Two independent random variables, change the line integral plus joint distribution function, outage probability, there are two random variables

1, the random variable hsubject to complex Gaussian distribution, namely h\sim CN(0,\lambda_{1}), the X = \ h green \ green ^ {2}exponential distribution, that is X \ sim E (\ lambda_ {1}).

XDensity function can be written as

f(x)=\left\{\begin{matrix} \lambda_{1}e^{-\lambda_{1}x}, x\geq 0 \\ 0,\ \ \ \ \ \ \ \ x<0 \end{matrix}\right.

XThe distribution function can be written as

\left\{\begin{matrix} P(X\geq x)=e^{-\lambda_{1}x}\\ P(X\leq x)=1-e^{-\lambda_{1}x} \end{matrix}\right.

2, during a communication outage probability requirements, you may encounter Pr(X\ge aY+b)form, wherein X \ yes E (\ {1} lambda_), Y \ yes E (\ {2} lambda_)two exponential distribution random variable, a, ba constant, is calculated as follows:

\begin{aligned} Pr(X\ge aY+b) &=E_{Y}[F_{X}(ay+b)]\\ &= \int_{0}^{\infty}f_{y}(t_{1})Pr(X\ge at_{1}+b)dt_{1}\\ &=\int_{0}^{\infty}f_{y}(t_{1})\int_{at_{1}+b}^{\infty}f_{x}(t_{2})dt_{2}dt_{1}\\ &=\int_{0}^{\infty}f_{y}(t_{1})e^{-\lambda_{1}(at_{1}+b)}dt_{1}\\ &=\int_{0}^{\infty}\lambda_{2}e^{-\lambda_{2}t_{1}}e^{-\lambda_{1}(at_{1}+b)}dt_{1}\\ &=\lambda_{2}e^{-\lambda_{1}b}\int_{0}^{\infty}e^{(-\lambda_{2}-a\lambda_{1})t_{1}}dt_{1}\\ &=\lambda_{2}e^{-\lambda_{1}b}/(\lambda_{2}+a\lambda_1) \\ \end{aligned}

 

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