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ADSL to ADSL2

Lesleyann500
Grafter
Posts: 35
Registered: 29-04-2014

ADSL to ADSL2

Hi,
Currently my account is set to ADSL1, my exchange supports ADSL2.
Please move me over to ADSL2, I understand it won't necessarily increase speed.
Thanks
10 REPLIES
Community Veteran
Posts: 38,460
Thanks: 1,027
Fixes: 62
Registered: 15-06-2007

Re: ADSL to ADSL2

When does your exchange say that 21CN was added as Plusnet would not normally provision you on 20CN if 21CN was available unless you were on 20CN with BT
If you carry out the BT speedtest - further diagnostics what are the results
Can you post your router stats as it is possible that you are on ADSL1 because of line line
Community Veteran
Posts: 5,109
Thanks: 465
Fixes: 17
Registered: 10-06-2010

Re: ADSL to ADSL2

You'll never know if ADSL2 is better or worse for your line and equipment if you don't try it.
If your line is provisioned as ADSL2+, if necessary you can then choose ADSL2+, ADSL2 or ADSL1 by configuring your modem/router accordingly.
I did find a possible source for the "ADSL2+ no benefit" claim:
Quote from: https
ADSL1 or upto 8Mbps on longer lines may offer the optimum service when compared with ADSL2+ upto 20Mbps, under certain conditions (Lines over 4Km's/40dB) there may not be potentially a performance gain by upgrading to ADSL2+

I have never seen any valid explanation for that. Also, according to kitz's max speed calc, 40dB line attenuation is about 2.9km, 4km is more like 55dB.
Lesleyann500
Grafter
Posts: 35
Registered: 29-04-2014

Re: ADSL to ADSL2

The router fails to sync  when trying to force ADSL2/ADSL2+ modulation so I believe I have been provisioned ADSL1.
I'm interested to see how my 52dB line performs with ADSL2/ADSL2+.
Community Veteran
Posts: 26,686
Thanks: 910
Fixes: 10
Registered: 10-04-2007

Re: ADSL to ADSL2

Please run the BT diagnostic speed tests and post the full results as Jim requested.
http://www.speedtest.btwholesale.com/PerformanceTesterWS/diagnostics.do
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
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x47c
Grafter
Posts: 878
Registered: 14-08-2009

Re: ADSL to ADSL2

Quote from: ejs

I have never seen any valid explanation for that. Also, according to kitz's max speed calc, 40dB line attenuation is about 2.9km, 4km is more like 55dB.

On long lines the higher frequencies as used by the full ADSL2+ service deteriorate into just 'noise'.
The attenuation of a signal at at specific frequency is much higher as the frequency used is increased
So the presence on the line of this junk/noise actually makes the line performance worse
Such lines benefit for deliberately restricting the ADSL output from the the DSALM to ADSL1/2 and not having the ADSL2+ "extra" part also there.
Community Veteran
Posts: 5,109
Thanks: 465
Fixes: 17
Registered: 10-06-2010

Re: ADSL to ADSL2

Yes, but once the line enters showtime, and none of the higher tones have any bits allocated to them, is there any signal output on those frequencies?
x47c
Grafter
Posts: 878
Registered: 14-08-2009

Re: ADSL to ADSL2

Yes,  So far as I understand it the DSLAM will still be outputting the higher frequencies regardless if the line is on ADSL2+
So while the router makes the decision that it cannot understand the data on say any specific frequency and allocates zero bit loading to it, the Dslam is still pumping it out.
By the time the BB signal has reach this sample long line those higher frequencies will have just become wideband 'general noise' across the entire frequency spectrum - making a general mess of the line's performance.
If you set the router to only work say on ADSL1 on a long line it will simply ignore the higher frequencies components of the signal and stop at the max ADSL1 frequency when analyzing the line at sync - above which in our example are unintelligible anyway - but you have to get the ISP to set the line to ADSL1 at their end if you want the DSLAM to stop sending out the higher frequencies in the first place.
From what I've seen/heard the main effect of removing the unused higher frequencies from a long line and restricting to either ADSL1 or plain 2 seems to be on stability rather than achieved sync level.  As a guess I'd say that the general mush of the disturbing ADSL2+ higher frequencies present creates a highly variable level of interference minute by minute on the line
PeeGee
Aspiring Pro
Posts: 1,090
Thanks: 47
Fixes: 3
Registered: 05-04-2009

Re: ADSL to ADSL2

My line (4.53km/61.9dB attn) increased a little short of 50% moving from ADSL to ADSL2 (and increased a further 50% since then) and never negotiated ADSL2+ for any significant (usable) time*. It normally uses tones up to 159 @6dB (currently 143 @7.5dB) with error rates escalating rapidly if higher tones (= lower SNRM) get used. I've only done a cursory check, but at least a few tones at the "upper limit" seem to get a bit or two allocated for short intervals - possibly when the tones below are reliable?
Phil
* I now limit to ADSL2 and, subjectively, it seems to re-sync slightly quicker Roll eyes
Plusnet Fibre (Sep 2014), Essentials (Feb 2013); ADSL (Apr 2009); Customer since Jan 2004 (on 28kb dial-up)
Using a TP-Link TD-W9980 modem-router.
Community Veteran
Posts: 5,109
Thanks: 465
Fixes: 17
Registered: 10-06-2010

Re: ADSL to ADSL2

Sorry x47c, but I think that your understanding is just completely wrong. Do you have any sources for it that you can provide links to?
If the line is operating on ADSL1 or ADSL2 (not 2+), regardless of which end selected it, then the DSLAM isn't going to be outputting anything on the 2+ frequencies.
I know my line syncs at higher rates with the modem set to ADSL1 or ADSL2, you don't need anything changed at the exchange.
Quote from: ITU
During the exchange process, each receiver shares with its corresponding far-end transmitter certain transmission settings that it expects to see. Specifically, each receiver communicates to its far-end transmitter the number of bits and relative power levels to be used on each DMT subcarrier, as well as any messages and final data rates information.
Plusnet Staff
Plusnet Staff
Posts: 6,346
Thanks: 31
Fixes: 5
Registered: 26-11-2011

Re: ADSL to ADSL2

Hi Lesleyann500,
I've placed the order for you, this should complete tomorrow morning for you. If the changes aren't that great or are worse, it'll only take 24 hours to revert back to ADSL1 Smiley
Chris Pettitt
Cloud Environments Engineer