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wizkid
Aspiring Expert
2,282 Views
Message 1 of 11

Noise Margin

Hi 

Is it normal for the Noise Margin to be as low as 3.0-3.5db in the evenings?  Am I correct in thinking that lower noise margins are better than higher ones?

Please can someone confirm this.


Many thanks

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10 REPLIES 10
Guru
2,271 Views
Message 2 of 11

Re: Noise Margin

Noise margins erode at night time as noise levels increase.

Lower margins are not better as such.... if your line is stable and has few errors, the lower the target margin is, the higher the sync rate will be.

But if your line has noise, it may need an increased margin to sustain a connection.

 

Read about SNR and SNRm here:

 

http://www.kitz.co.uk/adsl/linestats.htm#SNR

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wizkid
Aspiring Expert
2,261 Views
Message 3 of 11

Re: Noise Margin

Below are my line states does it look
ok ?


ADSL line status

Connection Information

Line state Connected
Connection time 0 days, 07:50:58
Downstream 16,465 Kbps
Upstream 888 Kbps
 
ADSL Settings

VPI/VCI 0/38
Type PPPoA
Modulation G.992.5 Annex A
Latency type Interleaved
Noise margin (Down/Up) 3.5 dB / 14.2 dB
Line attenuation (Down/Up) 26.3 dB / 10.5 dB
Output power (Down/Up) 22.8 dBm / 1.3 dBm
Loss of Framing (Local/Remote) 0 / 0
Loss of Signal (Local/Remote) 0 / 0
Loss of Power (Local/Remote) 0 / 0
FEC Errors (Down/Up) 14663 / 0
CRC Errors (Down/Up) 701 / 0
HEC Errors (Down/Up) 13540 / 0
Error Seconds (Local/Remote) 350 / 0
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wizkid
Aspiring Expert
2,216 Views
Message 4 of 11

Re: Noise Margin

Please can someone let me know if these errors are ok for the amount of time the connection has been on? The connection dropped out earlier 2 times in 30mins early afternoon.

 

 

ADSL line status
Connection Information
Line stateConnected
Connection time0 days, 03:59:53
Downstream17,052 Kbps
Upstream888 Kbps
 
ADSL Settings
VPI/VCI0/38
TypePPPoA
ModulationG.992.5 Annex A
Latency typeInterleaved
Noise margin (Down/Up)4.8 dB / 13.9 dB
Line attenuation (Down/Up)26.3 dB / 10.5 dB
Output power (Down/Up)24.5 dBm / 1.3 dBm
Loss of Framing (Local/Remote)0 / 0
Loss of Signal (Local/Remote)0 / 0
Loss of Power (Local/Remote)0 / 0
FEC Errors (Down/Up)1600 / 0
CRC Errors (Down/Up)87 / 0
HEC Errors (Down/Up)2241 / 0
Error Seconds (Local/Remote)69 / 0
 
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Guru
2,205 Views
Message 5 of 11

Re: Noise Margin

You have quite a few forward error corrections for a 4 hour connection.

 

I would ask the moderators if your target SNR could be adjusted up a little.

 

May account for your dropped connections.

 

BT Forum Moderation Team <forum.moderation.team@bt.com>

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Highlighted
wizkid
Aspiring Expert
2,204 Views
Message 6 of 11

Re: Noise Margin

Hi Roger, 


Thanks for your reply.

 

Would BT Tech Support be able to do this as well?

 


Please can you let me know



Thanks

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Guru
2,201 Views
Message 7 of 11

Re: Noise Margin

Use the forum moderators ....  nicely  😉

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wizkid
Aspiring Expert
2,194 Views
Message 8 of 11

Re: Noise Margin

OK.

I'm expecting a call back from someone in Tech Support to see if they can diagnose the problem, so just wanted to know if this is something they can change I am guessing it is?
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Guru
2,190 Views
Message 9 of 11

Re: Noise Margin

Well ask them to increase the target noise margin to cover the HECs and FECs ... a little better.

Dynamic Line Management is supposed to look after things .... but it seems in your case it's not covering all the error correction...

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wizkid
Aspiring Expert
2,176 Views
Message 10 of 11

Re: Noise Margin

Just dropped out again 2 times in a row came back on for a second then cut out.  Downstream speed has gone down and there seems to be quite a few errors considering that its only been on for a few minutes.  Hopefully BT will call soon and fix this.  I'm wondering if its worth me emailing the mods anyway, are they likely to reply to emails over the weekend?

ADSL line status
Connection Information
Line stateConnected
Connection time0 days, 00:04:48
Downstream15,333 Kbps
Upstream888 Kbps
 
ADSL Settings
VPI/VCI0/38
TypePPPoA
ModulationG.992.5 Annex A
Latency typeInterleaved
Noise margin (Down/Up)5.7 dB / 14.4 dB
Line attenuation (Down/Up)26.3 dB / 10.5 dB
Output power (Down/Up)23.1 dBm / 1.3 dBm
Loss of Framing (Local/Remote)0 / 0
Loss of Signal (Local/Remote)0 / 0
Loss of Power (Local/Remote)0 / 0
FEC Errors (Down/Up)97 / 0
CRC Errors (Down/Up)4 / 64
HEC Errors (Down/Up)105 / 0
Error Seconds (Local/Remote)2 / 0
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