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Author Topic: BT Infinity FTTC connection speed poor - graphs and stats available  (Read 16397 times)

burakkucat

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #15 on: August 05, 2012, 10:54:23 PM »

The interesting thing is that the max attainable rate drops by 2mb simply by picking up the phone and listening to the dial tone. Not sure if that is normal!

 :no:  No, definitely not normal. That is one of the potential indicators of a developing HR (or semiconducting) joint.
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asbokid

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #16 on: August 05, 2012, 11:12:00 PM »

sorry, i didn't even notice you had said that about the drop in max attainable rate when lifting the handset. Definitely worth getting to the bottom of that.  I don't know anything much about line faults, HR joints, etc..  Though the filters/splitters in the faceplates do sometimes fail.  And of course there's another splitter/filter at the other end (on the linecard in the cabinet). That potentially could fail.  Doesn't seem very likely though.

cheers, a
« Last Edit: August 05, 2012, 11:15:54 PM by asbokid »
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crystal_ship

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #17 on: August 06, 2012, 12:01:32 AM »

Thanks for the replies guys!

BT have moved me to the 80/20 profile, which I've been on since 02/08/2012. The only difference is a slightly higher upstream rate.

Prior to investigating any further, BT want me to wait until the 10 day training period is over - a few other folks have commented that the 10 day training period is a myth!

I've conducted a few ring backs on my line to see if it changes anything, but sadly no dice (apart from it temporarily reducing the max attainable line rate)

FYI - All my kit is directly connected to the master socket. No extensions here.

I could disconnect the phone and plug the modem directly into the test socket, as that would presumbly isolate the filter in the master socket?

The plot thickens!
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asbokid

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #18 on: August 06, 2012, 12:21:15 AM »

Thanks for the replies guys!

BT have moved me to the 80/20 profile, which I've been on since 02/08/2012. The only difference is a slightly higher upstream rate.   Prior to investigating any further, BT want me to wait until the 10 day training period is over - a few other folks have commented that the 10 day training period is a myth!

Oh well that's good.  Hmm.. So that pretty much says that DSM is determined / fixed independently of service profile.

I don't think even BT knows for sure about the detail of Dynamic Line Management.  Huawei/ECI probably won't disclose their DLM algorithms. The DSLAMs run totally closed source firmware. Perhaps BT has some role in its development, but probably not.   Flicking through some configuration manuals for the Huawei MA5616, and DLM doesn't even rank a mention. Maybe DLM is known by something else to Huawei?

Quote
I've conducted a few ring backs on my line to see if it changes anything, but sadly no dice (apart from it temporarily reducing the max attainable line rate)

FYI - All my kit is directly connected to the master socket. No extensions here.

I could disconnect the phone and plug the modem directly into the test socket, as that would presumably isolate the filter in the master socket?   The plot thickens!

Sure, and to eliminate the filtering/splitter in your faceplate as the cause of the drop in max attain. rate, maybe find one of those in-line DSL filters/splitters, and try that in the test socket behind the faceplate.   Although labelled usually as "ADSL" filters, they should work fine with VDSL2.

Good luck with it all :)

cheers, a
« Last Edit: August 06, 2012, 12:49:25 PM by asbokid »
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crystal_ship

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #19 on: August 06, 2012, 09:30:08 PM »

Today's line stats attached for information.

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Bald_Eagle1

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #20 on: August 08, 2012, 09:44:21 PM »


This is brilliant asbokid!

I found it rather difficult to compare images by scrolling up and down, this is really helpful!


That is indeed a very useful way to compare "snapshot" graphs.
I do it in a more "manual" manner via Windows 7.

Are you able to post the relevant Plink logs for these graphs?
They will need to be zipped first though, to make them a small enough size for posting in this forum.
Once zipped, each log should end up at around 62 KB in size.

In the meantime, I have attached an updated GRAPH6.BAT that you may wish to try out (store/rename your original version though - just in case you don't like the output).

You can also easily re-graph your existing Plink logs by dragging & dropping them onto the GRAPH6,BAT icon to generate output similar to the attached graphs.
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Bald_Eagle1

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #21 on: August 08, 2012, 09:54:13 PM »

Initial observations..
  • Bit Loading is a consequence rather than a cause, so best to leave it until last.
  • QLN (quiet line noise) has, overall, actually gone down between 29/07 and 05/08.. so it's not a crosstalk issue.
  • Hlog (line attenuation) is virtually unchanged between the two dates.
  • SNR (signal to noise ratio) .. that's the interesting one... SNR across the DSL spectrum has dropped, yet not in response to changes in QLN or Hlog.



Doesn't the QLN graph from 5th August actually show lower attenuation across all 3 bands i.e. increased noise?
(-140 being "quieter" than -120)

That could possibly explain why SNR has dropped.

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crystal_ship

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #22 on: August 08, 2012, 09:56:26 PM »

Evening!

I am generating new graphs as we speak!

I will post up the graphs and plink logs shortly.
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crystal_ship

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #23 on: August 08, 2012, 10:01:12 PM »

Here are the graphs from the new script you kindly posted up. Do you need anything to reflect today's state of play? The line dropped earlier :-(

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crystal_ship

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #24 on: August 08, 2012, 10:09:23 PM »

Tonight's line stats following the recent line drop. Let me know if you need anything else, thank you for volunteering your spare time to help, it is much appreciated. :-)



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asbokid

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #25 on: August 08, 2012, 11:15:22 PM »

Initial observations..
  • Bit Loading is a consequence rather than a cause, so best to leave it until last.
  • QLN (quiet line noise) has, overall, actually gone down between 29/07 and 05/08.. so it's not a crosstalk issue.
  • Hlog (line attenuation) is virtually unchanged between the two dates.
  • SNR (signal to noise ratio) .. that's the interesting one... SNR across the DSL spectrum has dropped, yet not in response to changes in QLN or Hlog.

Doesn't the QLN graph from 5th August actually show lower attenuation across all 3 bands i.e. increased noise?
(-140 being "quieter" than -120)

That could possibly explain why SNR has dropped.

You lost me. HLog measures attenuation.  QLN measures noise.

Hlog (attenuation) is essentially unchanged between 29/07 and 05/08.
There was more line noise measured on the 29/07 than on 05/08.
Yet, counter-intuitively, with attenuation unchanged and less noise, SNR nevertheless was reduced across the xDSL spectrum.

If we study the drop in SNR between 29/07 and 05/08 it indicates a managed cut-back in transmitter power at the DSLAM.  A different PSD mask applied by Openreach, perhaps?


EDIT:  see Baldy_Bird's correct understanding below..

cheers, a
« Last Edit: August 09, 2012, 02:10:07 PM by asbokid »
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Bald_Eagle1

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #26 on: August 09, 2012, 07:25:35 AM »

Initial observations..
  • Bit Loading is a consequence rather than a cause, so best to leave it until last.
  • QLN (quiet line noise) has, overall, actually gone down between 29/07 and 05/08.. so it's not a crosstalk issue.
  • Hlog (line attenuation) is virtually unchanged between the two dates.
  • SNR (signal to noise ratio) .. that's the interesting one... SNR across the DSL spectrum has dropped, yet not in response to changes in QLN or Hlog.

Doesn't the QLN graph from 5th August actually show lower attenuation across all 3 bands i.e. increased noise?
(-140 being "quieter" than -120)

That could possibly explain why SNR has dropped.

You lost me. HLog measures attenuation.  QLN measures noise.

Hlog (attenuation) is essentially unchanged between 29/07 and 05/08.
There was more line noise measured on the 29/07 than on 05/08.
Yet, counter-intuitively, with attenuation unchanged and less noise, SNR nevertheless was reduced across the xDSL spectrum.

If we study the drop in SNR between 29/07 and 05/08 it indicates a managed cut-back in transmitter power at the DSLAM.  A different PSD mask applied by Openreach, perhaps?



Sorry, I should have stated lower "sound" attenuation measured in dBm/Hz.
The way I have understood QLN is that as the QLN graph is "inverted", the higher the visual appearance the less the noise is attenuated i.e. the noisier the connection.

We quite often discuss noise "spikes" that have a value of say -120 dBm/Hz compared to the underlying value of say -140dbM/Hz.

The examples from July & August appear (to me) to overall show a general increase in "noise".
As you state, Hlog (signal attenuation) is virtually identical, so the signal to noise ratio has taken a hit as depicted in the SNR graph.

Overall DS SNRM levels had also deteriorated from around 10.6dB to 5.3dB, again suggesting either that the signal had weakened or that noise had increased.
This reduced SNRM had the effect of lowering attainable rates from 59168 Kbps to 40292 Kbps.

Over time, QLN appears to have deteriorated on my own connection (quite gradually), suggesting increased crosstalk as more customers are connected.
I believe I was one of the first to be connected to my cabinet as BT checks were stating that FTTC wasn't yet available at the time Plusnet arranged my connection.
(See the attached typical QLN graphs from my connection - October 2011 & July 2012)

Have I misunderstood the interpretation of QLN values (genuine question)?

« Last Edit: August 09, 2012, 07:28:39 AM by Bald_Eagle1 »
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burakkucat

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #27 on: August 09, 2012, 01:41:50 PM »

I guess a pair of sketch-graphs, one to show a typically "noisy" line and one to show a typically "quiet" line, would be what you would like to see?  :-\
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asbokid

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #28 on: August 09, 2012, 02:09:17 PM »

The way I have understood QLN is that as the QLN graph is "inverted", the higher the visual appearance the less the noise is attenuated i.e. the noisier the connection.

We quite often discuss noise "spikes" that have a value of say -120 dBm/Hz compared to the underlying value of say -140dbM/Hz.

The examples from July & August appear (to me) to overall show a general increase in "noise".
As you state, Hlog (signal attenuation) is virtually identical, so the signal to noise ratio has taken a hit as depicted in the SNR graph.

Overall DS SNRM levels had also deteriorated from around 10.6dB to 5.3dB, again suggesting either that the signal had weakened or that noise had increased.
This reduced SNRM had the effect of lowering attainable rates from 59168 Kbps to 40292 Kbps.

Over time, QLN appears to have deteriorated on my own connection (quite gradually), suggesting increased crosstalk as more customers are connected.
I believe I was one of the first to be connected to my cabinet as BT checks were stating that FTTC wasn't yet available at the time Plusnet arranged my connection.
(See the attached typical QLN graphs from my connection - October 2011 & July 2012)

Have I misunderstood the interpretation of QLN values (genuine question)?

Sorry, Paul, you are completely right! Ooops.. confusion reigned here :-)  I better delete that graphic otherwise everyone will be confused not just me!

cheers, a
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burakkucat

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Re: BT Infinity FTTC connection speed poor - graphs and stats available
« Reply #29 on: August 09, 2012, 02:16:45 PM »

Phew, that's a relief! I though I was due to be taken to the "funny farm".  :P
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