Exploiting SWIPT for Coordinated-NOMA Systems Under Nakagami-m Fading

In this paper, we consider and analyze the performance of exploiting simultaneously wireless information and power transfer (SWIPT) for coordinated-non-orthogonal multiple access (NOMA) systems under Nakagami-
${m}$
fading channels. Specifically, to deal with limited energy issues at the relay unit while taking into reusing resource efficiency, we propose to use SWIPT-based power splitting mechanisms in conjunction with NOMA approaches by means of proposing two separate scenarios, the first focus is on forward-based device-to-device (D2D) transmissions, called SWIPT-NOMA-D2D, and the second focus is on forwarding signal only, called SWIPT-NOMA-noD2D. Evaluating case by case, we derive exact and approximate closed-form expressions for the outage probabilities of cell-center and cell-edge users, respectively. Besides, we also obtain an exact closed-form solution for the ergodic rate of message transmission, which enables us to effectively characterize the system spectrum utilization. The correctness of our analyses and the tightness of the approximation developed are validated through Monte Carlo simulations and numerical techniques. Finally, we show that the two proposed schemes achieve the near ergodic sum rate in two cases of unconstrained power designs at the relay unit and their effectiveness in improving the outage performance of centre-cell users.