  In this paper, 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. We 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, node R, the stronger user,
has prior knowledge about the information of the weaker user, node D. To
satisfy the targeted rate of D, R also serves as an EH decode-and-forward (DF)
relay to forward the traffic from S to D. In the sense of equivalent cognitive
radio concept, node R viewed as a secondary user assists to boost the
performance of D, in exchange for receiving its own information from S.
Specifically, transmitter beamforming design, power splitting ratio
optimization and receiver filter design to maximize node R rate are studied
with the predefined QoS constraint of D and the power constraint of S. Since
the problem is non-convex, we propose an iterative approach to solve it.
Moreover, to reduce the computational complexity, a zero- forcing (ZF) based
solution is also presented. Simulation results demonstrate that, both two
proposed schemes have better performance than the direction transmission.
