Would you ever strap a PC to your ceiling and run it there? Probably not. What about inside the plenum space above the ceiling? Nope.
Accessibility aside, the ceiling and plenum are hostile environments for electronics that aren't specifically designed for the vibration, temperature extremes, and blown dust typical of these locations.
If you look inside devices designed for this environment - smoke detectors, passive infrared sensors, quality Wi-Fi access points - what you WON'T find are vibration-sensitive connectors (like SIMM sockets), moving parts (like fans), and modular circuit boards that could wiggle loose. These devices are typically designed to have high mean time between failure (MTBF) ratings, something impossible to achieve with commercial SIMMs or fan-based power supplies. It seems so intuitive...and yet.
Those who forget the lessons of Wi-Fi are doomed to repeat them. Lesson #6: sleight-of-hand is no substitute for good product design. Wi-Fi access points need to be designed from the ground-up to withstand the rigors of ceiling and outdoor mounting environments.
Consider Wi-Fi arrays, which are effectively PC motherboards with a fleet of sockets, add-on modules, plug-in connectors, and memory SIMMs. They even conjured up a fan-based PC-like power supply - no standard 802.3af Power-over-Ethernet here. And when it fails you've lost 4+ radios at one time. The only workaround is to double-up the number of arrays, a real budget sink. Arrays just aren't designed with long service life, energy efficiency, or network resiliency in mind. That's the reason why no leading vendors in the Wi-Fi market sell arrays.
Aruba Wi-Fi access points have no fans, no SIMM sockets. Our 802.11n access points are designed for the rigors of ceiling and plenum mounting, and run from standard 802.3af PoE. MTBF ratings are excess of 250,000 hours - more than 28 years. And should an access point go down, Aruba's Adaptive Radio Management adjusts the power of near-by access points to self-heal the coverage gap. Automatically.
They'll provide years of reliable service and are backed by a lifetime warranty. And they cost less than an array-based system. A lot less.
So the next time you consider upgrading your wireless LAN, think about the environment in which the equipment will be used. Reliable products don't happen by magic - they happen by design.