Patent ID: 9019151
Filing Date: 2015-04-28
Classification: G01S,G07B,G08G,H04W

Abstract:
1. A method for determining a distance between a radio beacon and an onboard unit passing the radio beacon in a road toll system, wherein at least one of the radio beacon and the onboard unit emits a signal with a known frequency curve over time, the method comprising: receiving the signal by the other of the radio beacon and the onboard unit during the passing and recording the curve of the frequency of the received signal over time, wherein the recording of the frequency curve is started when the strength of the received signal exceeds a minimum threshold and is ended when the strength of the received signal falls below the minimum threshold; detecting a change in the recorded frequency curve exceeding a first threshold value; determining two far regions in the recorded frequency curve lying before and after the detected change in time that show a frequency change below a second threshold value; scaling the recorded frequency curve in such a manner that the far regions assume predetermined values; and determining said distance from the scaled frequency curve.