Strategic frequency adaptation for mid-range magnetic induction-based Wireless Underground Sensor Networks

Some classes of sensing applications target scenarios where the overall system, including antenna and energy sub-system, is placed under the ground, through concrete, or under-the-debris (disaster scenario). A real-time soil moisture sensing system deployed at the root zone of a crop area for precise irrigation and an oil pipeline leak detection (PLD) system are particular examples of interest discussed in this work. Communication solutions for these scenarios have been recently investigated in the Wireless Underground Sensor Networks (WUSN) literature and magnetic induction (MI) technology is usually regarded as the best candidate for low-power and mid-range (i.e., 15..30m) wireless underground communication. Nonetheless, underground MI systems are still significantly impacted by changes at the electrical properties of the medium surrounding the MI nodes, such as due to the soil moisture variability. The design of a MI system for the worst-case scenario (e.g., high soil moisture) is a strategic approach but it may significantly reduce the application bandwidth. Therefore, the dynamic frequency adaptation has the potential of balancing robustness and higher bandwidth for MI-WUSNs. In this work, a novel design procedure is proposed for the optimization problem of selecting the proper operational frequency for MI-WUSN nodes according to the medium conditions.