Reliability-Aware Power Adjustment in Air-Soil Wireless Sensor Networks

We study the power conservation and disseminating reliability problem in precision agriculture applications in this paper. Precision agriculture needs to accurately evaluate farming environment, and soil monitoring is an important part of this effort. Soil measurement requires soil sensors being buried deep enough so as to avoid plowing and other mechanical activities. Due to dielectric loss, reflection and many other reasons, radio communication underground is difficult. But existing work find that the communication between aboveground and underground (air-soil) is feasible, thus aboveground sensor nodes are employed to connect the underground nodes. In such air-soil sensor network, most transmissions are dependent on the aboveground sensor nodes, thus, the energy consumption of them is a critical concern. On the other hand, the reliability of data dissemination must also be well considered as a result of important packets forwarding, such as query commands disseminating, control information delivering and binary reprogramming over the air. Given the situation of limited power and unreliable wireless links, we propose the K-matching problem, which is to minimize the energy consumption by setting optimal transmitting power so that each node underground is connected to at least K aboveground nodes in the air. We prove that this problem is NP-complete and two centralized and one distributed approximation algorithm are provided to solve this problem. Theoretical analysis and experiment results demonstrate the effectiveness of the proposed algorithms.