Communications: electrical – Selective – Intelligence comparison for controlling
Reexamination Certificate
2001-04-12
2004-10-12
Horabik, Michael (Department: 2635)
Communications: electrical
Selective
Intelligence comparison for controlling
C340S005640, C340S870030
Reexamination Certificate
active
06803851
ABSTRACT:
TECHNICAL FIELD
The invention pertains to the field of carrying out keyless access authorization control for checking, for example, whether a person is authorized to perform a certain action, such as opening a vehicle door. In particular, the invention pertains to a method for carrying out keyless access authorization control by means of wireless communication between a transceiver unit corresponding to a base station and a mobile identification transmitter (ID transmitter) in order to check the access authorization of the person carrying the ID transmitter. The method includes: transmitting a code signal from the transceiver unit of the base station, receiving this code signal by the ID transmitter, carrying out an action that can be detected by the transceiver unit and that is executed by the ID transmitter at the receipt of the code signal as a reply signal of the ID transmitter, and detecting the action of the ID transmitter and determining the distance between the base station and the ID transmitter.
The invention also pertains to a keyless access authorization control device with a base station featuring a transceiver unit as well as a control and evaluation element and a mobile identification transmitter (ID transmitter) featuring a transceiver unit for checking the access authorization of the person carrying the ID transmitter. This base station can calculate the distance from the base station to the ID transmitter.
BACKGROUND ART
Keyless locking systems are used in numerous applications, for example, in vehicles to increase user convenience. Conventionally, infrared and radio systems are used as remote-control systems wherein the authorized user activates the ID transmitter in order to transmit a signal to the base station, for example, to a receiver unit in a vehicle for opening the vehicle. To further increase user convenience, passive access authorization control systems can be used as the user passes between vehicles, so that an authorized user carrying a valid ID transmitter can open his vehicle without having to actively turn on the ID transmitter. Such a keyless access authorization control device is described, for example, in DE 43 29 697 C2. In the method disclosed in this document, a code signal is transmitted from a transceiver unit in a vehicle, and this signal is received by the ID transmitter when the transmitter is within the reception area of this signal. Then, a reply signal is sent back from the ID transmitter due to the action triggered by the receipt of the code signal. The validity of the reply signal is checked after it is received by the receiver unit of the vehicle. The receipt of a valid reply signal triggers the desired action in the vehicle, namely unlocking the vehicle doors. This passive system is problematic in that the transmission path between the base station and the ID transmitter can be extended by simple means that are unauthorized and unnoticeable to the authorized user. In this way, an unauthorized person can establish radio connection between the transceiver unit of the vehicle and the ID transmitter authorized for opening, even if the latter is not within the reception area of the request signal. Thus, the unauthorized person can gain unknown entry to the vehicle.
The object of DE 196 32 025 A1 addresses this problem. In the keyless access authorization control device described in this document, detection of the propagation time relative to the transmitted request signal and the received reply signal is carried out, in which the corresponding time span required by the transmitted code signal to be transmitted from a base station and then received as a reply signal is calculated. If the transmission path has been lengthened, then the time interval from the transmission of the code signal to the receipt of the reply signal is naturally greater than when the ID transmitter is definitely in the direct vehicle proximity and the corresponding return radio path is short. If the calculated signal propagation time exceeds a predefined value, the access authorization control method is stopped in order to prevent unauthorized entry.
In order to carry out the access authorization control method described in this document, it is necessary to detect the signal propagation time with high accuracy. Communication between the transceiver unit and the mobile ID transmitter is typically within a very limited area around the base station: for vehicles, an area between 5 and 10 m e.g. The propagation time of an ordinary transmitted and received signal within this distance is between 16.5 ns and 33 ns. The detection of such short time spans, in particular with the desired resolution, is only possible with significant expense, an expense that is not justifiable for numerous applications, for example, for a vehicle.
SUMMARY OF THE INVENTION
Starting with the previously discussed prior art, the task of the invention is based on proposing such a method for carrying out keyless access authorization control that not only features sufficient security relative to the possibility of detecting a manipulated path extension, but that can also be realized with the use of simple means.
The task of the invention is also based on proposing such a keyless access authorization control device that can detect a (manipulated) path extension with the use of justifiable means.
The task related to the method is solved according to the invention in that the distance determination is done based on a relative determination, in which the difference of a distance-dependent signal characteristic correlated with the signal propagation time between a reference code signal monitored in the base station and the reply signal received by the transceiver is evaluated.
The knowledge of the claimed invention is based on the fact that it is possible to determine distance with sufficient resolution over indirect paths by detecting a signal value correlated with the propagation time of a signal using simple means. In contrast to the previously known method, this distance determination is done by means of a relative determination, in which a reference code signal is monitored in the base station with reference to the transmitted signal characteristic and the signal characteristic of this reference code signal is compared with the signal characteristic of the reply signal returned by the ID transmitter and received by the transceiver unit. The distance-dependent signal characteristic to be compared with the reference code signal gives information about the return path of the code signal and reply signal when compared with the corresponding reference code signal. In this way, the reference code signal, for example, the transmitted code signal, can be monitored during the transmission period of the code signal by the base station. The detection by the base station of the actions executed by the ID transmitter is limited by the measurement time distance. These actions can be, for example, the return transmission of the code signal received by the ID transmitter. The actions executed by the ID transmitter can also be other actions that can be detected by the base station, such as the shutdown of a transmitter and thus the detection by the base station of the time when such a transmitter is turned off by the ID transmitter. The use of hardware to carry out such a relative distance determination is very minimal in comparison with that required to carry out an absolute propagation time measurement. Depending on the method used, numerous evaluation steps can also be eliminated during data processing.
Starting with the background of this embodiment and the description of the invention, either the delay times by the circuit elements used are much shorter relative to the actual signal propagation time or they are known, or they are calculated and taken into consideration in the evaluation.
To carry out such a relative distance determination, different signal characteristics can be used. For example, counting the cycles of the carrier wave of the transmitted code signal over a time period until, for examp
Fromm Michael
Kramer Detlev
Pretzlaff Volker
Raab Peter
Vens Rainer
Brooks & Kushman P.C.
Horabik Michael
Leopold Kostal GmbH & Co. KG
Nguyen Nam
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