Optimal time allocation for throughput maximization in backscatter assisted wireless powered communication networks

Integrating backscatter communication (BackCom) into wireless powered communication networks (WPCNs) makes it possible to transmit information and harvest energy simultaneously, which is regarded as a promising method to enhance the throughput. A very important issue is how to allocate the charging time and transmitting time to efficiently utilize the energy in hybrid access point (HAP) so as to improve the network performance. This paper adopts convex optimization to handle the time allocation for both WPCNs and BackCom users. A two-stage efficient algorithm is proposed to solve the problem of sum-throughput maximization (STM) subject to the basic throughput requirements of BackCom users, where the Lagrange duality method is applied at the first-stage, while golden section and bisection method are jointly used at the second-stage. In order to solve the throughput unfairness among nodes in the STM problem, the common-throughput maximization (CTM; i.e. the worst node's throughput) problem is further considered. This problem is decomposed into a master problem and a sub-problem, which are solved in a progressive manner. Simulation results show that the proposed methods obtain substantial improvement compared to the benchmark scheme.