Hey guys, I found out about the UAV scene and want to get involved, and was hoping that everyone could answer some questions. My queries are as follows:
(1) Is using a Wi-Fi signal and on-plane access point a possible way of telemetry using the Arduino Ethernet shield?
(2) How do you set up the Ardupilot to make use of the "Point Camera Here" function on Mission Planner?
(3) And finally, what are some ideas for a non-Xbee-based antenna tracker? I am hoping for some long range flying, and omnidirectional antennas wont cut it.
Thanks in advance for any help I receive.
Instead of a linksys router take a look at the Ubiquity bullet and NanoStation products.
A wireless LAN is probably not the best medium to remote control a drone. The best thing you could use it for would be digital video downlink or similar.
You can use any wireless link that will connect to serial IO and has sufficient bit rate. One can turn down update rates and still have a nice and reassuring tracking with less than 10k bits / sec.
You can connect directional antennas to XBees. I had an XBee connection at 15 km range using a quad biquad antenna on the ground and a simple 1/4 wave on the plane (similar to the typical little WLan plastic antenna). But there must be direct line of sight, and I had to fly high at that range!
Another alternative is GPRS / cellular data. Then you have practically unlimited range but quite a lot of latency.
Alright, so XBee for telemetry then. I feel a little ignorant for not looking more closely at their products before this. As for video downlinking, that's exactly why I want it! The whole IP PTZ thing was so I could control everything from one connection, not have XBee and a 900 MHz video downlink at one. GPRS is out, I don't want to pay a monthly bill to fly my drone, unless there is a way to use the signal without paying.
Have you also looked at Synapse Radios http://www.solarbotics.com/product/51768/
The one I have linked to can do 2MBps at 2.4Ghz close range and up to 3Kms LOS, but the baud drops at that distance. But there are a range of them, some using 900Mhz as well.
Well, my priorities have shifted a little. Are there any video setups that can reach up to 16 km? Sorry if that sounds outlandish, but that's what my needs call for. I may have to change a few pieces of hardware on my list now.
So maybe I will have to look at GSM band. Any idea how much data it would chew up? I already have a 3G data account/SIM card for my Toughbook, but it's only 5 gigabytes a month. How much data is transferred in video streaming?
Oh, and on this note, I still have to figure out how to get Mission Planner to communicate over the internet. How can this be accomplished?
Wait, as far as I know, all "WiFi" is, is the 802.11a/b/g/n protocols implemented over the standard 2.4/5.8Ghz frequencies. We put 2.4/5.8Ghz transmitters on our drones all the time, for FPV flight. What's stopping you from using the same antenna setups that FPV users use?
The problem is is that I need extreme range, up to 20km with lots of trees, no good line of sight. Try a street view of Soldotna, Alaska out on the highway. Less of mounting my groundstation on a mountain, cell would appear to be the only way to go. My Toughbook has embedded cell, so I guess it would be just as well that the drone would as well.
Have you considered the fact that in remote areas 3G coverage is along highways, but not further a field. So you may have coverage on the highway, but as you get further from it the signal will drop quite rapidly. Since 3G is in the 850/1900MHz bands, you still have the distance limitations from your current flying position to the closest cell tower as running your own transmitters direct on 915MHz ISM band. The cell towers have the same problems with "Tree dB" attenuation as a hobby set-up. The cell towers can put out more power and have more sensitive antennas, but the same electromagnetic laws apply. Tress are not our friends ;-) especially after rain!
As i stated before, the reason for satellite in military comms is that the bandwidth is huge and the line of sight (well when you own your own satellite) is straight-up, clear line of sight.
I'm sure Miles can give an indication of the distance way he can fly FPV, but in excess of 5Kms seems to me to be extreme and not achievable without your own repeater network.
The operating constraints are starting to lead you into the area of something like this: High bandwidth satellite modem. Alternatively, you might be able to use a UHF radio modem (could probably handle the trees, but wouldn't handle mountains/buildings as LOS obstacles).
Either solution though is getting away from a hobby system and the limiting factor will be cost. Solutions are out there and available within the civilian space... they just aren't comparatively cheap to the system you've been considering.