Upstream SNR All Over The Place

Hi all, I'm on Xilo, via C&W LLU.

ADSL2+
Downstream 13320Kbps, att 31.5db, SNR 9db
Upstream 1023Kbps, att 18db, SNR between 0.5 and 9db

Over the last couple of days my SNR on the upstream side has been all over the place. It's been between 0.5 and 9db and it's causing lots of connection drops. I then reconnect with a lower upstream speed usually between 600 and 900K. The drops/re-syncs can happen as often as every 2 minutes. I've tried the usual change filters, plug into test socket, reboot router etc, but this has made no difference.

Anyone have any idea of the things that are likely to be causing this?

Thanks in advance.

The upstream makes use of frequencies between 25 and 138 kHz (see http://en.wikipedia.org/wiki/File:ADSL_frequency_pla... ) so noise in this region is the likely candidate. Anything new in the house or locality which could be causing the interference?

But local noise will not be of sufficient power levels to affect upstream, but it could be noise close to the exchange and thus little that the OP can do.

It could well be a problem with the modem or front end filter (not the plug in one) but part of the modem interface.

In reply to a post by john2007:

The upstream makes use of frequencies between 25 and 138 kHz (see http://en.wikipedia.org/wiki/File:ADSL_frequency_pla... ) so noise in this region is the likely candidate. Anything new in the house or locality which could be causing the interference?

No nothing new

In reply to a post by MHC:

But local noise will not be of sufficient power levels to affect upstream, but it could be noise close to the exchange and thus little that the OP can do.

It could well be a problem with the modem or front end filter (not the plug in one) but part of the modem interface.

Xilo have been on the phone to C&W and they can see the noise apparently. So does this rule out my hardware?

I will try and borrow another router and see if that helps.

It would appear so, but trying another router is always a good thing - just in case.

Can you note me the ticket number and i'll keep an eye on it.

Matt

Hi Matt, the ticket number is 63967.

I have my eyes on it now and will review the progress throughout the afternoon.

Matt

In broad terms ...

If the noise was generated at your end, the amplitude of it being picked up by the cables would need to be at the same level as the signals and across the band. For that to happen it would need to be something generating excessively high EMI (noise) local to your equipment. But your transmitted signal will have attenuated significantly by the time it reaches the exchange and as such noise there could be at 1/1000 of the level (-30dB) and cause the same problems.

Try another router and if that has problems, turn off EVERYTHING in the house except router and PC and if the PC is a laptop run it from battery only.

Thanks Matt. First class service as always.