Outage Probability Analysis in Downlink SWIPT-Assisted Cooperative NOMA Systems

We study a downlink non-orthogonal multiple access (NOMA) system, in which a base station (BS) serves a near user and a far user on the same frequency band simultaneously. Due to physical obstacles or heavy shadowing, there is no direct link from the BS to the far user and the near user acts as a cooperative relay for the far user by adopting the simultaneous wireless information and power transfer (SWIPT) technique. In particular, we first derive the outage probabilities of the SWIPT-assisted cooperative NOMA system by considering both full-duplex and half-duplex relaying modes. Then, we analyze the approximated closed-form expression of exact outage probability by applying the Gaussian-Chebyshev quadrature formulas. Simulation results validate the correctness of the theoretical analysis and demonstrate the advantages of the SWIPT-assisted cooperative NOMA system over orthogonal multiple access (OMA) benchmarks.