Optimal Fair Resource Allocation for Downlink NOMA Systems

In non-orthogonal multiple access systems, the problem of resource allocation is generally addressed in two stages. These steps determine a proper power allocation and user pairing method for the system. In this work, optimal fair resource allocation has been proposed as the solution to the resource allocation problem in the literature. This method aims to provide superiority to orthogonal multiple access by providing fairness among users under certain constraints. Firstly, the necessary power allocation coefficients are calculated to maximize the system's achievable data rate by taking into account the quality of service requirements at the power allocation stage. A new algorithm is then proposed to ensure optimal user pairing. In the simulations, it is shown that the proposed method increases the efficiency as much as 35% in terms of sum rate of the system. In addition, the proposed method is compared to another well-known method that also proposes a user pairing algorithm, and better performance is achieved.