System for data transfer including a circuit for saving energy

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

0002A typical system of the type indicated is a cordless telephone as described, for example, in the essay "Cordless Telephone Sinus 11" in Jg. 45 4/1992, page 132 - 143 is explained. A cordless phone consists of two components, namely a base station and a battery-powered 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-efficient sleep mode. However, the receivers remain active in order to be able to determine when a connection is required by the other component. The receiver of the handset that is ready to receive limits its operating time with one battery charge.

0003Other systems of the type described above are proximity-sensitive systems for automatic wireless passenger and vehicle identification, for example in the context of traffic guidance systems, in toll collection or in the access control of people and vehicles to secured rooms. In 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 include two components, namely a base station and a transponder.

0005Between both a wireless data exchange takes place, which allows the base station to identify the transponder. In 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 record the data exchange as soon as the transponder approaches the base station without the intervention of an operator. This requires that both components are always on. The transponder is often just the size of a credit card or keyfob to be easily carried around. Therefore, it must be operated with tiny batteries that are exhausted in continuous operation after a short time.

0007To avoid this disadvantage, passively operated transponders are used, which merely reject a specific echo of a signal transmitted 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 which are correspondingly large and have a high power consumption. In addition, they are little foolproof.

0008The invention has for its object to provide a low power consuming system with two system components, between which a data transmission takes place. In addition, a method for operating such a system should be provided.

0009The solution of this object is achieved by 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 carry out a data transmission only a very small fraction of their total operating time. In an access control system, for example, often only a few seconds per day an identification or Access control protocol processed, namely, when a person actually requires access. The invention makes it possible to keep the system in standby with minimal energy consumption during the rest of the time and to jointly switch to an active mode with both components (base station and transponder), even if only one of them wishes to transfer data - for example, because they are approaching a person has noticed. 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 activated periodically for a short time, ie. H. switched on or be set to full readiness to receive and can otherwise be switched off or remain in an energy-saving sleep mode without readiness to receive. This is energy efficient, since receiving devices usually have a relatively high power consumption in the activated mode. The power consumption is determined by the quiescent current in analog circuits, which are necessary to amplify relatively weak received signals. When the reception readiness is canceled, these analog circuits can be switched off, so that the quiescent current is very low.

0011The invention furthermore makes it possible to greatly reduce the transmission powers necessary for the transmission of an activation signal or for the 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 are only for very short times are turned on.

0012The Signalüberträgungen between the system components is preferably carried out wirelessly by 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 allows a particularly simple detection of whether data transmission is desired. The switch can be operated manually or automatically by the person requiring access.

0015An increased ease of use, the embodiment according to claim 3, since it allows a non-contact, proximity-sensitive activation of the system. The particular embodiment of claim 4 results in reduced power consumption in determining whether there is a need for data transmission.

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

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

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

0019The proximity-sensitive control system according to FIG. 1 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 causes when approaching the base station 1, that this releases the access to a secure room, for example, a door opens electromagnetically.

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

0021Base station 1 and transponder 2 are also each provided with a state controller 9, 10 which are connected to the respective transmitters 3, 4, receivers 5, 6 and protocol controllers 7, 8 to set various operating conditions.

0022The majority of your operating time remain base station 1 and transponder 2 under the influence of the respective state control 9, 10 in an energy-efficient 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 controllers 9, 10 remain active.

0023When approaching the transponder 2 to the base station 1, either the base station or the transponder can now initiate the activation of the system leading to the execution of the control protocol. Accordingly, the state controllers 9, 10 are different from each other. In the following, that system component (base station 1 or transponder 2) which initiates the activation is referred to as "activating component" and the other system component (transponder 2 or base station 1) as "component to be activated".

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

0025In step 21, the state controller first causes all system devices (transmitter, receiver, protocol controller) of the enabling component to be turned off to put them into sleep mode. Only the state control itself remains switched on. The activating system component remains under its control for a certain waiting time T_{sleep, Tx} in sleep mode (step 22).

0026After expiration of the waiting time, the state controller causes a transition of the activating system component in a detector mode (step 23). In this mode, a device for detecting whether there is possibly a system component to be activated nearby is temporarily turned on. If the activating system component represents the base station, then, for example, by means of an infrared detector, a radar detector, an ultrasonic detector, a light barrier; an induction loop or a microphone are detected, whether a person or a vehicle approaches the base station, which could carry a transponder, or it is queried a button that can be operated automatically or manually by the approaching person.

0027In step 24, in the event that there is no system component to activate in the vicinity, it branches back to step 21 to return to sleep mode.

0028However, if there is a high probability of a system component to be activated in the vicinity, for example, because a person was festg estellt in the vicinity , all system devices, but in any case the corresponding transmitter 3, 4 and receiver 5, 6 are turned on and thus initiated an active mode (Step 25).

0029Then, an activation signal is sent and waits for a response signal (acknowledgment) by the system component to be activated (step 26).

0030If no acknowledgment, step 27 branches back to step 21 to bring the system component back into sleep mode. Upon receipt of a response signal, that is, when a system component to be activated is actually in the vicinity, the state control in step 28 first causes the execution of the control protocol and then the return to the sleep mode.

0031The operation of the system component to be activated controlled by its state control is shown in FIG. Thus, all system devices except the associated state controller are turned off to put this system component in a sleep mode as well (step 31). The sleep mode is for a waiting time T_sleep.Rx maintained (step 32).

0032Subsequently, the system component is brought into the detector mode in which the receiver 5, 6 is briefly turned on to check whether an activating system component sends an activation signal (step 33). If no activation signal has been received, then 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 enters 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 started processing the control protocol (step 37). After the control protocol has been processed, the system component to be activated also returns to sleep mode.

0034The energy consumption of the system is the lower, the longer the waiting times T_sleep.Tx and T._sleep.Rx to get voted. Too long waiting times, however, result in 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 is the waiting time T_sleep.Rx exceed by a small value, so that the activation signal is reliably detected in step 33.

0036Assuming that the system components usually return from the detector mode directly into the sleep mode and thus the power consumption of the active mode can 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="EP1585268A2_D0001.tif" /></maths> and for the power consumption of the system component to be activated, the following applies:<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="EP1585268A2_D0002.tif" /></maths> where P_sleep.Tx and P_sleep.Rx the power consumption of the activating and the system component to be activated in sleep mode, P_detect.Tx and P_detect.Rx the respective power consumption in the detector mode and T_{detect, Tx} and T._detect.Rx represent the respective dwell times in the detector mode before returning to sleep mode.

0037The waiting times in the sleep mode are advantageously about 100 to 1000 times greater than the residence times in the detector mode. Thus, approximately:<maths id="math0003" 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> + 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></math><img file="EP1585268A2_D0003.tif" /></maths><maths id="math0004" 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> + 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><mtext>.</mtext></mrow></math><img file="EP1585268A2_D0004.tif" /></maths>

0038The average power consumption of the system is thus 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 embodiment already mentioned, the base station forms the activating and the transponder the system component to be activated. In the detector mode, the base station determines whether a person or a vehicle is approaching by means of a proximity sensor. If this is the case, it is detected by means of the activation signal and possibly received back response signal (acknowledgment), whether the person or the vehicle also carry a transponder. During the processing of the control protocol, the access authorization is then verified.

0040Advantageously, this embodiment can also be modified so that the base station detects in the detector mode not (only) the approach of a person or a vehicle but directly the approach of a transponder. For this purpose, it emits a sensor signal and evaluates the returned echoes. Certain echoes are typical for transponders of the present type. For example, if the sensor signal consists of an electromagnetic pulse, a transponder with nonlinear reflection behavior can be detected by means of harmonics in the echo signal. Such a transponder may comprise a ferromagnetic metal strip brought into the region of saturation by the sensor signal, or a high frequency or radar tuned circuit approximately resonating with the sensor signal, to which a non-linear characteristic diode is added ,

0041It is economical to use the transmitter 3, 4 and the receivers 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 wait time T._sleep.Tx but caused 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. The steps 22 and 23 of Fig. 2 are replaced by a step of detecting the key depression or the touch of a sensor.

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

0044The two components of the system may also represent the base station and handset of a radiotelephone system, both of which initially operate as described above for the system component to be activated. However, when a user starts a call from the handset, the handset sends out the activation signal and assumes the role of the activating system component. Conversely, the base station operates to transmit the activation signal as an activating system component as soon as it receives a telephone call, which is to be forwarded to the handset. Steps 28 and 37 of FIG. 2 and 3 are always replaced by the transmission of a telephone conversation. Steps 22, 23 and 24 of FIG. 2 are replaced by a step in which the activating component, when representing the base station, detects a telephone call coming from the exchange network or, if it represents the handset, determines a keystroke with which the user indicates the beginning of a telephone conversation.