A novel solution to the energy hole problem in sensor networks

One major limitation in a Wireless Sensor Network (WSN) is the energy dissipation of the nodes and the lifetime of the node's battery. The traffic in a sensor network follows a many-to one pattern, where nodes nearer to the sink carry heavier traffic loads. Therefore, the nodes around the sink would deplete their energy faster, leading to what is known as an energy hole around the sink. The aim of this paper is to overcome the power constraints in WSN by wirelessly charging the nodes. We investigate both theoretically and through simulations whether the physical phenomenon of long-lifetime resonant electromagnetic states with localized slowly-evanescent field patterns can be used to transfer energy efficiently over multiple hops. We specify the hardware the modified sensor node needs in order to wirelessly transmit and receive energy and introduce a new layer called the charging layer into the sensor network protocol stack. Our results show that multi-hop wireless energy transfer can be done with an efficiency as high as 20% over 8 hops. The work in this paper is the first that addresses multi-hop wireless energy transfer in sensor networks and is the building block for our and other future research in this area.