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Possible to have CCSNR *AND* Banded Profile?

CX
Grafter
Posts: 745
Thanks: 2
Registered: 16-09-2010

Possible to have CCSNR *AND* Banded Profile?

Please note that I am happy with how my line is performing at the moment and don't want to action this change for the time being, I am mainly asking this out of curiosity.
When I first moved to 21CN, everything was great - I was getting higher speeds than ever before and no stability issues. After a line fault, DLM insisted on re-applying the 576-1152 banded profile which capped my sync rate at 1152kbps. Because the line was generally stable other than DLM's constant meddling, Plusnet used CCSNR to put me on a fixed 6dB Interleaved profile without banding and everything has been great since. My average sync rate is now in the 2000 to 2200kbps range, but occasionally it will sync higher, up at 2400, 2500 or even 2600kbps but is unable to maintain this.
I notice that there is a band for 1152-2272kbps which appears to suit my line characteristics perfectly. My question is, is it possible to be put on the 2272kbps cap AND keep the 6dB CCSNR, or is it one or the other? It seems that this would be the best solution for my line if it is possible since it keeps the connection from overreaching itself (capping at 2272) but at the same time keeps it from underperforming (aiming for 6dB SNR).
I can understand that in many cases allowing it to sync uncapped is ideal, but for me, the next IP Profile (2500k) is too far away to ever be reached (requires 2848kbps), so I never get any advantage from going above 2272kbps, which puts me just inside the 2Mb profile if I'm not mistaken (is this right, or would it be 1750k?).
My only concerns are:
1) If the 1152-2272 band is forced, does DLM then have free reign to mess with the target SNR, potentially pushing me to the low end of that band?
2) Is the 1152-2272 band sufficient to get a 2Mb IP profile assuming 'infinite' SNR?
Thanks. As I said, I don't want to change anything yet! Thanks for reading!
2 REPLIES
lexusuk
Grafter
Posts: 567
Registered: 20-10-2009

Re: Possible to have CCSNR *AND* Banded Profile?

The answer is Yes.  We can force the line to be banded between 1M and 2M (1152kbps to 2272kbps) and can at the same time force the line to remain on a 6db target SNR margin in both upstream and downstream.  The only minor disadvantage to forcing the line to be banded is that the interleaving settings will have to be set to High Delay instead of the normal No Delay (Interleaving Off) or Medium Delay (Interleaving On).  This however would have a negligible effect in real world terms.
With regards to the IP profile, in order to maintain an adsl2000 profile you must be synchronised at 2272kbps at minimum (i.e. maxing out the 1M to 2M band).  Looking at previous test results I'd say this would be touch and go.  When we first un-banded your line your sync rate was just under 2Mbps which was too low to hit the adsl2000 profile requirements.  Also, with your line loop loss (attenuation) at 74.2db we'd normally recommend using the 9db target SNR profile but in your case I can see we used 6db instead to try to boost performance and this does not appear to have had any negative effect regarding stability.
Personally I'd recommend keeping the line un-banded as you are more likely to maintain an adsl2000 IP profile but we are happy to band the line 1M to 2M if you wish.  Worst case scenario:  We simply return you back to your current line configuration if the change does not have the desired effect.  Let us know how you would like to proceed if at all.
CX
Grafter
Posts: 745
Thanks: 2
Registered: 16-09-2010

Re: Possible to have CCSNR *AND* Banded Profile?

Thanks for your detailed reply. I will go with your suggestion and leave things as they are for the time being.
I was having some slowdown in throughput in the evenings with a 2400+ sync rate, but this has ceased since swapping back to my old Netgear DG834G router which is connecting just as fast but is not suffering the noise margin drops. I will keep an eye on things over the next couple of weeks and may put in a request if the throughput drops begin to occur again but for now it appears to be behaving (great in fact for a line which 6 years ago was not predicted to support ADSL at all).
Thanks again.