Smoke signals

A long time ago, we already had wireless communication. Like we know from the western movies: people were making a small fire on a hilltop and with a piece of cloth, they shaped the stream of smoke in a sort of on-off-keying modulation.

Since we’re among nerds here anyway, let’s have a look at how power efficient this type of communication was. First, the harvesting of the energy we need: a decent fire has – say – 5 logs of wood, which burn well for half an hour. Extrapolated to one year, 24/7 communication requires 90,000 logs per year. With 500 logs per cubic meter of wood, this is 180 m³ per year. In a typical forest, wood grows with 7 m³ per 10,000 m² per year, so we need 250,000 m² of forest to keep this single fire burning.

Now the bitrate: my guess is that with a few smoke symbols and a bit of practice, one can send about 2 bits per second. This is 64 megabit/year.