Doubts about LoraWAN and Chirpstack transmissions


I create a new topic because the ones that exist have not clarified my doubts.
I am currently using a number of 264 water sensors that transmit every 8h to my RAK 7289C gateway and then to Chirpstack via UDP. All the sensors do not transmit exactly at the same time but they do it with a difference of a few seconds or 1-3 min, in addition, they are configured with ADR. This is where several questions arise:

  • Is the time limitation relative to each user or to each device? In both cases, would you be complying with the limitation of Spain, right?
  • I don’t know where I can look at the time in air of each sensor, the only thing I can find is a variable called timeSinceGpsEpoch, is that it? If it is, what unit is it in since a very large number appears and it doesn’t make sense?
  • Finally, I got several logs of “Uplink was flagged as re-transmission / frame-counter did not increment” and “COLLISION_BEACON”, what is this and how can I fix it?

Thank you very much for the help.
All the best.

Hello :wave:,

Here is an interesting ressource to answer your questions: Airtime Calculator

The Duty Cycle Limitations apply for each device, but also to the gateway (10% airtime for GW instead of 1% for devices). But don’t worry: even in worse conditions, sending 1 message every 8 hours won’t be a problem.

re-transmission is a warning, it just says that the gateway got the mesage twice or more.