在無線通訊中，「共頻道干擾」乃訊號傳收表現的主要限制，對數常態隨機變數之線性組合(以下簡稱LCLN)則是用以描述共頻道干擾的一般化模型。因為目前尚未得知LCLN之分佈的具體公式，且數值計算方面相當困難的緣故，找出簡單而準確的近似解便顯得符合需求。在本論文中我們使用兩種方法來近似LCLN。一種是Minimax近似法，即利用Minimax的法則找到一個可近似LCLN之分佈的對數常態分佈。另一種方法同樣應用了Minimax的法則，但使用冪次-對數常態分佈來提升近似的精確度。本論文會提出數值範例以比較我們使用的方法和現有近似法之間的效果差異。

In wireless communications, the linear combination of lognormal random variables (LCLN) is a general model for the cochannel interference, which represents main limitation to radio link performance. Since the distribution function of LCLN is not known in the closed form and is difficult to compute numerically, simple and accurate approximations of the distribution are needed. In this paper we use two methods to approximate LCLN. One is Minimax approximation, which uses Minimax method to find a lognormal distribution approximating the distribution of LCLN. The other method also follows the rules of Minimax approximation, but uses a power lognormal distribution to improve the accuracy of approximation. Numerical examples are provided to compare the approximations we used here with the existing ones.

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