Hello!
Periodically, I notice error of type UPLINK_F_CNT_RETRANSMISSION. The uplinks are being transmitted with the same FCNT, but I’m not sure why. I’m hoping you can help me out in determining whether this is a problem with RF connectivity or a configuration issue with gateway, chirp and device.
I’ve read that the LORAWAN1.1 release has fixed this issue, but since my end device is operating on LORAWAN1.0.3, communication is not occurring with this setup.
When the NBTrans value (specified in the LoRaWAN specification) is greater than 1, this error is expected. In this scenario, the device will transmit the same uplink many times. If so, how can the NBTrans value be controlled?
I’ve tried a few different configurations without success.
Thanks for the reply.
Fcnt is not 0. The end node successfully joins the server. A few packets with incrementing Fcnt are also sent by Node and I can see those packets at the server. However as the distance between the GW and the node increases, errors of type UPLINK_F_CNT_RETRANSMISSION occur and then the uplinks are being transmitted with the same FCNT.
The key thing to see is the retransmission in the error type.
Because the distance increases, sometimes the uplinks are lost due to poor signal. The LNS tries to counter this be asking the node to retransmit the same uplink a few times, hoping that at least one will get through. But it can also be the case that more than one of those retransmissions is received, generating the event you are seeing. This is not an actual error, but rather a warning. The device is doing exactly what is requested.
I agree with you. However, even when the distance between the node and the GW decreases, the error will persist once it occurs. Moreover, packet loss begins.
Yes, because the LNS can’t predict if it will or will not keep happening, so it usually takes a while before it asks the device to stop the retransmission.