Method for constructing a distributed boundary clock over a dedicated communication channel
A method for implementing a distributed boundary clock in situations where book-end devices such as microwave TX/RX pairs must collaborate in achieving PTP on-path support is described. A dedicated channel, generally low-speed compared to the main channel is used to transfer timing from the master side to the slave side using framing and super-framing applied to the digital channel. Time-stamps of events such as super-frame boundaries are communicated between the two sides to enable timing transfer.
1. A method, comprising synchronizing a first clock located at a receiving side to a second clock located at a sending side including aligning the first clock to the second clock by adjusting a frequency of the first clock using an estimate of a frequency error of the first clock δf m (i) based on change in time error from iteration to iteration where
δ
f
m
(
i
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=
(
1
mT
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·
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ɛ
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-
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where the frequency error estimate in the current iteration i is developed as the difference between the time error estimate, ε(i), in iteration i and the time error estimate, ε(i−m), m iterations in the past, scaled by the effective time interval mT, where T is the duration of each iteration and the iterations are contiguous.
2. The method of claim 1 , further comprising delivering a timing reference over a dedicated framed digital channel.
3. The method of claim 1 , further comprising building a distributed boundary clock using frequency error estimates to align the frequency of the first clock to the frequency of the second clock.
4. The method of claim 1 , further comprising deploying a radio relay link for backhaul of telephony traffic between base-stations and a wireless network, the radio link having a primary wide-band channel and a secondary narrow band channel to transfer timing.
5. A non-transitory computer readable media, comprising computer or machine readable program elements translatable for implementing the method of claim 1 .