Noise margin too low

Having some issues with my ADSL2+ Connection

http://gyazo.com/89f884313ce435d95ac8786bc8f3fe82

You might think 13.5 snr aint too bad, it isnt, it does hold the sync w/o a problem, but, i am planning to upgrade my service, i am only 2.5km away from exchange so i should be getting about 13 mbps if we go by attenuation, but the snr is whats holding me back, i was looking for tips on how to improve snr, i am not using a spliter btw.

Are you on LLU?

Yes.

Too low? How'd you work that out? It's too high!

In reply to a post by Xnbz:

so i should be getting about 13 mbps if we go by attenuation

Only with a NM of 3 to 6 dB, as is the normal standard.

Who's your ISP? I'd say you're being capped. Also on upstream.

What do you mean you are not using a splitter? Don't you have a phone plugged in? Have you tried connecting to the hidden test socket?

What uograde you planning & why?

Edited by XRaySpeX (Thu 16-Jul-15 21:56:53)

And what else other than a phone has he got plugged into his phone line/extensions.

In which case you can change your target noise margin manually (or your ISP can). BT has it set automatically by the DLM, but with LLU you can change it yourself. I suspect its set too high so a call to your ISP should be able to lower it if you tell them what to set it up (6db for example)

Also if you have migrated to TTB LLU, there default noise margin is 11db which is way too high.

Edited by bobble_bob (Thu 16-Jul-15 22:44:53)

In reply to a post by RobertoS:

And what else other than a phone has he got plugged into his phone line/extensions.

Nothing of course!

Ok so im kind of getting confused with this 'target' thingy, when i said im not using a splitter i ment that there is no phone being used on the line.



Isnt it better if you have lower attunuation?

And isnt it better if you have a higher SNR?


Well, right now, my SNR is 17, thats acceptable, but only for my current speed, if i upgrade its gonna drop, but the thing is that i cant even upgrade cuz the cap for 45 attunuation is 6-7 mb

So im confused as to how im being capped and i need some more explanation on target noise

Thank you

In reply to a post by Xnbz:

Isn't it better if you have lower attenuation?

Yes, but generally you can't change it. Is is basically your line length.

In reply to a post by Xnbz:

And isn't it better if you have a higher SNR?

No, The higher the (sync-time) NM, the lower the sync speed will be to compensate for the greater allowed noise within that margin.

If you upgrade to what?

i can't even upgrade cuz the cap for 45 attenuation is 6-7 mb

Don;t understand this at all? Please explain. What 45 attn? Yours is 35. What cap? Do you mean the estimate for a 45 db attn? It's not a cap but a prediction. It's not hard & fast.

Is the upgrade you are talking about a house move from a place with a 35 dB attn. to one with a 45 dB attn.? That's the only way your attn. will change.

Attenuation is almost completely determined by the cable length between you and the exchange on ADSLx, or you and the cabinet on FTTC.

Standard SNR (actually it isn't SNR it is SNR Margin) on BT Wholesale is 6dB and should be more than sufficient for most lines.

Except on lines with low attenuation, which sync at the maximum speed for their product, having the SNRM as low as will maintain connection is what is wanted. A rise of 3dB in sync-time SNRM costs 500-750kbps on ADSL Max and as much as 1.2Mbps on ADSL2+.

I have an in-depth explanation of how it works on this page.

Not sure you quite understand my situation here


http://gyazo.com/c78c096db37198f59c85ece8571cd08c
Speeds: 6mb and 512kb


On my old modem, i got 35 attenuation and 10 snr margin


I dont understand how the attenuation has changed by a simple swap of modem as i understand it to be the lines length...

The change in Snr margin is kind of understandable as it can relate to modems, but, ive been experiencing better quality internet after the switch, so i dont know how you guys are saying higher snr margin is worse...

The higher noise margin reduces the connection speed, as explained.

At lower speeds there are fewer errors. That's why the DLM raises the margin, to lower the speed.

Given the lower connection speed and error rates, your connection runs better, though usually not as fast.

If you are running with very high error rates it's possible the number of errors could slow the actual throughput to less than you get with the lower connection speed and lower error rates. I used to get that. My router was so busy correcting the errors it didn't get much data through at all.

It's also quite common for different makes of router to report different attenuation so, just from calculating it differently. But only by 3-5 dB, not 10dB. One of yours may be reporting it incorrectly.

User may not be UK based and some overseas providers have different rulesets for what they provision to people

Looks like you have 2 threads running discussing the same thing...

Ignore the attenuation - it is pretty much irrelevant to your current issue.

As others have said, the higher the SNR the lower the speed. High SNRs can help if a line has regular disconnects but in general most connections work well at 6dB SNR which would give you a fair chunk of extra speed compared to your current 17dB. It could be pushed to 3 but as RobertoS says that could cause errors which would negate the extra sync speed.

In reply to a post by Xnbz:

Not sure you quite understand my situation here

You need to provide more data - makes of modems, modulation type, PPPoA or PPPoE, LLC or VCMux, who is the ISP, etc.

http://prntscr.com/7tquwz

PPPOE LLC


I have two modems, both of them have the above settings.

One modem is on 45 attenuation and 17 SNR Margin

The other is on 35 attenuation and 10 SNR Margin


Which one of these circumstances can allow me to upgrade? and to what speed?

Thanks for the help guys.

Edited by deleted (Fri 17-Jul-15 13:22:13)

Remove the Annex M. You need Annex A. I would expect a gain of about 2.5Mbps down and no effect at all up.

Edit: Because of your high downstream noise margin on either router, the gain may be less than 2.5Mbps. Once the noise margin is sorted then the 2.5Mbps should be something like.

Also if you have a list like ADSL2+, ADSL2, ADSL, G.DMT, tick the ADSL2 as well as the ADSL2+.

Edited by RobertoS (Fri 17-Jul-15 14:33:35)

http://prntscr.com/7tr27h


No Annex A...


What other recommendations do you have.

In reply to a post by MrSaffron:

User may not be UK based and some overseas providers have different rulesets for what they provision to people

Doesn't alter the physics. They are universal .

If you are in Germany then to be expected due to the large use of ISDN

Never said the physics will change Just provider rule sets or they frequency plans uses different power levels, e.g. care little for AM radio, or AM lobby got it cut even lower

The ADSL2+ would do it, but so will Multimode.

Please can you clarify what country this connection is in? It is hugely important, because all the suggestions we are making assume the UK. Different countries have different setups, as another poster has pointed out. I in particular could be talking junk if you aren't in the UK.