Can someone explain about noise margins?

Discussion in 'Broadband' started by BJH, Dec 5, 2006.

  1. BJH

    BJH Guest

    Hi all

    I've just changed from a fixed 512k connection to 8M connection, I assume
    this is what is called ADSL Max? I won't bore anyone with my reasons for
    changing other than it got me away easily from Legend Communications (who
    won't release MAC codes).

    My noise marging with the 512K connection tended to be around 15dB

    Since my new speed went 'live' today I've noticed that the noise margin has
    dropped to 6dB.

    I assume this is a function of the different connection type?

    My current figures are:

    Downstream
    Noise Margin: 6dB
    Output Power: 20dBm
    Attenuation: 35dB

    Upstream
    Noise Margin: 26dB
    Output Power: 10.5dBm
    Attenuation: 17.5dB

    Upstream: 448Kbps
    Downstream: 6816 Kbps

    Any comments/explanation on the above figures would be greatly appreciated.
     
    BJH, Dec 5, 2006
    #1
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  2. BJH

    K A Nuttall Guest

    Ugh. Legend. Nightmare. Enough said.
    BTW aim to keep the s/n ration at 6dB or above. They do this by
    lowering the sync speed until the line is stable. S/N ratio is an
    indicator of stability, so they target this value initially at 6dB, and
    increase it in stages, if the disconnection rate doesn't improve. They
    also set Interleave on problem lines.

    As long as your line is stable, 6dB is fine. And you're probably
    getting the best speed possible from your line.
     
    K A Nuttall, Dec 5, 2006
    #2
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  3. I've just changed from a fixed 512k connection to 8M connection, I
    You are getting close to the theoretical maximum of 7MB. The up to 8MB is a
    myth because with overheads etc. the real up to is about 7.1MB or
    thereabouts,
    Quite a good explanation of ADSL MAX can be found here.

    http://portal.plus.net/support/broa...l?pn_session=b2197eb19a5361720bafa8ba50191b51


    Peter Crosland
     
    Peter Crosland, Dec 5, 2006
    #3
  4. BJH

    BJH Guest

    Thanks Guys, that's good. I had a heart stopping moment about 15 mins ago
    when the router 'lost' the connection.

    I was logged on with the Legend user ID and password, but all I had to do
    was switch off for a few minutes and reconnect with the new UserID and
    password.

    Now all fine and thanks again for the very clear explanations.
     
    BJH, Dec 5, 2006
    #4
  5. BJH

    green Guest

     
    green, Dec 5, 2006
    #5
  6. BJH

    green Guest

    dont sweat it m8

    mine goes every other day but alwsy comes back with an on/off router like
    you did

    bt "remotely stabilised mine" - from s/n of 6.6-7.5 - line going every
    couple of hours

    to sn above 10 sometimes 14 and a couple of days out of it

    so they can "tweak" things

    speed is down a bit but not fatal

    i can only get 2.something meg but it will do me



     
    green, Dec 5, 2006
    #6
  7. You are getting close to the theoretical maximum of 7MB. The up to 8MB is a
    myth because with overheads etc. the real up to is about 7.1MB or
    thereabouts,[/QUOTE]

    The figures quoted also include those overheads, so he is still over a
    megabit away from the maximum. If he had a perfect line, it would show
    the downstream as 8128Kb/s.

    -- Richard
     
    Richard Tobin, Dec 5, 2006
    #7
  8. BJH

    NoNeedToKnow Guest

    NoNeedToKnow, Dec 5, 2006
    #8
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