EM-BasedWireless Underground Sensor Networks

Wireless underground sensor networks (WUSNs) consist of buried nodes, which are connected to subsurface underground sensors, and use electromagnetic (EM) waves for underground communications. WUSNs are capable of operating in environments where no other computer network has functioned before, and has the potential to provide real-time, robust, and energy efficient sensing, and communication in these environments. The characteristics of the wireless underground (UG) channel are much different as compared to the conventional over-the-air (OTA) wireless communication channel. These differences are caused by the wave propagation mechanism in the UG channel. Electromagnetic (EM) waves interacting with the soil medium exhibit distinct characteristics, and experience higher attenuation. Physical properties of the soil texture, soil moisture, soil temperature, and bulk density impact UG wave propagation. These interactions introduce channel impairments, which varies with space and time. These spatiotemporal variations present challenges to maintain connectivity in WUSNs, and necessitate, to maintain connectivity, adaptive solutions tailored to the variations in soil moisture. To model the characteristics of the underground channel, and to validate interactions among different component of the WUSN, experimental studies are essential. Conducting underground channel characterization experiments is a very challenging and time consuming task (Salam et al., 2016; Silva and Vuran, 2010a). First, it is difficult to get a wide range of soil moisture levels, which are essential to ascertain its impact on UG channel, in a very short span of time because of climatic conditions. Digging process becomes difficult in extreme weather conditions due to soil becoming