Broadband Related > Broadband Technology

Variations in attenuation and tx-power figures

<< < (2/2)

burakkucat:

--- Quote from: Weaver on April 12, 2023, 08:41:46 PM ---Can anyone explain something for me, I realise that I don’t know what the power value means. In the case of downstream power, does this  value mean tx-power as reported by the ATU-C to the ATU-R, or is it something measured by the ATU-R? I’m assuming that this is not the case, as this would be mixing in the concept of attenuation.

--- End quote ---

I assume the former rather than the latter, for the same reason that you mention in the second sentence (which I have quoted above).

Weaver:
My calculator says that -0.7 dB is a drop of ~7.7% in voltage terms (as opposed to power). So given that we’re assuming that this is a report originating in the ATU-C received by the ATU-R and passed on to me giving the ATU-C’s opinion of its own output, then that ought to show a conscious decision by the ATU-C to reduce the output power. Why would it do that ? To reduce crosstalk? Could that be to do with a new bit loading in the ATU-C’s downstream? And that did indeed happen. There were two retrains in the afternoon, and those happened before the figures were captured. There was a loss of downstream sync rate of about 250k on that line, compared to the day before, for reasons unknown.

XGS_Is_On:
The DSLAM, if so configured, will lower power to the minimum required to achieve SNRM. Given your service can't rate adapt up no point wasting electricity driving a 15 dB margin if the target's 6 for instance.

Best guess you lost the 250 kbps due to a transient line condition and the DSLAM is happy that it can maintain the circuit at the target SNRM with that power level. It'll increase it if it needs to.

Navigation

[0] Message Index

[*] Previous page