Disciplined time scale generator for primary reference clocks
First Claim
1. A method of attaining syntonisation between a local clock and a universal time source, wherein the universal time is transmitted via a signal over a medium that is subject to adding linear and non-linear noise effects to the signal, the method comprising:
- providing a plurality of constituent time clocks, each time clock providing a clock signal at the output;
ensembling the outputs of the time clocks to provide ensembled time clock information, wherein the ensembled time clock information is more stable than any of the constituent time clocks;
receiving the universal time clock signalrepeatedly determining the difference in frequency between the universal disciplining clock signal and the ensembled time clock information; and
generating from a plurality of said frequency differences and at least one of the constituent time clocks and the ensembled time, a clock signal at the same frequency as the universal time clock signal.
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Abstract
Methods and apparati are disclosed for providing disciplined clock signals at a plurality of nodes located throughout a network. In the preferred embodiments, a plurality of clocks are ensembled to provide ensemble time base information. A universal clock signal such as from a global positioning satellite (GPS) or Loran receiver is also provided and the ensembled time information is disciplined to the frequency or the phase of the universal clock signal to provide syntonization or synchronization throughout the network.
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Citations
27 Claims
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1. A method of attaining syntonisation between a local clock and a universal time source, wherein the universal time is transmitted via a signal over a medium that is subject to adding linear and non-linear noise effects to the signal, the method comprising:
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providing a plurality of constituent time clocks, each time clock providing a clock signal at the output; ensembling the outputs of the time clocks to provide ensembled time clock information, wherein the ensembled time clock information is more stable than any of the constituent time clocks; receiving the universal time clock signal repeatedly determining the difference in frequency between the universal disciplining clock signal and the ensembled time clock information; and generating from a plurality of said frequency differences and at least one of the constituent time clocks and the ensembled time, a clock signal at the same frequency as the universal time clock signal. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A time scale generator having:
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a plurality of local clocks, each local clock producing timing information, the timing information having a level of reliability and stability; an ensembler responsive to the plurality of local clocks to produce time scale information, the time scale information having a level of reliability and stability greater than the levels of stability and reliability of the timing information of each of the local clocks; a receiver adapted to receive from a communications channel that is subject to adding linear and non-linear noise to a universal disciplining signal having timing information therein; a universal disciplining clock signal generator producing universal disciplining clock information having timing parameter information in response to the received signal; and a means for disciplining the ensembled time base information to the timing parameter information of the universal disciplining clock information to provide a disciplined output signal. - View Dependent Claims (8, 9, 10, 11)
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12. A telecommunication network having a plurality of switching offices having a plurality of local clocks having a frequency with a stability and reliability, wherein the telecommunications network exists in an area that receives a signal over a medium that is subject to adding errors to the signal containing universal disciplining clock timing information having a frequency, wherein the improvement comprises at a plurality of at least some of the switching offices:
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a means for ensembling the plurality of local clocks for that office to provide ensembled time base information having a frequency and the ensembled time base information having a reliability and stability greater than each of local clocks for the office; a means for determining repeatedly the frequency difference between the ensembled time base information and the universal time base clock information; and a means for providing a local time base signal for use by the local office having a frequency based upon the average frequency difference between the ensembled time and the universal time clock information, whereby the local time base signals at said each of the plurality of switching offices are in syntonisation with each other. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A method of providing in a network comprised of a plurality of nodes transmitting units of information between each other, wherein the network being located in an area where a signal including universal time clock information is receivable through a medium that is subject to adding errors to the universal time clock information, syntonisation between a plurality of the nodes, the method comprising:
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generating local clock information at each of the plurality of nodes; receiving the universal time clock information at each of the plurality of nodes; determining at each of the plurality of nodes from time to time the frequency difference between the local clock information and the universal time clock information; generating based upon a plurality of the determinations said syntonised clock signal at each of the plurality of nodes having the same frequency. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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26. A method for disciplining an ensembled group of clock signals to a universal time source signal provided over a channel having both linear and nonlinear noise effects, the method comprising:
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using a time scale algorithm on information relating to the group of clocks and the universal time source signal to provide state estimates of the difference between an ensemble time and each of the group of clocks and to provide an ensemble time state with no weight being given to the universal time source signal in the ensemble time state; disciplining the ensemble time state to the universal time source signal through a low pass filtering algorithm to provide a disciplined time state;
endgenerating a clock signal based upon the disciplined time state.
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27. An apparatus for disciplining a collection of clock sources to a universal time scale received over a noisy channel, the apparatus comprising:
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a controllable oscillator providing as an output a clock signal disciplined to the universal time scale; and a processor responsive to each of the clock sources and the universal time scale to provide an ensemble time scale giving the universal time scale zero weight and using the difference between the ensemble time scale and the universal time scale to control the oscillator.
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Specification