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Bits/Tone issue with ADSL2+

calvinvsmith
Dabbler
Posts: 18
Registered: 29-06-2010

Bits/Tone issue with ADSL2+

Attached are two Bits/Tone graphs from Routerstats.
These are pre and post an engineer visit.
The figures for the BT Speed test pre and post the visit are:
2010-07-13 01:30
Download speedachieved during the test was - 3610 Kbps
For your connection, the acceptable range of speedsis 1000-7150 Kbps.
Additional Information:
Your DSL Connection Rate :5204 Kbps(DOWN-STREAM), 444 Kbps(UP-STREAM)
IP Profile for your line is - 4000 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is - 16.37:23.13:60.5 (SBE:NBETongueBE)
These figures represent the ratio while sententiously passing Sub BE, Normal BE and Priority BE marked traffic.

BT Engineer visit @ approx 13:00

2010-07-13 14:00
Download speedachieved during the test was - 3593 Kbps
For your connection, the acceptable range of speedsis 1000-7150 Kbps.
Additional Information:
Your DSL Connection Rate :8272 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 4000 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is - 11.1:29.11:59.78 (SBE:NBETongueBE)
These figures represent the ratio while sententiously passing Sub BE, Normal BE and Priority BE marked traffic.
Incidentally the jump in sync speed was achieved by the engineer talking to someone in Plusnet support who magically produced an extra 3MB for me !!!!!
As I understand it from information on the Kitz site one of the differences between ADSL2 and ADSL2+ is the increased spectrum for the Bits/Tone graph.
Looking at the two attached graphs there doesn't seem to be a lot of activity in the 2+ part of the spectrum and I'm wondereing if this is why I'm not achieving what I would consider to be reasonable speeds.
So I'm wondering what is that is causing the holes in my graphs ?
The attenuation/noise figures from my router are :
Output Power (Up/Down) [dBm]: 11.5 / 20.5
Line Attenuation (Up/Down) [dB]: 22.5 / 39.0
SN Margin (Up/Down) [dB]: 19.5 / 6.5
It seems to me that unless I can achieve a bit loading that utilises all of the available spectrum then I'm never going to get a faster speed.
Is this caused by noise interference somewhere in the supply chain ?
Thanks in advance for any advice/help offered.
9 REPLIES
Community Veteran
Posts: 2,106
Registered: 06-02-2008

Re: Bits/Tone issue with ADSL2+

ADSL2+ uses (amongst other things) a higher frequency range to give a greater synchronisation speed. Your loops loss is 39dB so you shouldn't expect all of the higher frequencies to be used.
In an ideal world, your graphs would smoothly tail off, without the missing tones. They are likely to be unused because of noise in that particular frequency.
Your estimated speed is 5mbps and you're in sync at 8272kbps, with a 7150kbps profile expected. I'm sorry if you feel this is not reasonable but there's nothing further that we can do.
grahamt
Rising Star
Posts: 561
Thanks: 12
Registered: 05-04-2008

Re: Bits/Tone issue with ADSL2+

The estimated speed is a bit of a red herring, as clearly the line conditions changed after the BT visit. My estimated speed is 3.5mbps but (following a bell wire snip) I now get an actual throughput of between 6 and 6.5.
A sync speed of 8272 is not that bad for an attenuation of 39dB. By coincidence that's also the attenuation on my line, and my current speed is 7864, under ADSL2+. It varies between 78xx and 82xx, and my upstream speed is uncapped, varying between 792 and 816. If we could see your noise margin stats we could take a guess about whether you could expect anything better.
For comparison I'm attaching a picture of my line's bit loading. It's not quite comparable, as with my ZyXEL router I have to use a version of DMT that isn't designed for the UK (hence no bitrate or upstream graph). But you can see the pattern.
Graham
scootie
Grafter
Posts: 4,799
Registered: 03-11-2007

Re: Bits/Tone issue with ADSL2+

you can try switching off every bit of elcy equipment you have in your property apart from your router (but do a resync after everything is powered down) and then switch your pc on and check the bit/tones graph and if any of the gaps are now in use its a likely to be something in your property causing the interference (also check your router logs to insure that switching on the pc hasn't caused a resync by interference)
i do this by flipping the fuse switch's to everything apart from the main ring socket fuse that the router and pc is on and just power down anything else that's on that ring
its a slim chance that this may find some interference but its something i tend to do just make sure what the true max sync rate is when all end user controlled elcy interference is canceled out, this will not stop your next doors neighbors maybe dodgy pc monitor interfering tho
take it you have tried all the normal stuff to check like diffrent router, filters ect
calvinvsmith
Dabbler
Posts: 18
Registered: 29-06-2010

Re: Bits/Tone issue with ADSL2+

I suspect that the main cause of my sudden increase in sync speed is the drop from 15 to 6.5 for my noise margin.
My sync speed is now about 8Mb, my profile is 7150 but my actual download speed is still only 3.5, see BT Speedtest below.
2010-07-13 20:45
Download speedachieved during the test was - 3606 Kbps
For your connection, the acceptable range of speedsis 1000-7150 Kbps.
Additional Information:
Your DSL Connection Rate :7984 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is - 20.35:26.73:52.91 (SBE:NBETongueBE)
These figures represent the ratio while sententiously passing Sub BE, Normal BE and Priority BE marked traffic.
Is this a case of having to leave it for a while so that the download speed catches up with the sync/profile speed ?
I would also note that this 'fault' has had an open question for about the last four weeks but it took a single phone call from an onsite BT engineer to suddenly find an extra 3Mb of sync speed.
Community Veteran
Posts: 2,344
Thanks: 238
Fixes: 2
Registered: 04-08-2009

Re: Bits/Tone issue with ADSL2+

Am I missing something here? I was under the impression that on ADSL2+ IP profiles as such didn't exist, and hence banding isn't applied, unless the line is exceptionally unstable. Doesn't the DLM continuously adjust the line speed if the line is behaving?
Community Veteran
Posts: 2,106
Registered: 06-02-2008

Re: Bits/Tone issue with ADSL2+

@nozzer
ADSL2+ uses profiling (DLM) just like ADSL Max. There are also banded profiles - these are applied when the line is dropping connection. These enforce higher SNR margins to keep any ambient noise away from the broadband signal and hence allow for greater fluctuations in that noise, without causing drops in sync.
@calvinvsmith
Your profile has dropped to 4000kbps, probably due to the 7 disconnections yesterday. Please leave everything powered up and plugged in, you can expect a speed increase within 72 hours. If you notice any further drops then please report it to the faults team.
As an aside, the BT engineer probably called BTWholesale and asked them to move the profile manually. Unfortunately this is not a facility that is available to us.
Community Veteran
Posts: 3,366
Thanks: 15
Registered: 06-04-2007

Re: Bits/Tone issue with ADSL2+

Quote from: BenTrimble
@nozzer
There are also banded profiles .. and hence allow for greater fluctuations in that noise, without causing drops in sync.

Ah, you've swallowd the pill that BT give out I am afraid. The user will still expereince loss of sync, so there will be moment of lost connection, except now the DLM will force the connection to sync in a particular range of speeds. Now, if BT employed Seamless Rate Adaption (SRA) which is an inherent part of ADLS2+, this DLM thing would not be needed as it will dynamically change the speed according to the current line conditions without loss of sync. But BT know best. Sad
--
3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
calvinvsmith
Dabbler
Posts: 18
Registered: 29-06-2010

Re: Bits/Tone issue with ADSL2+

@Ben Trimble
My profile was consistent at 7150 until your server outage last night then it came back at 4000kbps.
I'll give it until the end of the week to see if the speed increases then I'll start looking for a new supplier.
I feel that I'm being fobbed off here with excuses about what you can't do rather than solutions to my issue.
It's been a month now and my speed readings are worse than when I was on the 8Mb service, see below:
2010-07-14 13:30
Download speedachieved during the test was - 3774 Kbps
For your connection, the acceptable range of speedsis 1000-7150 Kbps.
Additional Information:
Your DSL Connection Rate :7936 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 4000 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is - 18.6:20.88:60.52 (SBE:NBETongueBE)
These figures represent the ratio while sententiously passing Sub BE, Normal BE and Priority BE marked traffic.

Val Smith
Community Veteran
Posts: 2,106
Registered: 06-02-2008

Re: Bits/Tone issue with ADSL2+

@calvinvsmith
I'm sorry you feel that way Sad
We only have very limited access to adjust the MSAN directly, and strict rules as to when we can access it indirectly. Hopefully this was just a minor blip and you'll be back up to full speed shortly.