Energy-Efficient Resource Allocation for Wireless-Powered Backscatter Communication Networks

In this paper, we investigate energy-efficient resource allocation in a wireless powered backscatter communication network (WPBCN), which consists of two types of wireless devices. To fully exploit the information transmission time, the two devices are supported to operate in different modes, i.e., the harvest-then-transmit (HTT) mode and backscatter communication (BackCom) mode, respectively. To improve the efficiency of wireless power transfer, energy beamforming technique is adopted at the PB. We formulate the system energy efficiency (EE) maximization problem by jointly optimizing the energy beamforming vector, power allocation, and time allocation. Since the formulated problem is non-convex, we employ variable substitutions, fractional programming theory, and semi-definite relaxation (SDR) to transform the non-convex problem into a convex problem. An algorithm is finally proposed to derive the optimal solution. Simulation results show that the proposed resource allocation scheme can improve the system EE.