Rate-Constrained Energy Minimization in Hybrid SWIPT for Relay-Assisted NOMA Networks

We consider a relay-assisted non-orthogonal multiple access (NOMA) network consisting of a source (S), an energy-constrained relay (R), and two users, where a hybrid power-splitting (PS) and time-splitting (TS) scheme is applied at R for energy harvesting. We provide optimal system designs for such a network by jointly optimizing the transmit power of S, the TS and PS ratios, the power allocation ratios at S and R, and the user ordering (indicating which user should apply the successive interference cancellation). In particular, considering full channel state information at the transmitters (CSIT) availability, our proposed system design can minimize the energy consumption while ensuring that the two users correctly receive the desired information. Finally, numerical results are provided to validate the analytical results and to evaluate the performance advantage of the hybrid PS/TS scheme with the proposed optimal design.