| 摘要 |
By recognizing that it is not necessary to identify a synchronization failure immediately when the failure occurs, but rather not until the failure results in a detectable difference, the method and system described herein can distinguish between Cell Delay Variation (CDV) and loss of synchronization. Because CDV will have a larger effect on the stability than a failure of the frequency recovery system at the precise moment of the failure, a synchronization failure cannot usually be distinguished from CDV for several minutes or hours, depending upon the stability of the reference clock. The present invention monitors a fill level of a play-out buffer in the ATM network, and attempts to determine if a variation in the fill level is linear with time, which is indicative of a synchronization failure. Upon detecting such a failure, the method of the present invention switches to an adaptive method for frequency recovery. If the variation in the fill level of the play-out buffer is not linear, but an underflow/overflow (or slip) has occurred, then the method of the present invention can inform an intelligent buffer control that the underflow/overflow is not due to the presence of a synchronization failure, which enables the intelligent buffer controller to take appropriate action.
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