The public cell network seems like the perfect solution for long range drones as it covers most countries and now supports extremely high bandwith.
I've done some experimenting with the dronecell and various other options but they have all missed the mark somewhat in some way.
I stumbled across this solution the other day and it seems like the perfect solution for larger very long range drones.
The FATBOX GPRS2 is a wireless DTU with a few extra bits of trickery that lend it as the perfect long range solution for our needs.
- Serial port - The serial port can be interfaced to the APM mavlink port (the same one used by the XBee) with the simple addition of a TTL level converter.
- Dynamic DNS - it has a built in Dynamic DNS client, this means when you turn it on, it automatically connects to the internet via the builtin GPRS modem and registers its IP address with a DDNS provider. This means you can simply type in the DNS name into the mission planner to connect to the APM without needing to know the IP address.
- Transparent - unlike most GPRS modems, the Fatbox can be setup to be a transparent serial router. When you turn it on, it exposes the serial port over UDP on its IP interface. As the APM mission planner supports UDP, it should be plug and play.
- Dual SIM - if coverage is an issue, you can insert two SIMs from different providers, if it loses its connection, it will automatically connect with the other SIM and register its new address with DDNS. You will get a brief dropout on your APM planner but can then just reconnect.
- Ethernet interface - this is the kicker for me, it has a built in ethernet interface that can be used at the same time as the serial port. This opens the door for video or any other ethernet based device you might want to add to your drone. You could also add a wifi link for redundancy and access the serial port via wifi and fall back to GPRS if you go out of range.
The only downside is that out of the box it weights 420 grams.
It comes in a steel case and the board itself only weigh 120 grams so I am going to look at other case options or perhaps just fly it naked.
Mine should be here soon so watch this space for the results of my testing.
* note: In some countries, by default your SIM card is on a firewalled APN which means you can't contact the IP address over the internet. This is usually just a case of ringing your provider and asking for the name of a non firewalled APN.