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Standard User Bald_Eagle1
(member) Wed 14-Mar-12 22:25:16
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FTTC Output Power Levels v Sync Speed


[link to this post]
 
Hi All,


I have recently noticed from my HG612 modem's GUI that my DS Output Power levels fluctuate a little, quite often between GUI screen refreshes, so I have graphed power levels to get a visual idea of what it looks like.


The first graph is from a 18Mb Sync speed FTTC connection.
The second graph is from my 30Mb Sync speed FTTC connection
The third graph is from a 40Mb Sync speed connection

http://i1255.photobucket.com/albums/hh629/Bald_Eagle...

http://i1255.photobucket.com/albums/hh629/Bald_Eagle...

http://i1255.photobucket.com/albums/hh629/Bald_Eagle...


Just concentrating on DS Output Power levels for now, the difference in pure visual appearance is clear.

My own connection has been rather unstable over the last 7 months or so, eventually having a DLM reset 10th March, which initially provided a 35Mb sync speed for the first time since July 2011.

I first thought that stability had also improved, but following a number of "on the fly" resyncs at lower speeds, it is back down to 30Mb Sync speed, with Attainable rates around 33Mb to 36Mb, depending upon the time of day.

The 18Mb connection is stable, but around 1600m from the cabinet.
The 40Mb connection is also stable & around 500m from the cabinet.
My own 30Mb connection does not appear quite so stable & the 4 day graph above shows fluctuations in DS Output Power levels, whereas the other 2 connections show very steady Output Power levels.

I also notice the differences in DS Output Power levels for all 3 connections is not massive, despite the large differences in sync speeds.
The whole range is only between 11 dBmV & 13.7 dBmV.

I have seen other Output Power graphs from other users with varying speed connections & they also look steady.


The Windows Ongoing data harvesting script already stores any changes to Output Power levels, but the released graphing scripts do not plot the graphs (yet).



If anyone on the 80/20 trial would like to send me a copy of their ongoing modem_stats.log, could you please contact me via PM for an email address, or if you already have my email address, could you please forward a copy to me?
Alternatively, could you please upload the log file somewhere & post a link to where I could download it?
I will provide the graphs by return email, or post them here.


Does anyone know if the Output Power levels come from the actual sync speeds, or are sync speeds dictated by Otput Power levels?


Does anyone know if fluctuating power levels are a symtom or a cause of an unstable connection, or is it a "normal" phenomenon?

Paul.
Standard User dparry
(newbie) Thu 19-Jul-12 23:27:54
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Re: FTTC Output Power Levels v Sync Speed


[re: Bald_Eagle1] [link to this post]
 
Paul, only just stumbled across your thread when searching for info on output power levels for the HG612 on google.

I'm within 200m of my cabinet and receive the full 80/20. I was informed by the BT engineer that I was the first household to be hooked up to the cabinet (cabinet only went live a week before FTTC installed at address). Here are my line stats

Attainable rate = 136652 (kbit/s)
SNR margin - 21.5 (dB)
Output power (dBmV) 13.3

I'm fairly new to the HG612 so could you help me out with where I'll find modem_stats.log

Edited by dparry (Thu 19-Jul-12 23:29:34)

Standard User Bald_Eagle1
(committed) Thu 19-Jul-12 23:35:36
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Re: FTTC Output Power Levels v Sync Speed


[re: dparry] [link to this post]
 
In reply to a post by dparry:
I'm fairly new to the HG612 so could you help me out with where I'll find modem_stats.log


That's created when running the Windows 24/7 graphing scripts.

Have you installed the scripts?


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Standard User dparry
(newbie) Fri 20-Jul-12 12:11:09
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Re: FTTC Output Power Levels v Sync Speed


[re: Bald_Eagle1] [link to this post]
 
Not yet as only had the HG612 unlocked a few days.

I'm concerned that the quality on my line is partly due to me being probably the only one using the cab. How bad does crosstalk affect line speed? Can this be measured?
Standard User Bald_Eagle1
(committed) Sat 21-Jul-12 07:27:47
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Re: FTTC Output Power Levels v Sync Speed


[re: dparry] [link to this post]
 
With such high attainable rates & SNRM, it looks like you have loads of spare margin before crosstalk would become anything of an issue.

I have been connected for just over 12 months now & after a number of line faults, my connection is now stable again at around 30Mb or so sync speeds.

This is not as fast as when FTTC was installed in June 2011 (35Mb or so) & my QLN graphs look a little noiser as time has passed.

I suspect that is caused by crosstalk as more users get connected.
However, I am unaware of a method of actually measuring it.


November 2011:-
http://i.imgbox.com/adoEXbwS.png

July 2012:-
http://i.imgbox.com/acx0Svmn.png

Edited by Bald_Eagle1 (Sat 21-Jul-12 07:38:00)

Standard User MHC
(legend) Sat 21-Jul-12 12:19:59
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Re: FTTC Output Power Levels v Sync Speed


[re: Bald_Eagle1] [link to this post]
 
In reply to a post by Bald_Eagle1:
I suspect that is caused by crosstalk as more users get connected.
However, I am unaware of a method of actually measuring it.


You are right as it would be almost impossible with the current equipment. It would be necessary to differentiate between cross talk noise and atmospheric ... it could be achieved but not easily and at a high cost - and would need to be done at numerous points along the copper pair and in all directions.

Even vectoring only make a stab at it ...


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M H C


taurus excreta cerebrum vincit
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