A few last post were related modems and Communication only. This one again touch also same topic becuse there is another way to connect drone and ground station without public IP. We can call it authorization thru zerotier services.
https://zerotier.com/
ZeroTier delivers the capabilities of VPNs, SDN, and SD-WAN with a single system. It allows manage all your connected resources across both local and wide area networks in very easy way. Overall it works like OpenVPN but communication seems to be much more advanced but also more easy to setup. It combines everything VPN, NAT traversal, UDP hole punch technics. Details are available on company page.
Solution is used currently by Parrot Disco users and details you can find on following blog: https://github.com/uavpal/disco4g#parrot-disco-over-4glte-softmod
I hope it will work for my drone also very well. In next few of day I will try it and of course I will share latency tests.
.. and If this will work fine maybe I stop using public IP at all.
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post update: initial latency test:
