Question about stats

[Dan17]

Just registered.

I am not with O2, I am with sky but i thought that i would post this question on here as you seem to asnwer these kind of questions better. The question,

Its about the upstream speed, I have changed the router for one that has the same chipset as the exchange, which has improved my speed no end.
I want to know if the upstream SNR was decreased to say 6.5db to allow for the .5db movement, would that increase the upstream speed close to the 1.3Mb from what it is now. I have put my stats below.

ADSL Link Downstream Upstream
Connection Speed 14138 kbps 1164 kbps
Line Attenuation 43.0 db 18.5 db
Noise Margin 8.00 db 8.0 db

[Saturday]

Generally, decreasing the noise margin will increase the sync, though not beyond either the maximum the ISP allow for the package or more than the technology will support (obviously).

Upstream uses the first part of the available spectrum and downstream the remainder. Where line conditions are poor (noisy and/or long line) increasing the upstream can lower the available downstream.

Your line certainly isn't long or noisy. 14meg is very impressive for an attenuation of 43db and far higher than used to be possible with Sky - in fact I've never seen better.

You could certainly ask Sky to lower your noise margin (their default is 6.9db) but they do have a reputation of messing things up. It's a risk you'll have to decide whether to take.

[Dan17]

Having the upstream noise margin set to 6.9db, how much more would that add to what it is already, would that decrease in SNR get it over 1.2Mb.

Thanks for the help so far, much more help than skyuser offer on this subject.

[Saturday]

Sky should be able to push it up to close to 1.3meg if they choose to. I think it's early days for the new speeds that Sky offer and so far the upstream seems a little low for most customers. I don't know whether that's policy or just how they're setting up profiles with DLM. Were you ever to consider moving to O2, you could choose annex M which should give you comfortably over 2meg upstream with a possible small reduction in downstream.

Skyuser has thousands of active members (me included) but you have to take the rough with the smooth.

[Dan17]

With the upstream SNR at 6.9db roughly what should the speed be at.

[Saturday]

Impossible to say with any accuracy.

1.3meg is the maximum that ADSL2+ annex a will support. The actual sync speed you'd get is down to your individual line characteristics and how Sky set up the profile.

1285/1295 is typical for O2 on a relatively clean short line but as I said before, those sorts of speed don't seem to be appearing with Sky yet.

[Dan17]

Is there a reason why those upstream speeds are not being seen with sky yet.

[Saturday]

Only Sky would know the answer.

It could be that the levels of interleaving (for example) restrict the upstream sync, or any number of other technical reasons.

Or technical incompetency . . . . Or they want to limit upstream bandwidth on purpose

My guess is that it's a technical reason.

[Dan17]

Well I have sent an email to sky asking for the upstream SNR to be set to default, so i will see what happens and post the result.

Thanks for the help.

[Saturday]

Well it will be interesting to see the outcome.

If there are technical reasons for the lower sync or they just have profiles set at 1.1meg say, then reducing the noise margin won't have an effect - or more correctly, the noise margin can't be reduced i.e. that's the right noise margin for your line condition and profile.