萊斯分佈

在機率論與數理統計領域，萊斯分佈（Rice distribution或Rician distribution）是一種連續機率分佈，以美國科學家史蒂芬·萊斯（英語：Stephen O. Rice）的名字命名，其機率密度函數為：

${\displaystyle f(x|v,\sigma )=\,}$

${\displaystyle {\frac {x}{\sigma ^{2}}}\exp \left({\frac {-(x^{2}+v^{2})}{2\sigma ^{2}}}\right)I_{0}\left({\frac {xv}{\sigma ^{2}}}\right)}$

Rice

機率密度函數 Rice probability density functions for various v   with σ=1. Rice probability density functions for various v   with σ=0.25.
累積分佈函數 Rice cumulative density functions for various v   with σ=1. Rice cumulative density functions for various v   with σ=0.25.
母數	${\displaystyle v\geq 0\,}$ ${\displaystyle \sigma \geq 0\,}$
值域	${\displaystyle x\in [0;\infty )}$
機率密度函數	${\displaystyle {\frac {x}{\sigma ^{2}}}\exp \left({\frac {-(x^{2}+v^{2})}{2\sigma ^{2}}}\right)I_{0}\left({\frac {xv}{\sigma ^{2}}}\right)}$
期望值	${\displaystyle \sigma {\sqrt {\pi /2}}\,\,L_{1/2}(-v^{2}/2\sigma ^{2})}$
變異數	${\displaystyle 2\sigma ^{2}+v^{2}-{\frac {\pi \sigma ^{2}}{2}}L_{1/2}^{2}\left({\frac {-v^{2}}{2\sigma ^{2}}}\right)}$
偏度	(complicated)
峰度	(complicated)

其中${\displaystyle I_{0}(z)}$是修正的第一類零階貝索函數（Bessel function）。當${\displaystyle v=0}$時，萊斯分佈退化為瑞利分佈。

矩

極限情況

For large values of the argument, the Laguerre polynomial becomes (See Abramowitz and Stegun §13.5.1 （頁面存檔備份，存於網際網路檔案館）)

${\displaystyle \lim _{x\rightarrow -\infty }L_{\nu }(x)={\frac {|x|^{\nu }}{\Gamma (1+\nu )}}}$

It is seen that as ${\displaystyle v}$ becomes large or ${\displaystyle \sigma }$ becomes small the mean becomes ${\displaystyle v}$ and the variance becomes ${\displaystyle \sigma ^{2}}$

相關條目

• Stephen O. Rice (1907-1986)
• 瑞利分佈
• 萊斯衰落

外部連結

• Yongjun Xie and Yuguang Fang, "A General Statistical Channel Model for Mobile Satellite Systems" IEEE Transactions on Vehicular Technology, VOL. 49, NO. 3, MAY 2000. http://www.fang.ece.ufl.edu/mypaper/tvt00_xie.pdf （頁面存檔備份，存於網際網路檔案館）