Wireless Information and Power Transfer in Two-Way OFDM Amplify-and-Forward Relay Networks

Energy harvesting (EH) is promising to solve energy scarcity problem in energy-constrained wireless networks. In this letter, we investigate simultaneous power and information transfer in two-way amplify-and-forward orthogonal-frequency-division-multiplexing relay networks, where an energy-constrained relay node equipped EH device harvests energy from two terminals and uses the energy to forward information in a time-switching (TS) manner. By jointly designing TS ratios of EH and information processing at the relay, as well as power allocation over all the subcarriers at two terminals and relay, our objective is to maximize end-to-end achievable rate of two-way relay networks subject to transmit power constraint at two terminals and EH constraint at relay. The formulated problem is hard to tackle because the EH constraint is non-convex and the objective rate function has a highly non-convex structure. We propose to solve this non-convex problem by transforming it into a nonlinear fractional problem, which can be solved by successive convex approximation and Dinkelbach's procedure, and thus propose an efficient iterative algorithm that achieves superior performance with fast convergence speed.