Transceiver design for cooperative non‐orthogonal multiple access systems with wireless energy transfer

Abstract

In this study, an energy harvesting (EH)-based cooperative non-orthogonal multiple access (NOMA) system is considered, where node S simultaneously sends independent signals to a stronger node R and a weaker node D. The authors focus on the scenario that the direct link between S and D is too weak to meet the quality of service (QoS) of D. Based on the NOMA principle, R, the stronger user, has prior knowledge about the information of the weaker user, D. To satisfy the targeted rate of D, R also serves as an EH decode-and-forward relay to forward the traffic from S to D. In the sense of equivalent cognitive radio concept, R viewed as a secondary user assists to boost D’s performance, in exchange for receiving its own information from S. Specifically, transmitter beamforming, power splitter and receiver filter are jointly designed to maximise R’s rate with the predefined QoS constraint of D and the power constraint of S. Since the problem is non-convex, they propose an iterative approach to solve it. Moreover, a zero-forcing based low-complexity solution is also presented. Simulation results demonstrate that, both two proposed schemes have better performance than the direction transmission.