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Target SNR margin reset

rx7aiii
Dabbler
Posts: 22
Registered: 05-08-2010

Target SNR margin reset

Hi
I have swapped my modem for a billion 7800N in the hope of getting a little extra performance and the ability to adjust the SNR margin. In setting up the modem I have rebooted it several times. I am wondering if this has resulted in the target SNR being raised as my speed has now dropped where as initially it was faster than ever before. Is it possible to get an SNR margin reset?
Thanks
16 REPLIES
rx7aiii
Dabbler
Posts: 22
Registered: 05-08-2010

Re: Target SNR margin reset

Sorry, does this help:
DSP Firmware Version A2pB025f.d22k
DMT Status No Defect
Operational Mode G.DMT
Upstream 512
Downstream 2720
SNR Margin(Upstream) 10.0
SNR Margin(Downstream) 4.1
Line Attenuation(Upstream) 31.5
Line Attenuation(Downstream) 62.0
No errors have been recorded. Today speed is 1.5 mbs, was over 2mbs.
Thanks
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: Target SNR margin reset

Hi rx7aiii,
I wouldn't think that your target snr has changed judging by the current margin. Yes, rebooting too many times in a short period CAN result in target margins being affected. I usually recommend no more than 5 resyncs in an hour at no smaller than 10 minute intervals and then leave it alone for the rest of the day to give you a safe margin. That's on the assumption you haven't had any other resyncs previously that day.
I'm assuming you are on 21CN and your current Downstream sync speed is good for that attenuation, so you aren't doing too bad considering your distance from the exchange.
Depends which speed tester you've been using, the BT one and Mybroadband speed have all been reported as being borked for a lot of users, but working for others. That said, what does the BT one report your profile as - it should be around 2399. Also check the current line speed at the portal https://portal.plus.net/my.html?action=data_transfer_speed (login required).
For a more reliable speedtest try the one over on Thinkbroadband. Checkout your exchange VP status at http://usertools.plus.net/exchanges/?
Yes you could get an SNR reset and you could tweak it yourself, but with your current sync speed and noise margin, I'd leave things alone and see how it performs over the next few days.
There's quite a few threads with lots of info on the Billion 7800N around this forum, do a search (advanced - most recent first), have a good read of as many as you can. I'd start at the oldest, and don't just go by one or two threads, information isn't always reliable though most is, remember.
rx7aiii
Dabbler
Posts: 22
Registered: 05-08-2010

Re: Target SNR margin reset

Hi Anotherone
Thank you for the reply. Interestingly line speed at the portal says 1.6mbs. Something has changed or gone wrong today and i'm not sure what it is.
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: Target SNR margin reset

You probably had a lower sync speed at some point, what's the BT speedtester saying for your profile?
rx7aiii
Dabbler
Posts: 22
Registered: 05-08-2010

Re: Target SNR margin reset


Is this what you are asking for?


1. Best Effort Test:  -provides background information.
Download  Speed
1.11 Mbps

0 Mbps 4 Mbps
Max Achievable Speed
Download speedachieved during the test was - 1.11 Mbps
For your connection, the acceptable range of speeds is 1.2 Mbps-4 Mbps.
IP Profile for your line is - 2.4 Mbps
2. Upstream Test:  -provides background information.
Upload Speed
0.54 Mbps

0 Mbps 0.83 Mbps
Max Achievable Speed
Upload speed achieved during the test was - 0.54Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.83 Mbps

This test was not conclusive and further testing is required.This might be useful for your Broadband Service Provider to investigate the fault.
If you wish to carry out further tests,please click on 'Continue' button.If not, please close the window using 'Exit' button and contact your ISP for further assistance with these results.
Thanks
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: Target SNR margin reset

Yep, just the job, IP Profile for your line is - 2.4 Mbps. Don't reboot/resync. If the Plusnet Current line speed at the Portal doesn't update by Monday, then ask one of the Digital Care team to give it a nudge.
In the meantime did you try the Thinkbroadband speedtester also look at your exchange VP status?
Also try the BT Upto 24Mbps Speed Test (beta).
If your download speed remains poor, you could check which gateway you are on at http://usertools.plus.net/@gateway/ and you could try a Gateway hop by forcing a disconnect & re-connect of the ppp session via your modem/router interface (or, but NOT tonight, by a re-sync, wait until daylight hours - not the preferred method) and then checking if you are on another gateway which may improve things.
rx7aiii
Dabbler
Posts: 22
Registered: 05-08-2010

Re: Target SNR margin reset

Anotherone, thanks very much for the fast and really helpful advice. Hopefully this will resolve itself in a few days, if not I'll make contact. Interestingly my sync speed went up tonight but the speed is still the same. Showing no drops or errors
Parameters
DSP Firmware Version A2pB025f.d22k
DMT Status No Defect
Operational Mode G.DMT
Upstream 512
Downstream 2880
SNR Margin(Upstream) 10.0
SNR Margin(Downstream) 4.6
Line Attenuation(Upstream) 31.5
Line Attenuation(Downstream) 62.0
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: Target SNR margin reset

Yes, that's looking pretty good, lets hope the profile resolves itself. You haven't said what your exchange VP status is by the way!
rx7aiii
Dabbler
Posts: 22
Registered: 05-08-2010

Re: Target SNR margin reset

sorry, exchange VP status was green. I assume thats good?
Thanks
rx7aiii
Dabbler
Posts: 22
Registered: 05-08-2010

Re: Target SNR margin reset

Out of interest, if I set the target SNR on the modem to default and try to tweak it again. If I get a higher sync speed from tweaking, is the exchange likely to catch up and increase the line speed accordingly? BT suggest a top speed on my line of 4mb. I know thats unlikely but I have seen 3.5mbs on one occasion on speed tester.
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: Target SNR margin reset

VP Green is good  Smiley
As I said previously I'd leave the Target SNR as it for the moment and see how things perform. Any tweaks that you do take effect when there is a resync. Often the problem with long lines, more so if they are overhead as opposed to underground, is how much noise levels increase after dark. This of course means that the noise margin will go down and error rates can go up to the point that sync is dropped and a resync occurs at a (much) lower speed.
If you have a nice quiet line in all senses (audio and RF) then you can achieve better performance.
You might want to consider using something like Routerstats http://www.vwlowen.co.uk/internet/files.htm to monitor your Noise margin. If you do that search I mentioned earlier, I'm sure I spotted a thread or two about Routerstats running with the 7800N.
jojopillo
Grafter
Posts: 9,786
Registered: 16-06-2010

Re: Target SNR margin reset

Hi rx7aiii,
I have raised your profile to 2400 to allow for your new BT IP profile. This should take effect shortly.
Jojo Smiley
rx7aiii
Dabbler
Posts: 22
Registered: 05-08-2010

Re: Target SNR margin reset

Thank you very much. Speed has jumped substantially. If it remains stable at this IP profile over the next few weeks and my line speed (2752 atm) and SNR (3.9 - 4.6) remain at these levels might there be scope to tweak things a little further?
The other question is that the line is 21CN enabled. I am operating in G.DMT mode. Am i configured for 21CN or at these speeds is it preferring the G.DMT mode?
Thanks again
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: Target SNR margin reset

I would ignore that   "Operational Mode   G.DMT"  from your modem/router. You are likely to be in ADSL2 (not plus) mode at these speeds and you aren't vanilla ADSL as your Upstream is 512, which is I assume because you've had it uncapped?
I suspect that modem/router might report G.DMT whatever speed you are actually running at, but you could have a look around the forum posts or web for the 7800N to see if you can get any more info on that.