What happens when multiple transmitters start a transmission at the same time?

Wireless Connectivity Ultra-Wideband
1

Hello all,

I’m relatively new in the UWB topic. Please be patient with me when I ask stupid or total beginner questions…

The following scenario is likely to happen in my project:
There are two UWB devices that start a transmission at the same time (e.g. a Poll-Message via delayed transmission). Same time means within 4 ns (the resolution of the delayed transmission timers).
These Poll Messages can have different payloads or identical payloads.
A third device is listening and waiting for a transmission.
So this will result in some kind of collision, right ?

I wonder what is going to happen in the following two setups:
1.) The third device is closer to one of the sending devices
2.) The distance between third device is and the two sending devices is equal

Will the listening/receiving device see any message ?
Will it be able to receive/decode one of the two messages ?
Is there some kind of collision detection ?
Are there scenarios where the transmission signals “destroy” each other and none of them gets through ?

Thanks for your help
Pirmin

2

For just about all of your questions the answer is that it’s unpredictable and should be considered undefined.
You may receive one packet, you may receive the other, you may get none, you may get a receive error, you may not get any receive complete/error notification at all.

Generally an earlier or stronger signal is more likely to be received than a later or weaker signal but your system should never assume this is the case.

The answer to how do you cope with two things transmitting at once is that you design a system where that never happens. This is a lot of what makes multi-tag, multi-anchor systems a lot more complex than a simple point to point ranging system with only two devices.

If for some reason you can’t avoid that situation then design the system assuming that all collisions are lost and ensure you can cope with receive error conditions (which you should do anyway). You also need to include some means of ensuring you don’t receive a packet from device A but think it’s from device B unless in your system that doesn’t matter.