Billion 8800NL: increasing rather than decreasing target SNR

Does anyone here know the figures to insert into the Billion 8800NL's Target SNR tweaking configuration in order to INCREASE the SNR rather than to decrease it? Billion and others have published tables of SNR tweak figures on the Web but they all assume the user wants to DECREASE the Target SNR to get more speed, and that's not what I want. In my case, with the 8800NL working in ADSL mode, I'm wanting an INCREASE, in order to gain more line stability (with lower speed).

The figures required appear to have changed, starting with model 7800DXL. For instance:

7800:

150 = +3dB (increase of 3dB)
200 = +6dB
100 = 0dB (no change)
50 = -3dB (decrease of 3dB)
65500 = -9dB

7800DXL:

6 = 0dB (no change; stays at 6dB)
3 = -3dB (decrease of 3dB)
4093 = -9dB

8800NL:

2 = -4dB
3 = -3dB
6 = 0dB (no change; stays at 6dB)
4093 = -9dB

I use a 7800 at present and am planning to get an 8800NL, which will initially be used in ADSL mode for several months. Normally, I have to operate at a target SNR of 12 - 15 dB. Unless the DSLAM on my line is already engaged into a 12 or 15dB collaboration with whatever is attached at my end, when I swap the 7800 for the 8800NL I'll need to adjust the target from the standard 6dB to my required 12 or 15dB. But the figure(s) to insert into the 8800NL for that are what?

I've had the above posted for a week now. It's had many views but nobody has offered the sort of information I've been seeking. Clearly, there's lots of interest in the topic but either individuals with the 8800 are, for one reason or another, not in a position to offer figures that they've found worked or have had no need to experiment anyway, especially in trying to RAISE the SNR. However, I've been busy configuring the 8800 in more detail in the meantime and in the last few days have bitten the bullet and tried inserting some numbers into the SNR box in the 8800, to see if I could get the sort of downstream target SNR I've been wanting, namely 15dB. I believe I've now succeeded.

I found that my starting line SNR was 12dB. That figure stemmed from the SNR line value with the 7800 router, so happened to still be operational. However, even 12dB was giving marginal stability, so I decided to try to increase that by another 3dB, to 15dB. Looking at the numbers that are already known to work with the 7800DXL and 8800NL for LOWERING the target SNR from around the norm of 6dB, I reckoned that inserting numbers such as 7, 8, 9, 10, 11, .... 15 would add 1dB each time. Thus, if starting from 6dB, it seemed logical to input the number 15, since theoretically this would add 9dB of margin.

That didn't turn out to be quite the case, though, and I think it's because in my case the starting point was not 6dB, it was 12dB. Instead of getting 15dB, I got 21dB (12dB + 9dB = 21dB). Time for another think. I hadn't done a Restart of the 8800, so I then tried the number 9 instead. I reckoned that that should give just a 3dB increase. It did, and so I got to my 15dB.

Thus, although this is not definitive, we do now have a little bit more guidance on which numbers, in the 8800, will produce the requisite target SNR.

Contrary to what some people maintain, it looks as though the inputted numbers produce RELATIVE increases in target SNR, not absolute. Whilst 6dB may well be the initial line SNR for many new setups, or even pre-tweaked ones, it's not the situation in many others. In theory, the line SNR can be anything from 0dB up to 18dB (and even more, it seems). This is probably why Billion don't publish absolute figures for this.

However, it looks as though, starting with the 7800DXL, Billion may have changed their algorithm for this, in as much as making the required numbers a bit more logical and within-range than with, say, the 7800N. You just have to keep it in mind that, each time, the number you insert will need to be one that'll produce a RELATIVE change in SNR, ie. relative to the particular starting value. This is why it can become bewildering if you keep on changing the SNR and restarting the router each time, as there'll be a new starting point each time.

So, concluding this is what I found:

Inputting the number 15 renders a relative change of +9dB.
Inputting the number 9 renders a relative change of +3dB.

I guess that if I'd inputted 12, the result would have been +6dB above the starting SNR.

I didn't take it any further than that second attempt, as in my case I didn't need to. But I hope this will be of use to others now. I'll be keeping an eye on this posting to see if others also find that these numbers work.

Hello

I have this router, but Im having stability issues so haven't had chance to play. However I thought this now worked a lot more simpler e.g. SNR target of 5 you put in 5.

If you have a look here:

http://www.increasebroadbandspeed.co.uk/billion-8800...

This would also suggest this.

It looks like those instructions are assuming your default Target SNRM is 6db.
Billion have some info on SNR Tweaking at the bottom of this page http://billion.uk.com/edu/VDSL2/index.html

For the OP. I hear Billion support are pretty good at answering queries if you still need an answer.

Currently saving up for my own 8800nl to use on my FTTC line

I hope you are aware that Openreach say user tweaking of the noise margin is not allowed on FTTC?

Note : It is the DLM system that sets the line profile, and this should not be interfered with by CPs/users setting rates, SNR margins etc. at the modem.

I did in fact try it before that was stipulated, and the results were very unpredictable. In fact, a complete mess. The reason I think being that instead of the upstream then downstream frequencies being separate blocks as on ADSLx, on VDSL2 they are interlaced.

Edited by RobertoS (Mon 01-Dec-14 15:08:58)

I'm not considering tweaking.
The page I linked to mentions snr tweaking for ADSL lines.

I just mentioned I'm intending to buy a 8800nl for my FTTC(VDSL) line as this router works for ADSL as well

Yes, that happens to be the case if you're already at 6dB and you want to achieve 5dB, but the figures apply only to the 6dB starting point, as far as I can see. As I say, Billion themselves don't publish (as far as I'm aware) a definitive table of numbers and the new SNR values they produce, as they say that all situations will be different and there'd be far too many permutations. So, instead what you tend to see are just the figures for a 6dB starting point, going downward, as 6dB is probably what most new setups are and most users then try to get more speed.

Yes, I'm indeed aware of that, but this topic is not about using the 8800 in VDSL mode, it's about using it in ADSL mode.

Quite! The reason I myself got the 8800 was because I wanted for the present to remain on my ADSL connection but, at some later date (possibly next year when I'll have moved house) swap to an FTTC account. The 8800 is sufficiently complex in its ADSL configuration settings alone that I felt it prudent to get and use it first in ADSL mode, and then later work out at leisure how I'd need to set it up for FTTC operation. Clearly, tweaking a VDSL line in regard of SNR isn't made possible, only an ADSL line.

In reply to a post by meditator:

Yes, I'm indeed aware of that, but this topic is not about using the 8800 in VDSL mode, it's about using it in ADSL mode.

Note the post headers . I was replying to b4dger who intends to use this router on FTTC.

He has since said he doesn't want it for FTTC tweaking, so that's OK.