Tweaking the SNR on a Netgear.

[bennett69]

Hi,

My situation is that I must have had a fault on my line. The question I really want answered is do I still have a fault on the line.

Due to the fault BT have changed me from a 6-7db target noise margin to a 15-16db target noise margin. As such my connection speed dropped from the full 8128 down to 6200ish. Due to changing router and using the test socket etc my IP profile is now down to 4000 from 7150.

My current connection is at 6528kbps with a noise margin of 14.8db.

I am using a Netgear DG834 router as such I can tweak my SNR, by setting my target noise margin to 1 instead of 100 I can force my router to connect at 9.2db at a connection speed of 8032.

This seemed a solid connection and I tested it for 15mins or so. I was able to do a test download which came down at a solid 450K or so (max my profile will allow).

Having done this experiment I have now reset my router and everything is back to normal connected of 6528 at NM of 14.9db.

Am I correct in think this is showing that there is no longer a fault on the line and if I just leave it for a few weeks BT will drop my target noise margin back down to 7db?

Thanks guys for any help and advice.

EDIT:

Interestingly I obviously dropped my SNR in experimental steps down from 100 to 1. Along the way at some point I must have connected at 7392 and BT have upped my IP Profile back to 6500 based on this.

Max 7392 650 Auto 28/06/2008 18:21

Obviously this is now going to drop again due to my current connection only being 6528. But this does show the rate adaption UPWARDS working very quickly. I am impressed.

[dlloyd]

I have had some problems with my line in the past where my SNR has been dropped to 15 dB. I'm also using a Netgear DG834 router. On a couple of occasions I have ended up on an IP Profile of 130 kbps!

Usually it takes about 3-4 days of solid connection at a much higher sync speed before my IP Profile rises again. Admittedly, though, I have usually had about 10 days of a dodgy line first!

Interestingly, my SNR will never go down to 6 dB, no matter how long I wait. At the moment I am sync'ed at c. 7500 with an SNR of 8-11 dB. I assume that if I can ever get that target back to 6 dB I would actually sync at the 8128?

How did you set your target noise margin? Perhaps this would help me get back up to my full speed again. I only need to get up to 7950 or so to jump up to an IP profile of 7000. Or have I misunderstood something?

Daryl

[James]

The problem we have is that BT will no longer accept the changing of an SNR as it's not a "fault" as such. We can try and keep trying, but more often than not BT will not do it, as they are only interested in a stable line (which higher SNR provides) over the fastest speed.

Is it the DG834Gv4 or GT you have as with the GT you can upgrade the firmware to a custom one which allows you to save the SNR tweak thus even after a reboot it will keep a similar SNR and thus higher SYNC speed.

The target SNR levels BT's systems apply is 6, 9, 12 and 15dB. 6 is default, and 9, 12 and 15 are used if the line at any time flapped about a lot.

[dlloyd]

James

Thanks for the extra information. It sounds like my fickle line in the past has led to a permanent SNR target higher than 5 dB.

Unfortunately I only have a v3 (and a Zoom X6 which I do not use as I can get it to use my 8 IP addresses properly). From my reading elsewhere it seems that the v3 does not have the telnet commands required to set the SNR itself :-(.

Maybe I'll have to have another go at my Zoom X6 and see if I can understand that (which will be a pity, as I have just invested a week's time in getting MRTG to monitor all the possible outputs from by DG834!).

Thanks
Daryl

[kenedmonds]

Strangely, my target SNR has just been reset downwards without me wailing. It did take months though.

There must have been a problem back in November as the line dropped 20-odd times overnight and BT dropped the target. With an SNR of around 12 it's been pretty well rock solid with a sync speed of high 3xxx and a profile of 3000. I suudenly noticed a week or two ago that something was downloading much faster. I checked the Max reports and the SNR had been reset and the profile was 4000.

Admittedly it took 6 months but something happened eventually...

[atsw]

That's interesting, my Target SNR had been running at around 9db for the last year or so. When I switched ISP (not to ADSL24) back in Feb nothing changed (wasn't expecting it to), SNR stayed around 9db, sync speeds around 3K/3.5K. Then a couple of weeks ago, I noticed that target SNR was back to 6db (where it had been some two year ago when I first moved to MAX). Sync speeds now 3.5K/4K. So yes, the system does work, just seems to take a long time to work in your favor!

Andrew

[deezel]

Hmm my SNR has been around 11 db the past 4 years, it never changes , i even bought a 2nd hand dg834gt just to see if it made any difference, just the same as my 780 wl

ADSL Link Downstream Upstream
Connection Speed 8128 kbps 448 kbps
Line Attenuation 18.0 db 9.5 db
Noise Margin 11.4 db 25.0 db
do these stats look ok? i never have any problems with d/c etc

cheers.... John

[steaa]

Hmm my SNR has been around 11 db the past 4 years, it never changes , i even bought a 2nd hand dg834gt just to see if it made any difference, just the same as my 780 wl

ADSL Link Downstream Upstream
Connection Speed 8128 kbps 448 kbps
Line Attenuation 18.0 db 9.5 db
Noise Margin 11.4 db 25.0 db
do these stats look ok? i never have any problems with d/c etc

cheers.... John

You dont really have to bother since you are lucky that you are close to the exchange and have the highest possible sync (IIRC).

The SNR margin only really becomes a big issue when you are of any distance from the exchange, since a higher SNR margin results in a lower sync speed, thus lower overall speeds, however a higher SNR margin increases line stability.

Someone can correct me if I am wrong :$.

My SNR margin got knocked upto 15dB after storms 2 years ago, and im still on the waiting game for it to go back down to 6dB.

[bennett69]

Hmm my SNR has been around 11 db the past 4 years, it never changes , i even bought a 2nd hand dg834gt just to see if it made any difference, just the same as my 780 wl

ADSL Link Downstream Upstream
Connection Speed 8128 kbps 448 kbps
Line Attenuation 18.0 db 9.5 db
Noise Margin 11.4 db 25.0 db
do these stats look ok? i never have any problems with d/c etc

cheers.... John

You have a very good line 18.0 db.
At the full speed of 8128 the higher the Noise Margin the better, you line will benefit from this when you are ADSL2+ enabled.

At a given speed a higher noise margin is better.

BUT as I am trying to get back to the full 8128 line speed I need my router to negotiate to connect at a NM of about 6db, unfortunately BT have set my NM minimum connection noise to be 16db. My line was normally at 8128 with a NM between 7db and 9db, your is even better at 11.4db.

In your case you want a higher NM not lower, as you are at full speed.

I hope this makes sense.

EDIT:

You beat me to it steaa.

[deezel]

Thanks for the info guys, I'll stop trying to get it down now with DMT ! i'd read a lot about snr on forums and thought mine was a little to high, I think i'll have a long wait for ADSL2+ i'm in a small village here and we always the last to get anything new :(
http://www.speedtest.net/result/297409321.png (http://www.speedtest.net)