Paralleing XBees

[cyberfish]

I am thinking about using XBees to stream video from an RC chopper. The problem is, XBee throughputs are a little low.

Would it be a good idea to use 2 XBees in parallel, running on different channels? Or would interference still kill a lot of range.

Thanks

[cyberfish]

Upon further investigation, it seems like xbees are way too slow for video. Guess I'm stuck with wifi then.

[galannthegreat]

Just to add why, the protocol (802.15.4) is used for small data packet streams (ie. good for controlling systems and sending minor sensor data back to another system).

My real question is, how are you finding using wifi? As I myself have never dabbled with wifi, I would like to learn more about using it. What is your current setup?

[cyberfish]

My current setup is a Gumstix (single board computer with Cortex-A8 CPU and 256MB RAM) running Linux, so it's really just like connecting 2 PCs.

If you want to use microcontroller, though, some companies make modules that include wifi as well as the TCP/IP stack, and will allow you to talk to it like talking to an xbee (through UART).

If you have a more powerful microcontroller (eg. Cortex-M3) with a USB transceiver, it's probably possible to implement the TCP/IP stack in software (quite a few free implementations are available), and use a regular USB dongle. I'm not sure if a "driver" is available, though, or if not, how hard would it be to write one.

FTDI has a new chip that looks very promising. The FTDI Vinculum II. Basically a USB controller (dual ports host or client) with a microcontroller. They also have a lot of drivers already written (for HID, disk, still image devices, etc, and they also confirmed to be working on a driver for webcams/video class). I don't think they have a driver for wireless controller class, yet, though. Maybe it's not standardized enough to worth the effort?

[galannthegreat]

Nice! Sounds like you got quite a system. I've been wanting to take a look at the Gumstix for a while now, but I still can't find a source for them.

Maybe I can incorporate the power of one of these in my current project I'm working on at the moment?

[cyberfish]

I don't think they have any distributors.

I bought it from them directly, and paid a ton for shipping (to Canada).

[galannthegreat]

Yea, I'm Canadian too... so I guess I'll have to shell out if I really want one.

[Admin]

Use a video transmitter for transmitting video . . . lol

[cyberfish]

Looked into it. Couldn't find one that is small enough to fit on the aircraft, and has long enough range. And doesn't cost $200+.

I also want to just have one radio.

My current plan is to get a 1W bi-directional wifi amplifier. That should give me around 1km line of sight range. I'm not sure if they really work as advertised, though.

[knossos]

I have used 1W bidirectional WiFi amplifiers very successfully for point to point connections.  Have gotten >1 mile easily using directional antenna at a fixed position.  Have not tried them with omnidirectional antennas, nor tested with RC Control for interference.  Only problems I had were occasional dropout due to path fading and weather.

[cyberfish]

That's very good to know!

I'm planning to use lower gain omnidirectional, though, since I want to be able to fly both ways. What's the gain of the antenna you were using?

[knossos]

The antenna I used most often was this one primarily because of wind issues (mounted on top of a tall house on the side of a windy hill).  It has a 12dB of gain, but I also got acceptable connectivity with a 3dB omnidirectional rubber-duck antenna but only used it for a few hours before mounting my directional.  This amplifier is similar to the one I was using.