This topic

Noise Margin/Speed

domcoke — Sat, 05 Jun 2021 15:30:32 GMT

Total newb here... short explanation: I've had a 5 month long saga which I think I'm emerging from. Everything from drop wire replacements, lift and shifts, etc. etc.

Recently it was discovered that after a lift & shift, there was a failure to reset card profiling, which an engineer said was probably causing latest drops/errors, & since that visit, & card reset, things have been stable and great. Though, my speeds have not returned to what I think they should be... which is basically full whack. I'm on an 80/20 circuit, with a brand new line to cabinet [which is performing almost perfectly according to engineers' tests] which is a maximum of 50 yards away from my house. I think the fact I haven't returned to what I was getting prior to all these problems might be something to do with a noise margin setting - though I'm not sure. I was previously able to sync 80/20 & get a throughout speed of 74/18 - but I think recent engineer visit has cracked it. Cos I'm now not getting the daily drops I was. However, I seem to be stuck on 74/16 sync speed - which is below my previous. I know this is a "first world" problem, cos even that is pretty good - but with the work I do, as a documentary editor, I need as much juice as I can get out of it.

Any one have an idea as to whether the noise margin is the thing that's causing it not to rise back to normal? Is it higher than it should be? Can it be lowered? - any help really gratefully received - ta - Dom

Here are my stats:

Firmware version:v0.26.04.04227-BT

Firmware updated:Fri May 14 00:01:16 2021

Board version:R01

GUI version:1.74 12_11_2020

DSL uptime:4 days,05 Hours23 Mins24 Secs

Data rate:16.996 Mbps / 74 Mbps

Maximum data rate:25.075 Mbps / 87.522 Mbps

Full Fibre (FTTP) Mode:Off

Noise margin:10.8 / 9.3

Line attenuation:6.8 / 12.6

Signal attenuation:6.8 / 14.6

Re: Noise Margin/Speed

pippincp — Sat, 05 Jun 2021 15:51:01 GMT

Those look OK. Nothing to be done there.

Re: Noise Margin/Speed

domcoke — Sat, 05 Jun 2021 15:54:14 GMT

oh... I was reading that they should be around 6db? Have I got this wrong? also... given the maximum data rate is 25.075 Mbps / 87.469 - I'm not sure why I haven't returned to 80/20 - maybe this will happen over time after my recent stability issues? How long does this usually take?

Re: Noise Margin/Speed

pippincp — Sat, 05 Jun 2021 16:05:45 GMT

You will never have a 6dB noise margin due to the max attainable. If you now have a stable line then it can take up to 3 weeks to return speeds. Or longer.

Re: Noise Margin/Speed

domcoke — Sat, 05 Jun 2021 16:09:21 GMT

ok thanks for your help. I don't really understand the relationship between noise margin/max attainable. But, to be fair, I don't really understand noise margins in general. I just read somewhere about it being set to 6db. But to be honest, it's difficult to navigate the forums with such little technical knowledge - they can often be contradictory & impenetrable. But as long as my noise margin seems normal, then fine. Thanks

Re: Noise Margin/Speed

pippincp — Sat, 05 Jun 2021 16:21:22 GMT

The target noise margin is 6dB but if the line is capable of more then the noise ratio changes.

A way to explain it is this. If they line is capable of a higher rate then the hub doesn't have to shout as loud to be heard, therefore the noise margin is different to a hub that does. 6dB is the margin where noise equals the shouting. With a higher max data rate then the hub doesn't have to shout as much to be heard so the noise margin gets further apart, ie, higher than 6B

Re: Noise Margin/Speed

domcoke — Sat, 05 Jun 2021 16:23:29 GMT

ah... ok..... that's clear. Great. So hopefully, as my line seems more stable now than it has been in months... I'll return to 80/20 sync once again in the next few weeks - providing the stability continues

Re: Noise Margin/Speed

pippincp — Sat, 05 Jun 2021 16:27:39 GMT

Correct. Hopefully so.

Re: Noise Margin/Speed

samtheaspie — Mon, 07 Jun 2021 18:09:16 GMT

I had this myself at my old flat, I found after a DLM profile reset due to a few errors on my life my noise margin was at 8db, but I left it on for a few weeks and it dropped down to 4db eventually. Just leave the router on and let it do its thing. That's what I found anyway. Noise margin works differently on FTTC than it did on ADSL connections.

Re: Noise Margin/Speed

domcoke — Mon, 07 Jun 2021 18:11:27 GMT

Great, thanks for reply... - It's been a long running saga, with many twists and turns - but I think this profile reset has resolved errors/drops - so gonna let it do its thing, and hope it'll return back to my previous sync speed of 80/20 - fingers crossed

Re: Noise Margin/Speed

samtheaspie — Mon, 07 Jun 2021 18:14:35 GMT

Solved: Openreach wont drop SNR - Page 3 - BT Community

That was might long winded nightmare I had back in Feb in my old flat!

Re: Noise Margin/Speed

domcoke — Mon, 07 Jun 2021 18:17:03 GMT

ha. For me it was a "fix one problem, create another". I think the lift and shift actually created worse problems than I had before. But apparently, cabinet ports are often the cause of a lot of issues. Though, bearing this in mind, it was strange that they were pondering whether router issues or electrical interference were causes of my drops - which, they weren't - unless my router has mysteriously fixed itself, or the electrical interference has disappeared