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US-20260129451-A1 - METHOD FOR A RADIO-BASED DISTANCE MEASUREMENT, FREQUENCY SYNCHRONIZATION, TIME SYNCHRONIZATION, AND A DETECTION AND/OR PREVENTION OF RELAY ATTACKS WITH A SELECTION OF THE RADIO SIGNALS TO BE USED

US20260129451A1US 20260129451 A1US20260129451 A1US 20260129451A1US-20260129451-A1

Abstract

A method for radio-based distance measurement and in addition also to a method for detecting and/or preventing relay attacks and a method for time and/or frequency synchronisation. The method does not require coherence information, in particular neither phase-coherent switching nor switching in such a way that the phase after switching is known relative to the phase position before switching is required. The change in phase does not have to be determined locally, in particular at the transmitter before transmission and/or at the receiver with respect to the PLL of the receiver, and this change does not have to be corrected in the calculation. The object is achieved by a time synchronisation or a corresponding correction.

Inventors

  • Rönne Reimann

Assignees

  • LAMBDA:4 ENTWICKLUNGEN GMBH

Dates

Publication Date
20260507
Application Date
20240429
Priority Date
20240205

Claims (20)

  1. 1 . A method for determining distances using radio signals or for detecting relay attacks, each having a timer, using radio signals, in which the two objects transmit radio signals on a plurality of frequencies and the radio signals are received by a respective non-transmitting object of the two objects, on which said non-transmitting object which received the radio signal carries out at least one measurement of the phase or at least one measurement of the signal arrival time or the signal delay relative to its own timer per frequency or radio signal and replies to it by transmitting at least one radio signal, with the respective non-transmitting object of the two objects receiving the at least one radio signal transmitted as a reply carrying out at least one measurement of the phase or at least one measurement of the signal arrival time or the signal delay relative to its own timer per frequency or radio signal and from this carrying out at least one determination of the phase shift or at least one determination of the signal delay per frequency; on the basis of the at least one determination, an evaluation is performed, with said method including a determination of a time deviation between the timers of the two objects, said method containing a decision at least for each frequency or signal round trip time as to whether the measurements on the at least one signal of a first object or a second object is to be used for the determination of the distance or detection, with said decision being taken, with the selected measurements being corrected by the influence of the determined time deviation and or the determined drift for the determination of the distance or for the detection.
  2. 2 . The method according to claim 1 , in which at least one difference is determined between each of two phase shifts caused between the two objects by a transmission or by a signal round trip, in which the transmissions or different signal round trips are carried out with signals of different frequency and in which the determination of the distance, the detection of relay attacks or the determination of the time deviation is based on this at least one difference.
  3. 3 . The method according to claim 1 , in which the method is carried out in such a way that, in order to determine the time deviation or drift, the relative phase position of two radio signals of different frequencies by means of the PLL of an object is known in each case as a function of the time difference of the generation or transmission of the two signals at one of the objects relative to its timer, or the phase position of the PLL of each of the objects at different frequencies is known in each case relative to its timer, with the determination of the time deviation or drift between the objects being carried out radio-based by phase measurement(s) on a plurality of the radio signals of different frequencies transmitted between the two objects.
  4. 4 . The method according to claim 1 , in which the time deviation or drift is determined by determining the phase shift of the transmission of the forward path signal from the first object to the second object and the return path signal from the second object to the first object by means of in-line phase return.
  5. 5 . The method according to claim 4 , in which the in-line phase return is preferably effected by changing the phase position of the return path signal relative to a phase position known to the local timer of the second object, by the negated measured phase of the forward path signal received at the second object.
  6. 6 . The method according to claim 1 , in which a plurality of forward and return path signals, are exchanged between the objects.
  7. 7 . The method according to claim 1 , in which the phase position of a second signal received at the first object is determined at the first object and used together with the phase position of a first signal at the first object relative to the PLL of the first object, for time synchronisation.
  8. 8 . The method according to claim 1 , in which the determination of the time deviation or drift, is performed radio-based by means of repeated, unidirectional signal exchange from the first object to the second object, and on the basis of phase measurement(s) on the signal(s) received at the second object, with the phase position of the unidirectional signal of the first object received at the second object being determined.
  9. 9 . (canceled)
  10. 10 . The method according to claim 8 , in which the relative difference of the phase shifts caused by the transmissions, between the two unidirectional signals at a first frequency and a second frequency measured on received unidirectional signals at the first frequency and the second frequency, i.e. normalised to the difference between the first frequency and second frequency, is used for time synchronisation.
  11. 11 . The method according to claim 1 , in which the determination of the time deviation or drift is performed by determining the phase shift of the transmission of the forward path signal from the first object to the second object and the return path signal from the second object to the first object by means of in-line phase return, by the negated measured phase of the forward path signal received at the second object at the second object.
  12. 12 . (canceled)
  13. 13 . (canceled)
  14. 14 . (canceled)
  15. 15 . (canceled)
  16. 16 . (canceled)
  17. 17 . (canceled)
  18. 18 . (canceled)
  19. 19 . The method according to claim 1 , in which, if a relay attack is suspected or as an enable decision an access or enable is denied, a requested activity or action is not performed or an alarm or blocking is performed, or if a relay attack is not suspected or as an enable decision the access or enable is granted or the requested activity or action is performed or the alarm or blocking is not performed.
  20. 20 . (canceled)

Description

REFERENCE TO RELATED APPLICATIONS The present application is a National Stage Entry of International Patent Application No. PCT/EP2024/061779 filed on Apr. 29, 2024, which claims priority from International Patent Application No. PCT/EP2023/061372 filed on Apr. 28, 2023. International Patent Application No. PCT/EP2024/061779 filed on Apr. 29, 2024, also claims priority from European Patent Application No. EP24155873.3 filed on Feb. 5, 2024. International Patent Application No. PCT/EP2024/061779 filed on Apr. 29, 2024, also claims priority from International Patent Application No. PCT/EP2024/052807 filed on Feb. 5, 2024, which application claims priority from International Patent Application No. PCT/EP2023/061372 filed Apr. 28, 2023. BACKGROUND ART The invention relates to a method for radio-based distance measurement, frequency synchronisation, time synchronisation and in addition to a method for detecting and/or preventing relay attacks. Methods are known for determining the distance between two objects through the exchange of radio signals between the objects and for carrying out frequency synchronisation or time synchronisation. Methods are also known in which timers in two objects are synchronised via both wired and wireless links. There is, for example, the NTP protocol. Synchronisation is also possible in the context of a Bluetooth link in which each object has a free-running 28-bit clock with a pulse of 3.2 kHz and where each object determines its offset relative to a central clock and corrects it at regular intervals. Here synchronisation is achieved with an accuracy of approx. 125 ns. An improved time synchronisation is also known from, for example, DE112014004426T5 or “Synchronization in Wireless Sensor Networks Using Bluetooth”, Casas et al., Third International Workshop on Intelligent Solutions in Embedded Systems, 2005., ISBN: 3-902463-03-1. This can be used, for example, to save energy by keeping an object ready to receive only in certain time slots that are known to the other object in order for it to transmit at corresponding times. Synchronisation of the clocks is still possible, at least in the event of relatively strong interference on one side of the radio channel, although the distance measurement becomes impossible or very inaccurate or takes a very long time in the event of such interference. A clear distinction must be made between the accuracy of time synchronisation and synchronisation with a clock pulse of a received signal at the receiver of the signal. In this case no synchronisation of two clocks on two objects takes place; instead the receiving object is set so that it is synchronised with the incoming signal The signal delay is of no significance here, as it does not matter when the signal was sent and/or how long the transmission took. A method for determining the distance between two objects is also known from WO 2022/096 091 A1 in which the two objects are time-synchronised to 10 ns or better and in which a first and/or second of the two objects transmits signals at several frequencies and the distance between the first and second object is determined, and in which the method includes the decision as to whether/which signals of the first or second object are used, in particular on the basis of at least one estimation or determination of the effects of interference on the reception at each of the two objects. However, coherence information is necessary here. Furthermore, a method for recognising a relay attack is known from WO 2022/096 514 A1 in which radio signals with different frequencies are transmitted between a first and a second object and phase measurements and delay measurements are carried out on these radio signals and the change in the phase measurements with changes in frequency is compared with the signal delay measurements or their change, and in which a relay attack is assumed if a predetermined deviation or a deviation determined from measurements on the radio signals is exceeded. Methods are known for distance determination that work with in-line phase return, i.e. that use the measured phase on a received signal and then modify the phase of the response signal transmitted in response to it based on the measured phase by adding the measured phase to a predetermined phase position and transmitting the response signal with the phase position obtained by this addition. A method is known from U.S. Pat. No. 8,446,254 B2, for example, in which the response signal is returned with exactly the phase of the received query signal; this method still has the disadvantage, however, that it lacks time information. This shows a corresponding in-line phase return, in which, for example, the received phase of the query signal is always added to phase zero for the transmission of the response signal. If the predetermined phase here were not zero, but that of a PLL whose phase position relative to the common time is known, this would offer further advantages. SUMMARY OF THE