DMT and ADSL2+
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DMT and ADSL2+
06-04-2009 10:00 AM
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Have the guinea pigs here seen anything similar
Quote I've recently been switched to ADSL2+ on a WBC enabled exchange. I've always used DMT tool to tweak the SNR margin and get a much improved sync, but now around 3 weeks after the switch to ADSL2+ (which did nothing to improve my sync speed btw), I find that DMT is no longer able to force a lower SNR margin.
Various posts on this forum have suggested that BT now have the ability to prevent margin tweaking on WBC, although speaking to my ISP (Aquiss) they claim this isn't done. I'm at a loss to explain this sudden change in any other way, given that nothing has changed at my end.
Does anyone have any definitive information about this situation? Currently it looks like a move to an LLU provider is my only hope of restoring my line speed.
For reference prior to this change I routinely synced at 5.2Mbit with tweaking. Now it will only sync at a shade over 3Mbit on ADSL2+, which is a fairly substantial drop. If I force an ADSL1 connection it rises to 4.5, but again no tweak is possible.
Re: DMT and ADSL2+
06-04-2009 10:10 AM
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Re: DMT and ADSL2+
06-04-2009 12:24 PM
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Re: DMT and ADSL2+
07-04-2009 12:26 PM
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Re: DMT and ADSL2+
08-04-2009 5:22 PM
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Quote Well I've had confirmation that indeed BT have indeed put the block on tweaking on 21CN. Can't say it surprises me.
Re: DMT and ADSL2+
09-04-2009 12:40 AM
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Quote from: Euge That thread also seems to suggest that for some people adsl2 is better than adsl2+. I assume you'd have to pay extra for the uncapped upstream on adsl2 but is probably worth it for the better line speeds. So when I get moved over to adsl2+ soon and I witness no improvement will it be possible to be moved to adsl2?
I can confirm (from personal experience) that if you are making little or no use of the wider frequency spectrum of ADSL2+, that your modem will fall back to ADSL2 (which uses the same bandwidth as ADSL1).
You retain the same upstream bandwith - because low frequencies work well with ADSL. - it would appear that you may lose a small amount of downstream speed though.
I've got a ticket open and BT called today (useless!) - so I'll have to wait before I try a tweak.
I do recall running DMT to force my noise margin down to 4dB a few weeks ago, on ADSL2 - but this was in the midst of a sea of troubles etc...
Perhaps it depends on router model?
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: DMT and ADSL2+
09-04-2009 2:44 AM
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bitswapping seems to be doing a gd job on the msan's
Noise Margin: 9.2 dB
Connection Rate: 4143 Kbps
Line Attenuation: 50.0 dB
Max Rate: 4352 Kbps
Re: DMT and ADSL2+
09-04-2009 6:18 AM
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Since this is with the iPlate I recently installed (which had initially yielded good improvment), my speed with that removed would work out substantially lower than my pre ADSL2+. I'll try removing the iPlate tomorrow just to make myself really miserable.
BTs pointless, inconsiderate nannying has at least made LLU finally look good and helped me make a decision; my association with BT serviced ISPs will be ending with my contract, and along with it 8 years with PlusNet.
Re: DMT and ADSL2+
09-04-2009 12:16 PM
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"In The Beginning Was The Word, And The Word Was Aardvark."
Re: DMT and ADSL2+
09-04-2009 12:40 PM
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I suspect the deteriorating performance and occasional bouts of 'noise' (pushing the SNR up) might well be down to the line from my flat to the street which has deteriorated over time in the past, and I'd thought perhaps this was where the fluctuating SNR came from. I'm not so sure now.
But then the resyncs often seem to coincide with the frequent visits of an openreach van to the manhole over the street.
Having less speed than I did two years ago is tedious in the extreme.
Re: DMT and ADSL2+
09-04-2009 1:12 PM
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The two routers I've tried on 21CN have always reported
24dB (ADSL2)
37dB (ADSL2)
I had a BT man round yesterday who thought I had an excellent line.
He measured the attenuation to the exchange as 36dB
I'm on about 6.2Mbps sync, 10dB noise margin - rubbish!
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: DMT and ADSL2+
09-04-2009 1:19 PM
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Re: DMT and ADSL2+
09-04-2009 1:33 PM
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"In The Beginning Was The Word, And The Word Was Aardvark."
Re: DMT and ADSL2+
09-04-2009 2:26 PM
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time to have play with tweaking.
Re: DMT and ADSL2+
09-04-2009 2:56 PM
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Quote from: ASBO time to have play with tweaking.
If you're on ADSL2+, a fiver says it won't work Asbo.
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