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Thread: Noise floor

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  1. #1

    Default Noise floor

    Is -100 dBm the default value for noise floor when calculating for SNR?

  2. #2



    The -100 dBm you see in Chanalyzer and what a client will use as a noise floor are different.

    Stations can only detect and use 802.11 traffic to determine the noise floor.

    Once they find the noise floor it's just subtracting the RSSI and noise floor. It's not an actual ratio.

  3. Default

    Where can I get an actual ratio?

  4. Default

    So, guys, any update on this?

  5. #5


    Quote Originally Posted by Geortin View Post
    So, guys, any update on this?
    Sorry for the delay.

    Basically SNR is a misnomer. It's not an actual ratio, it's the difference between your RSSI and noise floor.

    So SNR = Noise floor - RSSI

    If your noise floor is -85dBm (a relatively high noise floor) and your RSSI is -65dBm (a relatively low RSSI) than the result is an SNR of 20, which would be problematic and only allow lower MCSs.

    In another example if your noise floor is -100dBm (a nice low noise floor) and your RSSI is -40dBm (what you could expect within ~25 feet of an AP) and the result would be an SNR of 60 and you may even get into 256-QAMs and some really excellent throughput.


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