Its is bad design….
How can we design for something we cannot measure? A wireless design needs to account for signal attenuation, one of the big design requirements is to account for the loss caused by walls, windows etc. We do this by measure the signal loss and accounting for it in our designs.
How would one measure this the objects that are located in a false ceiling…? Well it would be extremely difficult to safely, accurately and not to mention costly to measure the HVAC ducts etc located in false ceilings, especially when the everything is already in place, as well how do you measure the impact of reflections etc???
Impact to coverage and efficiency of the WLAN….
In a typical corporate office multi level building the false ceilings can contain, HVAC ducting, water pipes, metal cable trays etc, increasing reflections and sufficiently reducing signal propagation.
Reduced coverage will result in extra AP’s having to be used to account for the coverage holes ,which result in an increase to overall cost.
Increased multi path caused by reflections can decrease overall throughput for less capable devices. Can cause AP radios to reduce power to account for the reflected signal being detected by the radio elements. Not good when design is based on RRM
AP’s can produce a great deal of heat (Cisco 4802) false ceilings are usually hot, contain dust and other material when combined can become a fire hazard.
As mentioned above AP’s and false ceilings can be rather hot, when AP’s are installed in false ceiling it is usually on some metal frame or structure, the increase heat can cause AP’s to overheat or fail.