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    SNR question

    This is a discussion on SNR question within the Sky Broadband help forums, part of the Sky Broadband help and support category; My upstream noise margin is set at 7db, but on the stats it says 8.5db. Why is this, why does ...

    1. #1
      Andy17's Avatar
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      SNR question

      My upstream noise margin is set at 7db, but on the stats it says 8.5db. Why is this, why does it not connected at 7db.


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      Re: SNR question

      If your router is accurate to about 1.5dB thats very good. Truth is domestic routers are not to be relied on for absolute measurement, but are very handy when looking at the changes on a line.

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      Re: SNR question

      Quote Originally Posted by Andy17 View Post
      My upstream noise margin is set at 7db, but on the stats it says 8.5db. Why is this, why does it not connected at 7db.
      Upstream is allocated prior to downstream and it finds its own level up to the maximum possible for the ADSL mode and profile (interleaving etc. and capping) that has been set by the ISP which means that the upstream noise margin will often be higher than the default downstream noise margin.

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      Re: SNR question

      These are my final stats after alterations to speed setting.

      ADSL Link Downstream Upstream
      Connection Speed 13375 kbps 1203 kbps
      Line Attenuation 43.0 db 18.5 db
      Noise Margin 7.75 db 8.5 db

      Is interleaving different to lowering max delays, if it is would lowering the interleaving level on the upstream allow it to sync nearer the 7db target and therefore increase the upstream speed.

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      Re: SNR question

      OK, your stats show your upstream is near the limit for ADSL2+ Annex A. Once you start to get near the limit (Upstream or downstream) then your physical line condition (attenuation and quality) become very important. Your line can only physically achieve ~1200kbps upstream but has a little bit of overhead spare which gives you a slightly raised noise margin.

      Max delays is a component of interleaving, the other main one being depth. Yes, changing interleaving settings will impact achievable sync but , first that's not a good idea (and Sky probably won't do it) and second, you'd get maybe an extra 30-40kbps on your upstream. Can you honestly say you'd be able to notice that?

      As I think I've mentioned before, your connection is exceptionally good considering your attenuation - the best I've ever seen, and way off the normal graph. Trying to squeeze more out of it is going to be a waste of time.

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      Re: SNR question

      Quote Originally Posted by Saturday View Post
      OK, your stats show your upstream is near the limit for ADSL2+ Annex A. Once you start to get near the limit (Upstream or downstream) then your physical line condition (attenuation and quality) become very important. Your line can only physically achieve ~1200kbps upstream but has a little bit of overhead spare which gives you a slightly raised noise margin.
      Where you have said "a bit of overhead spare", lets say I wanted to use that spare overhead up, how would I do that.

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      Re: SNR question

      By adjusting a number of parameters that you don't have access to and Sky won't touch for you.

      As I said before, does it really matter? If every last ounce of upstream is important to you then move to an ISP that offers ADSL2+ annex M and you'd get ~2.3meg upstream at a small cost to your downstream.

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      Re: SNR question

      I have to agree with Saturday. I don't think you realise how lucky you are to be getting the speed you are with your attenuation. As I have said before it is exceptional, you are getting way above what you should and I do not believe that your router has a lot to do with it. You have an unbelievably good line, be happy with it. Asking Sky to do anything is likely to lead to a reduction in your speeds rather than an increase.

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      Re: SNR question

      I put the increase all down to the router I am using at the moment.

      I have tryed the sky router and the stats are.

      ADSL Link Downstream Upstream
      Connection Speed 12375 kbps 950 kbps
      Line Attenuation 40.0 db 23.3 db
      Noise Margin 6.80 db 8.5 db

      And the stats from the router I am using are.

      ADSL Link Downstream Upstream
      Connection Speed 13375 kbps 1203 kbps
      Line Attenuation 43.0 db 18.5 db
      Noise Margin 7.30 db 8.5 db

      The downstream was set to 14.5Mb, but i have had this lowered to 13.3Mb so that there isn't a resync at night.
      Last edited by Andy17; 25-08-09 at 02:29 PM.

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      Re: SNR question

      Updated stats, this morning. The upstream has increased hope it keeps going.

      ADSL Link Downstream Upstream
      Connection Speed 13375 kbps 1211 kbps
      Line Attenuation 43.0 db 18.5 db
      Noise Margin 8.00 db 8.0 db

     

     
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