Cell Phone instead of Radio?

[killr0y]

Has anyone tried using a Cell Phone setup to control their UAV? I guess it would require some kind of modem to communicate with the servo controller/receiver.. I don't know much about electronics, but this sounds like something that could be done relatively easily by someone who does.

So you have a PC with a radio controller hooked up via the trainer port.. or better yet, use some of those fancy PC flight controls. Then write an application that uses those controller inputs and sends them to a modem which in turn calls up the cell phone inside the plane. Then a small IC on the plane interprets the modulated sound and converts it into servo signals.

[stu78]

I would imagine all perfectly do-able, but you have to consider one very important factor.

How will you control the model if your local cell goes down for maintainance etc during your flight?

I think this may have been done (or maybe just talked about) in a RC heli, but I don't have the link handy, maybe someone else does.

Stuart

[wattsup_kz]

That scares me when I think about how many times my cell calls have been dropped.
I suppose altitude would reduce that significantly, as well as verifying signal strength before flight.

[killr0y]

I figure most cell interference comes from solid objects which block line of sight from the cell towers. Since you're flying well above most obstructions, this shouldn't be a factor. I envision a system like this to work in conjunction with a GPS/autonavigation system where it would change heading back to a "home" area if it were to lose a connection. While its returning home, it can try calling back into the PC to reestablish a connection.

Also, the video feed could still be active and should include an overlay of the plane's heading, speed, alt, etc.

[CenTexFlyer]

A friend of mine is an "inventor" for IBM here in Austin. They've already done that and have patented it. He says they have a UAS set up very much like our twin boom SlipStream that they've flown autonomously using Blackberry and cell technology combined. IBM figures there's not going to be much use for that for awhile and have tucked it away in their little "been-there-done-that" file.....

YEEESH!

CTF

[killr0y]

Do you know the patent #? :P

[typicalaimster]

That scares me when I think about how many times my cell calls have been dropped.
I suppose altitude would reduce that significantly, as well as verifying signal strength before flight.

Just dont' use a Sprint phone!

Most of the antennas are pointed toward the ground. Their also aimed so the 'Cells' barely overlap eachother. If you were under say 1000' you'd probably hold a signal.

[vpatron]

Centex, your friend is ahead of the pack. :)

killro0y, I get latency on Sprint's 1xRTT network (~64 kbps) from 300 ms to 1 second, and Verizon's wireless broadband (~900 kbps) is about the same or even 2 seconds at times so it would be hard for live remote use.

But a UAV (which can fly itself) would work great for uploading route commands and for getting telemetry data. The plane could be smart enough to hunt for a signal if it needed a command and couldn't find a signal.

Keep in mind that the cell system is not tuned for in the air use because the high altitude phone hits too many towers and can cause interference to other users, but would work OK.

It shouldn't actually be too hard. I know on Sprint, once you get the cell driver installed, it acts like a phone modem: ATDT commands to dial out and you can either dail up you own phone line or establish a PPP connection and use a telnet session.

Sounds like a neat idea and doable even at the hobby level. My plane is too small to carry a a phone AND micro-PC though, but others have big UAVs.

I was actually thinking about a ham radio repeater as a secondary data link, either an existing mountain repeater, or even a second airplane with a micro repeater.

Regards,

-Vince

[lvspark]

http://www.aerosonde.com/drawarticle/68

[killr0y]

Vince, good info on the phones.. Although I am surprised at the latency. One would think latency over 300ms would be noticeable by people talking to each other on their cell phones, and normally I don't experience any delay. Inputting waypoints on-the-fly would be a great idea that isn't dependant on latency, but how practical would this be in an electrical application? Can a Li-Poly UAV have the endurance to make something like this practical? This brings up another question probably better suited for another thread, but I'll ask anyway:

Are there any studies/experiments to determine optimal UAV size / shape to maximize endurance?

[vpatron]

On cell phones (at least CDMA ones I'm somewhat familiar with) latency on voice calls are like 200 ms or better. For data calls, latency is much higher I think because it can handle a lot more simultaneous users with higher latencies.

Also, come to think of it, you wouldn't need a PC on a plane. I think a micro like an AVR would have plenty of oomph to do a PPP connection over dialup.

-Vince

[LukeZ]

You certainly wouldn't need a PC onboard, in fact, a regular old PIC should do fine. Once the connection has been established the cellular modem looks just like a regular serial port, or so I understand. I don't know what baud rates are possible; I guess it depends on how much you want to pay.

Sparkfun has an interesting cell module (http://www.sparkfun.com/shop/index.php?shop=1&cart=369438&cat=75&) that I've thought of playing with. There are other similar things out there, I think you can even get this stuff at DigiKey.

I don't know much about this but I certainly do intend to use it. For long distance operations, which is what I'm interested in, Ham radio simply won't work. Cell is the only way I can think of that's readily available and affordable. As has been pointed out it's not the kind of connection where you could control an aircraft the way you can with a standard RC TX/RX. However, for uploading commands and for receiving telemetry it would be perfectly suitable.


Luke

[clolson]

I was poking around the net one day (and unfortunately I can't remember where I saw this) but some company makes what looks like the guts of a cell phone minus lcd display and minus the key pad specifically intended for raw data communication. They accept the little card from your regular cell phone which activates them. As far as the cell phone company is concerned, that unit becomes your phone once you move the card into it. So, "in theory" you could get two of these units, then sign up for some sort of "family" plan with 2 or more phones that gives you unlimited calling between family members, transfer the cards from the phones to these other units and now you have unlimited communication for the cost of a family plan.

Obviously you have to live within the limits of cell phone communication as described earlier in this thread, but you'd get essentially unlimited range within the country which is kind of a cool feature.

Curt.

[killr0y]

I was poking around the net one day (and unfortunately I can't remember where I saw this) but some company makes what looks like the guts of a cell phone minus lcd display and minus the key pad specifically intended for raw data communication. They accept the little card from your regular cell phone which activates them. As far as the cell phone company is concerned, that unit becomes your phone once you move the card into it. So, "in theory" you could get two of these units, then sign up for some sort of "family" plan with 2 or more phones that gives you unlimited calling between family members, transfer the cards from the phones to these other units and now you have unlimited communication for the cost of a family plan.

Obviously you have to live within the limits of cell phone communication as described earlier in this thread, but you'd get essentially unlimited range within the country which is kind of a cool feature.

Curt.

That's exactly what I was thinking (regarding the "family" plan w/ unlimited calling). If the latency is so bad regarding the data calls, why can't the phone just be used like an analog modem? Otherwise if all you're doing is sending waypoints & receiving telem data, you could just use a text pager and not have to worry about dialing in.

[ALtitudeap]

try looking here. scroll down the page a bit. these will do what you are looking for. what happens if telemarketer calls your UAV :)

http://www.sparkfun.com/shop/index.php?shop=1&cat=75

[HELModels]

I figure most cell interference comes from solid objects which block line of sight from the cell towers. Since you're flying well above most obstructions, this shouldn't be a factor. I envision a system like this to work in conjunction with a GPS/autonavigation system where it would change heading back to a "home" area if it were to lose a connection. While its returning home, it can try calling back into the PC to reestablish a connection.

Also, the video feed could still be active and should include an overlay of the plane's heading, speed, alt, etc.

Lose signal...proceed to home...gain signal...proceed to waypoint...lose signal...proceed to home............puttt puuuutttt....crash!!! Can you hear me now?

[vpatron]

This is true for all cell systems so each cell doesn't interfere with the next cell.

You might be surprised about Sprint. I've used both Verizon and Sprint and Sprint has better coverage for data.

My wife was shopping on Ebay as we drove from Las Vegas to Phoenix. We listened to Car Talk over the internet as we drove from Phoenix to San Diego.

-Vince

Just dont' use a Sprint phone!

Most of the antennas are pointed toward the ground. Their also aimed so the 'Cells' barely overlap eachother. If you were under say 1000' you'd probably hold a signal.

[sesat]

Vince, seeing you're looking at Sprint and Verizon as data providers, what devices are you looking at to provide the connectivity to your in-flight computer?


Ram.

[vpatron]

Hi Ram, I use Sprint's data network (and in the past Verizon) for my personal and small business use.

If I *had* to use cell phone data, I'd use Sprint. Just take an off-the-shelf small cell phone, remove the unnecessary stuff, hook up the data cable, and have the flight computer connect to the internet with a serial PPP connection. BTW, Qualcomm's OmniExpress, the cheaper version of their satellite system called OmniTracs, uses Sprint's data network.

But this is way more complicated than my simple plans call for.

My plans are to use simply piggy-back data onto the existing 72 MHz RC channel, and to possibly simultaneously transmit the same data on 50 MHz, with the plane receiving both for diversity receive.

For downlink data, I'll use the 2.4 GHz wireless video system via the audio channel, with possibly two ground receivers and antennas for diversity receive.

If the UAV is waiting for a command (circling) and looses the signal, it would back-track the route until it picks up the ground station again.

-Vince

Vince, seeing you're looking at Sprint and Verizon as data providers, what devices are you looking at to provide the connectivity to your in-flight computer?


Ram.

[dj2u]

Hi all!

have you ever been in europe? we have gprs here so you wouldn't need modem ppp and so on. it's an always on connection with volume fees. I think this would be the perfect match for your uavs.

diego

[typicalaimster]

have you ever been in europe? we have gprs here so you wouldn't need modem


We do have GPRS here in the states. Most GSM ready phones use the technology. The rate plans for GPRS data transfer can be costly!

[dj2u]

ok didn't know about that... only remembered to see quad or so band analogue thingies
You never stop learning ;)
diego

[vpatron]

Hi diego, yes, US has a confusing mish-mash of systems: CDMA (with 1xRTT and 1xEVDO data), GSM (with GPRS data), and a phone/walkie-talkie thing called Nextel on a separate 800 MHz band. It can also do direct phone-to-phone at 900 MHz. There's of course still some analog towers in the boonies so many phones also still support FM cell transmission.

Whether you use GSM or CDMA data, you would still connect a laptop (or data device) to a phone and the phone acts like a modem and use PPP. You can manually re-establish the connection if it breaks. You can write a program to automatically reconnect.

The PCMCIA data cards seem a bit different and re-establish broken connections themselves most of the time, but sometimes it helps to disconnect and reconnect. You still need to click on a button to establish a connection initially. I'm guessing it's still using PPP?

What we also have here and parts of Asia and other countries is a form of CDMA called 1xEVDO which can do data at a bit past 1 Mb/s depending on coverage. Most major cities have it now with plans at $60/month unlimited data.

For the old 64kbps CDMA data called 1xRTT, I only pay $5 in addition to my regular cell plan for unlimited data.

GPRS is limited to something like 56k or 64kbps so the GSM folks have also implemented high-speed data called "WCDMA" or wide-band CDMA. Not sure if it's commercially available yet. Is it deployed in Europe?

Anyway, that is the present state of confusion in the U.S. cellular market. Unlike Europe where the government dictated the phone standard, the U.S. let the companies fight it out in the marketplace... :) That's free market economics at work, but the downside is it is confusing for the consumer.

Regards,

-Vince

[sesat]

There's a great integrated GPS and GSM unit, with great GPRS features...

[sesat]

Sorry I was short on the details.

Falcom XF55-AVL, 12g 53x35x5mm, $140 in single quantity
GSM900 (2Watts) + GSM1800&1900 (1W)
GPRS (85.6kbs up / 42.8 kbps down)

Needs external antenna's and SIM card reader (inexpensive Molex part).

[vpatron]

sesat, sounds neat.

Here's a similar thing for CDMA data with GPS: http://www.arcelect.com/CDMA_digital_cellular_data_modem_with_GPS.htm

What gets me though, is that newer CDMA phones have added internal GPS capability to meet E911 (enhanced 911) requirements. This is so if you call 911, they can get a fix on you in a few seconds even if you don't know where you are.

The question is how do we access the internal GPS capabilities of these new phones?

-Vince