Set Noise Margin

Post Reply
dodge40
Posts: 2
Joined: Sun Jul 31, 2011 7:43 pm

Set Noise Margin

Post by dodge40 » Sun Jul 31, 2011 7:47 pm

With some routers I have previously owned, it was possible to set the noise threshold as a target in order to eek out a little more speed.

Currently the router (7800N) is connectiong with a downlstream noise margin of 8.5db. I would like to be able to set a target of 6db or so and thereby gain a littel more speed.

Is this possible with this router through teh telnet connecion?

If so what command do I need to issue?

Tomken
Posts: 467
Joined: Tue Jul 26, 2011 10:31 am
Location: Co Durham

Re: Set Noise Margin

Post by Tomken » Sun Jul 31, 2011 9:18 pm

After logging into the router, enter 192.168.1.254/snr.html or */snr.cgi and you will be presented with a hidden menu and the option to enter a value to tweak the target SNR

The table for these values can be found at http://www.spaldwick.com/broadband/billion-7800n

After you have entered your value and pressed Apply the router will reboot.

When all the lights return to green, then pressing the Back button will return you to the home page, where you will see the resync'd DSL - Save Config and if it's the best time of day where you are, you can restart a number of times to see the best DSL you can achieve. I have found it is best to be wired prior to initially logging in before doing this adjustment.

I was set to a 6dB profile and tweaked mine to 4.5dB and it held it fine wirelessly on a 50dB Attenuation, changing it to 3dB gave me a lot of lag - so it's back to 4.5dB with a DSL of 6849dB.

The fact that you have mentioned telnet, I take you will already know this is one of the means to view the full ADSL stats - something I had problems with :)

dodge40
Posts: 2
Joined: Sun Jul 31, 2011 7:43 pm

Re: Set Noise Margin

Post by dodge40 » Sun Jul 31, 2011 10:04 pm

Thank you Tomken. That was easy.

Off now to experiment.

Tomken
Posts: 467
Joined: Tue Jul 26, 2011 10:31 am
Location: Co Durham

Re: Set Noise Margin

Post by Tomken » Mon Aug 01, 2011 12:54 am

Happy experimenting :)

Don't know if you have noticed, but the values in the table reduce the SNRM by a fixed amount, regardless of your current target.

May help to enhance your experimentation :P

nozzer
Posts: 36
Joined: Wed Jul 20, 2011 4:34 pm

Re: Set Noise Margin

Post by nozzer » Tue Aug 02, 2011 8:49 am

Is this likely to work with ADSL2+? I was under the impression that BTs latest DLM wasn't tweakable.

Tomken
Posts: 467
Joined: Tue Jul 26, 2011 10:31 am
Location: Co Durham

Re: Set Noise Margin

Post by Tomken » Tue Aug 02, 2011 10:02 am

Don't know anything about BT, I'm with TalkTalk, but the router default ADSL mode is b+g+n and if your drivers are up to date then I wouldn't have thought there would be any problem.

The 7800N is a N router which means it does cover ADSL2+ otherwise you wouldn't be able to sync at the higher speeds, as it is my understanding (being a newbie)

DLMs only usually correct where there are excessive errors and would increase the SNRM to stabalise the BB

The sustainability of whatever it resyncs at will always be determined by the the quality of the copper wire in your line and your attenuation - mine is OK on a 4.5dB tweak with DSL of 6867 but lagged on a 3dB which resync'd at 7433. I had tried it on a lower profile to see what I could get and it came back in at 7977 but given the probs with the 3dB, I just reset it back to the 4.5dB.

Try it in a wired state and see, you can always change it back to the Default if you do get any probs.

knightnet
Posts: 12
Joined: Thu Aug 04, 2011 5:46 pm
Location: Sheffield, UK
Contact:

Re: Set Noise Margin

Post by knightnet » Thu Aug 04, 2011 8:41 pm

I'm with PlusNet on their ADSL2+ unbundled connection.

My experience with this is that the exchange end adjusts itself back to the SNR it is set for after a day or so. However, the router seems to retain the connection for longer if the SNR dips at any point.

I've been fairly extreeme with my adjustment and I've gone from 2M to 3.5M with only the occasional drop out.
Regards, Julian Knight

Tomken
Posts: 467
Joined: Tue Jul 26, 2011 10:31 am
Location: Co Durham

Re: Set Noise Margin

Post by Tomken » Fri Aug 05, 2011 10:10 am

Hi knightnet,

Going by that speed, I take it you are a fair way from the exchange.

I've found that the problem with extremes are that the errors become expotential - have you checked the errors when the SNR dips.

The errors could be why the DLM is reverting your profile, does it auto reinstate after a few days or do you do a restart to get back to your tweaked speed ?

I've been trying mine on a 3dB profile the last couple of days and the CRCs were over 700000 after only about 7 & half hrs with the SNRM dropping to 0.4 wired late evening, so have knocked it back to 4.5 again, as it seems quite happy with that on a 50.5dB attenuation.

I don't know if you or anyone else have this, but my SNRM is double when wired to that when wirelessly connected, so to help with stability, I use a wired connection when tweaked down from my 6dB interleaved.

nozzer
Posts: 36
Joined: Wed Jul 20, 2011 4:34 pm

Re: Set Noise Margin

Post by nozzer » Sun Aug 07, 2011 9:47 am

On ADSL2+, the BT DLM will always try to revert to the setting "it" thinks is best for your line. This takes usually around two days. If you manually alter the SNRM and the errors increase, then the SNRM will change automatically. If the errors don't increase it won't. The DLM system is looking at the mean time between errors, and if that figure is below the system's acceptable limit the reset will occur. If you keep changing the SNRM manually you also run the risk of the system thinking you have a fault (because in effect you are re-syncing), which will lead to a cap being automatically put on your connection. Best left well alone.

Not sure why the SNRM should be affected by a wired-vs-wireless LAN connection. It's got nothing to do with it!

Tomken
Posts: 467
Joined: Tue Jul 26, 2011 10:31 am
Location: Co Durham

Re: Set Noise Margin

Post by Tomken » Sun Aug 07, 2011 4:53 pm

Re, the SNRM variance wired vs wireless, Billion tech support got a 0.1 variance when they tried to assimilate this with their own equipment - so it must have some effect and when I plugged the HG532 back in, there was a 0.7 difference. I can only assume it to be a local issue, even though I have a RF free filter fitted prior to the master socket. It's possible I suppose that the 7800N could be more sensitive to picking up interference, but it certainly knows how to deal with it. :)

SNRM tends to drop quite quickly from about 10.00pm onwards but this variance is constant throughout the day.

Had a disconnect at 05.45 this morning (PhyR no longer enabled) and whatever the reason, it resync'd at a higher DSL speed - DLMs don't always knock you back down.

Post Reply