Question Please recommend a Router + AP solution for 500+ drones ?

[gafonator]

Hi, guys,

We've recently pulled off a pretty decent drone show with tens of drones — everything went smoothly using just one (expensive) MI-MO router. Now, we'd like to scale up. We're aiming for hundreds of drones — 500+, actually. But choosing the right WiFi solution for that is slowly becoming a bit of a nightmare. Everyone says something different.

The nutshell version:
We're talking about 500+ clients on a WiFi network, with a large number of concurrent UDP multicast streams running — and we need it all to run as close to perfectly as possible. The distance from the router/AP antennas can reach up to 250–300 meters.

If you’re familiar with such setups, or if you can offer some insight based on your broader networking experience (e.g. which router, brand, technologies, or wireless standards might help, how many APs, rough setup guidance — mesh, repeater, etc.), we’d be grateful for your input.

#RTK, UDP, Multicast, lots of concurrent low-bandwidth streams (several kB per drone), AP mesh

 

[Ralston18]

Security requirements?

 

[gafonator]

Security requirements?

Security is, at the moment, not a concern. Just classic WPA2.

 

[bill001g]

Do you actually use multicast. Multicast is very strangely implemented in wifi. It is kinda sent to a broadcast group since sending exactly the same data to multiple device all of which can actually hear the traffic being sent to the other device is kinda silly.

I have not looked at this in years. Multicast was never implemented on the internet where it would be great to reduce the bandwidth of live streamed data. Part of the reason is you can't really encrypt the data and you end up sending separate copies with the unique keys to each end device which defeats the purpose of multicast.

Since all wifi traffic is also now encrypted this makes all the strange issue with multicast on wifi even more complex. In effect it is not actually using multicast it is just sending data via UDP to each device.

In your application a better method would be to use broadcast and let the end devices pick out which messages are for them some where at the application level. You would also encrypt at the application level rather than at the wifi level to keep some silly kid from messing with your stuff. I would assume someone has already though about this. It would make the choice of wifi equipment much simpler and use much less bandwidth.

 

[gafonator]

Do you actually use multicast. Multicast is very strangely implemented in wifi. It is kinda sent to a broadcast group since sending exactly the same data to multiple device all of which can actually hear the traffic being sent to the other device is kinda silly.

I have not looked at this in years. Multicast was never implemented on the internet where it would be great to reduce the bandwidth of live streamed data. Part of the reason is you can't really encrypt the data and you end up sending separate copies with the unique keys to each end device which defeats the purpose of multicast.

Since all wifi traffic is also now encrypted this makes all the strange issue with multicast on wifi even more complex. In effect it is not actually using multicast it is just sending data via UDP to each device.

In your application a better method would be to use broadcast and let the end devices pick out which messages are for them some where at the application level. You would also encrypt at the application level rather than at the wifi level to keep some silly kid from messing with your stuff. I would assume someone has already though about this. It would make the choice of wifi equipment much simpler and use much less bandwidth.

Yup. I agree that it is a bit strange. But from what I understood, Multicast is used because as soon as you get many drones at once, the Unicast becomes unmanageable. How it is managed inside the devices themselves, I do not yet understand. Fyi, there are also GPS corrections being sent al the time.

The actual application layer is called RTK, but the whole thing goes somewhat deeper, the NTRIP protocl is as low as Layer 4 (OSI).

OSI Layer	Role in RTK context	Examples
Layer 7 – Application	Applications that generate or consume RTK corrections	GNSS receivers, RTKLIB, base station software
Layer 6 – Presentation	Data formatting, message types, encoding (RTCM protocol itself)	RTCM 3.x message formats
Layer 4 – Transport	Ensures delivery of RTK data streams over networks	NTRIP protocol

As for the "let the device choose...", I appreciate you taking time to think about it all, but I don't think we have another option — other than what the applications and control units themselves actually do (Ardupilot and Skybrush). At least not if we don't want to change the whole setup, from hardware to software, control units, etc. I guess...?