3+km HD FPV system using commodity hardware

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-transmission-of-live-video-data/

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.

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Replies

  • Hello !

    I have the system working on my 250 FPV Racing quad !

    I have a Pi A+ on the quad and an old Pi B as a receiver, both connected to the CSL 300, running on the same script as Fnoop Dogg.

    The range is somewhere around 200m before the first drops, wifi some crappy antennas, it could be improve with better antennas and diversity, and latency is somewhere between 200ms and 150ms.

    Next step is the HD HMD for real FPV !

    Thanks a lot befinitiv, the system is really promising !

    3702026391?profile=original

    3702026519?profile=original

    • Very nicely put together quad.  Mine is a complete random mess compared!

  • If latency is a big factor one should consider dropping to lower resolutions and higher framerates. I haven't yet jumped to wifi broadcast. But I have had very good results with 640x320 90fps. Unfortunately the project says 90fps is highest the sensor can do and its cropped not full sensor areas is used. This considerably reduces the latency on the player side. Its imperceptible now. If its too much data, one may also consider dropping down on bitrate to have better range and smoother video. 320p anyway is very close to what we currently fly with analog transmitters

  • Can somebody comment on Awus052NH chipset Ralink RT3572 ?

    MIMO 2T2R, up to 30 dBm or 1000 mW

    Thank you in advance.

    • I looked into this model but it's sold in very few places, it's a bit big and needs dual antennas.  At least to start with I liked the smaller simpler implementation of the Awus051NH which is more widely available.  If it really does have a 1w amplifier then for those that need the extra range it could be great :)

  • Hi, one noob here. I have a though and do not know where to put it, so, lets see what do you think about.
    Cameras like Mobius doing compression of the seen and seending that to the sd card. Why not to cheat that channel of compressed data?

    BTW, very interesting project, starting puting things together, with a combination of headtracker, googles, and modell tracking ground station for a biger glider.

    Is it possible to to get and calcualate the vector of the plane to manage the parabolic antena direction?

    Thanks,

    Regards,

    F.R.

    • Encoding for storage is a bit different than encoding for streaming. The compression is higher and less error tolerant when encoding for storage. Also, the latency will be much higher depending on the buffer size of the camera.

      Storage compression and FPV don't play well together.

      Take a look at the antenna tracker project --> http://diydrones.com/forum/topics/figuring-out-the-antenna-tracker

      • Ah, one more thought...Mobius speaks h.264 on webcam mode. Might there is a shorter way to send the compressed video to 802.11x?

  • Hi all,

    Just a NOOB question. Wouldnt a dual band adapter work better than a single band TX and RX setup? If yes, which chipset is best?

    It would be amazing if we could use a MIMO dual band adapter.

    thanks,

    Madhu.

  • The ground station side OSD also sounds promising, I'm hoping to be able to help with the development of a good looking OSD (we can take advantage of colours, transparency, etc.) once I get the hardware.  I'm also looking into having the image piped to an Oculus Rift and it would be best to display the OSD only in the central part of the image that can be seen with both of your eyes, and doing this on the receiver side helps here compared to an analog camera + minimosd + vtx.  In fact offsetting the two OSD overlays slightly could create an effect of the OSD floating in front of the video which might turn out to be useful or annoying.

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