UPLINK_FCNT_RETRANSMISSION error

ChirpStack Application Server
1

Hi,

I couldn’t find a similar topic that would have answered my question.

my question is what is the UPLINK_FCNT_RETRANSMISSION error, what is the cause of that and can it be fixed?

Could these system-generated error messages be added to the chirpstack document, then it would be easier to debug payload errors.

Thank you

2

The same uplink frame counter was retransmitted by the device - meaning the frame counter in the message did not increment.

This could be a couple things (more possibilities, but two I have encountered):

  • For confirmed messages, the uplink may have arrive at the Network Server and the downlink may have not gotten back to the device, therefore the device would retry a message that was already received by the Network Server and would be rejected.
  • For unconfirmed messages, the uplink was resent with the same frame counter value
3

We are using the repeat function that is part of LoRaWAN to repeat a packet 3 times and as far as I know they are completely identical, including the frame counter. Should the other 2 packets not be silently discarded or why the error messages? Same thing happens when a packet is received by 2 gateways, is that normal?

4

This could indeed be a feature to add to make this re-transmission silent until the number of re-transmissions has reached nbtrans.

1 Like
5

@1337 How do you repeat a LoRaWAN packet? Ie What is the special gateway or software to do so?

Thanks a lot.

6

It is done from the device, it is part from the LoRaWAN stack. In my code it looks like this, where 1 is the number of transmissions of the identical packet:

mibReq.Type = MIB_CHANNELS_NB_TRANS;
mibReq.Param.ChannelsNbTrans = 1;

1 Like
7

Thanks a lot. Let me try.