  In this article, we propose a reliable and low-latency Long Range Wide Area
Network (LoRaWAN) solution for environmental monitoring in factories at major
accident risk (FMAR). In particular, a low power wearable device for sensing
the toxic inflammable gases inside an industrial plant is designed with the
purpose of avoiding peculiar risks and unwanted accidents to occur. Moreover,
the detected data have to be urgently and reliably delivered to remote server
to trigger preventive immediate actions so as to improve the machine operation.
In these settings, LoRaWAN has been identified as the most proper
communications technology to the needs owing to the availability of off the
shelf devices and software. Hence, we assess the technological limits of
LoRaWAN in terms of latency and reliability and we propose a fully LoRaWAN
compliant solution to overcome these limits. The proposed solution envisages
coordinated end device (ED) transmissions through the use of Downlink Control
Packets (DCPs). Experimental results validate the proposed method in terms of
service requirements for the considered FMAR scenario.
