nbRep or nbTrans increased to 3 for no apparent reason

ChirpStack Network Server
1

My node receives a LinkADRReq from network server and the NS is requesting to transmit 3 repetitions. The SNR seems unchanged, RSSI is also not changing, packets are not lost but NS perform this request. What could be the reason?

NS version: 2.8.2
AS version: 2.6.1
LoRa version 1.0.3

2

Without the a log of the previously received packets by LoRa Server, this is hard to say but usually this indicates that there has been packetloss.

3

Hi,

I noticed the same behaviour. When a frame is loose, the NS (or the App Server) send a downlink with the fOpts option set with nbRep at 2. The next downlink is with a nbRep at 3.

The DL with nbRep at 3 :
image

After this sequence, the LoRaWAN stack send the message three times (trace above). The stack is the Semtech/ST stack.

The sensor is in SF7, SNR around 10 and RSSI around -70.

NS version: loraserver_3.3.0_linux_amd64.deb
AS version: lora-app-server_3.4.0_linux_amd64.deb
LoRa version 1.0.3

Is it a normal behaviour or not ?

Thanks a lot.
Regards

LoRaWAN stack trace

SEND REQUEST
TX on freq 868300000 Hz at DR 5
9840s212: PHY txDone
RX on freq 868300000 Hz at DR 5
9841s246: PHY rxTimeOut
RX on freq 869525000 Hz at DR 0
9842s448: PHY rxTimeOut
9842s449: APP> McpsConfirm STATUS: OK

9842s449: #= U/L FRAME 163 =# Class A, Port 2, data size 16, pwr 7, Channel Mask 00FF

SEND REQUEST
TX on freq 867700000 Hz at DR 5
9900s212: PHY txDone
RX on freq 867700000 Hz at DR 5
9901s265: PHY rxDone
9901s269: APP> McpsConfirm STATUS: OK

9901s270: #= U/L FRAME 164 =# Class A, Port 2, data size 16, pwr 7, Channel Mask 00FF

9901s270: APP> McpsInd STATUS: OK

9901s271: #= D/L FRAME 9 =# RxWin 1, Port 0, data size 0, rssi -60, snr 7

SEND REQUEST
TX on freq 868100000 Hz at DR 5
9960s217: PHY txDone
RX on freq 868100000 Hz at DR 5
9961s271: PHY rxDone
9961s275: APP> McpsConfirm STATUS: OK

9961s275: #= U/L FRAME 165 =# Class A, Port 2, data size 16, pwr 7, Channel Mask 00FF

9961s276: APP> McpsInd STATUS: OK

9961s276: #= D/L FRAME 10 =# RxWin 1, Port 0, data size 0, rssi -60, snr 7

SEND REQUEST
TX on freq 867300000 Hz at DR 5
10020s217: PHY txDone
RX on freq 867300000 Hz at DR 5
10021s250: PHY rxTimeOut
RX on freq 869525000 Hz at DR 0
10022s453: PHY rxTimeOut
TX on freq 868100000 Hz at DR 5
10022s545: PHY txDone
RX on freq 868100000 Hz at DR 5
10023s578: PHY rxTimeOut
RX on freq 869525000 Hz at DR 0
10024s780: PHY rxTimeOut
TX on freq 867700000 Hz at DR 5
10027s439: PHY txDone
RX on freq 867700000 Hz at DR 5
10028s471: PHY rxTimeOut
RX on freq 869525000 Hz at DR 0
10029s673: PHY rxTimeOut
10029s674: APP> McpsConfirm STATUS: OK

10029s674: #= U/L FRAME 166 =# Class A, Port 2, data size 16, pwr 7, Channel Mask 00FF