Energy-efficient optimization for secure wireless-powered backscatter communications with imperfect CSI and artificial noise

To resolve the impact of channel uncertainties and information leakage in wireless-powered backscatter communication networks, a robust secure resource allocation algorithm with non-orthogonal multiple access is proposed. Specifically, a secure energy-efficient maximization problem with spherical uncertainties is formulated under the constraints of the maximum transmit power, the minimum secure rate, the time allocation factors, and the minimum harvested energy. Then, the original non-convex problem with channel uncertainties is transformed into a deterministic one by applying the worst-case approach and inequality transformation. In addition, the deterministic problem is converted into a convex one by using the variable relaxation method, successive convex approximation, and Dinkelbach's method. Simulation results demonstrate that the proposed algorithm has higher energy efficiency and lower outage probabilities.