Just ran across
this Wired magazine article about a new cellular technology called SkySite to carry traffic. You launch a cellular transceiver attached to a disposable balloon, it rises to an altitude of about 20 miles, and then it relays cellular calls for hundreds of square miles with a single balloon. The balloon eventually drifts out of position, at which point, the electronics package is released and parachutes back to earth and it radios its position back to the company. The balloons are dirt cheap compared to building cell towers, so even though you have to repeatedly send up more balloons as they drift out of position, you're still way ahead, cost-wise. They're going to try a single trial balloon for North Dakota, and if successful, they claim they can go ahead and provide coverage for the whole state with just three balloons!
Of course, in higher density areas, you'd need more balloons, but the gain in efficiency and potential robustness is pretty impressive. If you need more capacity, say the Olympics are in town, just send up more relatively cheap balloons. Hurricane coming your way? No problem, the balloons fly higher than the weather systems. Earthquake? Major blackout? Ice storm? No problem--well, at least on the balloon's end. And North Dakota could economically provide cellular coverage where it is currently uneconomical to do so, so that's great for public safety out in the boonies. Cool, a poor man's sat phone network! <img src="/images/graemlins/grin.gif" alt="" />
I wonder if regular cellular handsets will perform the same with these balloons, particularly indoors, considering the distance from the balloon to the ground.