Outage Performance Analysis for SWIPT-Based Cooperative Non-Orthogonal Multiple Access Systems

This letter investigates simultaneous wireless information and power transfer (SWIPT)-based cooperative non-orthogonal multiple access (NOMA) system, where the near user close to the source node serves as a relay to help the far user. The near user adopts the power splitting (PS) protocol for harvesting energy and decoding the signals of both users. To ensure the user fairness, we propose a joint design for the power allocation coefficients and the PS factor to enhance the outage performance of the near user, and thereby to improve the system performance. Analytical expressions for the outage probabilities and diversity orders of both the far user and the near user are derived. The numerical results are exhibited to verify our analysis and further show that the proposed scheme significantly enhances the performance of the near user, and consequently enjoys a larger system throughput compared with the existing scheme.