E-Mail Sent to this address will be added to the BlackLists wrote:
Cell towers are already synchronized with stratum one
servers and / or GPS, and usually contain stable oscillators
e.g. rubidium, cesium, ...
Most (GSM/3G/4G) cell towers make do with OCXOs/TCXOs, but very good
ones, rated at a few ppb/day in drift rate.
I.e. pretty much perfect compared to what NTP usually has to work with.
Cell towers can't do seamless handoffs for moving cell phones
to adjacent towers without close synchronization.
The interesting part here is that the actual requirement is for
_frequency_ synchronization, not absolute time sync!
Better FLL corresponds directly with better hand-off performance at
speed: Driving at highways speeds require something like 50 ppb afair (I
was the chief architect for a national cell phone network for a couple
of years), a bullet train requires 20 ppb in order to handle the Doppler
effects.
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
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