This model visualizes the spread of wifi signals on a house, and their strength as they travel through air and walls. It is implemented using NetLogo.The model takes into account the mathematical model of Free Space Path Loss, and the attenuation of a wall. The patches of the model is scaled: 1 patch : 10 cm². Therefore, it is assumed that the walls are 10 cm in width.
An article about free space path loss can be found in Wikipedia: https://en.wikipedia.org/wiki/Free-space_path_loss
The paper by Davies et al predicts the wireless network signal strength of a building: http://collections.crest.ac.uk/205/1/fulltext.pdf