GB2362787A - Setting the time on a cellular terminal - Google Patents

Abstract

In order to set the time/date function of a cellular terminal 1 from a cellular network 30, the terminal sends an SMS text message addressed to itself which is subsequently received by the network, time-and-date stamped and sent back. The message may contain text identifying it as being for use with the time/date function of the terminal or this may be ascertained by determining that the address (eg telephone number) of the message sender matches with the address of the terminal. The terminal may initiate a timer when the message is sent in order to take into account any errors which may occur due to transit delays. Multiple messages with predefined time spacings may be used to further refine the time approximation.

Description

2362787 PROCESS FOR SETTING THE TIME ON A CELLULAR TERMINAL AND CE

LE-U-DAW -TERM I NAL FOR IMMEK-E NT I NG THE -P-R OTES-S- " The present invention relates to the setting of the time on terminals of cellular networks.

If one considers a portable. handset of -a cellular radiotelephony network, for example GSM, this handset includes a clock circuit which provides signals regulating the clock of the processor of the handset and which also controls a display so as to f orm an electronic watch.

Apart from the conventional use as a personal watch, this electronic watch function can also serve to synchronize transmissions of information between various handsets used for particular applications.

However, should the battery of the handset discharge completely, the clock circuit loses all memory of the date and time. Nevertheless, with neithel.

date nor time, it is still possible to telephone and to send SMS short messages. Now, these short messages are time-and-date stamped by the network and the applicant has had the idea of using this short message service to reset the time on the clock of a cellular terminal.

Accordingly, the invention relates firstly to a process for setting the time on a terminal of a cellular telephony network comprising a short message service (SMS), in which process:

- a short message is sefit, from the terminal, into the network, destined for the terminal itself; - the network receives the short message and returns it after having time-and-date stamped it, and - in the terminal. the time-and-date stamped short message is received and on the basis of the latter the time is set.

Thus, and even if the network does not include any specific service for disseminating the current time, the terminal procures the latter by activating the time-and-date stamping function of the network via its SMS message, so that it generates time-and-date stamping data thereof, and the terminal retrieves back the message, enhanced with these data, so as to update itself.

This updating can pertain to any time unit: year, month, day, hour, minutes and the like and, obviously, it is preferable for it to include all those cited above.

Preferably, - in the terminal, the time which elapses from the instant of sending of the short message is measured, - in the network, the short message is time-and- date stamped at the instant of receipt, and - in the terminal, the measurement of the time elapsed at the instant of re-receipt of the short message is recorded and this measurement is taken into account to set the time.

It is thus possible to take account of the time taken to cross the network.

The invention also relates to a cellular network telephone terminal for implementing the process of the invention, comprising:

- clock circuits, - circuits for setting the clock circuits to time, circuits for sending short messages over a cellular network, and circuits for receiving short messages from the network, terminal characterized in that the time-setting circuits are configured so as to read the short messages of the receiving means and so as to select therein and extract therefrom time-and-date stamping data for controlling the clock circuits.

The invention will be better. understood with the aid of the following description of a preferred mode of implementation of the process of the invention, with reference to the appended drawing in which:

- Figure 1 is a block diagram of a cellular network telephone terminal and of the associated network for the implementation of the process of the invention, Figure 2 is a flowchart of steps of the process is and - Figure 3, formed of Figures. 3A and 3 B-, illustrates a setting of the time by dichotomy.

In Figure 1, the terminal or telephone handset represented bounded by the partial dashed frame referenced 1 is linked by radio to a cellular radiotelephony network 30, here the GSM network, and comprises clock or time base circuits 10 which, via links (not represented), regulate the operation of the various circuits of the handset 1 and in particular of a microprocessor 11 for managing all the circuits of the handset 1. A battery (not represented) powers the handset 1.

Apart from conventional telephony circuits such as microphone and loudspeaker, these also not being represented for the sake of clarity, the handset 1 includes circuits 12 for time-setting or for updating the clock circuits 10, register circuits, 13, for sending short messages. SMS, by radio within the network 30 and register circuits, 14, for receiving SMS short messages by radio which originate from the network 30. A control and dialling keypad 18 is linked to the microprocessor 11, which controls a telephony and electronic watch display 19.

The microprocessor 11, which here includes a timer 111 and a circuit 113 for detecting power-up, furthermore contains read-only memory circuits 112 containing a short message 15 of specified content, which essentially includes a sender field, with the telephone number of the handset 1, and a destination field, with a telephone number which is in fact the actual telephone number of the handset 1. The microprocessor 11 is linked to the circuits 13 for copying the short message 15 therein and for controlling radio sending thereof by these circuits. A time-and-date stamping data field 16 is generated by the network 30 on receipt by this network 30 of the short message sent 15 and is associated with or 4 incorporated into the message 15 so as to constitute a time-and-date stamped short message 15, 16 returned by the network 30 and received by the circuits 14.

As an option, the short message 1S can include a text specifying that this is a short message 15 for setting the time on the handset 1. This information is in fact redundant since it is provided indirectly through the fact that there is identity between the number of the sender, which remains specified in the short message received 15, 16, and the number of the destination, available at least in the memory 112 and here in the message 15, 16 received.

The circuits 12 for setting the clock circuits 10 to time are linked at input to the receiving circuits 14 in order to read the field 16 therein, in order to select and extract, from a message 15, 16 from the network 30, the time-and-date stamping data of the field 16 and to adjust the clock circuits 10 in accordance with these data. The representation of the circuits 12 is here symbolic since, in practice, they are incorporated into. the microprocessor 11 and constitute a task which uses this microprocessor according to a time-sharing mode of operation, so as in particular to perform time calculations in an arithmetic unit 110 of this microprocessor.

The clock circuits 10 include an oscillator circuit 100 whose output signal, at a specified frequency which here is around 10 MHz (a frequency of 32 kHz could otherwise be used), controls a chain of circuit stages 101, 102 having frequency-dividing counters, providing the various circuits with the desired clock timings, and whose downstream stages 102 provide in particular (double-line arrow) a set of "time" signals: date, hours, minutes, seconds, displayed on the display 19 under the control of the microprocessor 11.

received The high frequency, upstream counter stages 101 are simple dividers, by two for the most part, which regulate the operation of the logic circuits 11 to 14.- The low frequency, downstream counter stages 102 controlling the display 19, comprise a first Pulse counter which changes state every second with a cycle of 60 seconds, successively taking the values from 0 to.59, which are displayed. A second counter, downstream, for minutes, detects the reverting to the 0 state of the f irst counter so as to advance by one minute on each occasion. A third, hour counter, detects the reverting to the 0 minutes state of the previous counter and increments by 1 hour its counting result, varying cyclically from 0 to 23 hours. A fourth, day is counter, advances by one unit with each reverting to b hours of the third counter. The chain of frequency dividers continues according to the same principle, so as to provide the number of the month or its name, by transcoding, and the year.

The time-setting circuits 12 are provided so as to load, into the downstream counter stages 102, time data specifying the current instant. Accordingly, apart from a change of state serial input and a serial output, respectively linked to the two adjacent stages, each stage of the counters 102 includes a parallel input for setting its state, these parallel inputs being controlled individually by a row of gates 103, AND with two inputs. Each gate 103 receives. on a first input, a specific bit for resetting the ',time,, originating from the circuits 12 (in fact here originating from the arithmetic block 110 used functionally by the circuits 12 in time-sharing mode). The second, disabling inputs, are controlled in common by an enabling bit, or setting command, originating from the circuits 12.

The above time data, specifying the current instant, are established on the basis of those generated by the network 30 in the field 16. The reference 21 designates a base station of the network

3o- managing the radio cell in which the handset 1 is located. The station 21 includes a register 23, for the radio reception of SMS short messages of any type, sent by the circuits 13 or by conventional handsets, and a register 24, for the radio sending of SMS short messages of any type destined for the circuits 14 or for those of conventional handsets. Depending on the destination specified in the short message 15, the output of the receiving circuits 23 can be looped back to the input of the sending circuits 24, this being the case here since, as explained above, the handset 1 self-addresses the time-setting short messages 15 which it sends. A short message 15 of the handset 1 therefore traverses a loop which crosses the network 30, so as, is on the one hand, to cause therein, by its transit through the network 30, the generation of time data specifying the current instant and, on the other hand, to gather them in the field 16 and transport them from the network 30 to the handset 1 where they will be utilized.

The station 21 includes a clock circuit 20, similar to the circuit 10, with backed-up power supply and/or redundant, that is to say one which is always available and up to date, which therefore has the desired time data.

The receiver register 23 includes an area or field reserved for the short message received 15 and an area or field reserved for the time-and-date stamping data 16 of the short message 15, which are provided, from the clock circuits 20, by a time-and-date stamping circuit 25 which detects the arrival of the message 15 in the register 23 so as to provide these time-and-date stamping data by writing them to the field 16 of this register.

For the sake of simplicity, based telephone management circuits, managing analysis and routing of the SMS short messages, have not been represented. It is they which here control the looping back of the registers 23 and 24.

microprocessorthe The process for setting the time on the handset 1 will now be explained in greater detail, with reference to Figures 2 and 3.

Should the power supply to the handset 1 by the battery be cut, the stages of divider counters 102, in particular, of the clock circuits 10 will be reset to zero and the electronic watch function of the display 19 then remains off on powering up again.

In order to reset the divider circuits 102 to time, the microprocessor 11 sends through the circuits 13, at a step 41 and at an instant tl (Fig. 3), a short message 15 for automatically resetting the circuits 102 to time. The references between brackets in Figure 2 are those of the circuits concerned in the relevant step. Overall, the short message 15 follows the looped path consisting of the circuits 112, 13 then 23, 24 and f inally 14, 12, 10 so as ultimately to end up at the display 19.

The microprocessor 11 thus dispatches, to the clock circuits 10 associated with it, a short message 15, which is enhanced with the time-and-date stamping data -of the. field 16, or electronic image T20. of the clock circuits 20, by crossing the network 30 and which after transformation reaches the clock circuits 10 in the form of time-and-date stamping data of the field 16, which are in fact substituted for the original message 15 on the final path in the circuits 14, 12 and 10.

At reception (14), any risk of confusion with a possible conventional short message originating from another handset and also time-and-date stamped,. is avoided, as alluded to above, by verifying the number of the sender, hence here the handset 1, and/or the text of the message.

Accordingly, for step 41, the user of the handset I could control the microprocessor 11 via the keypad 18. However here, the microprocessor 11 itself detects power-up of the handset 1 and automatically sends the initialization message 15. This detection is 8 performed by the circuit 113 by means of an exclusive OR gate whose two inputs are linked to the supply potential, one across a delay circuit, here --a resistance/capacitance circuit, which causes a temporary mismatch between the states of the two inputs, generating at output a time-resetting control pulse applied to the memory circuits 112.

The message 15 is then read from these circuits and transmitted to the circuits 13 which send it at the instant tl to the network 30 where it is received almost with no lag, at an instant t2 and at a step 42 by the receiver register 23 of the station 21. The message 15 is time-and-date stamped at a step 43, here substantially at the same instant t2, by the circuits 25 which associate therewith, or incorporate therewith-, the time-and-date stamping data of the field 16, the instantaneous electronic image of the clock circuits 20. Being addressed to the handset 1, the short message 15, enhanced with the time-and-date stamping data of the field 16, is transmitted to the register 24 which returns it to the handset 1 at an instant t3 and at a step 44. The circuits 14 having received the time-anddate stamped message 15, 16 at an instant t4 and at a step 45, the circuits 12 read the field 16 so as to extract therefrom the time-and-date stamping data or information at a step 46 and to update the counters of the divider circuits 102 on the basis of these data, at a step 47.

In this example, the short message 15 is, as explained, time-and-date stamped at the instant t2 of receipt in the network 30. Since the network 30 exhibits a certain crossing time t3-t2, even if in practice it is the same station 21 which receives and resends the short message 15, the time-and-date stamping data 16 are therefore slightly obsolete when the handset 1 receives them at the instant t4. To correct this effect of the time taken to cross the network 30, and in particular if the message 15 were stored in messaging mode in the network 30 for a - 9 certain time before being returned, the instant of sending tl of the short message 15 is tagged, in the handset 1, this tagging obviously being in relatixe time since the clock circuits 10 are not up to date.

Accordingly, via its pulse, the circuit 113 of the microprocessor 11 primes the timer ill which thus measures the time which elapses from the instant of sending tl of the short message 15 by the circuits 13. The short message 15 being time-and-date stamped at the instant t2 of receipt in the network 30, then returned time-and-date stamped to the handset I and the instant t3, the time-setting circuits 12 record, inthe timer ill, the measurement At of the time elapsed at the instant t4 of re-receipt of the short message 15, 16 and take this measurement At into account for the time setting.

This is taken into account here, in an overall manner, by adding, to the time-and-date stamping value T20 of the field 16, the lag At provided by the timer ill and corresponding substantially to the time of traversal of the loop 13, 23, 24, - 14. In practice, by means of the arithmetic unit 110 linked to the timer ill, the time-setting circuits 12 add, to the absolute time value T20 of the field 16 which they transmit to the arithmetic block 110, a number of minutes equal to that provided by the measurement At.

To take account of the seconds, the seconds value which is provided by the measurement At is taken into account in order to set the f irst counter of the circuits 102 to time. As a variant, this first counter is simplified and includes, for its time setting, only a common zero-setting circuit, controlled at an appropriate instant, as explained below. Accordingly, the circuits 12 take into account a value At rounded up to the next minute relative to its value at the instant t4, by adding an additional minute to the minutes value of At and delay their time-setting action by a number of seconds representing the complement, to within a whole minute, of the seconds of the measurement At.

Therefore, after receiving back the short message 15, 16 at the instant t4, the measurement of the time elapsed At since the instant of sending ti i's continued, until it gets to a whole number of elementary time units of the network 30, here the minutes. If for example the message back 15, 16 is received when At is equal to 1 minute and 22 seconds, the circuits 12 add 2 minutes to the value of the field 16 and update the counters of the circuits 102 with a delay of 38 seconds relative to the instant t4 of receipt of the field 16. The measurement of the timer ill is thus continued so as to have a whole, value for the minutes and hence make an exact correction from this point of view.

There may furthermore be provision to make, to the value At, an estimated correction corresponding, on the one hand, to the slight delay t2-L1 between the sending of the short message 15 by the circuits 13 and its reception by the register 23 and, on the other hand, to the time taken to cross the time-setting circuits 12.

Outside of the errors or uncertainties due to the transmission times just alluded to, the accuracy of the time setting is limited to an elementary time unit, here a minute, of the time-and-date stamping data of the field 16. Stated otherwise, the clock circuits 10 (circuits 102) are in principle slow relative to the master clock circuits 20 by an uncertainty duration lying within a range of from 0 to 1 minute, for want of a seconds figure in the value T20. Even if this range were recentred, by adding the mean uncertainty value of 30 seconds to T20, it still would not be reduced. In order to reduce this uncertainty, and after a first time setting with the uncertainty range of 1 minute, at least a second time setting is recommenced so as to reduce the uncertainty by dichotomy, as explained hereinbelow.

Each short message sent 15 makes it possible to gather in return the electronic image T20 of the master clock circuits 20 substantially (t2) at the instant tl of this sending, which image changes every minute. The handset 1 therefore performs a polling wit-h oversampling of the clock circuits 20, by sending a series of short messages 15, which are asynchronous with respect to the clock circuits 20, at different intervals of the period of these circuits, a minute. The short messages 15 thus have a phase, or instant of arrival t2, t 1 2, t 1 12 in the network 3 0, which varies within the period (Fig. 3) of minute M of the clock circuits 20, and the series of electronic images T 20 thus acquired allows better pinpointing of the instants tO, t60 of transit from one minute M to the next N in the clock circuits 20. These instants t2, t12, t112 are not random in this example but are chosen according t7o a procedure f or reducing by a f actor of 2, on each occasion, the remaining uncertainty of adjustment. This makes it possible to guarantee a specified accuracy of adjustment of 1 min/2 directly dependent on the number E of adjustments.

Figure 3 illustrates the dichotomy procedure, the time, t and t-30 seconds, being plotted along the abscissa on the two axes of the respective Figures 3A and 3B.

The two time axes are drawn as a thick line for the minute M and, likewise, there are represented as a thick line in each Figure 3A, 3B, a composite window and three temporally coinciding, or superimposed, corresponding restricted windows of three uncertainty ranges of 1 minute containing the instant t60.

With reference to the axis t of Figure 3A, a first short message 15 being sent at the instant tl by the handset 1, it is received and time-and-date stamped at the instant t2 (arrow F2) by the station 21 and, returned by the latter at the instant t3, it is received by the handset 1 at the instant t4, the circuits 12 performing the time setting without systematic error since they take into account the systematic delay At provided by the timer 111. For 12 - simplicity of explanation regarding dichotomy, the radio delays t2 - ti and t4 - t3 are here regarded as being negligible, or known and corrected.

The instant t2, of provision of the field 16 to the message 15 received, belongs to the range M of 1 minute duration which follows the absolute time instant to of transit to the state M minutes of the clock circuits 20 of the station 21.

Hence, at the instant t2, the clock circuits 20 had the value M of the field 16 received by the handset

1, their future instant t60 of transit to the minute N = M + 1 therefore being within the uncertainty range M11 of 1 minute which follows the instant t2 but without it being possible, at this step, to more accurately specify the position of the instant t60 add hence also of the instant to. The time-setting circuits 12, extracting, from the receiver circuits 14, the absolute time value T20 of the clock circuits 20 which was valid at the instant t2, they calculate the absolute time value T1 thereof which was that of the instant tl:

T1 = T20 - (t2 - tl) The absolute time value T4, valid for the instant t4 of rereceipt of the value T20, is that, T1, relating to tl, increased by At, i.e.:

T4 = T20 - (t2 - tl) + At Receiving at the instant t4 the absolute time value T20, the circuits 12 can therefore determine each of the absolute times of the temporal pattern t1, t2, t3, t4. Therefore, the following explanations are based solely on the instants tl and t2.

A second message, 151, is then likewise sent (instant t1l) to the network 30 with a phase shift of half a period relative to the previous message, hence 30 seconds later (modulo X minutes), and time-and-date stamped at the instant t 12 (arrow F 1 2). A second uncertainty range M21 (Fig. 3A) or N22 (Fig. 3B) of 1 minute is determined as above, this range following-the instant t'2 at whicli the message 151 is time-and-date stamped and hence shifted 30 s behind the range M11.

In the case of Figure 3A (t2 at the start of minute M), the time-and-date stamping data 16 of the second message 151 confirm the adjustment of the minutes of the clock circuits 10 performed on the basis of the data 16 of the first message 15, since the instants t2 and t'2 of receipt of the messages 15, 151, 30 seconds out of phase, belong (modulo X) to the same period M of the clock circuits 20. The second range therefore relates, just like the first range M11, to the minute M and this second range is that referenced M21. The instants of change of minute, such as tO, t6O, of the clock circuits 20 therefore lie (modulo X) in a reduced composite range of intersection M11.M21, of 30 seconds, which is common to the ranges M11 and M21, and precisely the second half-period of the range M11, which is superimposed with the first half-period of the.

range M21. The instant t6O is thus detected and bounded temporally by the values t'2 and t2+60 s.

In the converse case, of Figure 3B, (t2 at the end of minute M), the temporal events of the t-30 s axis correspond to those of the t axis (not all of which have been plotted thereon for the sake of clarity) apart from the fact that- the events of absolute time tO, t60, which are tied to the clock circuits 20, occur 30 s earlier. The time-and-date stamping data 16 of the second message 151 therefore provide the value N = M + 1 minute, so that the useful range of 1 minute, shifted by 30 s relative to the range M11, which is to be compounded with the latter, is not the range N22 which follows the instant t'2 but the preceding range of 1 minute, M22, which terminates at the instant t'2, relating to the minute M. The instant t2 was therefore, in this case, in the second half-period of the minute M and the slippage from t2 to - 14 the instant t'2, from one message 15 to the next 151, was accompanied by a transit through the instant tGO of change of minute of the clock circuits 20. The instaftt t6O is thus detected and bounded temporally by the values t2 and t'2.

The dichotomy procedure can be continued, with the sending of a third short message 1511 at an instant t,, 1 delayed by 15 s relative to the instant t 1 1 (or else relative to ti, modulo X minutes), received by the network 30 at the instant t'12 (arrow F'12) in the middle of the remaining composite uncertainty range M11.M21 or M11.M22. It provides a range M31(or N32) delayed by 45 s (or 15 s, modulo X minutes) relative to the range M11. The temporal intersection M61, of the ranges M11, M21, M33, or M62 of the ranges M11, M22, M32 provides the restricted range M61 or M62 in which the instant t60 is located.

In Figure 3A, the instant t 1 12 is located just ahead (less than 15 s) of the instant t60 on the t axis, so that the associated range M31 relates to the minute M.

In Figure 3B,_ the instant t'11 (or t''2) relating to the minute M has already passed when the circuits 12 determine that this instant should be delayed by 15 s only relative to the instant tl (or t2), so that it is in fact delayed by 1 minute + 15 s. The corresponding field 16 therefore contains the value N = M + 1 minutes, for the range N32, so that the useful range M32, relating to the minute M relevant here, is obtained by transferring the range N32 into the minute preceding the instant t''2.

If, conversely, the instant t' 12 were situated just after the instant t6o,the third ranges M31 and M32 would then occupy the position just ahead of those represented, the 15 s composite ranges, M61 and M62, therefore then being shifted ahead by 15 s so as to commence at the instants t'2 and t2 respectively.

Claims (9)

1. A process for setting the time on a terminal of a cellular telephony network comprising a short message service, in which process:

a short message is sent, from the terminal, into the network, destined for the terminal itself; the network receives the short message and returns it after having time- and-date stamped it, and in the terminal, the time-and-date stamped short message is received and on the basis of the latter the time is set.

2. A process according to claim 1, in which:

in the terminal, the time which elapses from the instant of sending of the short message is measured, in the network, the short message is time-and-date stamped at the instant of receipt, and in the terminal, the measurement of the time elapsed at the instant of re- receipt of the short message is recorded and this measurement is taken into account to set the time.

3. A process according to claim 2, in which, after re-receipt of the short message, the measurement of the time elapsed from the instant of sending is continued, until it gets to a whole number of elementary time units of the network.

4. A process according to any of claims 1 to 3, in which, after a first setting to time, with an uncertainty range equal to the duration of an elementary time unit, at least a second setting to time is recommenced so as to reduce the uncertainty by dichotomy.

5. A process according to any of claims 1 to 4, in which the terminal detects that it has been powered up and automatically sends the short message.

6. A cellular network telephone terminal for implementing the process of claim 1, comprising:

clock circuits, circuits for setting the clock circuits to time, circuits for sending short messages over a cellular network, and circuits for receiving short messages from the network, wherein the time-setting circuits are configured so as to read the short messages of the receiving means and so as to select therein and extract therefrom time-anddate stamping data for controlling the clock circuits.

7. A terminal according to claim 6, in which the time-setting circuits are incorporated into a microprocessor for managing the terminal so as to operate therein in time-sharing mode.

8. A process for setting the time on a terminal of a cellular telephony network, substantially as hereinbefore described, with reference to the accompanying drawings.

9. A cellular network telephone terminal, substantially as hereinbefore described, with referenc to and as illustrated in the accompanying drawings.