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

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.