Difference Engine: Phones up in the air
I ran across this article in the Economist which answered a question that had been nagging me; why are cell phones banned on airplanes during flight?

The usual reason given is that the transmitters might interfere with the aircraft's avionics. "Both Airbus and Boeing have bombarded their aircraft with electromagnetic radiation at frequencies and power levels used by mobile phones, only to come away empty handed."
There goes my plan to use my cell phone as a last ditch weapon against hijackers.
The real reason? Cell phone towers.

Cell phone networks assume that, at any given moment, a mobile phone is within range of only one or two nearby towers. Each tower uses a set of channels different from those allocated to the towers closest to it, but the same as other towers further away. This allows each channel to be reused to carry calls from multiple users.

But a cell phone operating in an aircraft flying overhead might be within reach of any number of towers using the same channels. Compounding this is that an airborne phone would be moving too fast across the sky for the ground-based network to respond.

This would wreck havoc on a mobile network.

Who knew?
Posted by: Mike Ramsey 2013-01-21