@jcaron Hi Jcaron, Thanks for your explaination. We'll make te intervals longer so that we don't breach the regulations. I understand what your saying, but could you describe how you calcluate the collision rate? The strange thing is, that almost every time it is a single node who is not recieved well by the gateway. Not always two nodes at the same time. They are indeed close to each other, but we're now testing it with one node, to see how that works. We'll add a random interval. I'll post if this changes solved our problem.

That's correct, the ack will only be sent with the next uplink Where is a gotcha (at least it was to me): once the data is received, typically LoPy goes to deepsleep. Once it does, it forgets the previous session and starts the new one without confirmation. Indeed this was a problem, but from the upcoming firmware release on it won't - we now save the pending ack status of downlinks as well when using nvram_save(), so if you use nvram_restore after restarting from deepsleep the LoPy will know to send the acknowledgement with the next uplink. This is already in our internal code and will be public on the next release.