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Author Topic: Upstream attenuation changes  (Read 4774 times)

lemzip

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Upstream attenuation changes
« on: May 18, 2011, 09:55:35 PM »

Hi

I have a sky llu line and seen something odd. My upstream attenuation moves from 13db (right for my line distance) to 20db.

I also have alot of errors only on the upstream, is there a common fault that would affect my upstream and not my downstream? There is no phone on the line (i will test with one shortly) but its very off.

Stats of sky llu line

ADSL Link   Downstream   Upstream
Connection Speed   13301 kbps   1087 kbps
Line Attenuation   32.0 db   19.9 db
Noise Margin   6.8 db   7.9 db

Noise Margin:     7.9   dB
Connection Rate:  1087  Kbps
Line Attenuation: 19.9  dB
Power:            12.3  dBm
Max Rate:         1080  Kbps
 
SuperFrames:      135315
SF (CRC) Errors:  7
Reed Solomon:     2318757
RS Corrected:     1231
RS Un-Corrected:  0
HEC:              11
Errored Seconds:  75
Severe ES:        150

Interleave Depth: 8
Bitswaps:         5

Thats only been connected for 40 mins (upstream stats
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jeffbb

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Re: Upstream attenuation changes
« Reply #1 on: May 19, 2011, 06:37:35 PM »

Hi
quote My upstream attenuation moves from 13db (right for my line distance) to 20db.

How have you determined the "right US  attenuation for your distance " ? I know how to get approximate Attenuation for given line length for DS ,but have never seen similar info regarding US .
Regards Jeff
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waltergmw

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Re: Upstream attenuation changes
« Reply #2 on: May 19, 2011, 07:02:01 PM »

I believe that the attenuation can only be observed accurately at the receiving end.
When I've been discussing line stats with ISPs  they can quote the upstream observation reasonably accurately (I think) but I see a value of about half the downstream; whereas I can tell them the downstream attenuation more accurately that the average estimation they can "see" from their end.

Kind regards,
Walter
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jeffbb

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Re: Upstream attenuation changes
« Reply #3 on: May 20, 2011, 02:48:15 PM »

Hi
quote but I see a value of about half the downstream;

Remember you may see figures of half face value but its logarithmic . every 3db is a doubling / halving  of the value depending which way you are comparing .
My question was where did "My upstream attenuation moves from 13db (right for my line distance)"
was is the information regarding US attenuation versus distance to be obtained ?

Regards Jeff
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lemzip

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Re: Upstream attenuation changes
« Reply #4 on: May 20, 2011, 11:08:24 PM »

thing is no matter if it is right or not, a change in attenuation from 13 to 20 displays a issue, i am just asking what issue it could be...
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jeffbb

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Re: Upstream attenuation changes
« Reply #5 on: May 21, 2011, 11:02:06 AM »

Hi
I was just hoping that you had found out how to correlate line length to US attenuation.

as to what could cause variations ? with it not affecting DS then its unusual. I assume you have done all the normal checks to improve your  connection

Regards Jeff
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lemzip

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Re: Upstream attenuation changes
« Reply #6 on: May 22, 2011, 01:50:54 AM »

yeah, line is new and watched the engineer do it. Filtered faceplate (tried a adslnation one and bt bte2000)

I was just using my other line as a baseline:

line 1
ADSL Link   Downstream   Upstream
Connection Speed   16859 kbps   1020 kbps
Line Attenuation   33.0 db   14.1 db
Noise Margin   3.6 db   12.7 db

line2
ADSL Link   Downstream   Upstream
Connection Speed   15889 kbps   766 kbps
Line Attenuation   32.0 db   20.0 db
Noise Margin   3.7 db   16.2 db

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jeffbb

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Re: Upstream attenuation changes
« Reply #7 on: May 23, 2011, 01:00:11 PM »

Hi

quote
line 1
ADSL Link   Downstream   Upstream
Connection Speed   16859 kbps   1020 kbps
Line Attenuation   33.0 db   14.1 db
Noise Margin   3.6 db   12.7 db

line2
ADSL Link   Downstream   Upstream
Connection Speed   15889 kbps   766 kbps
Line Attenuation   32.0 db   20.0 db
Noise Margin   3.7 db   16.2 db


Ok so this is the comparison between 2 lines from the same location.

One has changing Attenuation?

Are they both SKY LLU? where both of these stats taken at same time and synched at same time time ?

The striking thing is that line 2  (Sky LLu ?)
Its also noticeable that its not only is the attenuation greater than line one but the SNR Margin is greater which is counter intuitive. Though this might be explained by the lower US synch rate .

Seems to be more questions than answers

your original stats  showed the high US attenuation with a higher US synch rate ,but lower US SNR margin 
Stats of sky llu line

ADSL Link   Downstream   Upstream
Connection Speed   13301 kbps   1087 kbps
Line Attenuation   32.0 db   19.9 db
Noise Margin   6.8 db   7.9 db


Does the attenuation change during a session or does it change on resynch/reboot .

Can you swap the routers ?
Regards Jeff

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lemzip

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Re: Upstream attenuation changes
« Reply #8 on: May 24, 2011, 01:06:38 AM »

Hi

Yes, more questions!

The first is TT LLU and the second is SKY LLU.

It seems to only change when i resync, i try not to do it to much incase the DLM thinks there is a fault. once it syncs at this lower attenuation, it stays like that until resync. I have seen 3 resync's in a line before (sky rep doing it) and the attenuation changed by a few db each time.

I have a few different routers so will try with the stock sky one and see what it says.

cheers
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coolsnakeman

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Re: Upstream attenuation changes
« Reply #9 on: May 30, 2011, 12:50:41 PM »

Hey,

Are you using the sky supplied router from your router stats it looks like you have flashed the router considering the sky router does not give those type of in depth stats you only really get your attenuation, speed US and DS and your SNRM. Your also on ADSL2+. From what i am seeing you have 2 different broadband service providers at the property are you seeing the same fluctuations on the attenuation on both of them (sorry if this has been covered and i haven't noticed). What i am trying to get at is if you have flashed the sky router and the other line isn't fluctuating you could have reverted the router back to firmware that does not support ADSL2+ which will lead to alot of screw ups from your router. I could be wrong though.

Regards
Gary
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