A dual-band wireless energy transfer protocol for heterogeneous sensor networks powered by RF energy harvesting

Radio frequency (RF) energy harvesting promises to realize battery-less sensor networks by converting energy contained in electromagnetic waves into useful electrical energy. We consider a network architecture that allows heterogeneous frequency harvesting. One class of sensors harvests RF energy on the DTV band (614 MHz) while another uses the 915 MHz ISM band. We study the effective energy transfer that is achieved under these circumstances, and then design a link layer protocol called RF-HSN that optimizes the energy delivery to energy-hungry sensors with the optimal duty cycle. To the best of our knowledge, this is the first wireless energy transfer protocol for heterogeneous frequency RF energy harvesting, and through a combination of experimentation and simulation studies, we demonstrate over 59% higher duty cycle and 66% average network throughput improvement over the classical CSMA MAC protocol.