There are several environmental factors that can affect the range and performance of wireless networks. You must estimate the path loss and attenuation of your wireless signals as a result of these factors.
Walls and ceilings
Walls and ceilings between the AP and wireless clients can degrade signal strength. Wireless signals can penetrate walls and other structures, but the rate of penetration is directly related to the type of building materials, materials thickness, and the distance from the wireless antenna.
Building materials
Metal and aluminum doors, glass, concrete, metal studs, brick walls, glass, and other types of building materials can have a significantly negative effect on the signal strength of wireless signals.
EMI (Electro-magnetic interference)
EMI from other electrical devices, such as microwaves, cordless phones, and wireless headsets, can generate significant RF noise and degrade or disrupt wireless communications.
Distance
Wireless signals degrade quickly past their maximum range. You must plan your network carefully to provide adequate wireless coverage over the range you require in your environment.