Value of Information Aware Opportunistic Duty Cycling in Solar Harvesting Sensor Networks

Energy-harvested wireless sensor networks may operate perpetually with extra energy supply from natural energy such as solar energy. Nevertheless, harvested energy is often too limited to support perpetual network operation with full duty cycle. To achieve perpetual network operation and process the data with high importance, measured by value of information (VoI), sensor nodes have to operate under partial duty cycle and to improve the efficiency of harvested energy. A challenging problem is how to deal with the stochastic feature of natural energy and variable data VoI. We consider the energy consumption during the energy storage and the diversity of the data process including sampling, transmitting, and receiving, which consume different power levels. The problem is then mapped as a budget-dynamic multiarm bandit problem by treating harvested energy as budget and the data process as arm pulling. This paper proposes an opportunistic duty cycling (ODC) scheme to improve the energy efficiency while satisfying perpetual network operation. ODC chooses some proper opportunities to store harvested energy or to spend it on the data process based on historical information of energy harvesting and VoI of the processed data. With this scheme, each sensor node only needs to estimate ambient natural energy in short term so as to reduce computation cost and storage capacity for the historical information. It then can adjust its own duty cycle distributively with its local historical information. This paper conducts extensive theoretical analysis for the performance of our scheme ODC on the regret, which is the difference between the optimal scheme and ours. Our experimental results also manifest the promising performance of ODC.