Obstacles in the coverage area of an indoor or outdoor AP can cause an obvious loss of signals. The following table lists the path losses in 2.4 GHz and 5 GHz frequency bands caused by various obstacles.
If there are metal objects, load-bearing columns, or beams in the target coverage area, ensure that wireless signals are not blocked by them because they cause a large penetration loss.
The penetration loss is minimum when signals penetrate a wall vertically, and the penetration loss is much larger when wireless signals penetrate a wall obliquely. Therefore, when you install APs, try to reduce the incidence angle of signals.