Our plan is to first build a test bed consisting of two test-boxes
in a well known setup at the NCC and a third test-box at a remote ISP.
This test bed will be used for:
Tests of the clock cards and their performance, in particular:
Development of the interface for GPS clocks.
Measurements of the accuracy, drift and resolutions that can
be obtained with both GPS and NTP clocks as well as tests of
hardware modifications and filter algorithms to reduce
drift and increase the accuracy of the clocks.
Measurements of the differences between two identical clocks.
Tests of the effects of the environment (temperature!) on the clock.
Testing possible locations of the antenna and their effect.
Tests of the hardware stability.
Tests of the system maintenance procedures.
External checks: for example by connecting a scope to two
clocks and comparing the clock-pulses with an independent, reliable,
source.
In short, with this setup we should convince ourselves that the hardware
does what we expect it to do.
We will check the internal consistency of the data by comparing
one-way and two-way measurements. For example, the sum of the one-way
delays in traffic sent from A to B and B to A should, assuming that the
paths are the same, be equal to the delay measured with a two-way
measurement.
Also, a delay measured for traffic from A to C via B, should be
about the same as the sum of the delays for traffic sent from
A to B and B to C.
There are more tests like this possible, they should give us a handle
on the in-situ performance of the test-boxes.
The treatment of statistical errors is well-known and should not
present any problems.
In order to estimate the systematic errors, we will do tests where
the clocks are artificially set of by x ms and see if we
can detect this from the results.
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