Cooperative non-orthogonal multiple access (C-NOMA) is one of the promising techniques that support the massive connectivity of users and improve the fair allocation of network resources. However, the performance of C-NOMA networks is restricted due to the complexity introduced by multiple user-assisted relays coupled with their energy consumption bottleneck. In this paper, we develop a low-complexity network framework with the main goal of achieving a fair and optimal achievable rate. For the network model, we adopt a Space–time block code transmission scheme to increase the spatial diversity of the network with a minimum number of relays. Further to this, we consider a radio frequency-based energy harvesting technique known as simultaneous wireless information and power transfer in order to compensate for energy expended by the relays over the cooperating transmission links. Based on the proposed network model, we solve the achievable rate maximization problem from the perspective of joint optimal power allocation factor and power splitting ratio. Due to the non-convex nature of the problem and to also ensure fair resource allocation, we propose a low-complexity solution based on the concept of Nash bargaining solution. Further to this, we evaluate the achievable rate and energy efficiency of the system. Simulation results show that our proposed solution outperforms the baseline approaches.
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