Is using downlinks not a recommended use case?

TTN Network and Services
1

Base on the below documentation, it appears that cloud to device messages is not a recommended use case for TTN. Is that a correct assumption?
https://www.thethingsnetwork.org/docs/lorawan/limitations.html

If this is not the case, please help me locate some use cases and documentation for this.

Any help is highly appreciated.

Thanks.

2

If you need to send messages from the network to your device on a regular basis, then you need to be careful about what you intend. It’s not saying NO, it’s saying don’t make it a system critical element of your design that requires you to send to your device as a matter of course.

If you need to send a message occasionally, bearing in mind that it will ONLY be received after a node transmits and not ‘on demand’, then you’ll be fine.

So, use cases for downlinks, would be:

  • Small configuration changes - timing of sends, calibration, alarm parameters
  • Requests for specific readings to double check issues
  • Outputs that are non-critical (so don’t control your heart bypass machine with it)*

or anything else that that happens occasionally, not daily, rarely weekly, perhaps monthly, more likely quarterly tuning.

*Your application should be autonomous - it should NOT rely on downlinks for safety elements, for instance, pumps may be remotely commanded for peculiar situations, to take advantage of lower priced supply to top up the tank as an example, but there should be interlocks to prevent over or under fill.

Additionally, you should have firmware that provides an acknowledgement that the change request was received and correctly processed - do not use confirmation flags, it increases transmissions and ONLY confirms that the downlink was received, not processed correctly or actioned.

1 Like
3

There is also the TTN fair access limit of 10 downlink messages per day to consider.