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ADSL Standards - confused!

Superuser
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Registered: 22-08-2007

ADSL Standards - confused!

I thought I understood the ADLS standards / options quite well, until I recently looked very closely at my current service settings / performance.
I believe that I am on a 21CN WBC service, however my TG582n router suggests that I'm on an ADSL1 connection / configuration...
  xDSL Standard:                ITU-T G.992.1
  xDSL Annex:                  Annex A
  Channel Mode:                      Interleaved
However my US synch rate is 864kbs which rather implies an uncapped ADSL2 / ADSL2+ US profile.  Am I confused in believing that US uncapping is a function of the ADSL modulation standard, rather than a function of the 20CN / 21CN infrastructure provisions?
I had asked if I could be regarded to ADSL2 (see ticket 83682646) however the responding agent felt that I'd see little benefit and that (understandably) fibre would be better - both in terms of performance for me and revenues for PN  Grin
Presently I'm seeing
US
Noise Margin:  10.0  dB
Bandwidth:    864    kbps
Attenuation:  29.5  dB
Power:        12.6  dBm
Errors:
  FEC:  2769
  CRC:  2007
  HEC:  N/A
DS
Noise Margin:  7.2    dB
Bandwidth:    4832  kbps
Attenuation:  50.0  dB
Power:        19.6  dBm
Errors:
  FEC:  63444
  CRC:  1117
  HEC:  7730
Failures since last reset:
  LOF:  0
  LOS:  0
  LPR:  0
  ES :  668
That is on 3+ days since last reconnect.  I've seen 6.5Mbs at 6dB on a similar line (old business account) over ADSL2 with a standard 445 (ish) US profile - is it likely that this line if changed to ADSL2 could deliver similar with stability?  2Mbs is a lot more than the 0.5M suggested by the CSA responding to the ticket.
Cheers,
Kevin
32 REPLIES
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Re: ADSL Standards - confused!

The easy one
You can have an uncapped upload on ADSL1 on 21CN
Superuser
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Re: ADSL Standards - confused!

Jim,
Thank you - I lives, I learn.  Cheesy  Uncapped upload is therefore a function of the infrastructure (21CN) not the DSL modulation method / standard.
Cheers, Kevin
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Re: ADSL Standards - confused!

I don't really see why "there would be little benefit" or "it might be worse" are valid reasons not to use ADSL2. Staying on ADSL1 might be worse than not switching to ADSL2.
[tt]US Connection Rate:    882    DS Connection Rate:    4059
DS Line Attenuation:    58.0    DS Margin:              5.0
US Line Attenuation:    36.4    US Margin:              4.8[/tt]
Those are my current line stats on ADSL2, but then I'm not using a 582n.
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Re: ADSL Standards - confused!

These are mine on ADSL2 - and that is about the best for a stable connection - 6dB default noise margin
Noise Margin:  3.6    dB
Bandwidth:    3854  kbps
Attenuation:  49.5  dB
Noise Margin:  9.8    dB
Bandwidth:    888    kbps
Attenuation:  26.4  dB
PeeGee
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Re: ADSL Standards - confused!

just to push the limits a bit, my current ADSL2 stats  (TD8816):
near-end interleaved channel bit rate: 3139 kbps
far-end interleaved channel bit rate: 603 kbps
noise margin downstream: 7.6 db
attenuation downstream: 61.8 db                                                                                                                                   
                                                                                                                               
noise margin upstream: 6.5 db                                                                                                                                     
attenuation upstream: 37.7 db
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.
Superuser
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Re: ADSL Standards - confused!

Jim,
On my business line which also had a DS attenuation of 50dB, I saw a stable 5.5Mbs at 6dB with a capped US - hence my question about switching on my residential service.  We do though need to remember the attenuation figures are different between ADSL and ADSL2.
It did though take PN 6+ months of battling with BTOR to get a clean pair to deliver that excellent performance.  Just so sad that we had to leave the business premises - so much better service than the ADSL at the residential premises.  Not knowing what are our future plans makes a 18 month fibre contact unattractive at present.
I could suggest that your line (at 49.5dB) should do better than it is.  Have you looked for / eliminated sources of rein / shine?  I unplugged an "unused" power supply in the same double socket used by the router and got a 1.5dB improvement in SNRM.  I have yet to do a resynch to see if that translates into a higher synch rate.
Cheers,
Kevin
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Re: ADSL Standards - confused!

All the available lines from the exchange to the main cab are equally bad and BTo aren't going to put in new feeders just because my speeds are a bit low
Of course I am supposed to get fibre in a couple of years time  Roll eyes
I actually used to get 4,800kbps but with major drop out problems or high error rates when the phone rang. This lower speed is stable without problems on the new pair from the exchange
Superuser
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Re: ADSL Standards - confused!

Jim,
Sounds like your local infrastructure is shot to bits.  The experience suggests that attenuation is not the complete picture in predicting performance.  There must be other metrics / issues for similar line impedance delivering markedly different results.
From what you've shared, I'm guessing that you will never see the full benefit of fibre given the poor state of your d-side circuits, which is something a lot of people do not realise.  My fibre estimate is sub 38Mbps which is nothing like BTOR's headline claims of super fast broadband.  It might be supersaturated to their green boxes, but their poor quality d-side infrastructure show Akers the shine off hat figure fr the majority of subscribers outside of the major cities.
Cheers,
Kevin
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Re: ADSL Standards - confused!

In my case - assuming they only put one fibre cab in at about the place where the main cab is located I will probably only get 25/9 at the best unless they put some subsidiary cabs in
In our area there is a master cab with 3 multicores to the exchange and a number of subsidiary cabs each feeding a group of houses
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Re: ADSL Standards - confused!

Quote from: Townman
We do though need to remember the attenuation figures are different between ADSL and ADSL2.

I think my router reports about 58db attenuation on ADSL1 and ADSL2, and about 60db+ attenuation on ADSL2+. Yes there is a difference between ADSL2 and ADSL2+, and my router/exchange doesn't automatically drop down from ADSL2+ to ADSL2.
If your line is provisioned as ADSL2+ you can choose ADSL2+, ADSL2 or ADSL1 by changing your modem/router configuration. I suppose the only benefit of having a line provisioned as ADSL1 is that it can't be banded, but if your line was bad enough to be in danger of being banded if it were on ADSL2+, then your target noise margin would probably end up at 15db with the corresponding bandwidth decrease.
Superuser
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Re: ADSL Standards - confused!

Back to my original questions...
Quote from: Townman
I had asked if I could be regarded to ADSL2 (see ticket 83682646) however the responding agent felt that I'd see little benefit and that (understandably) fibre would be better - both in terms of performance for me and revenues for PN  Grin
..
I've seen 6.5Mbs at 6dB on a similar line (old business account) over ADSL2 with a standard 445 (ish) US profile - is it likely that this line if changed to ADSL2 could deliver similar with stability?  2Mbs is a lot more than the 0.5M suggested by the CSA responding to the ticket.

Since the removal of an unused PSU in the other socket next to the router, I've been seeing a very steady SNRM at 6dB delivering 5.2Mbs...

Link Information
Uptime: 1 day, 21:44:04
DSL Type: ITU-T G.992.1
Bandwidth (Up/Down) [kbps/kbps]: 832 / 5.280
Data Transferred (Sent/Received) [MB/MB]: 111,74 / 373,94
Output Power (Up/Down) [dBm]: 12,6 / 19,6
Line Attenuation (Up/Down) [dB]: 29,5 / 50,0
SN Margin (Up/Down) [dB]: 10,0 / 6,1
System Vendor ID (Local/Remote): TMMB / ----
Chipset Vendor ID (Local/Remote): BDCM / IFTN
Loss of Framing (Local/Remote): 0 / -
Loss of Signal (Local/Remote): 0 / -
Loss of Power (Local/Remote): 0 / -
Loss of Link (Remote): -
Error Seconds (Local/Remote): 832 / -
FEC Errors (Up/Down): 7.349 / 200.254
CRC Errors (Up/Down): 666 / 1.393
HEC Errors (Up/Down): -66 / 1.393 / 9.480

Errors though not non-existent are not excessively high - is there merit in trying either a switch to ADSL2 or setting my target SNRM to 3dB?  I'm doing way over the BT forecast for the line, I'm doing 9% over the Kitz forecast for ADSL and nearly 2.5% over Kitz forecast for ADSL2.  Is it likely that I could sweat more out of this line on ADSL2 still with reasonable stability?  Getting 0.5mbps (ADSL2) or even 0.4 to 1.2Mbps (-3dB on SNRM on ADSL) might sound like not much in the realms of fibre, but on my line speed it is a massive +10% or even more.
What do you think?
Cheers,
Kevin
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Re: ADSL Standards - confused!

As I understand it 3dB isn't available on ADSL1 so going to ADSL2 would give that option
Edit - wrong again
Plusnet Staff
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Re: ADSL Standards - confused!

3db is available on 21CN ADSL but not 20CN ADSL.
Chris Pettitt
Cloud Environments Engineer
Superuser
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Re: ADSL Standards - confused!

Chris,
That's part of the 'rub' on my query... why am I on ADSL(1) over a 21CN service?
Given the initial response from Old Jim explaining how I can have uncapped US with a ITU-T G.992.1 DSL - I must be on 21CN to get 832 US.  (edit: oops did not notice Jim's intervening reply!)
So from your reply, do I correctly conclude that I can have a 3dB target SNRM on 21CN using ADSL(1) modulation?
Cheers,
Kevin