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To meet with both the energy and spectral efficiency, cooperative non‐orthogonal multiple access (NOMA) (termed as CNOMA) and simultaneous wireless information and power transfer (SWIPT) are integrated in this paper. Two different protocols such as CNOMA‐SWIPT‐PS and CNOMA‐SWIPT‐TS are proposed, by employing power‐splitting (PS) and time‐switching (TS) energy harvesting (EH) techniques, respectively. In the proposed protocols, a base station (BS) directly communicates with a NOMA near user, whereas the communication with a NOMA far user is performed with the assistance of an energy‐constrained relay node. The relay node harvests energy from the transmitted signal by the BS, employing PS or TS EH technique. We investigate ergodic sum capacity and outage probability of the proposed protocols along with analytical derivations over Nakagami‐m fading channels. Finally, the effectiveness of the proposed schemes over existing strategy and conventional multiple access is demonstrated through analysis and simulation.

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This paper addresses the issues related with conventional near-far user pairing in non-orthogonal multiple access. Performance effects of near-far pairing on regions with negligible channel gain differences between users are investigated. These regions occur when pairing is performed between cell center and cell edge users, thus leaving the cell mid users to be either paired with each other or kept unpaired. Pairing these mid users with each other causes successive interference cancelation (SIC) performance degradation resulting in capacity reduction for these users. On the other hand, leaving these mid users unpaired perfectly avoids the SIC issue but makes these users unable to benefit from the capacity gains provided by non-orthogonal multiple access. Therefore, two user pairing strategies have been proposed that can provide capacity gains to almost all the users by accommodating them in pairs, while avoiding or minimizing the mid users pairing problem. A generalized M-users pairing scheme is also proposed. Simulations have been performed to investigate the performance of proposed schemes for both perfect and imperfect SIC receiver scenarios in comparison with conventional pairing where the mid users are kept paired with each other. Simulation results show that proposed schemes achieve high capacity gains, especially when imperfect SIC is considered.