Capacity and interference management of wfb-ng Links for drone fleets

[Cyberalle]

Hello,

I’m using wfb-ng on multiple drones. I’m experiencing interference when several drones are operated simultaneously, even though I’m using non-adjacent channels (for example, 161 and 153).

How many wfb-ng links can we use at the same time in the same area—what’s the maximum number of drones? And wouldn’t it be possible to implement a collision-management mechanism like CSMA/CA so that we could run multiple wfb-ng links on the same channel while still enjoying the benefit of no ACK?

[svpcom]

CSMA/CA is still active but there are no retransmissions. Try to use bandpass filters to reduce interference.
wfb-ng is for long-range links and reasonable small amount of drones. For high-density drone areas ordinary wifi (with retransmissions) is preferred. There are no any magic - without base station (like in LTE networks) it is impossibly to achieve perfect synchronization of multiple radios. So there are always tradeoff between distributed operation of radio spectrum usage efficiency

[Cyberalle]

Thank you for your quick response and for the tip about band-pass filters.
Would you put them on the ground station or on the drone?
I wasn’t aware that CSMA/CA was still in use. Standard Wi-Fi seems too limiting in terms of range…
Do you think it would be possible to implement a TDMA-type mechanism on wfb-ng?
Perhaps using a base station or GPS to synchronize the clocks?

[svpcom]

You can put filters to GS (rx) side because wifi radios are not Superheterodyne receiver. If you use bidirectional link then put them on the both sides.
TDMA is possible in theory, but existing wifi usb cards don't have builtin precise timers and usb bus has too much latency and buffering

[Cyberalle]

Ok, if the timers on the Wi-Fi cards aren’t precise enough, there’s no point in trying to synchronize clocks. My goal is to fly multiple drones simultaneously (dozens of them at reasonable distances). Low latency is crucial, which is why wfb-ng is ideal. I thought I could assign one channel per drone, but in practice that’s proving complicated. What do you recommend? 5G (expensive), or standard Wi-Fi 6 or 7 with multiple access points? Perhaps there are Wi-Fi cards that “bleed” less when using a 10 MHz channel width—if so, would they be compatible with wfb-ng?

[svpcom]

I'll recommend to use wifi 5G band and 10 MHz channels. wfb-ng + rtl8812eu supports this

[Cyberalle]

Thanks, I’ll explore that. Right now my drones have OpenIPC Runcam WiFiLink cameras, so I’ll need to check the chipset. Is the rtl8812eu required for tx only, or on both ends?

[svpcom]

On the both ends. 8812au doesn't support 10 MHz channels