Upstream / Downstream Noise margin + Line attenuation

[kinginter]

Hi, quick question, is there a reason my upstream noise margin is much higher than downstream - also the line attuenation 1/2 that of the downstream?

My BT profile is 6500    
                          
      ADSL Link                          Downstream          Upstream            
      Connection Speed          8128 kbps          448 kbps             
      Line Attenuation          26.0 db          12.0 db             
      Noise Margin                          6.9 db          23.0 db

Also, if I plug my router into master socket (lid off) with a filter the downstream noise margin drops to 6.4 db

Cheers!                             

[roseway]

Hi and welcome.

Those are perfectly normal statistics for an ADSL Max connection. Because the upstream part of the connection uses lower frequencies than the downstream, the upstream attenuation is lower than downstream. Because the upstream connection speed is fixed at 448 kbps (max) there's loads of noise margin to spare so you get that high value. With a more expensive 'premium' package you could have an upstream connection speed of 832 kbps, and the noise margin would then be lower.

The small difference in noise margin when you plug into the test socket isn't really enough to be significant. Noise margin can vary a bit anyway, as interference conditions change.

[kinginter]

Thanks, that's reassuring. Is there also a way of telling if interleaving is on/off?

[roseway]

That information is probably available in your router statistics. Different routers have different ways of reporting it. Some say simply "Channel: Interleaved" or "Channel: FastMode" and others state a value for interleaving depth. If you don't see anything like this, have a look at the error section - if you see a value for FEC errors this will imply that the connection is interleaved.

You can read more about interleaving here.