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Standard User ppppenguin99
(regular) Tue 13-Sep-11 05:35:18
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Pushing s/n ratio to the limit


[link to this post]
 
Just looked at my router stats. While I have no complaints about the speed isn't 1dB downstream s/n ratio a bit low for comfort? The DSL link is rock solid as you can see from the 27 days up time. The PPPoA connection is less so, that tends to drop at least once per day for a few seconds. Though to be fair it was also doing this when my connection speed was lower and s/n ratio higher.

I didn't realise that ADSl could optimise itself like this to within an inch of its life. Is this normal?

Uptime: 27 days, 19:11:24
DSL Type: G.992.5 annex A
Bandwidth (Up/Down) [kbps/kbps]: 1,176 / 18,319
Data Transferred (Sent/Received) [kB/kB]: 0.00 / 4.00
Output Power (Up/Down) [dBm]: 11.5 / 0.0
Line Attenuation (Up/Down) [dB]: 9.0 / 21.5
SN Margin (Up/Down) [dB]: 6.0 / 1.0
Vendor ID (Local/Remote): TMMB / IFTN
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 12 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 0 / 29,625
HEC Errors (Up/Down): 0 / 12,324
Standard User 5km
(knowledge is power) Tue 13-Sep-11 07:40:42
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Re: Pushing s/n ratio to the limit


[re: ppppenguin99] [link to this post]
 
Unless you have set the SNR Margin to 1dB the quality has dropped since it connected 27 days ago. If your margin continues to fall then it will re-sync, perhaps at a lower rate.

I have my margin set to 3dB using DMT. It's stable enough with a 16Mbps connection which is far better than the 14Mbps connection default SNR Margin would give.

O2 Broadband Premium LLU
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Standard User ppppenguin99
(regular) Tue 13-Sep-11 08:03:53
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Re: Pushing s/n ratio to the limit


[re: 5km] [link to this post]
 
I haven't taken any action to affect the s/n ratio. Nor have I asked Plusnet to take any action. I thought it was something that was negotiated automatically between the DSLAM/MSAN and the modem. I know about the training period but the last time the ADSL connected 27 days ago (after a power failure) the speed was over 18Mb/s, the fastest it has ever been, and it has stayed at that speed. Previously it has been in the 16-17MB/s range.


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Standard User ian72
(knowledge is power) Tue 13-Sep-11 08:10:11
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Re: Pushing s/n ratio to the limit


[re: ppppenguin99] [link to this post]
 
Noise changes over time. If you were to reconnect now it would reconnect at the target noise margin and you would probably lose a little speed. You probably had particularly good conditions the last time it connected (the fact you say it is the fastest you have ever sync'ed bears this out). Either leave it and keep the speed or reboot the router and let it settle to a higher SNR (and likely lower connection rate).
Standard User ppppenguin99
(regular) Tue 13-Sep-11 08:16:38
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Re: Pushing s/n ratio to the limit


[re: ian72] [link to this post]
 
I honestly don't care about the difference between 16M and 18M. Both are amply fast for my needs and enough to make many people jealous.Just curious to know if there's any downside of running right at the limits.
Standard User jelv
(knowledge is power) Tue 13-Sep-11 09:32:08
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Re: Pushing s/n ratio to the limit


[re: ppppenguin99] [link to this post]
 
The error counts don't look worrying for a connection of that length of time so I wouldn't be particularly concerned. Have you monitored the margin to see how much it varies during the day?

jelv

Plusnet user since November 2001
Standard User yarwell
(sensei) Tue 13-Sep-11 09:33:29
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Re: Pushing s/n ratio to the limit


[re: ppppenguin99] [link to this post]
 
Just curious to know if there's any downside of running right at the limits

there will probably be a few more errors. The SNR margin is defined in terms of an acceptable error rate so at a smaller margin you should see more errors - some routers have a BER test function to determine this.

0 dB SNR margin is (from memory) an error rate of 1 in 10 million

Phil

MaxDSL - goes as fast as it can and doesn't read the line checker first.

MaxDSL diagnostics
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Standard User Oldjim
(fountain of knowledge) Tue 13-Sep-11 09:35:23
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Re: Pushing s/n ratio to the limit


[re: ppppenguin99] [link to this post]
 
Looking at the reported errors - in your case the answer is definitely no
It is possible that after the last sync the highest tones dropped out over night due to bit swapping and haven't been re-enabled
Standard User ppppenguin99
(regular) Tue 13-Sep-11 09:35:52
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Re: Pushing s/n ratio to the limit


[re: jelv] [link to this post]
 
Usually check my connection once per day in the morning. Seems very consistent with little or no day to day speed or s/n variation. The only slight worry is the relatively frequent PPoA drops. Thes are usually daily, sometimes more often, sometimes less.
Standard User atsw
(experienced) Tue 13-Sep-11 19:19:46
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Re: Pushing s/n ratio to the limit


[re: ppppenguin99] [link to this post]
 
My connection has settled to a snr of around 2.8 in recent months (used to be 6.0 when ADSL1, with the move to ADSL2+ it's now 2.8). My router re-starts itself each morning at 6:00am so I have a fresh connection each day. It always connects at snr 2.5 to 3.0, with a download sync of around 7400. In the days of ADSL1, the snr was 6.0 and the connection sync around 4500, so a clear improvement driven by a lower snr. The connection is stable at 2.8, although, like you, the PPPoA will sometimes re-connect once early evening.

Andrew

PlusNet - Extra smile
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