Modems support request (gsm is everywhere why not to use)

I want copters flyes to the points within the whole city (and back home), but why do I need to buy powerful antennas to cover the city if there’s already a LOT of GSM/3g antennas of mobile operators?
Control commands (to copter) and position info (to pilot) is not a lot of traffic, so many cheap 2G GSM modems/modules would be suitable.
If need FVP – there’s 2 options for video transfer: 3g modem and directional antenna (on copter). If for somebody 3g modem and/or video traffic is too expensive (or they just would like to reduce the whole cost like me) – directional antenna on Compass (on copter) is working option when you need copter goes only to some point and back home. For example you need copter flyes to some north point – then you need to turn atnenna on compass to south – then it will look to base side while flying to north point and back.

There are 4G solutions out there look out for Drone Deploy

Вon’t know why moderator put this tipic to software subforum. Ыhouldn’t FC support modem hardwardly?
4G i’m sure is expensive thing, while i’m saying “gsm is everywhere” meaning that it’s pointless to pay for powerfull (expensive) antennas if we could just buy 2g/3g modem. And another thing is to pay for 4g is also pointless when 2g is cheaper and it’s everywhere, in some places even 3g is not available.

Could you tell me though what’s needed for modem support? Some ports (usb for ex.) and software?

Using serial interface (telemetry port) is great, like SIM900 modem, like this … eTelemetry but adapter to newest version.

what’s this link about? support SIM900?

Do you know the status of DroneCell module. I would also enjoy going for a cheap solution like that, but I see that it is out of stock everywhere. Any reason for that ?
I couldn’t find any comments related to that unfortunately…

Thanks in advance,
Have a nice day !