Experimental analysis of Underground-Underground communication channel in WUSN

A wireless network of sensor nodes which is primarily used to extract a variety of underground information, is termed as Wireless Underground Sensor Network (WUSN). These networks are successfully implemented and utilized in the fields of precision farming, human safety, mining, structural health monitoring and many more. In WUSN, signals carrying vital underground information experience severe path-loss, as the signal completely travels through the soil medium. Path-loss during communication through soil medium is much more as compared to that through the air medium. Hence, in this work, the underground-underground (UG-UG) communication channel of WUSN is analyzed. Further, the theoretical model is validated against LoRa-based experimentations which have not been done before. The impact of varying burial depths and horizontal inter-node separation on the quality of the underground transmission is also examined in terms of path-loss and received power values. The path-loss during underground transmission rises from 25 dB to 110 dB, as inter-node separation increases from 0.25m to 4m. Hence, prior analysis of the path-loss during underground signal transmission helps to design an energy-efficient WUSN.