Mxsmanic wrote:
Miguel Cruz writes:
The most reasonable way to ensure they are relatively accurate is to
ensure they are absolutely accurate.

Not necessarily. It may be cheaper to provide very stable time
references for the network for relative measurement rather than try to
derive those measures from an ultra-accurate time-of-day source. This
is especially true since the accuracy required might be microseconds
or better, and this is expensive to derive from the time of day.

If you know where you are then you can synchronize with microsecond
accuracy against other devices that also know where they are, using
freely-available time-of-day sources.

On the other hand, synchronizing in any other way would be more
complicated and expensive.

I do not see any reason to believe cellular phone companies would spend
more money and effort just to prove you right.

For example, most time of day sources provide extremely high long-term
accuracy at low cost, but they provide poor short-term accuracy unless
a great deal of effort and money is expended.

Hint: Cell towers are not using NTP.

A radio source will keep your network locked to the correct time of
day with long-term accuracy equal to that of the best atomic clocks,
but the short-term accuracy may be off by hundreds of milliseconds
per day unless you spend a great deal on either continuous
synchronization or a local reference that is extremely accurate when
free-running. In the latter case, you might as well skip the
time-of-day reference.

No, because the point is to get the clocks at multiple locations
synchronized with each other.

[ boring crap that everyone knows and has nothing to do with the issue
omitted ]

miguel
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