An Efficient Method for Resource Allocation and User Pairing in Downlink Non-orthogonal Multiple Access System

Non-orthogonal multiple access (NOMA) provides a significant impact on meeting high capacity achievements of the fifth generation (5G) wireless cellular systems. In NOMA, an efficient resource allocation is essential to achieve high performance. In this study, we solve power allocation and user pairing problems of a downlink NOMA system by proposing a novel method called (NOMA-PKKT-HNG) that maximizes system sum rate. The power allocation problem is identified as non-convex constrained problem. Therefore, we derive the closed form solutions of the optimal Power allocation using Karush-Kuhn-Tucker (PKKT) conditions. Moreover, the Hungarian (HNG) algorithm is proposed to pair two users that have different channel conditions. The findings indicate that, when the number of users is 20, the proposed method achieves higher sum rate by 6.7% compared to Difference of Convex (DC) method. The NOMA system with the proposed method can be considered for future 5G networks to achieve high system sum rate performance.