Scheduling and relay selection for full-duplex wireless powered cooperative communication networks

Abstract

In this manuscript, we consider a full-duplex wireless powered cooperative communication system where the users communicate with a hybrid access point through relays. We formulate an optimization problem with the objective to minimize the total transmission time through user scheduling and relay selection while considering the traffic demand, energy causality and initial battery levels of the users. The formulated optimization problem is a mixed integer non-linear programming problem, hence difficult to solve for the global optimal solution. As a solution strategy, we decompose the problem into sub problems: time allocation, scheduling and relay selection. In the time allocation problem; the schedule and relays are assumed to be pre-known, we derive the optimal solution by using the optimality analysis. For the scheduling problem; we assume that users know their relays, we determine the optimal schedule. For the relay selection problem; users transmit their information in a pre-determined order, we determine the optimal relays for each user. For the overall scheduling and relay selection problem, we propose a heuristic algorithm which iteratively determines the scheduling and relay selection in polynomial time by using the optimal solutions of the individual relay selection and scheduling problems. Through simulations, we demonstrate that the scheduling length can be significantly reduced through proper scheduling and relay selection. The proposed algorithm performs very close to the optimal solution for different maximum user transmit power, network densities, initial battery levels and hybrid access point power levels.