Energy-Efficient Design in RF Energy Harvesting Relay Networks

In this paper, the energy-efficient design of wireless relay networks with radio frequency (RF) energy harvesting capability is studied. A decode-and-forward relay is used to forward information and harvest energy simultaneously from the same signal with a power splitting architecture. Given the power and quality-of-service constraints, a non- convex energy- efficient optimization problem is formulated, in which the transmit power and power splitting ratio are coupled together. With our proposed algorithm, the problem is decoupled and solved. The question of when RF energy harvesting relay is preferred is also discussed. Simulation results demonstrate that the proposed algorithm improves the energy efficiency over the power allocation scheme for capacity maximization. The RF energy harvesting relay is shown to be preferred over the direct transmission when the environmental noise level is high.