Environment aware connectivity for wireless underground sensor networks

Wireless underground sensor networks (WUSNs) consist of sensors that are buried in and communicate through soil. The channel quality of WUSNs is strongly impacted by environmental parameters such soil moisture. Thus, the communication range of the nodes and the network connectivity vary over time. To address the challenges in underground communication, above ground nodes are deployed to maintain connectivity. In this paper, the connectivity of WUSNs under varying environmental conditions is captured by modeling the cluster size distribution under sub-critical conditions and through a novel aboveground communication coverage model for underground clusters. The resulting connectivity model is utilized to analyze two communication schemes: transmit power control and environment-aware routing, which maintain connectivity while reducing energy consumption. It is shown that transmit power control can maintain network connectivity under all soil moisture values at the cost of energy consumption. Utilizing relays based on soil moisture levels can decrease this energy consumption. A composite of both approaches is also considered to analyze the tradeoff between connectivity and energy consumption.