Verification of Time Signals

Abstract

A method is proposed for verification of time data from a time signal modulated on a continuous carrier signal with steps to receive a first time signal with a first reference time, to receive a second time signal with a second reference time, which follows the first reference time in time, for calculation of the target time interval lying between the reference times from the time data contained in the received time signal, to determine a time interval and determine a reference time interval, using counting of periods of the continuous carrier signal within the time interval, for comparison of the target time interval with the reference time interval and to send an error signal, if the deviation determined by the comparison surpasses a stipulated tolerance value.

Claims

1. A method for verification of time data from time signals modulated on a continuous carrier signal, comprising: receiving a first time signal with a first reference time; receiving a second time signal with a second reference time which follows the first reference time in time; calculating a target time interval lying between the first reference time and the second reference time from the time data contained in the received first and second time signals; determining a time interval and a reference time interval by counting of periods of the continuous carrier signal within the time interval; comparing the target time interval with the reference time interval; and outputting an error signal, if the deviation determined by the comparison surpasses a stipulated tolerance value.

2. The method according to claim 1, wherein, for verification of time data from the first and second time signals transmitted in a fixed time grid for determination of the reference time interval, the method further includes counting periods of the period carrier signal in the time interval between the first and second reference times of the received first and second time signals.

3. The method according to claim 1, wherein: the first time signal and the second time signal comprise time telegrams transmitted in packet-oriented fashion from a loose time grid; and for determination of the reference time interval, the method includes counting periods of the continuous carrier signal in the time interval between the received time telegrams; and obtaining the reference time interval by addition of packet times.

4. The method according to claim 3, further comprising determining the packet time by counting of the periods of the continuous carrier signal during transmission of one of the time telegrams.

5. The method according to claim 4, further comprising weighting the counted periods with the period times that vary by frequency modulation during counting of the periods of a frequency-modulated continuous carrier signal.

6. The method according to claim 5, further comprising establishing variation of the period time of the frequency-modulated continuous carrier signal according to data derived from it by demodulation.

7. The method according to claim 5, further comprising establishing the variation of period time of the frequency-modulated continuous carrier signal during determination of the packet time according to a time telegram corresponding to the first reference time.

8. The method according to claim 3, wherein a pre-determined value is added as the packet time.

9. A device for providing a remotely synchronized verified time base, the device comprising: one or more receivers to receive a continuous carrier signal with modulated time signals; one or more decoding devices to extract the time signals from the continuous carrier signal and to mark a time interval with start and end mark signals; one or more calculation devices to calculate a target time interval lying between reference times from time data contained in the received time signals; one or more counting devices to count periods of the continuous carrier signal in the time interval between the start and end mark signals; one or more conversion devices to convert the counted periods to a reference time interval; and one or more comparison devices to compare the target time interval with the reference time interval and to send an error signal to an error control unit, if the deviation determined by the comparison exceeds a stipulated tolerance value.

10. The device according to claim 9, wherein the one or more receivers are designed as direct receivers and especially include a selective amplifier.

11. The device according to claim 9, wherein the one or more decoding devices include: a demodulator for demodulation of a frequency-modulated signal; and a frame synchronization unit for frame synchronization of data units transmitted in packet-oriented fashion.

12. The device according to claim 9, wherein the device is designed as a billing unit in a charging station, a taximeter, a wind power unit, solar unit or as another unit in which time-dependent actions are conducted and in which correctness of an available time base must be present.

13. The device according to claim 9, wherein the device is designed as a time service calculator, time server, trusted platform module or hardware security module.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Exemplary methods for verification of time data from a time signal modulated on a continuous carrier signal and an example of a device for execution of such a method are shown in the appended drawings. In them:

[0029] FIG. 1 shows a schematic signal path of an amplitude-modulated continuous carrier signal with a fixed time grid as basis for a first method;

[0030] FIG. 2 shows a depiction of the time sequence of data packets in a packet-oriented transmission scheme as a basis for a second exemplary method; and

[0031] FIG. 3 shows an exemplary device for performance of the second exemplary method for the transmission scheme according to FIG. 2. In the following discussion, the same reference numbers are used in the various embodiments to indicate the same or similar elements.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0032] The schematic depiction in FIG. 1 shows a typical time signal path 100 for transmission of time signals 110, 120, 130 on a transmitter and receiver. The received signal is present during undisturbed reception uninterrupted in time because the transmission uses a continuous carrier signal. Several immediately consecutive time signals 110, 120, 130 are coded by amplitude modulation on the continuous carrier signal. The time signals 110, 120, 130 lie in a stipulated time grid and each contains time information. In addition, the time signals mark the reference time 112, 122, 132 pertaining to the time information.

[0033] In the exemplary situation the time information and references times 112, 122, 132 are coded on the continuous carrier signal by three different symbols, which are sent in a time second grid. The logic values 0 and 1 are represented by a short or long reduction of signal amplitude at the beginning of the corresponding second. The symbol for the reference time is produced by omitting the reduction. The subsequent falling flank in signal intensity can therefore be used to recognize the reference time. Transmission is repeated in a 60-second frame. Accordingly, symbols with binary data, in which the time information belonging to the reference time is appropriately coded, precede the symbol for display of the reference time 59 in each time signal 110, 120, 130.

[0034] The measures and devices for reception of the time signals 110, 120, 130, for extraction of the time information and for recognition of the reference times 112, 122, 132 are known and are therefore not further presented here. During reception of a time signal 110, 120, 130, time information is decoded and this can be used relative to the subsequently recognized reference time 112, 122, 132 for synchronization of a local clock of the receiver or for any other purpose.

[0035] In particular, if the carrier frequency of the continuous carrier signal is stabilized with the same time base, from which the time information transmitted with time signals 110, 120, 130 is derived, this permits simple verification or consistency checking of subsequently received time signals 110, 120, 130 through the first exemplary method explained below.

[0036] In the first exemplary method, for verification after reception of a first time signal 110 and specifically in the present case on recognition of the reference time 112 for decoded time information, counting of the periods of the continuous carrier signal is started, which is stopped with reception of a second subsequent time signal 120 or 130 at this reference time 122 or 132. The second time signal 130 need not directly follow the first time signal 110. A longer period with a number of additional time signals 120 can also extend between reception of the first and second time signal 110, 130, as long as uninterrupted reception of the continuous carrier signal is guaranteed in each case for counting of the periods.

[0037] After completion of counting, a target time interval is calculated from the time data of the first and second received time signals 110, 120 or 110, 130. A time interval 170, 180 is calculated from the counted periods of the continuous carrier signal via the known carrier frequency, which is referred to here as reference time interval owing to referral to the continuous carrier signal of the time reference. If the deviations determined by comparison between the target time interval and reference time interval surpass a stipulated tolerance value, an error signal is produced.

[0038] An exemplary packet-oriented data transmission scheme 200 is shown in FIG. 2. This data transmission scheme is produced, for example, in the known ripple control and especially in radio ripple control for power supply grids. Since this transmission scheme largely corresponds to the well known approaches for packet-oriented transmission schemes, the subsequent presentation will be restricted to the second exemplary method for verification explained below in its essential aspects.

[0039] In the course of time, from left to right, several data packets 210, 220, 230, 240, 250 are transmitted. In particular, these data packets are four time telegrams 210, 220, 240, 250 and a data telegram 230. The times of corresponding transmission are not rigidly established but are determined on the transmitter side. However, the data packets 210, 220, 230, 240, 250 are delimited in time relative to each other during transmission by packets and in particular may not overlap in time. The modulation also maintains a stipulated time grid within the data packets 210, 220, 230, 240, 250. From it the time position of a received data packet in the received signal can be established by a measure referred to as frame synchronization. At least one small time interval that is not used for transmission is typically found between data packets 210, 220, 230, 240, 250, and therefore contains the continuous carrier signal without any modulation pattern.

[0040] Based on a signal with the time transmission scheme according to FIG. 2, the second exemplary method for verification of time data from time telegrams is obtained with the following measures.

[0041] For this purpose a first time telegram 210 is initially received for a first reference time 212. In particular, a data stream is generated by demodulation of the received continuous carrier signal, from which the corresponding first time information is recovered by decoding. The reference point 212 for the first time telegram 210 is also obtained by frame synchronization of the received time telegram 210.

[0042] Coherent with frame synchronization of the first time telegram 210 a start mark signal 214 is generated, which coincides with the reference time 212 of the first time telegram. The start mark signal 214 designates the beginning of a time interval 216, during which periods of the continuous carrier signal are detected and counted. This counting is ended by an end mark signal 224, which is derived from frame synchronization of the second time telegram 220 and coincides with the beginning of the second time telegram 220. Moreover, the second time telegram 220 is received in the same manner and processed like the first one. The time information contained in it is extracted in particular.

[0043] The target time interval 218 lying between the reference times 212 and 222 is also determined from the time data of the first and second time telegrams 210, 220. This target time interval 218 corresponds to the time elapsed on the transmitter side for transmission between reference times 212, 222 in the measurement according to the time normal used by the transmitter.

[0044] In addition, a reference time interval 270 is determined via the periods of the continuous carrier signal counted during the time interval 216 between the start mark signal 214 and the end mark signal 224. The packet time 260, i.e., the time length of the second time telegram 220, forms a first contribution to the reference time interval 270.

[0045] This packet time 260 is presumed to be present as a uniform and stipulated value for all time telegrams. The further contribution 216 to reference time interval 270 based on time interval 216 is derived from the periods counted between the start mark signal 214 and the end mark signal 224. Derivations can occur based only on the counted value, if the frequency of the continuous carrier signal during counting is unchanged or the fluctuations of period time present from possibly present frequency modulation is compensated in the sum via the time interval 216.

[0046] In the exemplary data transmission according to FIG. 2, the presence of this condition in the sense of a first alternative can be assumed in the gap between the first 210 and the second time telegram 220.

[0047] If, on the other hand, in the sense of a second alternative the period time of the continuous carrier signal undergoes a change due to frequency modulation during counting, as is the case, for example, at the location of data telegram 230, this change should be appropriately considered to improve the accuracy in determining the reference time interval 280. In principle, several approaches are considered for this purpose.

[0048] Initially, the modulation state of the continuous carrier signal could be continuously detected directly. However, this detection is beset with indistinctness because the time limits of the individual symbols of modulation can no longer be precisely established by processing other received signals. In addition, the determinability of these time limits can be compromised by disturbances on the transmission link.

[0049] These problems can be at least partially eliminated by a modified approach. For this purpose, the data stream read from the continuous carrier signal by demodulation and decoding is used as a basis for a model of the transmitted continuous carrier signal. The received signals are therefore reconstructed in the stipulated exact time grid. If the symbols are correctly demodulated and decoded, the ideal frequency response at the transmitter is obtained by this reconstruction. In addition, measures of error correction on the data coded with the symbols can further contribute to finding this ideal frequency response. With this approach the content of the data telegram 230 is read and the frequency response ideally sent for its transmission reconstructed based on the stipulated data and symbol layout.

[0050] The more extensive approach could prescribe determination of the frequency response and modulation pattern independently of the actually received continuous carrier signal. However, this is only possible if the data sent on the transmission link are fixed beforehand to the extent that the contents of the following data packet can be determined starting from a correctly recognized data packet. This would be the case, in particular, if the continuous carrier signal is used exclusively for transmission of the time telegrams and these time telegrams are exclusively transmitted at the stipulated reference times. A conclusion concerning the content could then be made from the time of reception of the data packet. However, this would not be the case in most practically relevant application scenarios.

[0051] In one possible embodiment of the exemplary method, it could be prescribed to also determine the packet time 260 by one of the previously explained approaches. A method modified in this way could get by with data packet of alternating length.

[0052] Finally, in the second exemplary method, the target time interval 218 is compared with the reference time interval 270. For this purpose, the difference is formed from the two values. If this difference exceeds a stipulated tolerance value, an error signal can be produced.

[0053] The second exemplary method for verification of time information from time telegrams presented above can be conducted with the exemplary device 300 for furnishing a remote synchronized verified time base according to FIG. 3. This comprises the assemblies or functional units explained below along the processing path, i.e., in the direction of signal and data flow.

[0054] At the beginning of the processing path, receiving devices 310 are provided to receive the continuous carrier signal with the frequency-modulated data structures. In particular, the receiving devices 310 include an antenna loop 312 adapted to the frequency of the continuous carrier signal, which is connected to the input of a direct receiver 314. The direct receiver 314 is preferably a frequency-selective amplifier, which can provide particularly good suppression of interference signals and noise.

[0055] A direct receiver 314, relative to the superheterodyne receivers typically used in comparable situations, has the advantage here that it does not suppress or weaken the continuous carrier signal. The continuous carrier signal can consequently be used by counting the elapsing periods as a time base. The amplified continuous carrier signal available at the output of the direct amplifier 314 is also expediently fed via filter 316 to subsequent processing.

[0056] The processing path also contains decoding devices 320 to extract data from the continuous carrier signal and establish the timeframe of data transmission. In particular, the decoding devices 320 in the exemplary situation contain a demodulator 322 in order to extract the transmitted data packet (namely the time and data telegrams) by demodulation of the continuous carrier signal and make them available for subsequent processing to additional devices. The decoding devices 320 in the exemplary situation also contain a frame synchronization unit 324 to determine the frame, i.e., the time position of the transmitted data packets.

[0057] The frame synchronization unit 324 in the exemplary embodiment is also set up to produce the start and end mark signals for indication of a time interval. These start and end mark signals are derived in particular from stipulated reference points in the frame of the packet transmission. In particular, the frame synchronization unit 324 in the exemplary embodiment is set up to generate the start mark signal at the end of a previous time telegram and the end mark signal at the beginning of one of the subsequent time telegrams.

[0058] The processing path also contains calculation devices 330 to calculate the target time interval 218, 228 between the reference times from the time data of the corresponding received time telegrams 210, 220 or 220, 250. This target time interval 218, 228 is obtained, in particular, by subtraction of the time data and, if necessary, by subsequent conversion to a time-continuous representation. The latter is especially critical, if the time data in the time telegrams are coded in a manner broken down into year, month, day, hour and second.

[0059] The processing path also contains counting devices 340 to count the periods of the continuous carrier signal within the interval stipulated by the frame synchronization unit 324 by the start and end mark signals. In the present exemplary embodiment of the device 300 the start mark signal generated by the frame synchronization unit 324 starts the counter 340, which counts the periods of the continuous carrier signal up to arrival of the end mark signal. The counter 340 is also set up to output the result of this count as a digitally coded numerical value.

[0060] The processing path also contains conversion devices 350 to convert the numerical value supplied by counter 340 to a reference time interval. In the exemplary embodiment of device 300 the conversion devices 350 are set up in particular to consider a frequency modulation pattern on the continuous carrier signal during conversion, as described previously. For this purpose the conversion device 350 has the capability of weighting parts of the counter result with different period durations for the entire result.

[0061] The processing path also contains comparison devices 360 to compare the target time interval 218, 228 with the reference time interval 270. The comparison devices 360 are set up to produce alternative signals for indication whether the deviation determined by comparison maintains or surpasses the stipulated tolerance value. The signal produced to indicate maintenance by the comparison devices 360 is fed to a control unit 380, which processes the corresponding time telegram based on the incoming signal as verified and conveys it to an actuator 390 that operates in time-dependent fashion. A remotely synchronized verified time base is therefore available to actuator 390. Any error signal produced to indicate surpassing, on the other hand, is fed in the exemplary device to an error control unit 370 and further processed there. Further processing can include production of a signal to be sent to the control unit 380.

[0062] The device 300 just explained can advantageously be used to hamper manipulation of time data received via the time telegrams. It therefore works as part of a billing unit for time-based billing, for example, in a charging station, a taximeter, a wind power unit, a solar unit or for units in which time-dependent actions are conducted in which correctness of the available time base must be present.

[0063] The device 300 just explained can also be expediently used as part of a time service calculator, time server, trusted platform module (TPM) or hardware security module (HSM).

LIST OF REFERENCE NUMBERS

[0064] 100 Signal path [0065] 110 First time signal [0066] 112 Reference time of a first time signal [0067] 120 Second time signal [0068] 122 Reference time of a second time signal [0069] 130 Third time signal [0070] 132 Reference time of a third time signal [0071] 170 Reference time interval [0072] 180 Reference time interval [0073] 200 Data transmission scheme [0074] 210 First time telegram [0075] 212 Reference time of the first time telegram [0076] 214 Start mark signal [0077] 216 Time interval [0078] 218 Target time interval [0079] 220 Second time telegram [0080] 222 Reference time of the second time telegram [0081] 224 End mark signal [0082] 226 Time interval [0083] 228 Target time interval [0084] 230 Data telegram [0085] 240 Third time telegram during disturbed transmission [0086] 250 Fourth time telegram [0087] 260 Packet time [0088] 270 Reference time interval [0089] 280 Reference time interval [0090] 300 Device for providing a remotely synchronized verified time base [0091] 310 Receivers [0092] 312 Adapted antenna loop [0093] 314 Selective amplifier [0094] 316 Filter [0095] 320 Decoding devices [0096] 322 Frequency demodulator [0097] 324 Frame synchronization unit [0098] 326 Data decoder [0099] 330 Calculation devices [0100] 340 Counter [0101] 350 Converting devices [0102] 360 Comparison devices [0103] 370 Error control unit [0104] 380 Control unit [0105] 390 Actuator