Over the last couple of days, I enhanced my DSL line monitoring software for the ipad to have it watch for variations in attenuation and tx-power figures.
Almost immediately I got the following warning, which is correct (checked the figures by hand):
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* Warning: line properties out of range: this may indicate a line fault, but this is not automatically assumed here. Significance depends on the direction of change and the size.
Link #3: upstream: the current value of the attenuation 40.4 dB differs from the expected 40.5 dB
Link #3: downstream: the current value of the tx power 18.2 dBm differs from the expected 17.9 dBm
That’s the whole report, no changes for other lines. This report was obtained in the middle of the night, and the comparison expectation values were obtained in daytime. So I’m wondering if this is a daytime-night time thing as far as the attenuation is concerned, but a difference that low could just be in the noise, a rounding change. I don’t understand the tx-power change though. Also there are no changes for other lines.
What kind of daily variation and occasional variations do other people see?
This is the first release, and I’m going to put in ignore-tolerance bands of some sort, yet to be determined.
This being an early release, I’m thinking that I could extend the use of this code. My aim is to spot indicators of line faults or any kinds of serious weirdness. Are there other important DSL line properties that I should monitor to check their values remain constant?
One final thing, I’m concerned about what might happen with bogus differences if the SNRM and hence the sync speeds change, as I seem to remember that Kitz has pointed out that the calculation of the SNRM might be bits-per-bin spectrum dependent - is that correct? I don’t really want to make my existing database of expected comparison values SNRM-dependent, that would be a lot of typing and it would be well nigh impossible to obtain all those values.