各位辛苦，我在做一个对数正太分布的阴影衰落仿真。协议中初始的阴影衰落矩阵描述如下：

•     Shadowing (in log domain): S(0) – NxN i.i.d. (with the exception that shadowing between two vehicles should be the same in the two directions) normal matrix generated as per agreed shadowing model

我现在的理解是要产生N*N独立的正太分布的矩阵，但是对其中的normal matrix不理解，麻烦各位知道的告诉我一下。