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Author Topic: SNR margin and snr target  (Read 1761 times)

jeffbb

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SNR margin and snr target
« on: February 13, 2009, 08:11:30 PM »

HI
If the SNR target is set at 15 then with NO tweaks will you always synch at 15 SNR margin   or over ,or is there some leeway ie synch at 14.5 Snr margin .


I am tweaking  using routestats  to tweak from 15 To 9  (60%)  on the  assumption that  if my snr margin is 14.5 or thereabouts then my target is 15  :-\.  My tweaked SNR margin has dropped to 11.8 .Is that a target of 9 or 12 ?

Regards Jeff


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sevenlayermuddle

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Re: SNR margin and snr target
« Reply #1 on: February 13, 2009, 08:45:35 PM »

Sorry, are you saying it drifted down to 11.8 or was that what you say immediately after a resynch?  Assuming the latter, most likely, I'd say, it synched at 12 and then by the time you (or routerstats) got around to looking at it a fraction of a second later, it had dropped to 11.8.

If your tweaked margin has moved from 9 to 11.8, then it sounds to me like DLM has put you from a 12dB margin to 15dB. 

I'm not familiar with how the GUI tools adjust the margin as I'm a dedicated luddite and only happy at the command line.  With the DG834GT, the maximum variation via CLI is -6dB relative to DLM target, so I could speculate that 60% is something around -3dB.   That's with the Netgear f/w, I'm sure somebody will clarify if the DGTeam is different, or if my speculation about GUI % adjustments is wrong.
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roseway

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Re: SNR margin and snr target
« Reply #2 on: February 13, 2009, 10:44:55 PM »

If the target noise margin is 15 dB then the router will connect at the best speed it can without going below 15 dB noise margin. In other words, the target is the firm minimum. However, after connecting, the actual noise margin can change from second to second as interference levels change. So you can't tell for certain what the target is, but if you check the router stats immediately after a re-sync, then most probably the target is very close to the value you see at that time.
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