VDSL Performance & Tuning

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#929712 8-Nov-2013 20:47

All I know is that there are people on 17a with 7db attenuation, despite what the Chorus site says.

hio77

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#929713 8-Nov-2013 20:48

SamF: All I know is that there are people on 17a with 7db attenuation, despite what the Chorus site says.

yeah, i just wish it was properly published in that case...

it seems chorus's site doesn't actually follow through with what we see..

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stevehodge

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#929723 8-Nov-2013 21:00

hio77:
SamF: Pretty sure the attenuation threshold is 7db. Not sure if there are any error thresholds or not.

see, thats what we have understood.. but the posting on the chrous site, infers more around a 4db mark due to it saying 200M IIRC..

Is that 4db = 200m for adsl or vdsl?

stevehodge

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#929725 8-Nov-2013 21:02

SamF: All I know is that there are people on 17a with 7db attenuation, despite what the Chorus site says.

If that's 7db once they're on 17a, that would correspond to about 5db in 8b and maybe 3db on adsl.

hio77

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#929731 8-Nov-2013 21:09

stevehodge:
hio77:
SamF: Pretty sure the attenuation threshold is 7db. Not sure if there are any error thresholds or not.

see, thats what we have understood.. but the posting on the chrous site, infers more around a 4db mark due to it saying 200M IIRC..

Is that 4db = 200m for adsl or vdsl?

stevehodge:
SamF: All I know is that there are people on 17a with 7db attenuation, despite what the Chorus site says.

If that's 7db once they're on 17a, that would correspond to about 5db in 8b and maybe 3db on adsl.

im basis my argument off my stats, currently at 4db, electrically calculated comes to 201M (although, my electrical calculation seems to vary all the way up to 285M..)

as vdsl, 8b marks..

4~5db in 8b, that sounds more like it..

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hio77

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#929733 8-Nov-2013 21:11

i guess to be completely unambiguous about it, could compare prequel attention values.. arguably, that would be just as inaccurate.

but you have to consider, different modems show different attenuations, hell.. the .51 firmware for me adds 2db attenuation..

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SamF

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#929735 8-Nov-2013 21:23

stevehodge:
SamF: All I know is that there are people on 17a with 7db attenuation, despite what the Chorus site says.

If that's 7db once they're on 17a, that would correspond to about 5db in 8b and maybe 3db on adsl.

Hmm, good point, I can't recall, but maybe that is after so perhaps 5db on 8b is a better measure.

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SamF

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#929738 8-Nov-2013 21:27

That said, to quote myself from the first post:

According to Chorus VDSL documentation, line attenuation must be less than 2.75db (in other words; you are less than approximately 200m from the cabinet) for 17a to be activated, however attenuation figures as high as 7 have been observed prior to some lines being swapped to 17a.

stevehodge

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#929807 9-Nov-2013 00:46

SamF: That said, to quote myself from the first post:

According to Chorus VDSL documentation, line attenuation must be less than 2.75db (in other words; you are less than approximately 200m from the cabinet) for 17a to be activated, however attenuation figures as high as 7 have been observed prior to some lines being swapped to 17a.

That 2.75db is based on 13.81db/km which, according to http://www.speedguide.net/faq_in_q.php?qid=373, is the attenuation for 26 AWG cable at 300kHz. The Fritz at least seems to report attenuation across all the frequencies in use so a line could show considerably considerably higher attenuation on 8b and still qualify for 17a. It wouldn't surprise me if 7db reported on 8b was low enough to meet that 2.75db @ 300kHz requirement.

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#929808 9-Nov-2013 00:49

stevehodge:
SamF: That said, to quote myself from the first post:

According to Chorus VDSL documentation, line attenuation must be less than 2.75db (in other words; you are less than approximately 200m from the cabinet) for 17a to be activated, however attenuation figures as high as 7 have been observed prior to some lines being swapped to 17a.

That 2.75db is based on 13.81db/km which, according to http://www.speedguide.net/faq_in_q.php?qid=373, is the attenuation for 26 AWG cable at 300kHz. The Fritz at least seems to report attenuation across all the frequencies in use so a line could show considerably considerably higher attenuation on 8b and still qualify for 17a. It wouldn't surprise me if 7db reported on 8b was low enough to meet that 2.75db @ 300kHz requirement.

brings the question then, is there a way to find exact figures out at the 300khz rate..

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#929809 9-Nov-2013 00:54

another interesting little mode i just came across, which could be handy with this..

Get Near End SNR Margin and Attenuation for Bme: 1 Port 1
=================
SNR Margin: 6.1 dB
Attenuation: 4.5 dB
Avg SNR Margin: 9.3 dB
Avg SNR: 47.4 dB

SNR Margin (SNRMpb-0): 9.2 dB
SNR Margin (SNRMpb-1): 9.7 dB
SNR Margin (SNRMpb-2): 0.0 dB
SNR Margin (SNRMpb-3): 0.0 dB
SNR Margin (SNRMpb-4): 0.0 dB

Line Attenuation (LATNpb-0): 2.4 dB
Line Attenuation (LATNpb-1): 12.3 dB
Line Attenuation (LATNpb-2): 0.0 dB
Line Attenuation (LATNpb-3): 0.0 dB
Line Attenuation (LATNpb-4): 0.0 dB

Signal Attenuation (SATNpb-0): 2.1 dB
Signal Attenuation (SATNpb-1): 12.1 dB
Signal Attenuation (SATNpb-2): 0.0 dB
Signal Attenuation (SATNpb-3): 0.0 dB
Signal Attenuation (SATNpb-4): 0.0 dB
Downstream attainable Line rate : 49672 kbps
Downstream attainable payload rate : 43820 kbps

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#929811 9-Nov-2013 01:02

based on that first bracket, LATNpb-0.. that sounds about right for the prequal (cant compare adsl as i never had adsl here..) electrical distance of my line, sounds about right.. might be slightly off the 300khz range, but could be a slightly more accurate judgement factor..

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stevehodge

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#929812 9-Nov-2013 01:23

hio77: based on that first bracket, LATNpb-0.. that sounds about right for the prequal (cant compare adsl as i never had adsl here..) electrical distance of my line, sounds about right.. might be slightly off the 300khz range, but could be a slightly more accurate judgement factor..

Yeah, I'd say that would be more accurate.

hio77

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#929814 9-Nov-2013 01:24

another interesting read i just stumbled across..

http://juha.saarinen.org/8452

http://juha.saarinen.org/8521

http://juha.saarinen.org/8522

the most interesting bit of all, the date. 27-Aug-2013... reading through it, chorus have willingly disabled DLM, and enforced a 17a profile..

at 14db attenuation too!

"EUBAV-VDSL2-4" wonder if snap will push for that profile upon request for any of us..

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hio77

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#929816 9-Nov-2013 01:35

stevehodge:
hio77: based on that first bracket, LATNpb-0.. that sounds about right for the prequal (cant compare adsl as i never had adsl here..) electrical distance of my line, sounds about right.. might be slightly off the 300khz range, but could be a slightly more accurate judgement factor..

Yeah, I'd say that would be more accurate.

vdsl, option 13 on telnet, encase anyone else wants to compare..

i just noticed i have a habit of leaving the vdsl client open in telnet, from past experience, that can cause a connection to be in a frozen state, and not reconnect... wonder what it would do to DLM... thats being too hopeful too though i suppose!

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