awgn channel for wireless optical channel

[Virginia]

hello, am using gaussian noise as my channel for my project ,transmission of optical signals in free space. how do i know what variance value to use?? and how do i use it for different values of distance say between 10m to 50m distnace

 

[kalyanasv]

the gaussian channel is modeled by considering noise as a gaussian variable. Typically you vary the variance value over a range to analyse how your channel performs over different variance values. i.e. SNR is a function of variance and you need to consider the for different values.

How to determine the corresponding variance for the corresponding distance. This is more complicated question and in reality requires you to measure the SNR value at these locations. To make hypothetical approximations, you can use a simplified model where the emitted optical power gets attenuated as the inverse of the distance from the source i.e. 1/r^2.

Hope this helps