Method and apparatus for reducing waiting time jitter in pulse stuffing synchronized digital communications
First Claim
1. A method for reducing the jitter and wander of a data signal that is passed through a pulse stuffing synchronizer and desynchronizer, said method comprising the steps of:
- (a) sequentially adjusting the phase of a reference clock signal so as to cause said reference clock signal to closely track the phase of a clock signal recovered from said data signal;
(b) storing information representative of the net effect of phase adjustments of said reference clock in step (a);
(c) conveying said net effect representative information stored in step (b) to said desynchronizer;
(d) generating a sequence of phase adjustments in accordance with said net effect information; and
(e) generating a clock signal for controlling the operation of said desynchronizer in accordance with said sequence of phase adjustments generated in step (d).
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Accused Products
Abstract
A wander reduction mechanism in an HDSL pulse-stuffing synchronization system provides a more precise measure of the phase of the incoming asynchronous signal than is obtained in conventional schemes, in which the only information available is the presence or absence of stuffing pulses. An auxiliary phase comparator and phase adjuster are incorporated into the synchronizer-multiplexer to generate a reference data clock (derived from the synchronized data clock), so that the incoming unsynchronized data clock can be tracked. As the clock is iteratively phase-adjusted, the respective changes are accumulated. At the end of a prescribed measurement interval, the net contents of the accumulator are encoded and transported over the synchronous digital data communication channel to the receiver. By decoding this sequence information, the desynchronizer is able to generate a desynchronized data clock having the same number of net phase adjustments during a measurement period as the reference clock at the synchronizer.
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Citations
31 Claims
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1. A method for reducing the jitter and wander of a data signal that is passed through a pulse stuffing synchronizer and desynchronizer, said method comprising the steps of:
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(a) sequentially adjusting the phase of a reference clock signal so as to cause said reference clock signal to closely track the phase of a clock signal recovered from said data signal; (b) storing information representative of the net effect of phase adjustments of said reference clock in step (a); (c) conveying said net effect representative information stored in step (b) to said desynchronizer; (d) generating a sequence of phase adjustments in accordance with said net effect information; and (e) generating a clock signal for controlling the operation of said desynchronizer in accordance with said sequence of phase adjustments generated in step (d). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for reducing the jitter and wander of a data signal that is passed through a pulse stuffing synchronizer at a transmit site, conveyed over a digital data communication link to a receive site, and recovered by a desynchronizer at said receive site, said system comprising:
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at said transmit site, a timing signal extractor which is operative to recover a clock signal contained in said data signal; a reference clock generator which generates a reference clock signal; a phase adjuster which is operative to sequentially adjust the phase of said reference clock signal so as to cause said reference clock signal to track the phase of said clock signal recovered from said data signal; a phase adjustment accumulator which stores information representative of the net effect of sequential phase adjustments of said reference clock by said phase adjuster; and a pulse stuffer which is operative to controllably insert into digital data stream to be conveyed over said digital data communication link to said receive site, stuffing pulses and signals containing said information stored by said phase adjustment accumulator. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for reducing the jitter and wander of a data signal that is passed through a pulse stuffing synchronizer at a transmit site and transmitted over a digital data communications channel to a desynchronizer at a receive site, said method comprising the steps of:
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at said transmit site, (a) sequentially adjusting the phase of a reference clock signal so as to cause said reference clock signal to closely track the phase of a clock signal recovered from said data signal; (b) storing information representative of the net effect of phase adjustments of said reference clock in step (a); and (c) encoding signals representative of said net effect representative information stored in step (b) for transmission to said desynchronizer at said receiver site. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
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27. A demultiplexer-desynchronizer arrangement for a receive site of a communication system, said receive site being coupled to receive a digital data stream conveyed over a data communication link from a transmit site, said digital data stream including stuffing pulses that have been inserted at said transmit site and signals containing information representative of the net effect of sequential phase adjustments of a reference clock by a controlled phase adjuster at said transmit site, said arrangement comprising:
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a stuffing pulse decoder which is operative to derive said net effect representative information signals contained in said digital data stream; a phase adjustment generator which is operative to generate a sequence of phase adjustments in accordance with said net effect representative information signals; and a controlled clock signal generator which is operative to generate a clock signal for controlling the operation of said desynchronizer in accordance with said sequence of phase adjustments generated by said phase adjustment generator. - View Dependent Claims (28, 29, 30, 31)
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Specification