How to organize a communication channel?

Question

Cryptography

How to properly organize a wireless, secure communication channel?
The distance is about 5 km.
Interested in hardware and software solutions.
One communication channel for control, the second for data flow.

Answer 1

fixed channel? for WiFi at such distances, permissions from the frequency supervision are needed, if for good. Even at low powers, because in this case a directional antenna will be used, and frequency supervision is more interested in the radiation density and not in the transmitter power as such.
It can also be used in such cases AOLS, on specialized emitters or laser pointers.
Microwave equipment can be used - at 80 GHz, radio relay communication lines do not require permission. The equipment, however, is still expensive.

Answer 2

and what does not suit the mobile Internet with encryption?

Answer 3

Negotiate any permissions possible