SNR Margin

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bigal_nz

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Topic # 23972 12-Jul-2008 06:25

I am just trying to understand this SNR Margin a bit better.

I was talking to a Chorus tech who said that Orcon and VF are pushing it out at 6db. Does this mean that anyone on the Red Network will have the same SNR Margin, 6db?

-Al

cyril7

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Reply # 147024 12-Jul-2008 08:45

No, not nessecarily. The DSLAM is given targets to aim between for noise margin, power and data rate((tone/bin counts), one being sacrifised to achieve another. It simply means that other operators have set the possiblity of lower noise margins to get higher but potentailly less stable connections.

Cyril

bigal_nz

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Reply # 147027 12-Jul-2008 09:04

Yes, thanks Cyril. I understand now.

Trying to get chorus to cut dead ahead, or remove the BT is going to be hard! They only agrre to make the line good enough for voice right?

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cyril7

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Reply # 147040 12-Jul-2008 09:45

ahhh, yes there primary interest is voice, however it has to be good for DSL also. What exactly are the issues.

Cyril

bigal_nz

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Reply # 147153 12-Jul-2008 15:24

Wow, I know people have said this before, but the D-Link filters are crap. I swapped my faulty D-Links out for Dynalinks and my upload speed went from 860, to 1100.

Now, the big test will be if my line is more stable......

The 6db SNR was only a problem with incoming calls, the rest of the time it seems fine, so possibly a filter problem. In fact I could even see the modem disconnet during the ringing stage, and reconnect while the wife was yaking on the phone and it would hold the connect fine while she was on the phone - it was just that inital stage that killed the connection.

-Al

cyril7

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Reply # 147166 12-Jul-2008 16:52

The disconneciton during ringing etc indicates a filter issue still exists, a central filter may be the go.

Cyril

bigal_nz

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Reply # 147174 12-Jul-2008 17:03

Havent had the disconnection issue since the Dynalink filters were installed.....fingers crossed!

cyril7

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Reply # 147190 12-Jul-2008 17:32

Exactly what stats do you get, ie noise, sync rate, attenuation.

Cyril

bigal_nz

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Reply # 147218 12-Jul-2008 19:41

ADSL status shows the ADSL physical layer status.

ADSL Firmware Version: 7.03.01.00 - 7.03.01.00 - 7.03.01.00 Annex A - 01.07.2c - 0.54
ADSL Software Version: V3.02B01T01.NZ.20071119
Line State Connected
Modulation ADSL_2plus
Annex Mode Annex A
Max Tx Power -38 dBm/Hz

Item Downstream Upstream Unit
SNR Margin 6 6 dB
Line Attenuation 28 14 dB
Data Rate 16128 1142 kbps

cyril7

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Reply # 147690 14-Jul-2008 10:49

Hi, your numbers are pretty much on the money, I also have noted that Telecom ISAMs have been showing lower S/N margins on ADSL2+, so maybe they also are pushing them lower. Also dont forget that ADSL2 has quite different power control systems that are dynamic, hence during low throughput demand it reduces power at the sacrifice of throughput but as a result inflicts less interference on other pairs in the wrapper, so the S/N may be read in that low power mode, the details of that and how Telecom/Alcatel run their DSLAMs as opposed to Siemens or Huwai I am not too sure of.

Cyril

webwat

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Reply # 148716 17-Jul-2008 01:55

Target is set to 12dB by default. If its unstable and no way to repair anything, get them to find a more stable port profile.

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