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.
Replies
All fixed - silly mistake! Wasn't in the wifibroadcast directory so the .rx/ command wasn't working. CD $wifibroadcast fixed it for anyone else in same boat. Test flight soon!
Any progress on OSD??
In befinitiv's setup instructions there's an optional step to set the TX dongle's output power to 30db. I was wondering if anyone's done that and if they could post (maybe in dropbox or whatever) the compiled binaries? I'd just like to save the trouble of having to do that build myself. Ideally I'd like to have a 10db and a 30db binary (10db is the legal limit here in Japan I think).
> 10db is the legal limit here in Japan I think
Doubtful, that would be 10mW.
I think you need a bit of work on your dB figuring. 30dB = 1W BTW.
Ah yes, txs for the correction.
I'm actually not sure if the limits in Japan. This web page says 10mW / Mhz but the "/Mhz" part confuses me.. surely it can't mean "per Mhz" or the limit would be very high.
It would be really nice if this technique could be ported to something like an ESP8266 module with a decent frontend added for good range.
Hi Andreas, I got similar results to you, between 50-100m. I think these dongles are junk for tx. I asked CSL several times what the power these dongles are capable of but they couldn't answer - not even vaguely - I suspect they just package/badge a generic chinese dongle and don't really know anything about it. The driver disk that comes with it just contains files downloaded from ralink website.
I'm intending to use these as RX only with an Alfa AWUS051NH V2 as TX. I'm waiting for these to be shipped over here from the UK so will have some preliminary results by Tuesday.
Any word on how putting a wifi booster onboard would help increase range?
My experience (echoed by many) is that a T/X booster usually causes more problems with RF interference, than its worth.
The best answer is quality antennae on both T/X and R/X sides.
Amen!
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