EP0565180A2
Expired / Lapsed
EP
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A method of time measurement in a communications system, a communications system and a receiving apparatus for use in the system
Assignee: Philips Electronics UK Ltd
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Filing: 1993-04-01
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Granted: —
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Expires: 2013-04-01
Abstract
Abstract In certain signal transmission systems such as selective call systems it is desired to stamp the date and time of the receipt of a call addressed to a receiver. For battery powered equipments such as radiopagers it is not practical to provide a clock because it will require resetting after each battery change. Fairly accurate times can be obtained by the system base station transmitting date and time message signals at regular intervals. However due to signal formatting delays and signal propagation delays, both of which are variable, the time indicated in a received time message signal is incorrect relative to real time. A radiopager includes a timing stage which is able to measure real time relative to a time reference. In order to obtain the best time reference, a comparison is made between the real time difference (Tr n - Tr ref ) between the times of receipt Tr ref , Tr n of a current time reference signal and a more recently received time message signal Ts ref , Ts n , and the time difference (Ts n - Ts ref ) between the times Ts ref , Ts n indicated in the corresponding time message signals, and depending on the result either the time reference signal Ts ref is confirmed as the current time reference signal or the more recently received time message signal is substituted as a new current time reference signal causing the real time clock to be reset so as to relate the real time to the new current time reference signal.
Inventors
- 👤 Anthony Keith c/o PHILIPS TELECOM-PMR Sharpe
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 06:23
CPC Classifications
H; H04; H04W; H04W88/00; H04W88/02; H04W88/022; G; G04; G04R; G04R20/00; G04R20/14; G04R20/18; G08; G08B; G08B3/00; G08B3/10; G08B3/1008; G08B3/1016; G08B3/1091
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
110 words
A receiving apparatus for use in a communications system in which a succession of time messages are transmitted by a central station, characterised in that the receiving apparatus comprises means for receiving and decoding successive time message signals, means for storing the time indicated in the time message signals, timing means for determining the real time of receipt of each time message signal, and means for determining by using the time message signals and the real times of their receipt, which of the time message signals is to be treated as a current time reference signal to which the real time signals of the timing means are to be related.
Claim 2
Dependent Claim
110 words
A receiving apparatus for use in a communications system in which a succession of time messages are transmitted by a central station, characterised in that the receiving apparatus comprises means for receiving and decoding successive time message signals, means for storing the time indicated in the time message signals, timing means for determining the real time of receipt of each time message signal, and means for determining by using the time message signals and the real times of their receipt, which of the time message signals is to be treated as a current time reference signal to which the real time signals of the timing means are to be related.
Claim 3
Dependent Claim
150 words
An apparatus as claimed in claim 1, characterised in that the means for determining which of the time message signals is to comprise the current time reference signal, comprises means for determining the time difference between the indicated times in the current time reference signal and a more recently received time message signal, means for determining the time difference between the real times of receipt of the current time reference signal and the more recently received time message signal and comparison means for comparing the indicated time difference with the real time difference and depending on the result either the time reference signal is confirmed as the current time reference signal or the more recently received time message signal is substituted as a new current time reference signal causing the real time clock to be reset so as to relate the real time to the new current time reference signal.
Claim 4
Dependent Claim
86 words
A communications system comprising a central station having means for transmitting a succession of time message signals, each time message signal containing an indication of time, receiving means for receiving the time message signals, the receiving means having a real time clock and means for determining by using the time message signals and the real times of their receipt which of the time message signals is to be treated as a current time reference signal to which the time of the real time clock is related.
Claim 5
Dependent Claim
86 words
A communications system comprising a central station having means for transmitting a succession of time message signals, each time message signal containing an indication of time, receiving means for receiving the time message signals, the receiving means having a real time clock and means for determining by using the time message signals and the real times of their receipt which of the time message signals is to be treated as a current time reference signal to which the time of the real time clock is related.
Claim 6
Dependent Claim
154 words
A system as claimed in claim 3, characterised by means for determining whether the time message signal treated as the current time reference signal is more accurate than a more recently received time message signal, said means comprising means for determining the difference between the indicated times in the current time reference signal and the more recently received time message signal, means for determining the difference in the real times of receipt of the reference signal and the more recently received time message signal, and means for comparing the indicated time difference with the real time difference and depending on the result either the time reference signal is confirmed as the current time reference signal or the more recently received time message signal is substituted as a new current time reference signal causing the real time clock to be reset so as to relate the real time to the new current time reference signal.
Claim 7
Dependent Claim
35 words
A system as claimed in claim 4, characterised by means responsive to the real time difference exceeding a predetermined value for treating the most recently received time message signal as a new time reference signal.
Claim 8
Dependent Claim
45 words
A system as claimed in claim 3, 4, or 5, characterised in that the central station includes means for generating a time indication signal and means for updating the time indication signal by a correction relating to the minimum delay incurred in the central station.
Claim 9
Independent Claim
85 words
A system as claimed in any one of claims 3 to 6, characterised in that the central station transmits digital paging signals in accordance with a time division protocol comprising a succession of batches, each batch comprising a plurality of frames, said time message signals being transmitted periodically, and in that the central station has means for inserting into a batch an indicator signal including function bits denoting that codewords in the same and at least the next following frame(s) comprise the time message signal.
Claim 10
Independent Claim
85 words
A method of time measurement in a communications system, comprising transmitting a succession of time message signals from a central station, each time message signal containing an indication of time, receiving the time message signals in a receiving apparatus having a real time clock, determining by using the time message signals and the real times of their receipt which of the time message signals is to be treated as a current time reference signal to which the time of the real time clock is related.
Claim 11
Independent Claim
85 words
A method of time measurement in a communications system, comprising transmitting a succession of time message signals from a central station, each time message signal containing an indication of time, receiving the time message signals in a receiving apparatus having a real time clock, determining by using the time message signals and the real times of their receipt which of the time message signals is to be treated as a current time reference signal to which the time of the real time clock is related.
Claim 12
Dependent Claim
143 words
A method as claimed in claim 8, characterised by determining whether the time message signal treated as the current time reference signal is more accurate than the more recently received time message signal by determining the difference between the indicated times in the current time reference signal and the more recently received time message signal, determining the difference in the real times of receipt of the reference signal and the more recently received time message signal, comparing the indicated time difference with the real time difference and depending on the result either the time reference signal is confirmed as the current time reference signal or the more recently received time message signal is substituted as a new current time reference signal causing the real time clock to be reset so as to relate the real time to the new current time reference signal.
Claim 13
Dependent Claim
83 words
A method as claimed in claim 8 or 9, characterised in that the central station transmits digital paging signals in accordance with a time division protocol comprising a succession of batches, each batch comprising a plurality of frames, in that time message signals are transmitted periodically and in that a time message signal in a batch is preceded by an indicator signal including function bits denoting that codewords in the same and at least the next following frame(s) comprise the time message signal.
References Cited (Backward Citations)
No citation records indexed.
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