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Math Help - help for Q function query

  1. #1
    Member moonnightingale's Avatar
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    help for Q function query

    I have got a solution of a question but i m unable to understand this equation

    Q (a) > 99 %

    so a < -2.33

    i know Q function and know to read its table but how -2.33 has come here.plz explain
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  2. #2
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    Quote Originally Posted by moonnightingale View Post
    I have got a solution of a question but i m unable to understand this equation

    Q (a) > 99 %

    so a < -2.33

    i know Q function and know to read its table but how -2.33 has come here.plz explain
    What youve posted makes no sense. Please post the entire question, including the part where Q is defined.
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  3. #3
    Member moonnightingale's Avatar
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    I have attached the solution.
    Kindly tell me why he has written -2.33
    Attached Thumbnails Attached Thumbnails help for Q function query-problem.jpg  
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  4. #4
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    Quote Originally Posted by moonnightingale View Post
    I have attached the solution.
    Kindly tell me why he has written -2.33
    The solution does not define any of the notation that is used. So, again, you are asked to provide the entire question.
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  5. #5
    Member moonnightingale's Avatar
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    The question is

    In this problem we will explore the impact of different log-normal shadowing parameters on outage probability.Consider a a cellular system where the received signal power is distributed according to a log-normal
    distribution with mean
    μ dBm and standard deviation σψ dBm. Assume thereceived signal power must beabove 10 dBm for acceptable performance.

    (a) What is the outage probability when the log-normal distribution has
    μψ = 15 dBm and σψ = 8dBm?
    (b) For
    σψ = 4dBm, what value of μψ is required such that the outage probability is less than 1%, a typical
    value for high-quality PCS systems?

    Solution is


    attached file

    Attached Thumbnails Attached Thumbnails help for Q function query-solution.jpg  
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  6. #6
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    Q function query

    1 - Q(a) < 0.01
    1 + Q(-a) < 0.01
    Q(-a) > 0.99

    from table
    -a > 2.33, which is same as a < -2.33

    hope it helps
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  7. #7
    Member moonnightingale's Avatar
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    ur last statement stillnot clear
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