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3+km HD FPV system using commodity hardware

Posted by befinitiv on May 6, 2015 at 12:43pm

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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Tags: fpv, linux, raspberry, wifi, wifibroadcast
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Replies

      • Kendall Wells > Nicolas June 3, 2015 at 6:54am

        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

        • Fnoop > Kendall Wells June 3, 2015 at 7:18am

          Unfortunately not, eth0 is the raspberry ethernet not the rocket.  You talk to the rocket over IP only as a standalone device - configuration is done through ssh or web interface.  You don't have any control over it as a 'device', unless someone has managed to hack it otherwise.  Some of the ubiquiti devices can run openwrt or other hacked software, possibly that's a way.

        • Kendall Wells > Kendall Wells June 3, 2015 at 7:16am

          Found this definition;

          Monitor mode

          Monitor mode is a passive-only mode, no packets are transmitted. All incoming packets are handed over to the host computer completely unfiltered. This mode is useful to see what's going on on the network.

          With mac80211, it is possible to have a network device in monitor mode in addition to a regular device, this is useful to observe the network whilst using it. However, not all hardware fully supports this as not all hardware can be configured to show all packets while in one of the other operating modes, monitor mode interfaces always work on a “best effort” basis.

          With mac80211, it's also possible to transmit packets in monitor mode, which is known as packet injection. This is useful for applications that wish to implement MLME work in userspace, for example to support nonstandard MAC extensions of IEEE 802.11.

    • Paul Meier > Kendall Wells June 3, 2015 at 6:27am

      Bullit mod by digital_wadik of http://fpv-community.de/3702570577?profile=original

      • Fnoop > Paul Meier June 3, 2015 at 6:45am

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

        • Paul Meier > Fnoop June 3, 2015 at 7:19am

          Did not know about the wispstation, agree with you should be the better solution.

          Will try to get one

          • Paul Meier > Paul Meier June 3, 2015 at 9:09am

            Same specs as the Bullet

      • Kendall Wells > Paul Meier June 3, 2015 at 6:31am

        Perfect Solution!

        Thanks

    • Fnoop > Kendall Wells June 3, 2015 at 5:34am

      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.

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