DE102009014975A1 - Method for remotely controlling access and/or start-up operation of motor vehicle, involves performing verification of authorization to access and/or start-up operation of vehicle based on coded communication and ultrasonic signal - Google Patents

Abstract

The method involves locating a quasi-stationary controller (2) in a vehicle (1). Radio signals (4, 6) are transferred between the controller and a mobile transponder (5) via a wireless connection in a direction. An ultrasonic signal (11) is transferred between the controller and the mobile transponder via an ultrasonic connection in another direction. Verification of authorization to access and/or a start-up operation of the vehicle is performed based on coded communication via the wireless connection and the ultrasonic signal.

Description

The The invention relates to a method for remotely controlling a vehicle access and / or vehicle starts.

In a variety of vehicles, especially motor vehicles, is already today a multiplicity of functions over mobile, carried by users transponder triggered or controlled. This is what is called a modern vehicle PASS system used. PASS stands for PAsive Start and Entry and describes a keyless Access and start system. In this keyless vehicle access system the driver only needs an identification transmitter (transponder) carry with them. Transponders are communication arrangements that record incoming signals and answer automatically. The transfer Of signals to and from transponders is usually done wirelessly from and to one or more corresponding broadcast and Receiving units.

Such Transmitting and receiving units can while stationary, for example, on a building, or quasi-stationary, for example in an airplane, a watercraft or a Be arranged motor vehicle. The quasi-stationary transmitting and receiving units search through Cyclic or event-controlled transmission of transponder excitation signals in the low frequency range after the presence of associated transponders and an authorized user gains access to the vehicle when he is in the range of low-frequency signals one or several quasi-stationary, im and / or arranged on the vehicle transmitting and receiving units. The transponder typically responds to a received low frequency signal with a radio frequency response signal, the coded information, For example, the access authorization to the vehicle may have. By using low-frequency signals with certain Levels between the transmitting and receiving units and associated transponders while the range is limited for security reasons so that an activation of a passive access and start system from greater distances not possible is.

It However, there is the possibility For vehicles with passive entry and exit systems, this range limitation too bypass, by the emitted from the vehicle to the transponder low-frequency Signal over recorded a mobile transmitting and receiving unit and transmitted via further transmission and receiving units (relay stations) over long distances and is sent out. This procedure is also called as Suited case attack, in which a transponder also to Transmission of a high-frequency radio response signal is excited, if he is not in the specified proximity to the transmitting and receiving units of the vehicle. As a result, the originally specified range limitation of the canceled low frequency signal, and the response signals of the transponder over the relay stations transferred back to the vehicle become. In this way, it becomes possible for the vehicle to be opened or started can be without putting the associated transponder near the vehicle located.

task The present invention is a method for remote control indicate the vehicle access and / or vehicle start, in which the mentioned disadvantages are avoided.

The Task is solved by a method for remotely controlling vehicle access and / or vehicle startup according to claim 1. refinements and developments of the inventive concept are the subject of dependent claims.

The Task is solved in particular by a method of accessing the vehicle and / or starting the vehicle between a quasi-stationary control unit located in the vehicle and a mobile transponder over a common radio link in at least one direction radio signals and over a common ultrasonic connection in at least one direction Transmit ultrasonic signals become. This is done by evaluating the transit time of the ultrasonic signals determines the distance between the vehicle and the mobile transponder and an exam Authorization for vehicle access and / or vehicle start based on coded communication via the radio connection and carried out on the basis of the determined distance.

The Invention will be described below with reference to the figures in the drawings illustrated embodiments explained in more detail, wherein the same elements are provided with the same reference numerals. It shows:

1 in a schematic diagram a passive access and start system in case of circumvention of the range limitation;

2 in a schematic diagram of an inventive passive access and start system;

3 in a diagram schematically the waveform of an acoustic signal (ultrasonic signal) and a high-frequency electromagnetic signal (radio signal), which are transmitted successively for transit time measurement;

4 in a diagram schematically the Waveform of a low-frequency electromagnetic signal (radio signal) and an acoustic signal (ultrasonic signal), which are transmitted successively for transit time measurement;

5 in a diagram schematically the waveform of an electromagnetic signal (radio signal) and an acoustic signal (ultrasonic signal), which are transmitted simultaneously for transit time measurement; and

6 in a diagram schematically the design of ultrasonic signals with changing transmission direction.

1 shows in a block diagram an arrangement of a passive entry and start system according to the prior art with a vehicle 1 and a mobile transponder 5 , The vehicle 1 has a controller 2 , a transmitting antenna 3 for low frequency radio signals 4 and a receiving antenna 7 for high-frequency radio signals 6 on. The transmitting antenna 3 and the receiving antenna 7 are electrically connected to the control unit 2 connected. The control unit 2 sends over the transmitting antenna 3 a low frequency radio signal 4 certain (border) range.

The (border) range of the low-frequency radio signal 4 (Frequency for example <1 MHz, in particular <200 kHz range) is, for example, by the level of the radio signal and the transmission characteristic of the transmitting antenna 3 established. The transmitting antenna 3 For example, in the door handle of the vehicle 1 be arranged. For safety reasons, the range is limited so that direct operation of the passive entry and start system over long distances is not possible.

In a passive access and start system are low frequency radio signals 4 periodically (or event-driven) for the presence of a mobile transponder 5 in the range of action of the low-frequency radio signal 4 to search. Is the transponder located? 5 in the range of action of the low-frequency radio signal 4 and receives this, he answers the low-frequency radio signal 4 with a high-frequency radio signal 6 Frequency range for example> 1 MHz, in particular> 100 MHz). This high frequency radio signal 6 is via the receiving antenna 7 received and for review and / or processing to the controller 2 forwarded. Through the radio signals 4 and 6 is between the controller 2 and the mobile transponder 5 as described a radio link formed.

This shows the high-frequency radio signal 6 Usually a unique coded information, which is an authentication of the mobile transponder 5 through the control unit 2 allows. This will determine if the transponder 5 a for the vehicle access and / or vehicle start of the vehicle 1 authorized transponder. If this is the case, the vehicle access and / or vehicle start by the control unit 2 or one to the controller 2 Downstream immobilizer (not shown) released or enabled. In this case, such an immobilizer and in the control unit 2 be integrated.

1 also shows how the range limitation of the low frequency radio signal can be undesirably bypassed. An example of this is a relay station 8th and a relay station 9 intended. The number of relay stations used to circumvent the range limitation is arbitrary and depends, for example, on the distance over which unauthorized access to the vehicle 1 or whose launch is to be achieved. At least one relay station (here, for example, relay station 8th ) is in the range of the transmitting antenna 3 arranged. The over the transmitting antenna 3 emitted low frequency radio signal 4 is from the relay station 8th received and over a radio link 10 to the relay station 9 transfer. The by the radio connection 10 bridged distance can be a multiple of the original range of the low-frequency radio signal 4 be, where more than two relay stations can be used to He extension of the bridged distance. The radio connection 10 is typically designed as a high-frequency radio link with corresponding transmitting and receiving units, via which the information of the intercepted low-frequency radio signal 4 is forwarded.

The relay station 9 usually becomes inconspicuous near the mobile transponder 5 positioned. The relay station 9 can be arranged for example in a discreetly parked suitcase. Such an undesirable circumvention of the range limitation of a passive entry and start system for a vehicle is therefore often referred to as a suitcase attack. From the over the radio range 10 received information forms the relay station 9 the low frequency radio signal 4 after, that from the mobile transponder 5 can be received when it is within range of the relay station 9 located.

The mobile transponder 5 is in turn by the received low-frequency radio signal for transmitting the high-frequency radio signal 6 stimulated (see also 1 ), from the relay station 9 received and over the radio link 10 to the relay station 8th is transmitted. In a suitcase attack of sufficiently short range that would high-frequency signal even not be extended if the range of the identification transmitter (for example, 10-80 meters) is already sufficient. The relay station 8th sends the high frequency radio signal 6 in turn, so this over the receiving antenna 7 from the control unit 2 Will be received. The control unit 2 recognizes the received signal 6 as the valid, coded radio signal of the transponder 5 and allows vehicle access and / or vehicle launch, although the mobile transponder 5 actually at a great distance to the vehicle 1 located. That way, the vehicle can 1 without triggering an alarm unnoticed by a remote user of the mobile transponder 5 unlocked and / or stolen.

• – Variationen des Trägersignals des niederfrequenten Funksignals 4 und/oder des hochfrequenten Funksignals 6. Nachteilig wirkt sich dabei aus, dass diese Variationen des Trägersignals wirkungslos sind, wenn in den Relais-Stationen analoge Verstärkerstufen verwendet werden.
• – Laufzeitmessung des hochfrequenten Funksignals 6.
• Nachteilig wirkt sich dabei aus, dass solche Laufzeitmessungen eine sehr aufwendige Messtechnik im Steuergerät 2 und/oder im mobilen Transponder 5 erfordern.
• – Triangulation durch Messung der Signalstärke des niederfrequenten Funksignals 4 über mehrere Sendeantennen 3. Nachteilig wirkt sich dabei aus, dass dies eine bestimmte Antennenanordnung der Sendeantennen 3 am Fahrzeug 1 und eine aufwendige Messtechnik erfordert.
• – Periodische Authentifizierung des mobilen Transponders 5 während des Fahrbetriebs. Nachteilig wirkt sich dabei aus, dass dies einen unberechtigten Fahrzeugzugang und/oder Fahrzeugstart nicht verhindert und darüber hinaus zu unsicheren Situationen im Fahrbetrieb führen kann, wenn der mobile Transponder 5 nicht gefunden wird (nicht antwortet).
• – Gleichzeitige Messung von physikalischen Größen, wie zum Beispiel dem Erdmagnetfeld, im mobilen Transponder 5 und im Fahrzeug 1 und nachfolgender Vergleich im Steuergerät 2. Nachteilig wirkt sich dabei aus, dass nur wenige physikalische Größen geeignet beziehungsweise nur mit erheblichem technischem Aufwand messbar sind.

To the described circumvention of the range limitation of the low frequency radio signal 4 To prevent, the methods described below have been used each alone or in any combination with each other:

• - Variations of the carrier signal of the low frequency radio signal 4 and / or the radio frequency signal 6 , The disadvantage here is that these variations of the carrier signal are ineffective if analog amplifier stages are used in the relay stations.
• - Runtime measurement of the high-frequency radio signal 6 ,
• A disadvantage is that such transit time measurements a very expensive measurement in the control unit 2 and / or in the mobile transponder 5 require.
• - Triangulation by measuring the signal strength of the low-frequency radio signal 4 over several transmit antennas 3 , The disadvantage here is that this is a specific antenna arrangement of the transmitting antennas 3 at the vehicle 1 and requires a complicated measuring technique.
• - Periodic authentication of the mobile transponder 5 while driving. A disadvantage has the effect that this does not prevent unauthorized vehicle access and / or vehicle start and beyond can lead to unsafe situations when driving when the mobile transponder 5 not found (does not answer).
• Simultaneous measurement of physical quantities, such as the Earth's magnetic field, in the mobile transponder 5 and in the vehicle 1 and subsequent comparison in the control unit 2 , A disadvantage is that only a few physical variables are suitable or measurable only with considerable technical effort.

2 shows in a block diagram a passive entry and starting system according to the invention with a vehicle 1 and a mobile transponder 5 , As in 1 points the vehicle 1 turn a control unit 2 , a transmitting antenna 3 for low frequency radio signals 4 and a receiving antenna 7 for high-frequency radio signals 6 on. The transmitting antenna 3 and the receiving antenna 7 are electrically connected to the control unit 2 connected. The control unit 2 sends over the transmitting antenna 3 a low frequency radio signal 4 certain range.

The specific range of the low-frequency radio signal 4 in turn is due to the level of the radio signal and the transmission characteristic of the transmitting antenna 3 certainly. The transmitting antenna 3 For example, in the door handle of the vehicle 1 be arranged. For safety reasons, the (limit) range is chosen so that direct operation of the passive entry and start system over longer distances is not possible.

The low frequency radio signals 4 are in turn periodically (or event-driven) sent to the presence of a mobile transponder 5 in the range of action of the low-frequency radio signal 4 to search. Is the mobile transponder located? 5 in the range of action of the low-frequency radio signal 4 and receives this, he answers the low-frequency radio signal 4 with a high-frequency radio signal 6 , This high frequency radio signal 6 is via the receiving antenna 7 received and for review and / or processing to the controller 2 forwarded. Through the radio signals 4 and 6 becomes the radio connection between control unit 2 and mobile transponder 5 educated.

• a) den zeitlichen Abstand zum Aussenden des niederfrequenten Funksignals 4 oder den zeitlichen Abstand zum Empfang des hochfrequenten Funksignals 6, und/oder
• b) den Dateninhalt (Kodierung), und/oder
• c) den Lautstärkepegel, und/oder
• d) die Frequenz, und/oder
• e) die Phasenlage des Ultraschallsignals 11 bezogen auf das niederfrequente Funksignal 4.

It contains the high-frequency radio signal 6 usually a unique coded information, the authentication of the mobile transponder 5 through the control unit 2 allows. This will determine if the transponder 5 a for the vehicle access and / or vehicle start of the vehicle 1 authorized transponder. In addition to the system after 1 points the vehicle 1 an ultrasonic transducer 12 on, which can be configured as a transmitter and / or receiver. Receives the mobile transponder 5 a low frequency radio signal 4 , it transmits immediately or at a certain time interval to the high-frequency radio signal 6 a coded ultrasonic signal 11 via a corresponding integrated ultrasonic transducer 18 out. This signal is from the ultrasonic transducer 12 received and sent to the control unit 2 forwarded. The control unit 2 evaluates the ultrasonic signal 11 with respect to the following parameters:

• a) the time interval for transmitting the low-frequency radio signal 4 or the time interval to the reception of the high-frequency radio signal 6 , and or
• b) the data content (coding), and / or
• c) the volume level, and / or
• d) the frequency, and / or
• e) the phase position of the ultrasonic signal 11 based on the low frequency radio signal 4 ,

Already by the parallel to communication via the radio signals 4 and 6 Successful transmission of the ultrasonic signal 11 the attack threshold is compared to the embodiment according to 1 significantly increased because the relay stations would also need to be equipped with suitable ultrasound receivers and transmitters to transmit ultrasonic signals between vehicle 1 and mobile transponder 5 transferred to. In addition, it is technically possible with relatively little effort, the transit time difference between the signals, as electro-magnetic radio signals 4 and 6 or as an acoustic signal, ie as an ultrasonic signal 11 be transmitted to measure. The difference in terms is approximately 1:10 ⁶ . At a spatial distance of 1 meter, for example, results in a transit time difference of 3 msec between an electromagnetic and an acoustic signal, which were sent simultaneously.

3 to 5 show waveforms (amplitude A over time t) low-frequency or high-frequency electromagnetic signals (radio signals 4 . 6 ) and an acoustic signal (ultrasonic signal 11 ), for the transit time measurement by means of transit time difference 14 between the electromagnetic signal (radio signals 4 . 6 ) and the acoustic signal (ultrasonic signal 11 ) are transmitted successively or simultaneously. It can, for example, between a parallel sequence (see. 5 ), where ultrasonic signal 11 and radio signal 4 or 6 overlapping, ie at least temporarily transmitted simultaneously, and a serial sequence (see. 3 and 4 ), where the ultrasonic signal before the radio signal (see. 3 ) or vice versa (cf. 4 ) if necessary, with the inclusion of delays in the signal change will be distinguished. As a radio signal come the low-frequency ( 4 ) and the high-frequency ( 6 ) Radio signal in each case and in combination with each other in question, wherein the transmission directions of the ultrasonic signal and radio signal can be arbitrary on their own or in combination with each other and include any possible combination.

The transit time difference 14 results from the different propagation speeds of radio and ultrasonic signals, possibly taking into account an optional specific time interval of these signals when transmitting. In this way, the controller 2 too large distances between the mobile transponder 5 and the vehicle 1 , as they are to be expected in the described suitcase attack due to the extended transmission link, recognize and lock ent speaking vehicle function and / or trigger an alarm.

The receiving unit (here the control unit 2 ) from the measured time difference between the arrival of radio signal 6 and ultrasonic signal 11 the distance between the mobile transponder 5 and vehicle 1 and correlate these with the measured acoustic level. If these values do not match, for example, a too high volume level at a long distance (runtime difference 14 ), selected vehicle functions can also be disabled.

The evaluation of the phase position of the ultrasonic signal 11 based on the low frequency radio signal 4 or high-frequency radio signal 6 also allows to detect if any additional filters were connected in the transmission link. Since relay stations typically have to use low-pass or band-pass filters to suppress noise, the phase of the relayed ultrasonic signal becomes 11 changed significantly. This may be the receiving unit, for example the controller 2 , by comparison with the phase of the low-frequency radio signal 4 determine.

This is also possible if the phase position of the low-frequency radio signal 4 by extending the range of the relay stations changes, because the different filters and the different frequencies of the two signals result in different phase shifts for the acoustic and the electromagnetic signal.

If an unwanted signal manipulation is detected via the evaluation of one or more of the signal parameters listed above under a) to e), the vehicle access and / or vehicle start is, for example, by the control unit 2 or one to the controller 2 Downstream immobilizer (not ge shows) not released or not possible. In addition, for example, an audible alarm can be triggered.

In a further development of the arrangement according to 2 is, for example, the transmission direction of the ultrasonic signal 11 such that in the vehicle 1 one or more ultrasonic transmitters are arranged with the control unit 2 are connected. The mobile transponder 5 has in this case an ultrasonic receiver. The vehicle-side ultrasonic transmitter, for example, in a warning buzzer for outdoor use (see ultrasonic transmitter 12 ) or in an alarm system for the interior (eg 13 ) or be formed by them. In this case, the vehicle sends 1 the ultrasonic signal 11 (for example via the ultrasound transmitter 12 ) simultaneously with or offset in time from the low-frequency radio signal 4 out.

In this variant evaluates the mobile transponder 5 the received signal with respect to the above parameters a) to e). The advantage of this embodiment is that in the mobile transponder 5 used battery is less loaded than in the first variant, in which by the mobile transponder 5 the ultrasonic signal 11 must be sent. According to the invention, the vehicle 1 Furthermore, in the low-frequency radio signal (encoded) specify certain parameters for the ultrasound communication, such as the data content, the transmission level, the frequency, etc. These parameters can also at fixed intervals or for each communication between transponders 5 and control unit 2 be changed, making an attack even more difficult.

In a further embodiment of the arrangement according to 2 are both the vehicle 1 as well as the mobile transponder 5 equipped with ultrasonic transmitters and receivers. In this way, a bidirectional ultrasonic connection is formed, via which both ultrasonic signals 11 from the vehicle 1 to the mobile transponder 5 as well as from the mobile transponder 5 to the vehicle 1 can be sent. Both units can thus the described test of the ultrasonic signals 11 make. In this third variant, it is also possible that the vehicle 1 by appropriate information in the radio signal 4 specifies the transmission direction for the ultrasound communication.

The transmission direction of the ultrasonic signals 11 between vehicle 1 and mobile transponder 5 can also be changed several times. Since an attacker does not know which transmission direction has been selected or when the transmission direction changes, the relay stations used for range extension (see 1 ) always be designed for simultaneous transmission and reception. In such a constellation, acoustic feedbacks between the relay station and the transmitters or the receivers of the vehicle can easily occur 1 and mobile transponder 5 result, which would have to be technically elaborate recognized and damped. An unwanted range extension of the signals 4 . 6 and 11 Relay stations make it even more difficult in this way.

6 shows in a diagram schematically an example of the design of ultrasonic signals 11 with changing transmission direction. It is indicated by the arrows in 5 the respective current transmission direction called. The transmission direction 15 may be sending the ultrasonic signal 11 from the vehicle 1 to the mobile transponder 5 denote and the transmission direction 16 may be sending the ultrasonic signal 11 from the mobile transponder 5 to the vehicle 1 denote or vice versa.

A respective change of the transmission direction 15 . 16 is indicated by the vertical dashed lines. In addition, for example, as shown, the transmission level 17 of the ultrasonic signal 11 be changed in the course of each individual signal transmission, for example, starting from a certain (variable) output level linearly to a lower level 17 or the other way around. Also a lowering and again rising of the transmission level 17 in the course of a single signal transmission or vice versa as well as various other variations (for example, sinusoidal course of the transmission level 17 with an overall decreasing or increasing average level) are possible. Likewise, the signal sequence of ultrasonic signal and radio signals) is arbitrary.

Finally, for generating and / or receiving the ultrasonic signal 11 in the vehicle 1 as a sound transducer 13 a sound transducer is used, which is part of the interior monitoring (by means of ultrasound) and thus part of the alarm system. Furthermore, also for generating and / or for receiving the ultrasonic signal 11 in the transponder 5 a sound transducer 18 can be used, which is already used as an acoustic signal transmitter (for example, as a so-called beeper) in the listening area (20-20000 Hz).

1

vehicle

2

control unit

3

transmitting antenna

4

radio signal

5

transponder

6

radio signal

7

receiving antenna

8th

Relay station

9

Relay station

10

radio link

11

ultrasonic signal

12

transducer (Ultrasonic transmitter and / or receiver)

13

transducer (Ultrasonic transmitter and / or receiver)

14

Time difference

15

send direction

16

send direction

17

transmission level

18

transducer (Ultrasonic transmitter and / or receiver)

Claims (24)

Method for remotely controlling a vehicle access and / or vehicle start with a vehicle ( 1 ) quasi-stationary tax device ( 2 ) and a mobile transponder ( 5 ), between which via a radio link in at least one direction a radio signal ( 4 . 6 ) and via an ultrasonic connection in at least one direction an ultrasonic signal ( 11 ), wherein a check of the authorization for vehicle access and / or vehicle start based on coded communication via the radio link and on the basis of the ultrasonic signal ( 11 ) he follows. Method according to Claim 1, in which by evaluating the transit time of the ultrasound signal ( 11 ) the distance between the vehicle and the mobile transponder is determined and a check of the authorization for vehicle access and / or vehicle start based on the coded communication via the radio link and on the basis of the determined distance takes place. Method according to Claim 1 or 2, in which the quasi-stationary control device transmits a first radio signal ( 4 ) to the mobile transponder ( 5 ) and the mobile transponder in response sends a second radio signal ( 6 ) and an ultrasonic signal ( 11 ) to the quasi-stationary control unit ( 2 ) sends. Method according to Claim 3, in which the response upon receipt of the first radio signal ( 4 ) immediately or at a certain time interval. Method according to one of Claims 1 to 4, in which the quasi-stationary control device ( 2 ) a first radio signal ( 4 ) and an ultrasonic signal ( 11 ) to the mobile transponder ( 5 ) and the mobile transponder ( 5 ) in response a radio signal ( 6 ) to the quasi-stationary control unit ( 2 ) sends. Method according to one of Claims 1 to 4, in which the quasi-stationary control device ( 2 ) a first radio signal ( 4 ) and an ultrasonic signal ( 11 ) to the mobile transponder ( 5 ) and the mobile transponder ( 5 ) in response a radio signal ( 6 ) and ultrasonic signals ( 11 ) to the quasi-stationary control unit ( 2 ) sends. Method according to Claim 5 or 6, in which the response upon receipt of the ultrasound signals ( 11 ) immediately or at a certain time interval. Method according to one of Claims 5 to 7, in which the quasi-stationary control unit transmits the ultrasonic signals ( 11 ) simultaneously or at a certain time interval to the transmission of the radio signals ( 6 ) sends. Method according to one of Claims 3, 4, 6, 7 or 8, in which the mobile transponder transmits the ultrasonic signals ( 11 ) simultaneously or at a certain time interval to the transmission of the radio signals ( 6 ) sends. Method according to one of Claims 1 to 9, in which the evaluation of the transit time of the ultrasonic signals ( 11 ) by the control unit ( 2 ) he follows. Method according to one of Claims 5 to 8, in which the evaluation of the transit time of the ultrasound signal ( 11 ) by the mobile transponder ( 5 ) he follows. Method according to one of Claims 1 to 11, in which the ultrasonic signal ( 11 ) is evaluated with regard to its data content and / or its level and / or its frequency. Method according to one of claims 3, 4, 6, 7, 8, 9 or 12, in which by corresponding in the received radio signals ( 4 . 6 ) transmitted variable parameters a data content and / or a level and / or a frequency for the transmitted ultrasonic signals ( 11 ). Method according to one of Claims 1 to 13, in which the radio signals ( 4 . 6 ) and the ultrasonic signals ( 11 ) are transmitted several times. The method of claim 14, wherein the variable Parameters changed several times become. Method according to one of claims 14 or 15, wherein in each case only in one direction ultrasonic signals ( 11 ) and the transmission direction of the ultrasonic signals ( 11 ) is changed several times. Method according to one of Claims 1 to 16, in which the level of the ultrasonic signals ( 11 ) is varied in the course of a single transmission. Method according to one of Claims 1 to 17, in which the phase angles of the radio signals ( 4 . 6 ) and the ultrasonic signals ( 11 ) are evaluated to each other. Method according to one of Claims 1 to 18, in which the signal from the quasi-stationary control unit ( 2 ) to the mobile transponder ( 5 ) transmitted signal is a low-frequency radio signal with a certain range. Method according to one of claims 1 to 19, in which that of the mobile transponder ( 5 ) to the quasi-stationary control unit ( 2 ) transmitted signal a high-frequency radio signal ( 6 ), which carries a unique coded information for the authorization check of the mobile transponder ( 5 ) for the vehicle access and / or vehicle start by the control unit ( 2 ). Method according to one of Claims 1 to 20, in which the authorization for vehicle access and / or vehicle start is not granted if the determined distance between the vehicle and the mobile transponder ( 5 ) is greater than a predetermined limit. Method according to one of Claims 1 to 20, in which the authorization for vehicle access and / or vehicle start is not granted if the level and / or the frequency of the received ultrasound signals ( 11 ) is greater or smaller than predetermined limits and / or a phase shift of the radio signals and the ultrasonic signals ( 11 ) is greater than a predetermined limit value. Method according to one of the preceding claims, that for generating and / or receiving the ultrasonic signal ( 11 ) in the vehicle ( 1 ) a sound transducer ( 13 ), which is part of the interior monitoring. Method according to one of the preceding claims, that for generating and / or receiving the ultrasonic signal ( 11 ) in the transponder ( 5 ) a sound transducer ( 18 ) is used, which is provided as an acoustic signal transmitter in the listening area.