Releasing the shackles - how far do you want to go?

FATBOX_GPRSV2.JPGSince I got into building my own drones I have been fascinated with the prospect of extremely long range drones that are not restricted by the limits of point to point wireless technology.

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.



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  • Developer

    Please join the Telemetry over cellular IP group. It is a new gathering place for all those interested in long range IP comms.

  • Toby.... have you considered using openvpn? You would need to run an openvpn service from either your router or pc running the mission planner. I have tested this and it works using a similar device. I also use exactly the same technology to communicate with my home network while travelling on the train. Basically the device in your UAV runs an openvpn client. This client continually tries to remain connected to the openvpn server (running on your pc). You need to look at this backwards and think about the UAV contacting you and not the other way around. One thing you do have to bear in mind is that you will probably lose your cell signal above 2000ft. I've found this in the UK but not sure about other countries. You would need to get the fatbox supplier to add the openvpn client to the unit and make it configurable but it isn't brain surgery.

  • You will also experience interesting challenges with handovers when your mobile station needs to change between cells, especially with GPRS which is the slowest of them all at doing it. Don't expect too much to begin with and you can hopefully work around things. I wish you good luck in your trials! Some time ago I was looking for hackable android phones or suitably small form factor routers to do something similar, and gave up after either finding nothing usable existing on the market or with every promising piece of hardware being already out of production.

  • Toby,

    I'd be super interested in your review of this in relation to APM/ACM. Please let us know how you get on!!!

  • The fatbox does run Linux. It has a built in web server for configuration.
  • Or you can upgrade to a linux machine that supports GSM modem.Take a look at video surveillance systems.Those run Linux and also transmit camera over modems.

  • Yes most cells loose coverage soon after T/O due to tower signals being broadcast in a horizontal coverage pattern, if you stay low it might be OK. Satellite anyone?

  • yes, it will interesting, i'm looking forward to testing thoroughly and will report back the results. Luckily we have a lot of mountains in my country so the cell network works across a wide range of altitudes. We also have very good coverage to 97% of the country so I'm picking it should work really well here.

  • Developer

    Toby, Idea is great but in real life application might not be so great after all. Many small plane pilots have reported that they lost all signal to cellular networks already on altitudes of 200 meters sometimes even less. This is due how cellular network signals are broadcasted from basestations. On places where you have highrise buildings it is not so bad like in city areas and close by but areas that are mostly flat altitudes are getting lower as no tall radio masts etc.

    It might work on one country/area really good but on next place you will loose signals. Multicopters usually fly under 100m so for those it would work better but for fixedwings and FPV pilots mostly not. Especially FPV flyers as they tend to go rather high.

  • I would go with the WL-520gu, but only if you're ready to learn a little programming/Linux if you don't already know any. Most of the major Open Source router firmwares out there can support 3G/GPRS modems, it's just a matter of preference and taste. Here's some pages/firmwares to read up on:


    Router info page:

    USB modem as WAN tutorial for DD-WRT:

    Tomato USB

    General Info:

    Build Types and Compatibility matrix: (WL-520gu would have to use Lite)

    Forum Post regarding 3G on WL-520gu:

    Oleg Firmware

    Main page and info:

    3G/modem configuration options:

    That should get you started at least. Remember, this is just for the WL-520gu, which is one of the cheapest USB routers you can buy that supports these firmwares; if you were to spend a little more (~$60) on a WL-500gpv2, you can get a little more features and have access to newer/updated firmware. In any event, good luck on your quest and do keep us updated on what you end up using!

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