An accurate channel model for optimizing effect of non-LOS component in RF energy transfer

Self-sustainability of wireless sensor nodes can be realized with the help of controlled radio frequency energy transfer (RF-ET). However due to significant energy loss in wireless dissipation, there is a need for novel schemes to improve the end-to-end RF-ET efficiency. In this work we propose a new channel model for accurately characterizing the harvested DC power at the receiver. This model incorporates the effects of non-line of sight (NLOS) component along with the other factors, such as, polarization of transmitting field, radiation pattern of transmit and receive antennas, polarization loss factor, and efficiency of power harvester circuit. We have validated accuracy of the proposed model by carrying out experiments in an anechoic chamber. In addition to this characterization, we formulate an optimization problem by accounting for the effect of NLOS component to maximize the RF-ET efficiency. To solve this nonconvex problem, we present a computationally-efficient golden section based iterative algorithm. Finally, via numerical investigation we show that significant efficiency improvement can be achieved with the help of the proposed optimized model, which cannot be captured by the Friis formula.