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Understanding Noise Margin

twizzler
Newbie
Posts: 5
Registered: 28-04-2009

Understanding Noise Margin

My download speed has dropped recently so I checked my router stats:
              Connection Speed 7808 kbps  448 kbps
              Line Attenuation  20.0 db  13.0 db
              Noise Margin  14.4 db  24.0 db
Is that noise margin ok? I am 565 metres from the exchange, or 1.29 km by road.
Ran the bt speed check:
    Your DSL connection rate: 7808 kbps(DOWN-STREAM),  448 kbps(UP-STREAM)
    IP profile for your line is - 500 kbps
    Actual IP throughput achieved during the test was - 422 kbps
I had a dodgy handset which may have resulted in my IP profile being lowered. I replaced that with a BT phone about 3 weeks ago and the line sounds fine - even on the quiet line test. The line also seems stable - been up for about 25 hours at 7808 kbps.
So I'm just staying connected and hoping the IP Profile corrects, but am I wasting my time with that noise margin being so high? I understood lower was better?
10 REPLIES
James
Grafter
Posts: 21,036
Registered: 04-04-2007

Re: Understanding Noise Margin

No - that looks okay.
It looks like the line is synching at it's theoretical maximum with the level of interleaving being applied.  So basically, you can't sync any higher, so the noise margin won't go any lower.
It's actually a really good Smiley
Speeds should pick up in a couple of days.
twizzler
Newbie
Posts: 5
Registered: 28-04-2009

Re: Understanding Noise Margin

Thanks for your help.
I still have a 500k IP Profile (BT speed test) after 96 hours of continuous connection at 7808k. As far as I can tell from routerstats my sync speed, noise margin and line attenuation are unchanged since my original message.
What should I do next? Wait another day? Do I need to disconnect/reconnect to see a change in the BT IP Profile?
James
Grafter
Posts: 21,036
Registered: 04-04-2007

Re: Understanding Noise Margin

I'd certainly consider raising a fault to http://faults.plus.net
It shouldn't be taking that long for the profile to increase.
scootie
Grafter
Posts: 4,799
Registered: 03-11-2007

Re: Understanding Noise Margin

Quote
Do I need to disconnect/reconnect to see a change in the BT IP Profile?

No.
But if both bt's and pn's profile go up but your still seeing your old profile speeds on speed tests then a quick login into your router and just disconnect/reconnect the internet( no need to resync) would then pick up the new PN profile
twizzler
Newbie
Posts: 5
Registered: 28-04-2009

Re: Understanding Noise Margin

Thanks. As James suggested I've raised a fault and am now awaiting the results.
Community Veteran
Posts: 19,099
Thanks: 434
Fixes: 21
Registered: 31-08-2007

Re: Understanding Noise Margin

You haven't got any unfiltered devices plugged in anywhere have you, such as Sky box or fax machines etc.?
twizzler
Newbie
Posts: 5
Registered: 28-04-2009

Re: Understanding Noise Margin

Quote from: Anotherone
You haven't got any unfiltered devices plugged in anywhere have you, such as Sky box or fax machines etc.?

No. I have the wall socket, followed by a filter with my router and phone extension+phone plugged into it. That's all.
But given the info I posted earlier (my line is stable at 7808k and so on) doesn't that point away from an internal wiring fault?
All that's changed here is the replacement of a bad handset at the beginning of April, and I upgraded from Broadband Plus to Plusnet Pro then too. It's possible that I had this problem for weeks before and didn't notice because I thought I was just being throttled back for over use on my old product.
The result of the plusnet line check was:
Test result summary: Inconclusive
We have not been able to complete the checks of your broadband service. This may be the result of a fault in the testing system rather than your service.
and they have escalated the issue. So I'm just waiting to hear. Wish they'd tell me I can turn my firewall back on though!
Community Veteran
Posts: 38,436
Thanks: 1,013
Fixes: 60
Registered: 15-06-2007

Re: Understanding Noise Margin

The only firewall which may have needed turning off is the router firewall not the PC firewall.
Community Veteran
Posts: 19,099
Thanks: 434
Fixes: 21
Registered: 31-08-2007

Re: Understanding Noise Margin

Quote from: twizzler
..................after 96 hours of continuous connection at 7808k. As far as I can tell from routerstats my sync speed, noise margin and line attenuation are unchanged since my original message............
Just for clarification do you mean the stats from your router or  the program RouterStats? If from your router's line stats, did you check that the line count hasn't increased? When you are close to an exchange and you are syncing at a "ceiling" it would mean disconnects could occur and resync at the same speed. Some people would think things are stable just because they hadn't notice a disconnect ..... hence the questions.
Quote
But given the info I posted earlier (my line is stable at 7808k and so on) doesn't that point away from an internal wiring fault?

I suspect you simply have a stuck profile if your line is rock solid and there have been no disconnects or low sync events at all. This would then clearly suggest there was no fault anywhere, just a stuck profile.
twizzler
Newbie
Posts: 5
Registered: 28-04-2009

Re: Understanding Noise Margin

Quote from: Anotherone
Just for clarification do you mean the stats from your router or  the program RouterStats? If from your router's line stats, did you check that the line count hasn't increased? When you are close to an exchange and you are syncing at a "ceiling" it would mean disconnects could occur and resync at the same speed. Some people would think things are stable just because they hadn't notice a disconnect ..... hence the questions.

Hmm "line count" Huh Quick google ... Ok no I didn't do that - actually doesn't seem to be shown in my router's stats or logs. What I have done is have my router's log emailed to me once per hour to remind me to keep an eye on it. And I've set alarms in routerstats for changes in SNR, sync speed and IP address. So far none of these have changed (although noise does fluctuate a few 10ths of 1db of course).
Quote
I suspect you simply have a stuck profile if your line is rock solid and there have been no disconnects or low sync events at all. This would then clearly suggest there was no fault anywhere, just a stuck profile.

Well I mentioned the duff handset but that was weeks ago, and even then I didn't notice any disconnects (though I wasn't really paying attention). So maybe it's possible that my profile was reduced because of that.
I've now had a reply to my ticket and the fault is "being raised with our supplier", so I just need to sit tight.