Energy management for event capture in rechargeable sensor network with limited capacitor size

Wireless rechargeable sensor nodes are usually equipped with capacitors which collect the the energy from RF signals and support the functioning of sensing, computation, and communication components. However, the highly limited capacitor size as well as the intrinsic energy cost during the node activation imposes critical design challenge for effective energy management. It is also desirable to realize effective coordination among nodes without too much intercommunication due to the highly limited energy capacity. In this paper, we consider the problem of how to schedule the activation of wireless rechargeable sensor nodes in order to maximize the event capture rate for random event process with the consideration of both highly limited capacitor size and activation energy cost. For the events following Poisson distribution, we theoretically prove that one optimal scheduling scheme for single node case is to activate the node only when the capacitor is fully charged and sleep only when the remaining energy is unable to support one activation. Then for the more general multi-node case, we propose a coordinated periodic scheduling scheme which reduces the activation overlap among different nodes without requiring the intercommunication. Extensive simulations are conducted to verify the effectiveness of our proposed methods.