Cellular remote control

[ScatterPlot]

OK this is my third post for the last five minutes I know but I got a lot of ideas and just discovered this part of automags.org. What if you used a cell phone to control an RC car or plane? It would be much cheaper than the high cost thingies that control them now, and have a massive range. For simple joystick, you could use the buttons on the phone with something on another phone attached to your car/plane/whatever. You could use a tone decoder on there and a microcontroller to make it steer and all. For more advanced things, like proportional controls, you could use a tone generator hooked up to the microphone and use another microcontroller to transmit positions of a better PC style joystick. If this has been done, tell me please. Any ideas about it? Thanks
Bert

[rhetor22]

thats really a great idea, but i'm not sure of the lag time between sending and recieving.

Also if you fly your plane into "bad reception" you're into some crap.

[Pand0ra]

Due to the fact the voice is send in burst, the processing done in the phone, and the processing done at the switch level (echo cancelling, ...) there's a lag around 300ms I guess.

It would be more expensive than the current transmitters, as you would need 2 phones (with one in an embeeded configuration), plus the interface to the servos. You would also have to pay the communication.

There's also another problem: the network is not designed to cover the sky.
Antennas are always tilted in the direction of the ground, to avoid troubles of interferences between different cells, and what we call resurgences (when a cell covers an area it shouldn't). So you'll loose quite quickly the reception.
The higher you go, the higher the number of cells you'll also receive, but as we reuse the same frequencies on different cells, you'll have more and more interferences, and loose the communication.

So all in all, it's not a very good idea.

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[ShinyGuy]

It also could be illegal. The FAA prohibits the use of cellphones in airplanes to prevent overloading the cell networks. Each "cell" has a limited number of phones it can support. When you're using your cellphone while standing on the ground you are connected to between 1 and 5 cells at a time. When you get a cellphone 2000 feet up you can easily connect to 20-200 cells wasting cell network resources. Once you operate a model airplane over a certain altitude (I don't remember the limit but it's pretty low) FAA restrictions apply to it.

[Pand0ra]

Nop. In fact the mobile is always in standby on one cell, and monitor continiously a max of 5 other cells. Those are called neighbouring cells.
When a com is established, a time slot is used on the serving cell, but that's all. For a GSM network, you can have up to 8 coms per transceiver (8 time slots available), and have up to 16 transceivers per cells. Multiply this by 3 because in general a site (a pylon) contains three cells, and you get a good idea of how many coms you could have on a very very big site :) .
I don't think they're yet bigger configurations than that, and it's not needed in fact.

The problem with the airplanes come from the interferences you could create when your mobile is transmitting informations.
In fact the main causes are design errors in the onboard equipements of some planes.
They shouldn't be sensitive to those kind of interferences. They just don't want to take any risks, which is understandable.

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