On Underground Coal Mine Environment Monitoring with LoRa Range Extension

The present work proposes a wireless sensor network for underground coal mine environment monitoring using LoRa communication technology. The system consists of several inexpensive IoT sensors to assess environmental factors including temperature, humidity, air quality, and gas concentration. The designed monitoring unit is connected to the LoRaWAN network so that the units can interact with one another and also with the central server placed in the control room located above the ground. The work also presents a technique to extend the range of LoRa nodes so as to increase the coverage of LoRa network by relaying messages between devices and gateways inside the mine. Additionally a method based on spreading factor (SF) optimization is utilised for range extension. This work adjusts the SF of LoRa transmissions based on the distance between the devices. The range extension technique, which is integrated into the firmware of the devices, greatly extends the range and improves the dependability of LoRa communications in underground mines.