Abstract:
To minimise the power consumption when registering an electronic ticket, a bidirectional communication in a higher frequency band is initiated when the electronic ticket has received a wake-up signal in a lower frequency band via a highly sensitive receive module. During entry stamping, a wake-up telegram containing an identity of the detection space is transferred to and stored in the electronic ticket. The wake-up telegram is received in the lower frequency band by another receive module in the electronic ticket.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method for registering tickets and an electronic ticket for executing the method in accordance with the precharacterising clause of claims  1  and  8  respectively. 
     The present invention relates to the registration of objects in a delimited space, in order to establish a service which is to be purchased and/or a defined presence. This field is also known as “electronic ticketing” or “fare management”. The term “electronic ticket” or simply “ticket” is synonymously used instead of object in this document. In technical terms, such a ticket is usually a so-called “SmartCard”. In other nomenclatures, the term transponder is also commonly used instead of SmartCard. 
     The document WO 01/03057 A1 [1] discloses a method for detecting objects by means of a transponder, wherein a first information unit is transmitted in the frequency range 127 kHz to the transponder when a detection zone is entered, thereby waking up said transponder. On the basis of the information which is contained in the first information unit, a send module which is present on the transponder is activated immediately or following a delay, in order at least once to transmit a second information unit to a receive unit which is located in the detection zone. 
     The method and system for registering tickets as disclosed in the document EP 1,210,693 B1 [2] differ in that a receiving module which is present on the ticket is “woken up” from a sleep state by means of a first information unit and is periodically switched to active. Using further information units, a bidirectional communication is established on a higher frequency of e.g. 868 MHz by a send/receive unit which is assigned to the detection zone, and the relevant presence of a ticket is registered as a ticket record. 
     EP 0,766,215 B1 [3] proposes a method in which an electronic ticket can be woken up in various stages. A level detector is initially provided for this purpose, whereby only wake-up telegrams on a low frequency of e.g. 6.78 MHz of a defined minimum level result in a first activation. In a subsequent method step, provision is made for checking whether the received wake-up telegram has the predetermined modulation. If this modulation is recognised as correct, a further circuit part is activated and inter alia the correspondence of an access code with a security code which is stored on the ticket is checked on a higher layer. 
     The aforementioned systems, as described in accordance with [1] and [2], have the so-called “timing mode” in common: as a result of waking up and periodically activating either the send module and/or receive module which is located on the ticket, the power consumption is actually reduced very clearly in comparison with a permanent activation. In many cases, the ticket is woken up in this way without a subsequent registration taking place or being allowed to take place, as is the case when an accompanying person who is carrying such a ticket merely stays on the platform. The “timing mode” method featuring a single prior wake-up has the serious disadvantage that a significant share if not the largest share of the battery power which is available on the ticket must be used in order to ensure that, during the overall journey, the ticket periodically becomes briefly active (“wakes up”) in the agreed time slot pattern and must switch on its receiver, e.g. on the frequency 868 MHz, merely for the purpose of re-establishing its synchronisation. In this case, a communication for the purpose of actual detection takes place only very briefly and preferably only once per journey section. 
     SUMMARY OF THE INVENTION 
     The present invention therefore addresses the problem of specifying a method for the registration of tickets and an electronic ticket for carrying out the method, wherein the power consumption is further minimised and wherein the bidirectional communication using the “timing mode” method takes place in such a way that the associated receivers need only be switched into ready-to-receive state as briefly as possible. 
     One aspect in accordance with the present invention is a method of bidirectional communication using telegrams in a second frequency band which is initiated by means of a wake-up signal in a first frequency band. The wake-up signal is received beforehand by a second receive module which is contained in the ticket. The activation of the send/receive module and hence also of the processor module can be limited to those cases in which a telegram really must reach the ticket concerned. The power requirement of the ticket is consequently minimised, thereby significantly increasing the autonomy. 
     This invention has the particular advantage that, within the detection space, no adaptation of the send units and other infrastructure such as on-board computer is required with regard to hardware. Only the software for controlling the first send unit  31  and the second send/receive unit  32  needs to be adapted. To a significant extent, parts of the communication software on the second frequency band can be transferred almost unchanged in this way. 
     In one advantageous aspect of an electronic ticket according to the invention, a second receive module is provided in the first frequency band. The second receive module has a higher receive sensitivity and is able to receive at least one wakeup signal. The activation of the send/receive module on the ticket, and of the processor module, can be limited to those cases in which a telegram really must reach the ticket concerned. 
     In a particularly advantageous embodiment, provision can be made to connect a passive filter or a demodulator in front of the second receive module, so that this space wake-up does not occur due to any random carrier as a result of the high sensitivity of the second receive module, but only occurs if the wake-up signal has a defined modulation, e.g. frequency modulation or amplitude modulation (envelope). 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Advantageous configurations of the invention are specified in further claims. 
       Exemplary embodiments of the invention are explained in greater detail below with reference to the drawing, in which: 
         FIG. 1  shows an arrangement of the sender/receiver unit on the vehicle, together with the associated zones; 
         FIG. 2  shows a schematic circuit diagram of an electronic ticket for carrying out the claimed method; 
         FIG. 3  shows the sequence of the different phases. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a railway carriage  1 . Its passenger space  3  can be accessed by the public via an entrance area  2  through the doors or through a passage area  4 . A first send unit  31  is arranged in the relevant entrance area  2 . This send unit  31  works on a first frequency band, preferably at 6.78 MHz. The frequency of the first frequency band is selected in such a way that the resulting field is developed within a circumcircle of up to 7 m as a “near field”. Near field means that the H field is dominant in this case. The near field is usually defined as r&lt;λ·0.6, where λ represents the wavelength. Within the near area, the magnetic field strength H decreases rapidly with the cube of the distance from the sender. It is therefore possible to achieve a circle of influence which is defined and limited in a spatially narrow manner. 
     A second send/receive unit  32  is arranged preferably centrally in the passenger space  3 . It is also possible to arrange e.g. a plurality of such send/receive units  32  in larger vehicles. The second frequency band, which is provided for the bidirectional communication with the tickets  10 , is clearly higher than the aforementioned first frequency band, and a frequency of 868 MHz is preferably used. The frequency band around 868 MHz has particularly good propagation properties within a vehicle. 
     The sequence of the method according to the invention is illustrated in  FIG. 3 , in which the letters A, B, B1 relate to the method steps in accordance with the claim  1 :
     A When boarding, i.e. when a ticket  10  moves from a sleep state into the entry wake-up zone  21  in the halted state  5  of a vehicle  1 , the ticket  10  is woken up via a level in the first frequency band of 6.78 MHz and given the required information such as an identity of the detection zone, location of the vehicle and the time. This phase is also called “entry stamping”. The tickets  10  which have been “stamped” in this way then revert to a sleep state. The area which is designated by the reference character  21  in accordance with the  FIG. 1  is defined by a minimum level, so that the tickets  10  can be woken up and given the aforementioned information in this area  21 .   B1 Following departure or following the beginning of a service purchase, the space wake-up  7  takes place. For this, a space wake-up signal  42  is broadcast by the first send unit  31  and immediately afterwards, or even simultaneously, a telegram  44  is repeatedly broadcast via the second send/receive unit  32 . The telegram  44  contains at least the identity and the timing information for the subsequent detection in the “timing mode”. The area which is identified by means of the reference character  22  in the  FIG. 1  is defined by a minimal level, such that the tickets  10  in this area  22  are “woken up” by a signal  42  having a specific modulation. An information transmission on a higher layer does not take place on the first frequency band in this case, unlike entry stamping, cf. the method step A above. Instead, the necessary information is transmitted simultaneously or immediately afterwards on the second frequency band using the telegrams  44 .   B Following this space wake-up  7 , B1 the tickets are in “timing mode” with a time slot pattern as described in EP 1,210,693 B1 [2], for example. Now the actual detection  8  can take place via the second frequency band.   

     After detection is complete  8 , B the tickets  10  switch directly to the sleep state  9 . In a subsequent journey section, e.g. following a halt and any passenger boarding or disembarking, the aforementioned space wake-up  7 , B1 and subsequent detection  8 , B take place again. 
     In a further embodiment of the present invention, provision can be made for an additional method step A1: 
     Reference is now made to the  FIG. 2  for an electronic ticket  10  for carrying out the aforementioned method in accordance with the invention: For the space wake-up  7 , the ticket  10  must include a second, highly sensitive and extremely low-current receive module  12 —also called a wake-up receiver  12 —for 6.78 MHz. This wake-up receiver  12 —like the existing first receive module  11 —works in a sampled mode in order to save electrical power. Its on/off duty cycle can be even more extreme than in the case of the first one, e.g. 100 times greater. The second wake-up receiver  12  must be a certain amount more sensitive than the first receive module  11 , e.g. by 20 dB. However, the wake-up receiver  12  does not have to receive any data. It merely samples the air for the presence of a 6.78-MHz carrier signal. In order to ensure that it does not respond to any alien 6.78-MHz signal that might be randomly present, a passive filter  12 . 1 —also called a demodulator—can be connected in series, said passive filter allowing only those signals to pass which are, for example, modulated at a suitable frequency. If such a signal  42  is detected, the processor  16  is woken up and the 868-MHz receiver  13  is activated for a certain amount of time on the ticket  10 . The ticket  10  then receives a continuously repeated signal from the send/receive unit  32 , said signal containing timing information and a reader ID which corresponds to that which the ticket properly received via a correct wake-up telegram and saved previously in this vehicle at the time of boarding, i.e. at the time of the entry stamping  5 . If this is the case, the ticket now switches into the “timing mode”. Otherwise, it returns to the sleep state. However, it must first remain for several seconds in a power-saving wait state, because it would otherwise be immediately woken up again by the alien 6.78-MHz signal which might still be present, and would activate its receive module  12  again. A duty cycle principle for power saving is again produced using this method. This wait time should be, for example, 10 times longer than the time for which the ticket  10  would again activate its receive module  12 . 
     For the sake of completeness,  FIG. 2  also includes the antennas  15 . 1  and  15 . 2 , a power supply module  18  and a battery  19 , as well as a processor module  16  and a memory module  17  for implementing the required intelligence. For the purpose of optimisation, a single antenna  15 . 1  is provided for the first and second receive module  11  and  12 . The illustration of the antennas  15 . 1  and  15 . 2  is only schematic, and the antennas are obviously adapted to the range of 6.78 MHz or 868 MHz in accordance with the intended frequency bands. 
     As a result of applying a maximal permitted send level and a significantly higher receive sensitivity of the second receive module  12  on the ticket  10 , it is possible to achieve a considerably higher transmission range  22  than the customary transmission range  21  which is intentionally restricted to 3 m for the normal wake-up. Consequently, there is no requirement for additional space wake-up antennas in the vehicle  1 . 
     Within the meaning of the present invention, it is also possible to implement different frequencies from the same first frequency band for the so-called entry stamping in the method step A and the space wake-up in the method step B1. In order to reduce the complexity of the components which are used, however, it is advantageous to provide the identical frequency for the entry stamping and the space wake-up. 
     The invention is in no way restricted to the application in a vehicle such as a railway carriage or bus, but can be applied anywhere where electronic tickets for detecting a defined presence require a particularly high level of autonomy. 
     Autonomy in this context means that, for as long as possible, there is no need to replace a battery or perform any other maintenance intervention in relation to power supply or interoperability. Examples of other applications are: access systems, position-fixing systems for people and goods. 
     The aforementioned variants of the different method steps can be freely combined and, in particular, a ticket  10  can return to the sleep state  9  after a detection has taken place in the timing mode, and then be activated again by means of space wake-up.