Joint Energy Flow and Time Duration Optimization for Harvested Energy Driven WPCN

This paper studies a harvested energy driven wireless powered communication network (WPCN), where ambient energy such as solar energy and wind energy can be harvested by the hybrid access point (HAP) and then transmitted to multiple users through wireless channels to transfer users' own information respectively. An energy flow and information transfer time duration allocation joint optimization problem under the energy causality constraints for maximizing the multiple slots sum-rate is investigated. By decomposing the optimal problem into two subproblems, information transfer time duration allocation and energy flow with sum energy constraint subproblem, and taking advantage of the characteristics of subproblems, the optimal proportional time duration allocation scheme and the directional energy flow algorithm is proposed. Simulation results indicate that the proposed algorithm can deliver a significant sum-rate gain compared with greedy energy flow and average information time duration allocation when HAP is energy limited, i.e., under a low energy arrival rate.