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Old 13-01-2009, 19:16   #14
Ignitionnet
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Location: Leeds, West Yorkshire
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Re: 55 DbmV upstream power level

Quote:
Originally Posted by moaningmags View Post
Another edit after quick tutorial from said friend, the upstream can be adjusted by an attenuator.
This would usually happen at the cab, but if low downstream SNR is causing the upstream power level to increase to be heard by the ubr, fitting an attenuator would fix the SNR issue, lowering the upstream power level.
I had another thought about this.

If bad downstream SNR were causing issues with upstream it would be because the modem were not seeing the periodic station maintenance responses from the uBR / CMTS, so it would increase transmit power thinking it was not being heard. When it did actually get a response from the CMTS it would be along the lines of 'Oi stop shouting, drop your transmit power down xdBmV' so I can't really see how it would reduce Tx power long term.

What it might resolve is large numbers of power adjustments due to the modem not seeing the range response from the CMTS and hence incrementing transmit power by the DOCSIS standard amount, however if the downstream path is so munted that the modem is missing large amounts of range responses and periodic station maintenances from the CMTS the upstream power is a total non-issue.

A connection that would suffer issues like this would be very, very broken indeed and upstream Tx power would be the least of worries on a connection like this. It would likely be too busy losing QAM sync on the downstream to be bothered what the upstream is doing.

---------- Post added at 18:16 ---------- Previous post was at 18:14 ----------

Quote:
Originally Posted by caph View Post
I've been told by an engineer that my local increase in upstream power is being caused by my "exchange" being upgraded to 50Mb.
That sounds like BS to me. Doesn't make any sense at all that your upstream power would need to rise to accomodate 50Mbit and the DOCSIS 3 overlay.
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