Radiation Constrained Fair Wireless Charging

Recently wireless power transfer technology (WPT) attracts considerable attention, its incurred electromagnetic radiation (EMR), however, is largely overlooked by most existing literatures. In this paper, we first propose and study the radiation constrained fair wireless charging problem, i.e., maximizing the minimum utility of devices by adjusting the power of wireless chargers with no EMR intensity at any location in the field exceeding a given threshold . To address this problem, we first adopt an area discretization method to transform it from nonlinear to linear. Then, we propose two algorithms to deal with the reformulated problem. One is called Primal-Dual algorithm, which is semi-distributed and uses lagrangian dual and subgradient methods to solve the problem iteratively. The other is called area division algorithm. It is not only fully distributed and scalable with network size, but also provably achieves an approximation ratio of (1- ϵ). We conducted extensive simulations and built a field test-bed to verify our theoretical findings. Our simulations show that the approximation ratio of the area division algorithm holds; the Primal-Dual and area division algorithms can have comparable and over 90.9% performance of the optimal results, respectively; and both of the algorithms outperform a baseline algorithm by more than 37%.