EFCon: Energy flow control for sustainable wireless sensor networks

The rapid advances in processor, memory, and radio technology enable the development of small, inexpensive sensor nodes that are capable of sensing, computation, and communication. However, the severe energy constraints of the sensors present major challenges for long-term applications. In order to achieve sustainability, environmental energy harvesting has been demonstrated as a promising approach. In this work, the energy utilization scheme is investigated for wireless sensor networks with energy harvesting nodes. The energy utilization system is divided to three parts: energy harvesting, energy consuming and energy storage. Then the sustainability problem is formulated as an energy flow control problem. An energy flow control system, called EFCon, is proposed to keep the balance between energy supplies and demands. EFCon consists of two phases, energy flow direction control and flow rate control. In the phase of energy flow direction control, the system dynamically switches among four patterns: flood flow, direct flow, compensate flow, and backup flow, according to current environmental energy condition and the residual energy condition. Once the energy flow direction is determined, a corresponding energy flow rate control strategy will be adopted for efficient energy utilization. The EFCon is implemented and validated by a long-term deployment in real testbeds. The experimental results indicate that the EFCon outperforms existing designs.