Periodic join request and accept after some minutes

End Devices (Nodes)
1

Hello everyone :wave: I am running some electricity meters in one house and they are working fine. Now I have installed a new gateway and a new meter in another house, but it is not working.
There is a join request and some seconds later a join accept. But after a short time, the same meter is sending another join request. I never received any data, so I think something in the join communication is not working.
Any idea how this could happen and why or how to solve this problem?
Already thank you very much :wink::+1:

image

image

Join Request:

{
  "gw_id": "eui-a840411d2570",
  "payload": "AKq7zN3u/xEi/ZYG/v/loMwCBKGFSvo=",
  "dev_eui": "CCA0E5FFFE0696FD",
  "lora": {
    "spreading_factor": 12,
    "bandwidth": 125,
    "air_time": 1482752000
  },
  "coding_rate": "4/5",
  "timestamp": "2020-11-03T17:37:25.726Z",
  "rssi": -43,
  "snr": 8.5,
  "app_eui": "2211FFEEDDCCBBAA",
  "frequency": 868500000
}

Join Accept:

{
  "gw_id": "eui-a840411d25704150",
  "payload": "IPnE5L5yUHzW1SI2zPElTTuhHNzanyaU2DAQZTNBvNPb",
  "lora": {
    "spreading_factor": 12,
    "bandwidth": 125,
    "air_time": 1810432000
  },
  "coding_rate": "4/5",
  "timestamp": "2020-11-03T17:37:30.726Z",
  "frequency": 869525000
}
2

The response frequency does not match the timeslot it is being scheduled for. The frequency used is for RX2 which should be 6 seconds, not 5 seconds after the join request.

1 Like
3

@kersing Thanks :wink::+1: Is there any way how I can change this behavior?

I just tried it here at home with the „working“ meter. There was the same frequency of 869.525, and so RX2. The response was also after 5 instead of 6 seconds.

Then suddenly the response was on 868.500. I think that means RX1 but the response was after 4 instead of 5 seconds. But then it was working :woman_shrugging:

I there an easy way to solve this or am I doing something completely wrong? Sorry I’m new to the whole LoRaWAN topic. I was so happy that it worked in my house out of the box. But now I think it was wrong all the time and just accidently worked :see_no_evil:

image

4

Oh and corresponding to https://www.thethingsnetwork.org/docs/lorawan/frequency-plans.html shouldn’t 869.525 always be SF9BW125. How could it be SF12BW125 in the first time?

5

Not while joining.

If you can force the meter to join using a lower spreading factor it should answer in RX1. That requires SF9 or below.

Something else to consider, if the gateway and the node are too close (anything below 3 meters) there might be issues with RF crosstalk. If possible increase the distance between the two or make sure some RF absorbing material like a stone wall is in between them.

That points to the one second difference you are seeing in the console being the allowance to get the packet back to the gateway in time.

2 Likes
6

@kersing thank you very much for the explanations :wink::+1:
Increasing the distance really improved the situation. I thought the shorter the better. For further meters I will also go down to SF9.

2 Likes