Energy-Efficient Transmission Design in Cooperative Relaying Systems Using NOMA

In this letter, we investigate the optimal power allocation scheme in a cooperative relaying system using non-orthogonal multiple access from the perspective of global energy efficiency (GEE), where a source node communicates with two destination nodes simultaneously via a decode-and-forward relay. We optimize the transmit power at the source node and relay node jointly under quality of service requirements. It is proved that the optimal GEE is strictly quasi-concave with regard to the transmit power at the source node. Based on this quasi-concavity, we decompose the original nonconvex problem into a bilayer optimization problem and obtain the optimal power allocation solution. Simulation results show the effectiveness of our theoretical findings.