[Paparazzi-devel] Wireless communications

[Filipe Varela]

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Hey

I'm developing a project for long range wireless communications for  
both telemetry+video downlink and simmultaneous control uplink.

The idea is not to have an a/v transmitter + r/f receiver on the  
platform and r/f transmitter + a/v receiver on the ground but to  
merge these two "streams" together on a single long-range radio link.

Now, has anyone experimented with radio-modems? My only doubt is  
whether it is feasable to multiplex a telemetry packet plus a video  
packet and transmit it to the ground and at the same time demux a  
control packet from the ground and still maintain real-time video.

If course that multiplexing control, telemetry and video on a single  
channel requires transferring the pwm generation from an r/f  
"joystick" to the computer which is an idea i like a lot.

I guess there is a pretty good alternative. Your standard  
unidirectional transmission of video+telemetry(audio channel) and use  
a cheap gsm module for emergency backup link to control the platform  
or override waypoints, maybe force a system shutdown, whatever.

Basically my interest is achieving a specification for VERY CHEAP  
long-range bidirectional communications using a single link instead  
of r/f + a/v.

BTW, by long range i mean 1Km to 10Km. Any more than that is not of  
any interest and should be addressed with propper expensive  
transmitters.

To the paparazzi developer: what's your tried and tested max range  
for both telemetry/video transmission (air-to-ground) and control  
transmission (ground-to-air)?

Thanks for reading,
Filipe


BTW To those looking for a cheap IMU, check this out:
http://www.sparkfun.com/shop/index.php? 
shop=1&cart=281909&cat=1&itemid=406&

It's a 6DoF for $399 ($339 no bluetooth) ASSEMBLED. Does not filter,  
but that should be done by the flight controller anyway. It's still  
expensive but a lot cheaper than rotomotions, cloudcap's, etc plus it  
IS asssembled with Analog Devices mems gyros and accelerometers which  
are, by the way, a real pain-in-the-ass to solder manually (i'd say  
impossible but i saw someone do it on a website)...

Plus there's another cool thing. It's modular. You can order the  
carrier with either 1, 2 or 3 imu sensor boards (exactly the same).  
That way you can test it as you buy it and not pay $339 in a single  
payment. cool...
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