Hi

Over the last couple of months I have been working on a project that might be of interest to you: https://befinitiv.wordpress.com/wifibroadcast-analog-like-transmiss...

Basically it is a digital transmission of video data that mimics the (advantageous) properties of an analog link. Although I use cheap WIFI dongles this is not one of the many "I took a raspberry and transmitted my video over WIFI"-projects.

The difference is that I use the cards in injection mode. This allows to send and receive arbitrary WIFI packets. What advantages does this give?

- No association: A receiver always receives data as long as he is in range

- Unidirectional data flow: Normal WIFI uses acknowledgement frames and thus requires a two-way communication channel. Using my project gives the possibility to have an asymmetrical link (->different antenna types for RX and TX)

- Error tolerant: Normal WIFI throws away erroneous frames although they could have contained usable data. My project uses every data it gets.

For FPV usage this means:

- No stalling image feeds as with the other WIFI FPV projects

- No risk of disassociation (which equals to blindness)

- Graceful degradation of camera image instead of stalling (or worse: disassociation) when you are getting out of range

The project is still beta but already usable. On the TX and RX side you can use any linux machine you like. I use on both sides Raspberrys which works just fine. I also ported the whole stack to Android. If I have bystanders I just give them my tablet for joining the FPV fun :)

Using this system I was able to archive a range of 3km without any antenna tracking stuff. At that distance there was still enough power for some more km. But my line of sight was limited to 3km...

In the end, what does it cost? Not much. You just need:

2x Raspberry A+

2x 8€ wifi dongles

1x Raspberry camera

1x Some kind of cheap display

Happy to hear your thoughts/rebuild reports :)

See you,

befinitiv.

Views: 70268

Reply to This

Replies to This Discussion

MP runs natively under Linux. No need to use wine.

Is there any reason why we could not use ethernet device rather than usb?

Such as the Ubiquity Bullet M5 or M5-TI:

http://www.amazon.com/Ubiquiti-BULLET-M5-HP-Outdoor-802-11n-M5HP/dp...

http://www.amazon.com/UBIQUITI-NETWORKS-BM5-TI-BULLETM5-TITANIUM/dp...

It is atheros AR2316 and is compliant with fOSS Linux driver ath5k: 

https://wireless.wiki.kernel.org/en/users/drivers/ath5k

15vdc POE injection would be very easily done using on board Lipo Source

For the Ground Station you could use MIMO Rocket M5:

http://www.amazon.com/Ubiquiti-ROCKETM5-5GHz-Power-BaseStation/dp/B...

At 150mbps should be plenty of room for HD video, Joystick control and OSD.

There are also two GPIO ports to add control functions

Hi Kendall

The bullets are huge, and very heavy, mostly thanks to the N connector.  The POE is a bit of a nightmare onboard and it seems the raspberry is very sensitive to poe devices - I've blown three raspberries (that sounded more technical in my head) recently and eventually confirmed it was the POE device I was using through ethernet:

 http://www.msdist.co.uk/product_Ubiquiti-WispStation-M5.php

The wispstation is nice and light and relatively small so OK in a UAV, and I used a bullet on the GCS end.  I must say the quality of the product is excellent, and the firmware is very good with lots to play with, and it's excellent out of the box for long distance.

However, the whole setup is rather unwieldly - you need PoE at the GCS end as well, and on the UAV it takes up quite a bit of space, is relatively heavy and complex.  These USB adaptors are far, far simpler and smaller, if they can be made to work as well.

Also the ethernet port on the raspberries actually works off the USB bus so you're not gaining any speed anyway (and it's not available on the A+ model, which is most suitable for small UAVs).

For larger UAVs though these might make excellent options if they can be made to work in monitor mode.

ps - the ubiquiti devices have onboard power regulators so you can fire lipo 3s/4s power straight down the poe injector which is quite nice.  I did make sure it wasn't going anywhere near the raspberry, I don't think that's what was blowing them.

I have the BM5 here so I wanted to test with them, I would strip it down removing the housing. Adding, N female to SMA female adapter would only be about 65 grams total. On my hexa or big quads it would hardly be noticed. POE direct to the board is also really easy too, with the onboard regulator so no fear as the Raspi is powered  separately and not through the ETH0

As for the ground station I have a Mobile Command Post with onboard 220/110 vac 


I would like to test this but need a bit of help with the scripts to try it for SAR operations

Thanks 

Perfect Solution!

Thanks

This is an another RPi FPV project --> http://fpv-community.de/showthread.php?46646-Low-Cost-HD-Video-%DCb...

I've given it a go and it runs fine out of the box. It also has a nice android app and a web interface for controlling the stream.

The latency might be a tad bit higher and it doesn't handle packet loss as well as befentiv's solution.

The beauty about wifibroadcast is, that it doesn't use "normal" wifi, it just sends out the packets without the whole ack/retransmission mechanism and association thing. There is also no IP or UDP in the packets, it's just the raw video stream.

That's not possible with those Bullets as far as I know. Maybe it's possible to patch or hack the firmware of them.

Lol well yes more suitable then :)  Really cool setup.  I did take a quick look around the other day and it looks like Ubiquiti are refusing to make any effort to support monitor mode though.  Are you saying it can be driven directly somehow by the raspberry?

Why not just get a wispstation m5 which is cheaper, smaller and comes with a ufl connector?  Is there a benefit from the rocket?

It is only a matter of defining the port from wlan0 to eth0 I believe.. I could be wrong as I'm not an expert in this area. All of these devices are at the base, serial devices right

Reply to Discussion

RSS

Groups

Season Two of the Trust Time Trial (T3) Contest 
A list of all T3 contests is here. The current round, the Vertical Horizontal one, is here

© 2019   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service