DownLink Issues

Question

"Number": 108, "ResourceId": "", "Timestamp": "2024-10-08T14:35:16.503351126Z", "MessageId": "", "fPort": "-", "devEui": "-", "Event": "Downlink_Data", "LogLevel": "ERROR", "Resource": "WirelessDevice", "messagePayload": { "ResourceId": "", "Timestamp": "2024-10-08T14:35:16.503351126Z", "CustomerLog": { "wirelessDeviceType": "LoRaWAN", "resourceId": "", "logLevel": "ERROR", "resource": "WirelessDevice", "messageId": "8b9e3f4f-4416-4394-a2be-66c22fe4f328", "event": "Downlink_Data", "message": "Downlink message failed. MessageId: 8b9e3f4f-4416-4394-a2be-66c22fe4f328. Downlink metadata: {"FPort":2}", "wirelessDeviceId": "9", "devEui": "", "timestamp": "2024-10-08T14:35:16.503351126Z" } }

I am seeing a lot of downlink message failed. I correctly configured my device profile to Class A device , which is what it is. I have my region in US915 A shown below:

dev Profile MacVersion 1.0.3 RegParamsRevision Regional Parameters v1.0.3rA RxDelay1 5 RxDataRate2 10 RxFreq2 9230000 FactoryPresetFreqsList 9039000,9041000,9043000,9045000,9047000,9049000,9051000,9053000,9046000 MaxEirp 15 MaxDutyCycle 10 RfRegion US915 SupportsJoin true Supports32BitFCnt true

Service Profile

RaAllowed false PrAllowed false UlRate 60 UlBucketSize 4096 DlRate 60 DlBucketSize 4096 AddGwMetadata true DevStatusReqFreq 24 DrMin 9 DrMax 13 MinGwDiversity 1

Can you please assist me with that?

Greg_B · Accepted Answer

Hi. Is this a typo?

```
RxFreq2 9230000
```

As far as I know, that's not a valid downstream channel frequency. See section 2.3.2 here: https://resources.lora-alliance.org/technical-specifications/lorawan-regional-parameters-v1-0-3reva. If you have that wrong though, I would have expected no downlinks to succeed for that device.

Besides that, nothing obvious is jumping out at me. You're using some non-recommended values, but they're valid as far as I know. It will be useful to:

- use the Network Analyzer to confirm messages are being sent at correct times/frequencies/etc
- check the Basic Station log for `[AIO:XDEB] [4|WS] < {"msgtype":"dnmsg"` to see what/when downlinks AWS IoT Core for LoRaWAN is sending to the gateway.
- any logs you can get from your device.

re:Post Agent · Answer

Based on the information provided, there are a few potential reasons for the downlink message failures you're experiencing:

1. Class A device behavior: Class A devices only open receive windows after sending an uplink message. If your device is not sending regular uplinks, it may miss the downlink messages. Ensure that your device is sending uplinks frequently enough to receive downlinks.

2. Timing issues: For Class A devices, the downlink timing is critical. The AWS IoT Core for LoRaWAN needs to send the downlink message precisely during the device's receive window. If there's any misalignment, the downlink will fail.

3. Gateway connectivity: Ensure that the gateway your device is connecting to is online and properly configured. If the gateway is not available when the downlink is scheduled, the message will fail.

4. Frequency plan: While you've specified US915, make sure that the frequencies used for downlink (RxFreq2) align with the US915 band plan.

5. Message queue management: Check if there are multiple downlink messages queued for the device. Sometimes, if messages are not properly cleared from the queue, it can cause issues with new downlinks.

6. Payload size: Ensure that your downlink payload is not exceeding the maximum allowed size for the data rate you're using.

To troubleshoot:

1. Monitor your device's uplink messages to ensure they're being received regularly.
2. Check the gateway logs to see if there are any issues with downlink transmission.
3. Verify that the FPort (2 in this case) is correct for your application.
4. Try sending a downlink message immediately after receiving an uplink to increase the chances of hitting the receive window.
5. Consider temporarily changing the device to Class C (if supported) to test if downlinks work in that mode.

If the issue persists, you may need to gather more detailed logs from both the device and AWS IoT Core for LoRaWAN to identify the root cause of the failure.
  
**Sources**  
[Queue downlink messages to send to LoRaWAN devices - AWS IoT Wireless](https://docs.aws.amazon.com/iot-wireless/latest/developerguide/lorawan-downlink-queue.html)  
[ERROR when sending downlink to class A devices | AWS re:Post](https://repost.aws/questions/QUj6uut84GQ721uDrVgZ6ELg/error-when-sending-downlink-to-class-a-devices)

DownLink Issues

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