* Closed licensed users: cell providers, public safety, etc
* Location limits: immobile antennas like broadcast FM
* Technical limits: ISM devices, Wifi, or FRS walkie talkies
* Content limits: Amateur radio
Amateur Radio gets to bypass a ton of these restrictions:
* Anyone who can pass a test can get a license to use these frequencies
* You can transmit from nearly anywhere
* You can use tremendous amounts of power (1500W vs Wifi's piddly 0.5W or less)
* You can use whatever equipment you can solder together, no certifications other than an honor system of "I'm fairly confident it's within spec"
Encryption would negate the ability to police the few limits left but also notably, the content. And that primarily means preserving noncommercial purposes but additionally, you're required to periodically identify yourself using your FCC callsign.
The Amateur Radio community is already a little nervous with the influx of cheap $30 radios falling into the hands of unlicensed and inexperienced users (notably "prepper" types that read disaster readiness articles like this one).
Here's a fun one: wifi 802.11b channel 1 is in an amateur band, so if you have an amateur license, you identify with your callsign (using the ESSID works), and you transmit everything in the clear, you can use modified/amplified wifi equipment at higher power levels than wifi normally allows. (The standard common-sense restriction of "no more power than needed for the application" applies.)
An amateur rocketry group I worked with (http://psas.pdx.edu/) uses this to receive wifi at 1W from a rocket miles away (and going Mach 1.1).
Doppler shift might come into play if the rocket went much faster, but Mach 1 just isn't that fast compared to the speed of light. A quick calculation suggests that a 2.4GHz signal would get shifted by ~3kHz. Wifi isn't that sensitive.
> Why bother with a TCP/IP link, though? Seems like a less verbose protocol would be a better choice to use to get a simple data stream from your rocket to ground control.
We used UDP/IP for telemetry data (and had almost no packet loss). TCP/IP did allow us to SSH to the (Linux-powered) rocket for debugging, though.
Also, being able to SSH into a rocket is pretty fucking awesome on it's own. :)
For a preview of what this would look like, consider the push to run cellular service in the wifi bands (LTE-U). Wifi/Bluetooth/Zigbee devices are about to get crapped on, if Verizon gets their way.