determine distance values (distances and/or runtimes) and/or localization systems, e.g., for a localization system with fixed anchors, e.g., a lawnmower, for beacons, or for traffic signs.

[0022] In some embodiments, to elevate reliability, a measurement is performed on one or several distance values relating to distances between more than two transceivers. For example, a comparator can be used to compare the at least one current distance value and at least one stored (e.g., previously measured and/or stored) reference distance value by calculating at least the following (given a combination of two or three alternatives with potentially elevated reliability): [0023] a correlation value in the form of the sum of squares of the differences between a respective current distance value and a stored reference distance value, and/or [0024] a correlation value that indicates how many times a threshold value is exceeded for the correlation or difference between a respective current distance value and a stored reference distance value, and/or [0025] a correlation value that indicates how many times a threshold value is exceeded for the correlation or difference between a respective current distance value and a stored reference distance value.

[0026] In some embodiments, reference distance values can be reference distance values created during vehicle production and/or reference distance values measured and/or stored earlier than the current distance values. For example, current distance values can be measured periodically and/or at prescribed times and/or given the presence of prescribed situations, such as in particular attempts to open the vehicle. Some embodiments can use distance values in the form of runtime values and/or distances.

[0027] As one configuration of the invention, FIG. 1 shows an authentication Aut and an activation Act for a function (e.g., open door, open trunk, or start motor vehicle, etc.) of a motor vehicle MV via radio (e.g., UWB and/or LF and/or RF) from a terminal key user Usr (e.g., a radio key and/or an access card, etc.) of a user Usr, wherein the terminal key Usr of the user Usr (automatically or after activation by the latter) communicates with one or several or all of the motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 (e.g., respective modules with a transmitter and/or receiver—or with several transmitters and/or receivers, e.g., for USB, LF, RF, etc.) on a motor vehicle MV.

[0028] Transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 are located on the motor vehicle MV, e.g., installed and/or mounted and/or welded and/or adhesively bonded and/or bolted, etc. For example, transceivers TRX1, TRX2 are here situated on the front bumper of the motor vehicle MV on the left or right. As shown, both are located outside on the motor vehicle MV. Transceivers TRX5, TRX6 are here situated on the rear bumper of the motor vehicle MV on the left or right, for example, and may also both also located outside on the motor vehicle MV. A transceiver TRX4 is located in a roof antenna module of the motor vehicle MV (e.g., here in the fin and/or under the roof). A transceiver TRX3 is located inside of the motor vehicle, e.g., in the roof liner.

[0029] The terminal key Usr (e.g., a radio key or access card, etc.) of the user Usr here communicates by radio with one or several or all (motor vehicle) transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 of the motor vehicle MV (e.g., UWB, LF, RF), e.g., for authentication Aut and/or transmission of a command Act for implementing a function (e.g., open door (Dooropen), open trunk, or start motor vehicle) of the motor vehicle MV.

[0030] At least one controller Cont in the motor vehicle MV denoted in a simplified manner is used to check whether the terminal key-Usr (e.g., a radio key or access card) is authorized to command the motor vehicle MV with a function (e.g., open doors, open trunk or start motor vehicle, etc.) (Act), and/or whether a function (e.g., Dooropen) is to be implemented, if necessary among other things, based on the distance dKeyMV of the terminal key Usr from one or several of the transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 of the motor vehicle MV, and/or whether the motor vehicle MV is to implement this function (e.g., Dooropen).

[0031] On FIG. 2 and FIG. 3, d.sub.ij (current d.sub.ij,k current) represent distance values in the form of distances from a respective two of the motor vehicle transceivers TRX.sub.i, TRX.sub.j (i, j=1 . . . 6, i.e., two other of the TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 here). A respective one of the motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 transmits (e.g., controlled by a controller Cont inside of it and/or in a controller Cont connected with it (Lin)) at least one query signal, e.g., periodically and/or as warranted, to which a respective response signal can be transmitted back, e.g., by all other motor vehicle transceivers (entirely/partially/modified/other), which allows the motor vehicle transceiver that transmits the query signal and/or a controller, e.g., by way of a timer, to determine the runtime, and thus potentially the distance to each of the other transceivers (as current distance values) from the difference between the query signal transmission time and response signal arrival time (and halving). There are numerous alternative ways to determine runtime, e.g., by transmitting a query signal with a time indication and running a comparison with its arrival time, and/or interleaving several queries and/or responses.

[0032] At least one controller Cont (separate and/or located in the motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6) here checks (aside from potential additional checks, such as authorization checks with codes and/or continuously used case-by-case codes and/or signal runtime measurements, etc.) a change in transceiver position by detecting changes in currently measured distance values d.sub.ij, current; t.sub.ij, current relating to distances (and/or runtimes) of motor vehicle transceivers TRXi, TRXj (i, j=1 . . . 6, i.e., a respective two other of the here TRX1, TRX2, TRX3, TRX4, TRX5, TRX6) on a motor vehicle MV relative to each other, as compared with stored (older) reference distance values (d.sub.ij, ref; t.sub.ij, ref) relating to distances of the motor vehicle transceivers TRXi, TRXj (i, j=1 . . . 6, i.e., a respective two other of the here TRX1, TRX2, TRX3, TRX4, TRX5, TRX6) relative to each other, specifically with at least one distance determining device (e.g., with a runtime determining device, e.g., here integrated into the controller Cont as a program).

[0033] As a consequence, a change in position of a motor vehicle transceiver, e.g., that of motor vehicle transceiver TRX4 on FIG. 3, as compared with its position on FIG. 2 can be detected based upon varying radio signal runtimes of radio signals (and hence distances) from and/or to one or several or each of the additional motor vehicle transceivers TRX1, TRX2, TRX3, TRX5, TRX6 to or from the motor vehicle transceiver TRX4 whose position has changed, since the motor vehicle transceiver TRX4 is farther away from the additional motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 in the situation on FIG. 3 than in the situation on FIG. 2, so that radio signals (e.g., transmitted for measuring the distances of the additional motor vehicle transceivers from each other (if necessary with authentication, etc.)) exhibit a respectively different runtime t.sub.ij (e.g., measured with timers and subtraction in TRX1 . . . TRX6 and/or Cont), and hence (since d.sub.ij=c(air)*t.sub.ij) a different measured current distance d.sub.ij on FIG. 3 than the reference distance (stored, e.g., stored in the Cont ex works and/or measured before the current distance) on FIG. 2.

[0034] The transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 on the vehicle MV thus measure the distances between them via radio (e.g., controlled by a controller connected with them, e.g., by a LIN bus and/or controlled by controllers in the motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6), and thereby generate one or several (in comparison with (the) current older) reference profiles with reference distance values (d.sub.ij, ref; t.sub.ij, ref) and/or generate (continuously/case-by-case) a test profile with currently measured distance values d.sub.ij, current; t.sub.ij, current, so as to determine changes in the distance of motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 relative to each other by comparing them.

[0035] Several examples for a configuration of the invention will be described below involving the check performed by a controller Cont to determine whether there was a change in distance values d.sub.ij, current; t.sub.ij, current of (at least) one motor vehicle transceiver TRX4 relative to one or several or each of the additional motor vehicle transceivers TRX1, TRX2, TRX3, TRX5, TRX6 (as for TRX4 from FIG. 2 to FIG. 3), wherein a respective distance value d.sub.ij is the distance between a transceiver (also referred to as anchor) i and a transceiver j (e.g., distance measured by the transceiver i), and i,j here have the values i,j=1 . . . 6 (correspondingly other values given a higher or lower number of transceivers):

[0036] Arranged in a distance matrix D (I lines, j columns), for example, distance values look as follows (for a test distance matrix D.sub.current with currently measured distance values and/or for a matrix D.sub.ref with reference distance values:

[00002]$D=\left(\begin{array}{ccccc}0& d_{12}& d_{13}& \mathrm{.Math.}& d_{1.Math..Math.j}\\ d_{21}& 0& d_{23}& \mathrm{.Math.}& d_{2.Math.j}\\ d_{31}& d_{32}& 0& \mathrm{.Math.}& d_{3.Math.j}\\ \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}& \ddots & \mathrm{.Math.}\\ d_{i.Math..Math.1}& d_{i.Math..Math.2}& d_{i.Math..Math.3}& \mathrm{.Math.}& 0\end{array}\right)$$i.e.:.Math.D_{\mathrm{aktuell}}=\left(\begin{array}{ccccc}0& d_{12,\mathrm{aktuell}}& d_{13,\mathrm{aktuell}}& \mathrm{.Math.}& d_{1.Math..Math.j,\mathrm{aktuell}}\\ d_{21.Math..Math.\mathrm{aktuell}}& 0& d_{23.Math..Math.\mathrm{aktuell}}& \mathrm{.Math.}& d_{2.Math.j,\mathrm{aktuell}}\\ d_{31.Math..Math.\mathrm{aktuell}}& d_{32.Math..Math.\mathrm{aktuell}}& 0& \mathrm{.Math.}& d_{3.Math.j,\mathrm{aktuell}}\\ \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}& \ddots & \mathrm{.Math.}\\ d_{i.Math..Math.1,\mathrm{aktuell}}& d_{i.Math..Math.2,\mathrm{aktuell}}& d_{i.Math..Math.3,\mathrm{aktuell}}& \mathrm{.Math.}& 0\end{array}\right)$$D_{\mathrm{Ref}}=\left(\begin{array}{ccccc}0& d_{12,\mathrm{Ref}}& d_{13,.Math.\mathrm{Ref}}& \mathrm{.Math.}& d_{1.Math..Math.j,.Math.\mathrm{Ref}}\\ d_{21,.Math.\mathrm{Ref}}& 0& d_{23.Math..Math.\mathrm{Ref}}& \mathrm{.Math.}& d_{2.Math.j,\mathrm{Ref}}\\ d_{31,.Math.\mathrm{Ref}}& d_{32,.Math.\mathrm{Ref}}& 0& \mathrm{.Math.}& d_{3.Math.j,.Math.\mathrm{Ref}}\\ \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}& \ddots & \mathrm{.Math.}\\ d_{i.Math..Math.1,.Math.\mathrm{Ref}}& d_{i.Math..Math.2,.Math.\mathrm{Ref}}& d_{i.Math..Math.3,.Math.\mathrm{Ref}}& \mathrm{.Math.}& 0\end{array}\right)$

[0037] For example, such a distance matrix D can be square and/or (approximately) symmetrical (d.sub.ij≈d.sub.ji); it can also be used for a plausibility check.

[0038] For example, the starting point for calculating a correlation value is the element-by-element comparison of the reference and test distance matrix, i.e. (e.g., via subtraction of the test distance matrix D.sub.current with measured, current distance values d.sub.ij, current; t.sub.ij, current and the reference matrix D.sub.ref with stored reference distance values d.sub.ij, ref; t.sub.ij, ref) e.g., a comparison matrix V:

V=D.sub.current−D.sub.ref

With elements v.sub.ij=[d.sub.ij,current]−[d.sub.ij,ref]

[0039] Possible (combinable) metrics for the correlation value k include:

[0040] The sum of square errors:

[00003]$k=\underset{i,j}{.Math.}.Math.v_{\mathrm{ij}}^2$

and/or

[0041] The frequency with which a threshold s of the elements v.sub.ij is dropped below, k=|{v.sub.ij|v.sub.ij>s}|

and/or

[0042] The maximum value of elements v.sub.ij:

[00004]$k=\underset{i,j}{\max }.Math..Math.v_{\mathrm{ij}}$

[0043] Signal runtimes can be correspondingly considered, in particular subtracted, in place of (matrices with) distances.

[0044] For example, configurations of the invention make it possible to generate a reference and test profile for a PASE system:

[0045] For example, the reference profile D.sub.ref (with reference distance values) is initiated one time during production of the vehicle (e.g., final test).

[0046] It can be identical for a specific vehicle platform (with identical installation sites), or be generated individually for a vehicle.

[0047] For example, the test profile D.sub.current (with current distance values) is generated in a timely manner in each authentication process (e.g., with integration into the communication sequence, e.g., when pulling on the door handle, and/or at the same time as an LF trigger).

[0048] For example, the test profile D.sub.current (with current distance values) can also be compared with previously measured profiles D.sub.ref (with reference distance values) (instead of with a profile generated by the manufacturer). In this case, the profile measured earlier would represent the reference profile for the comparison. For example, this can be advantageous for dynamically adjusting the system to changing environmental influences. The “reference profile” D.sub.ref (with reference distance values) could in this way be generated when locking the vehicle, and would thus encompass all environmental influences at this moment (e.g., garage walls). It is possible that these environmental influences will not change significantly up until opening.

[0049] For example, a profile detection for teaching motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 for a PASE system can take place as follows according to configurations of the invention:

[0050] When installing or replacing motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 (e.g., in a production environment or workshop), there might be a problem in allocating the motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 reported to a bus (see FIG. 2) to a (known) installation position, or in verifying a previously defined allocation.

[0051] For example, a current, measured profile D.sub.current (with current distance values) is used to resolve this problem, to compare it for all possible permutations of transceiver allocations with a previously determined (e.g., platform-specific) reference profile D.sub.ref (with reference distance values).

[0052] For example, the actually present installation situation is detected by evaluating the correlation value k, e.g., according to one or several of the variants mentioned above.

[0053] For example, a safe and efficient detection strategy can include previously known information and boundary conditions, e.g. distinguishable transceiver categories (e.g., transceivers in the interior space/exterior space).

[0054] In particular, for example, the feature of a UWB distance measurement that only essentially positive errors are generated (which can be ensured by calibrating the UWB transceivers) can be combined with the information about distances of the known installation positions: If a measured distance between two of the motor vehicle transceivers x (TRXx) and y (TRXy) is shorter than the distance between two installation sites i and j, the combination [i=x, j=y] or [i=y, j=x] can be precluded.

[0055] For example, this quality (positive errors only) can ultimately yield the strategy of giving more weight to distance measurements with a small measured value when making the decision than to measurements with large values (the latter could be diluted by multipath effects). As a consequence, small measured values would be more reliable than large ones.

[0056] For example, a bus attack for a PASE system can be detected as follows: for example, the system on FIG. 2 is initially designed for detecting a so-called “relay attack” and/or for detecting a radio path extension FV from the automobile MV to the key Key-usr.

[0057] For example, the counter is here based on the runtime measurement of the runtimes t.sub.ij, current between the key Key-usr and at least one vehicle transceiver TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 (in the “worst-case” scenario, the key Key-usr only reaches one of the six vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6).

[0058] For example, as on FIG. 3, a bus attack is based upon a radio extension FV (with two denoted radio extension modules FV1, FV2 connected with each other via (mobile/WLAN/etc.) radio, etc., of which one communicates with the disassembled transceiver TRX4, for example, and/or one can be connected to the LIN bus of the MV, for example, etc.) of the LIN bus of a motor vehicle MV, which probably can be accessed given motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 installed on the outside. It is here possible that the LIN bus and transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 be secured (e.g., via cryptology) and not be changed by the attacker Usr.

[0059] An attacker Usr thus removes a transceiver TRX4 from the automobile and brings it in proximity to a key Key-usr. For example, the (LIN, etc.) bus communication with the vehicle MV is here kept intact by an extension (e.g., wired and/or radio).

[0060] For example, a UWB runtime measurement alone (without inventive configurations of the process of checking how transceiver distances change relative to each other) could determine a valid distance between the key Key-usr and vehicle transceiver; the attack would have been successful.

[0061] In order to detect the bus attack, the authentication sequence also incorporates a measurement of a test profile (e.g., with current distance values d.sub.ij, current; e.g., from runtimes t.sub.ij, current of signals) and a comparison (Cont; V) with a reference profile (e.g., reference distance values d.sub.ij, ref), and it is only decided to execute a command Act (e.g., open doors (Dooropen) or start engine) of a terminal Key-usr (e.g., a radio key or access card) of a user Usr if (potentially aside from other checks) no change in distance (as for TRX4 on FIG. 3 relative to FIG. 2) is determined.

[0062] For example, a system response (of a controller Cont of a motor vehicle MV) can be as follows:

[0063] Localization: For example, depending on the result or achieved correlation value k, one or more specific transceivers (TRX4 on FIG. 3) are disqualified in one configuration of the invention, e.g., these transceivers TRX4 are no longer used for communicating with a terminal Key-usr (e.g., key/card) and/or determining the distance dKeyMV of the terminal Key-usr to the motor vehicle MV), and/or a warning or corresponding quality value is output for the calculated position and/or a command Act is ignored.

[0064] PASE-RAD: If at least one specific correlation threshold (e.g., a threshold for at least one correlation value k or for several) is not exceeded, an attempted repetition is introduced or authorization is denied according to a configuration of the invention.

[0065] PASE Learning: In a configuration of the invention, for example, all possible correlation values are calculated via the permutation of possible transceiver positions, the installation position is determined through “maximum likelihood”, and possible constellations are delimited, e.g., by weighting or checking the plausibility of measuring results (for example, short distances are trusted more, since UWB can be used to preclude negative errors in the measurement given a suitable TRX calibration).

[0066] For example, various embodiments allow the following: [0067] Detection of changed anchor positions [0068] Little or no additional hardware outlay

[0069] For example, configurations of the invention can be used and/or implemented for the following applications: [0070] Localization (e.g., of a MV in a garage and/or an electric vehicle charging station) [0071] Autonomous driving (with localization of infrastructure beacon) [0072] Robotics (e.g., iRobot™=etc. lawnmowers, manufacturing automation) [0073] Maintenance (plausibility check after replacement of individual motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6) [0074] Calibration (accuracy improvement).

[0075] Some embodiments can be used in a motor vehicle, but also, for example, in fixed infrastructure beacons, such as in particular in a traffic light, traffic sign, etc., in particular if (e.g., in an intersection) equipped with UWB beacons (e.g., to check the constellation, or detect obstructions or objects), or for mobile infrastructure beacons, e.g., for construction site tours by means of UWB beacons (the beacon constellation can here be checked).

[0076] In order to send signals between the motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 (and receiving the signals), whose runtimes t.sub.ij, current between a respective two of the motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 can be determined, so as to determine current distances d.sub.kj, current between a respective two motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6, the motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 can use transmitter and/or receiver units, for example, which they also use for communicating with a terminal/key/card Key-usr, or with other authentication codes and/or protocols, for example.

[0077] FIG. 4 shows motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 and other components (gateway EZS/GW/KG, etc.) on a motor vehicle MV that communicate with each other by way of various radio systems (e.g., UWB, LF, HF (or RF or high frequency)) and buses (e.g., LIN, serial, CAN). A controller Cont receives and/or considers inputs from motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6 and/or other antennas and/or an SSB and/or door handles and/or LF antennas and/or a tailgate handle, for example.

[0078] With respect to a configuration of the invention, FIG. 5 shows steps S1-S4 of a sequence for checking whether a terminal (e.g., a radio key or card) Key-usr is to be granted access by radio to a function (e.g., open door or start engine) of a motor vehicle MV (e.g., based upon its distance dKeyMV and/or an authentication and/or a command Act), e.g., whether a function (e.g., open door or start engine) is to be initiated by a controller Cont of the motor vehicle MV.

[0079] Step S1 involves generating a reference profile (e.g., one-time (during production) and/or, for example, situation-related) in the form of a matrix D.sub.ref with distances d.sub.ij, ref between a respective two of the motor vehicle transceivers TRX1, TRX2, TRX3, TRX4, TRX5, TRX6.

[0080] Step S2 involves measuring (periodically or situation-related) a current test profile D.sub.current with current distances d.sub.ij, current between a respective two of the transceivers.

[0081] Step S3 involves calculating at least one correlation value k=f (D.sub.ref, D.sub.current) for deciding whether current distance values (d.sub.ij, current; t.sub.ij, current); D.sub.current and stored reference distance values (d.sub.ij, ref; t.sub.ij, ref); D.sub.ref are sufficiently similar.

[0082] Step S4 involves a system response taking place as a function of at least one correlation value k, e.g., a classification of a position estimate (reliable, not reliable) and/or integration into an authentication for system functions (e.g., release/block functions like open door (Dooropen)/engine start).