My normal stats are around:
3dB SNR
24.5 Attenuation
Downstream of between 18500 - 19500 kbit/s
Loop length around 1100m
For a day or two I had noticed a drop in sync speed after a couple of random disconnections. It turned out the my microfilter had kicked the bucket. I had lots of CRC errors etc (Interleaved). I replaced it today with a new one (ADSL2+ compatible) and my sync rate went back up to normal.
This evening we had had quite a bad thunderstorm which caused my connection to drop a few times. Now my SNR has shot up to 12.9dB and my sync speed is around 12000 kbit/s. Even with the SNR at 12+dB I am still getting lots of CRC errors. This could simply be down to the storm still being in the area.
I have tweaked my SNR down to about 6.3dB (Netgear 834GT with DGTeam firmware) and now I am sync'd at 15588 kbit/s. I know that tweaking is probably not the best idea considering that there are errors on the line but to be honest, the error rate is about the same.
I have read some not so encouraging things about BT's DSLAM on this subject but I wondered if anyone has any experience or knowledge with regards to SNR recovery times?
Cheers, Adam
Before:
(http://speedtest.net/result/2133946486.png)
After:
(http://speedtest.net/result/2140053229.png)
EDIT: Turning the SNR tweak off now, terrible speed, too many errors and overheads lol
Just a thought on BT adsl2+ connections I didnt think that you could over ride the margin. I know you can with IDNet LLU. I might be wrong of course.
Quote from: Steve on Aug 25, 2012, 20:19:47
Just a thought on BT adsl2+ connections I didnt think that you could over ride the margin. I know you can with IDNet LLU. I might be wrong of course.
Yeah, you definitely can. I tweaked from 12+dB SNR and got 12,000 kbit/s, down to 6.3dB SNR and got 15,588 kbit/s. You can do it via Telnet or DMT (http://lop.im/m68eU (http://lop.im/m68eU))
The storm seems to be passing and errors are not as bad. The RCO has risen to 18,364 kbit/s so things are looking good. SNR is still high though. Hopefully it will come down.
Fingers crossed :fingers:
Are you definitely with BT DSLAM. The only way I know to tell the difference on a Be* enabled exchange is failure to perform a BT speedtest (old version which gives IP profile or via support.
Yes, I'm on BT DSLAM. The only LLU round here is TalkTalk. The BT speedtest works for me. Just wish it was quicker :D
Thanks for that. :thumb:
Hmmm, SNR has now gone down to 6dB. No CRC errors at all but my profile seems to be stuck. I am stuck on 14333kb/s (used to get 19000+kb/s) Maybe the cap will be removed once it's been stable a while. We'll see.
BT uses banded profiles on adsl2+ to limit speed on unstable connections ie high error rates, noise etc. The highest banding ends at 14336 which is very similar to your current sync. As far as I am aware they can only be removed via request.