Can an anchor disrupt the other ones?

Hi all,

I use the DWM1000 to estimate the position of two beacons placed on a flying drone (they are acting as “tags” in the TWR scheme), using 4 ground beacons at fixed location (acting as “anchors” in the TWR scheme).

Sometimes when the drone is flying far away from the ground beacons, what we see is that the ranging with the first beacon still works, while the ranging with the next beacons are degraded or even impossible for the last one. And even when the drone comes back to close range, this situation keeps going.

Because the ground anchors are quite close to each other, I’m wondering if the first ground beacon, emitting its RESPONSE message to the drone’s tags, could cause the other beacons to lower their level of RX sensitivity (because they are receiving a strong signal) and therefore they can’t receive the next POLL messages from the drone tags (because they are too weak in comparison with the RESPONSE message of the first anchor). Do you think that is possible ? Or do you suggest other tracks to investigate ?

Any help would be much appreciated ! Thanks !

Two devices talking at the same time can cause disruptions. If things get out of sync and start transmitting on top of each other or close enough that one packet hasn’t been processed before the next starts then you will get packet loss.

You didn’t indicate whether you were using PANS or some other system, this time sync between tags is something that the higher level positioning protocol needs to handle.

Hi Andy,
Thanks a lot for your reply. As I understand, there is no possibility that a very strong emission just before a weak one will mask it (provided they don’t overlap).
I don’t use PAN but own code, and you are right, timing is very important :slight_smile:

I’m not saying it’s impossible that there is some impact from being very close but I’ve never noticed one. Most of the time we have a reasonable spacing but for some tests I’ve run with units 30-40 cm apart and not run into any issues.
Timing synchronisation between multiple independent tags has however caused a lot of headaches.