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PMX LoRaWAN Troubleshooting


PMX LoRaWAN TroubleshootingWhich RSSI and SNR are considered as good for Parametric LoRaWAN devices?TTNv3: Downlinks are not received. What can I do?Device does not join the LoRaWAN network. What can I do?What does DevNonce Error mean?


Which RSSI and SNR are considered as good for Parametric LoRaWAN devices?

RSSI and SNR must be considered to evaluate the radio link quality. You can find these levels somewhere on your LoRaWAN Network Server.

  • RSSI is the received signal strength
  • SNR is the signal noise rate and give indication on the ambient noise level


  • Radio link can be considered has GOOD when RSSI > -115dB and SNR > -7dB
  • Radio link is BAD (range limit) when RSSI <= -120 dB or SNR <= -13dB

Between this 2 cases

If RSSI is good (> -115dB) but SNR bad (<= -13dB)

It means that the environment of the gateway is very noisy. SNR must be checked during many days to be sure that the radio link is enough stable to receive all messages.

If RSSI is bad ( <=-120dB) but SNR good (> -7dB)

It means that device is probably far away from the gateway.

TTNv3: Downlinks are not received. What can I do?

If you see error messages like _Downlink transmission failed with result TOO_EARLY, your gateway may suffer from a slow internet backhaul.

You might schedule a time delay in TTN's gateway settings. The better option of course is looking for a better internet connection.


Device does not join the LoRaWAN network. What can I do?

Step 1: Check LoRaWAN Region Setting

Please check the LoRaWAN Region of your device. Connect your device via an USB Cable and open PPX. You should find the LoRaWAN Region String in the device type e.g. TCR-DLE/LS/EU868

See Users Manual for a description on how to change the LoRaWAN Region.

Step 2: Check LoRaWAN Keys

Check if you entered the right keys by using PPX.

Step 3: Check LoRaWAN Connectivity Settings

TCR with Firmware V2.x.x uses the following network parameters by default:

  • LoRaWAN® 1.0.3
  • Class A
  • OTAA
  • Confirmed Uplinks
  • ADR On
  • LinkChecks enabled

These settings need to mach the settings on your LNS

Step 4: Check Link Quality

If your see Join Requests in your LNS but device still does not join you may have one of the following issues:

  • The device is located in a very noisy area and not receiving ACK messages from the gateway. Try to displace the device or increase TX power on the gateway
  • Check Signal Quality of ACK by using the LoRaWAN Status View in PPX
  • Use devices with external antennas such as TCR-SLE or TCR-DLE
  • Displace the gateway

What does DevNonce Error mean?

DevNonce is a counter starting at 0 when the end-device is initially powered up and incremented with every Join-Request. A DevNonce value SHALL never be reused for a given JoinEUI value.

If you see an error message like "DevNonce is too small" you should try the following:

1. Clear LoRaWAN Context Memory

DevNonce is a 2-byte counter, starting at 0 when the device is initially powered up and incremented with every join-request. The DevNonce value is used to prevent replay attacks.

This means a DevNonce value will never be reused and therefore the device stores the DevNonce in a non-volatile memory. The memory is cleared with the save command either in the PPX Tool or when using the CLI.

2. Reset DevNonce counters on the LNS

TTN V3

When using TTNv3 you will find a button Reset used DevNonces under General Settings>Join Settings

 This will set the expected DevNonce counter back to zero, allowing the join procedure to start from scratch.