Data communication system

0001The invention relates to a system with system components, between which a data transfer takes place, and a method for controlling such a system, in particular when recording the data transfer.

0002A typical system of the type specified is a cordless telephone, as is explained, for example, in the essay "Cordless Telephone Sinus 11" in instruction sheets vol. 45 4/1992, pages 132-143. A cordless telephone consists of two components, namely a base station and a battery-operated handset. These are each equipped with a transmitter and a receiver for mutual communication. If no telephone call is made, parts of both components are switched to an energy-saving sleep mode. However, the receivers remain active in order to be able to determine when the other component is asked to establish a connection. The handheld receiver that is kept ready to receive limits its operating time with one battery charge.

0003Other systems of the type specified above are proximity-sensitive systems for automatic wireless identification of people and vehicles, for example in the context of traffic control systems, in toll collection or in the access control of people and vehicles to secure rooms. With access control, they can replace purely mechanical locking systems. Examples are disclosed in DE-A-41 11 582, DE-C-41 34 922 and DE-A-42 30 011.

0004These systems also contain two components, namely a base station and a transponder.

0005A wireless data exchange takes place between the two, which enables the base station to identify the transponder. With access control, the base station triggers the opening of a lock as soon as it identifies the transponder of an authorized person nearby.

0006Conventional systems of this type have the following disadvantages. Ideally, they should be proximity sensitive, ie they should be able to automatically start the data exchange as soon as the transponder approaches the base station without an operator having to intervene. This requires that both components are always on. The transponder is often only the size of a credit card or a key fob so that it can easily be carried anywhere. Therefore, it must be operated with tiny batteries that are exhausted after a short time in continuous operation.

0007In order to avoid this disadvantage, passively operated transponders are used which only return a certain echo of a signal emitted by the base station, or transponders have been proposed which take their operating energy from the signal emitted by the base station. These systems require powerful base stations that are large enough and consume a lot of power. In addition, they are not deceptive.

0008The invention has for its object to provide a system with low power consumption working with two system components between which a data transfer takes place. In addition, a method for operating such a system is to be made available.

0009This object is achieved with the method specified in claim 1 or the device specified in claim 8.

0010The invention is based on the consideration that the specified systems often only transmit a very small fraction of their total operating time. In an access control system, for example, an identification or access control protocol is often only processed a few seconds a day, namely when a person actually requests access. The invention makes it possible to keep the system in readiness for the rest of the time with minimal energy consumption and to switch to an active mode with both components (base station and transponder), if only one of them wishes to transmit data - for example because it is approaching of a person. During this readiness, a possibly existing receiving device of a first component can remain switched off and a receiving device of a second component only needs to be briefly activated periodically, ie switched on or set to full readiness for reception, and can otherwise be switched off or remain in an energy-saving sleep mode without readiness to receive. This is energy-saving, since receiving devices usually have a relatively high power consumption when activated. The current consumption is determined by the quiescent current in analog circuits, which are necessary for amplifying relatively weak received signals. When the readiness for reception is canceled, these analog circuits can be switched off, so that the quiescent current is very low.

0011The invention also makes it possible to greatly reduce the transmission powers required for the transmission of an activation signal or for data transmission and thus to achieve a further energy saving effect, since powerful reception devices can be used without adversely affecting the energy consumption, since they only last for very short times are switched on.

0012The signal transmissions between the system components are preferably carried out wirelessly by means of electromagnetic waves, light waves (for example infrared light) or by means of ultrasound.

0013The subclaims relate to advantageous embodiments of the invention.

0014The embodiment according to claim 2 represents an access control system which enables particularly simple detection of whether data transmission is desired. The switch can be operated manually or automatically by the person requesting access.

0015The embodiment according to claim 3 has increased ease of use, since it enables a contactless, proximity-sensitive activation of the system. The special embodiment according to claim 4 leads to a reduced energy consumption when determining whether there is a need for data transmission.

0016The embodiment according to claim 5 also contributes to low energy consumption, since the receiving device of the first component is only switched on when this is necessary.

0017Claims 6 and 7 relate to advantageous applications of the invention.

0018Preferred embodiments of the invention are shown in the drawings, in which<ul id="ul0001" list-style="none" compact="compact"><li>Figure 1 shows schematically an approach-sensitive control system, and</li><li>Figures 2 and 3 flow diagrams for the operation of such a system</li></ul> represent.

00191 has a base station 1 and a transponder 2. The base station 1 is suitable for replacing conventional mechanical locks. The transponder 2 is mobile and, when approaching the base station 1, causes it to give access to a secure room, for example to open a door electromagnetically.

0020Base station 1 and transponder 2 are each provided with a transmitter 3, 4 and a receiver 5, 6. These are each connected to a protocol controller 7, 8. The protocol controller 7 of the base station 1 communicates wirelessly with the protocol controller 8 of the transponder 2 via the transmitters 3, 4 and via the receivers 5, 6 in order to determine whether the transponder is assigned to an authorized person. For this purpose, base station and transponder-specific data are transmitted encrypted according to an identification or control protocol.

0021Base station 1 and transponder 2 are also each provided with a status control 9, 10, which are connected to the corresponding transmitters 3, 4, receivers 5, 6 and protocol controls 7, 8 in order to set different operating states.

0022Most of your operating time, base station 1 and transponder 2 remain under the influence of the respective status control 9, 10 in an energy-saving sleep mode. In this sleep mode, the transmitters 3, 4, the receivers 5, 6 and the protocol controls 7, 8 are switched off. Only the state controls 9, 10 remain active.

0023When the transponder 2 approaches the base station 1, either the base station or the transponder can initiate the activation of the system which leads to the processing of the control protocol. Accordingly, the status controls 9, 10 differ from one another. In the following, the system component (base station 1 or transponder 2) that initiates the activation is referred to as the “activating component” and the other system component (transponder 2 or base station 1) as the “component to be activated”.

0024The mode of operation of the activating component, controlled by the corresponding state control, is shown in FIG. 2.

0025In step 21, the status control firstly causes all system devices (transmitter, receiver, protocol control) of the activating component to be switched off in order to put it into sleep mode. Only the status control itself remains switched on. The activating system component remains under their control for a certain waiting time T_{sleep, Tx} in sleep mode (step 22).

0026After the waiting time has elapsed, the status control initiates a transition of the activating system component into a detector mode (step 23). In this mode, a device for detecting whether a system component to be activated is nearby is briefly switched on. If the activating system component represents the base station, it can be determined, for example, by means of an infrared detector, a radar detector, an ultrasound detector, a light barrier, an induction loop or a microphone, whether a person or a vehicle is approaching the base station could carry a transponder, or a key is queried that can be actuated automatically or manually by the approaching person.

0027In step 24, in the event that no system component to be activated can be in the vicinity, the process branches back to step 21 in order to return to sleep mode.

0028If, however, there is a high probability of a system component to be activated in the vicinity, for example because a person has been found in the vicinity, all system devices, but in any case the corresponding transmitter 3, 4 and receiver 5, 6 are switched on and an active mode is thus initiated ( Step 25).

0029An activation signal is then sent and a response signal (acknowledgment) is waited for by the system component to be activated (step 26).

0030If there is no acknowledgment, step 27 branches back to step 21 in order to bring the system component back into sleep mode. When a response signal is received, ie when a system component to be activated is actually in the vicinity, in step 28 the state control first triggers the processing of the control protocol and then returns to sleep mode.

0031The mode of operation of the system component to be activated, controlled by its state control, is shown in FIG. 3. Accordingly, all system devices except the associated status control are switched off in order to also put this system component into a sleep mode (step 31). The sleep mode is for a waiting time T_sleep.Rx maintained (step 32).

0032The system component is then brought into the detector mode in which the receiver 5, 6 is briefly switched on in order to check whether an activating system component sends an activation signal (step 33). If no activation signal was received, step 34 branches back to step 31 and the system component returns to sleep mode.

0033However, if an activation signal has been received, the system component switches to the active mode in which all system devices (transmitters 3, 4 and protocol control 7, 8) are switched on (step 35). In the active mode, a response signal is first sent as an acknowledgment to the activating component (step 36) and then the processing of the control protocol is started with it (step 37). After the control protocol has been processed, the system component to be activated also returns to sleep mode.

0034The longer the waiting time T, the lower the energy consumption of the system_sleep.Tx and T_sleep.Rx to get voted. If the waiting times are too long, there is a noticeable delay between the approach of the transponder to the base station and the activation of the system. Favorable values ​​are between 1/100 sec and 5 sec.

0035The duration of the activation signal should be the waiting time T_sleep.Rx by a small value so that the activation signal is reliably recognized in step 33.

0036Assuming that the system components generally return directly from the detector mode to the sleep mode and the energy consumption of the active mode can thus be neglected, the average power consumption of the activating system component is:<maths id="math0001" num=""><math display="block"><mrow><msub><mrow><mtext>P</mtext></mrow><mrow><mtext>Tx</mtext></mrow></msub><msub><mrow><mtext> = (P</mtext></mrow><mrow><mtext>sleep.Tx</mtext></mrow></msub><msub><mrow><mtext> * T</mtext></mrow><mrow><mtext>sleep.Tx</mtext></mrow></msub><msub><mrow><mtext> + P</mtext></mrow><mrow><mtext>detect.Tx</mtext></mrow></msub><msub><mrow><mtext> * T</mtext></mrow><mrow><mtext>detect.Tx</mtext></mrow></msub><msub><mrow><mtext>) / T</mtext></mrow><mrow><mtext>sleep.Tx</mtext></mrow></msub><msub><mrow><mtext> + T</mtext></mrow><mrow><mtext>detect.Tx</mtext></mrow></msub></mrow></math><img file="EP0744843A2_D0001.tif" /></maths> and the following applies to the power consumption of the system component to be activated:<maths id="math0002" num=""><math display="block"><mrow><msub><mrow><mtext>P</mtext></mrow><mrow><mtext>RX</mtext></mrow></msub><msub><mrow><mtext> = (P</mtext></mrow><mrow><mtext>sleep.RX</mtext></mrow></msub><msub><mrow><mtext> * T</mtext></mrow><mrow><mtext>sleep.RX</mtext></mrow></msub><msub><mrow><mtext> + P</mtext></mrow><mrow><mtext>detect.RX</mtext></mrow></msub><msub><mrow><mtext> * T</mtext></mrow><mrow><mtext>detect.RX</mtext></mrow></msub><msub><mrow><mtext>) / T</mtext></mrow><mrow><mtext>sleep.RX</mtext></mrow></msub><msub><mrow><mtext> + T</mtext></mrow><mrow><mtext>detect.RX</mtext></mrow></msub></mrow></math><img file="EP0744843A2_D0002.tif" /></maths> where P_sleep.Tx and P_sleep.Rx the power consumption of the activating system component and the system component to be activated in sleep mode, P_detect.Tx and P_detect.Rx the respective power consumption in detector mode and T_{detect, Tx} and T_detect.Rx represent the respective dwell times in detector mode before returning to sleep mode.

0037The waiting times in the sleep mode are advantageously about 100 to 1000 times longer than the dwell times in the detector mode. This approximately applies:<maths id="math0003" num=""><math display="block"><mrow><mtable><mtr><mtd><mrow><mtable><mtr><mtd><mrow><msub><mrow><mtext>P</mtext></mrow><mrow><mtext>Tx</mtext></mrow></msub><msub><mrow><mtext> = P</mtext></mrow><mrow><mtext>sleep.Tx</mtext></mrow></msub><msub><mrow><mtext> + P</mtext></mrow><mrow><mtext>detect.Tx</mtext></mrow></msub><msub><mrow><mtext> * T</mtext></mrow><mrow><mtext>detect.Tx</mtext></mrow></msub><msub><mrow><mtext>/ T</mtext></mrow><mrow><mtext>sleep.Tx</mtext></mrow></msub></mrow></mtd></mtr><mtr><mtd><mrow><msub><mrow><mtext>P</mtext></mrow><mrow><mtext>RX</mtext></mrow></msub><msub><mrow><mtext> = P</mtext></mrow><mrow><mtext>sleep.RX</mtext></mrow></msub><msub><mrow><mtext> + P</mtext></mrow><mrow><mtext>detect.RX</mtext></mrow></msub><msub><mrow><mtext> * T</mtext></mrow><mrow><mtext>detect.RX</mtext></mrow></msub><msub><mrow><mtext>/ T</mtext></mrow><mrow><mtext>sleep.RX,</mtext></mrow></msub></mrow></mtd></mtr></mtable></mrow></mtd></mtr></mtable></mrow></math><img file="EP0744843A2_D0003.tif" /></maths>

0038The average power consumption of the system is therefore essentially determined by the low power consumption of the sleep mode and a very small fraction of the power consumption of the detector mode.

0039In an exemplary embodiment already mentioned, the base station forms the activating system component and the transponder the activating system component. In the detector mode, the base station uses a proximity sensor to determine whether a person or a vehicle is approaching. If this is the case, the activation signal and the possibly received response signal (acknowledgment) are used to identify whether the person or the vehicle is also carrying a transponder. The access authorization is then verified when the control protocol is processed.

0040Advantageously, this embodiment can also be modified so that the base station in the detector mode does not (only) recognize the approach of a person or a vehicle, but directly the approach of a transponder. To do this, it emits a sensor signal and evaluates the echoes that are received back. Certain echoes are typical of transponders of this type. If the sensor signal consists, for example, of an electromagnetic pulse, then a transponder with non-linear reflection behavior can be recognized on the basis of harmonics in the echo signal. Such a transponder can have a ferromagnetic metal strip which is brought into the area of ​​saturation by the sensor signal, or a high-frequency or radar resonant circuit which is approximately matched to resonance with the sensor signal and to which a diode with a non-linear characteristic curve is added .

0041It is economical to use the transmitter 3, 4 and the receiver 5, 6 for transmitting the sensor signal and receiving the echo, which also serve to transmit the activation signal, the response signal and the data transmission according to the control protocol.

0042In another embodiment, the transition from sleep mode to detector mode does not automatically occur after a waiting time T_sleep.Tx but by manual operation of a switch or touch sensor. When used in apartment door locks, the switch or touch sensor is advantageously mounted in the door knob. Steps 22 and 23 from FIG. 2 are replaced by a step for recognizing the keystroke or touching a sensor.

0043In a further exemplary embodiment, the base station forms the system component to be activated and the transponder the activating system component. Pressing a button causes the transponder to exit sleep mode and to send an activation signal to the base station in accordance with step 26.

0044The two components of the system can also represent the base station and the handset of a radio telephone system, both of which initially work as described above for the system component to be activated. However, when a user starts a call from the handheld device, the handheld device sends out the activation signal and assumes the role of the activating system component. Conversely, the base station works by sending the activation signal as an activating system component as soon as it receives a phone call that is to be forwarded to the handset. Steps 28 and 37 of FIGS. 2 and 3 are always replaced by the transmission of a telephone call. Steps 22, 23 and 24 of FIG. 2nd are replaced by a step in which the activating component, if it represents the base station, detects a telephone call coming in from the exchange or, if it represents the handset, determines a key press with which the user indicates the start of a telephone call.