Nortel Networks Corporation

Blackberry Corporation

Apple Inc.

Philippe Wu

Charles Tremlett Nicholls

Gregory Carleton

Steve Andre Beaudin

Charles W T Nicholls

Eric Gagnon

Yu Yang

Embodiments of the invention include a method for use in a device having a local oscillator. The method includes performing, for the local oscillator that is disciplined by an external reference signal, while locked to the external reference signal, training at least two mathematical models of the oscillator to determine a predicted correction signal for each mathematical model based at least in part on a correction signal that is a function of the external reference signal and which is used to discipline drift in the oscillator. The method also includes selecting a mathematical model of the at least two mathematical models that results in a smallest time error when disciplining the oscillator to use when the external reference signal is unavailable and an alternative correction signal is to be used to discipline drift in the oscillator. The method further includes testing the selected mathematical model using a sampled version of the correction signal such that the selected mathematical model can be used without the need for a testing duration that is in addition to a period of time used for the training.

System and method for built in self test for timing module holdover

Aspects of the embodiments include a method for synchronizing a device having an oscillator to a reference signal. A correction signal can be determined based on the reference signal. A mathematical model of the oscillator can be trained based at least upon the correction signal. A predicted correction signal for the trained mathematical model can be determined. A time error using the predicted correction signal can be generated to assess suitability of the trained mathematical model for disciplining drift in the oscillator and synchronizing the device when the reference signal is not available.

A method and apparatus for correcting oscillator frequency drift due to crystal aging. Correction signals that reflect a difference between an oscillator timing signal and a reference timing signal over a reference timing signal interval are modeled so that auxiliary correction signals can be generated in the event of loss of the reference timing signal. A temperature curve is generated to model how temperature variation impacts oscillator frequency drift. A rate of frequency drift due to crystal aging is also determined. During loss of a reference timing signal, auxiliary correction signals can be generated to maintain the oscillator at a desired frequency until the reference timing signal becomes available again.

Method and system for correcting oscillator frequency drift

A reference timing signal apparatus with a phase-locked loop (PLL) has a computer algorithm which adaptively models the multiple frequencies of an oscillator following a training period. The oscillator is part of a PLL and the oscillation frequency thereof is controlled in response to the phase detector output. The computer algorithm processes the control signal applied to the oscillator. The computer algorithm updates the characteristics of the model relating to the aging and temperature of the oscillator, using for example, a Kalman filter as an adaptive filter, in accordance with a cumulative phase error in the PLL calculated during a given time interval. By the algorithm, the subsequent model predicts the future frequency state of the oscillator on which it was trained. The predicted frequency of the model functions as a reference to correct the frequency of the oscillator in the event that no input reference timing signal is available. Also, the calculated phase error is stored and is used while no input reference timing signal or accurate predicted frequency value is available. With the model updating algorithm, oscillators of low stability performance may be used as cellular base station reference oscillator, which is based on satellite systems, for example, GPS, GLONASS or Galileo systems.

Reference timing signal apparatus and method

An input reference timing signal oscillator of a phase-locked loop has a computer algorithm which adaptively models the multiple frequencies of an oscillator following a training period. The oscillator is part of a phase-locked loop and the oscillation frequency thereof is controlled in response to the phase detector output. The computer algorithm processes the control signal applied to the oscillator. The computer algorithm updates the characteristics of the model relating to the aging and temperature of the oscillator, using for example, a Kalman filter as an adaptive filter. By the algorithm, the subsequent model predicts the future frequency state of the oscillator on which it was trained. The predicted frequency of the model functions as a reference to correct the frequency of the oscillator in the event that no input reference timing signal is available. With the model updating algorithm, oscillators of low stability performance may be used as cellular base station reference oscillator.

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Kanata, Canada

Philippe Wu