Publishing MQTT messages from Thread device using NCS

Question

I have a system that consists of a sensor (nRF52840), hub (nRF5340), and gateway (nRF9160). The high level end goal is to be able to publish a MQTT message from the sensor , and have it travel to a device that can forward it a the cellular network. One concept was to the publish the MQTT message from the sensor, route the data to the hub via OpenThread, and from there route the data to the gateway via PPP. The gateway will then be responsible for sending the data over the cellular network to the MQTT broker. Is this possible? I have been hard pressed to find examples or documentation to support this. A good start would have been a MQTT over Thread demo for NCS which does not exist.

Sigurd Hellesvik · Accepted Answer

This sounds reasonable. 
 If we had a border router solution for the nRF9160, it might be an idea to use the same protocol for both. But since we do not have such a thing, I can see not see any reason to use the same protocol for both Thread and LTE. 
 In summary, the two main reasons for using CoAP over MQTT is: 
 
 CoAP use UDP, which likely use less power. (*) 
 We do have samples for CoAP in the nRF Connect SDK.

(*) I have not actually tested the power consumption of CoAP vs MQTT for Thread, but it makes sense that a heavier protocol(TCP vs UDP) will use more resources and therefore more power. My colleague agrees on this. 
 Regards, Sigurd Hellesvik

Publishing MQTT messages from Thread device using NCS

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