Resource Allocation and User Association for Load Balancing in NOMA-Based Cellular Heterogeneous Networks

Small cells, specially femtocells, are deployed in the coverage of macrocells and form underlay heterogeneous networks (HetNets) to increase the capacity of cellular networks. Load balancing is necessary to increase the resource utilization in HetNets. Non-orthogonal multiple access (NOMA) technique has been proposed to increase the spectral efficiency in the fifth-generation (5G) of cellular networks. The aim of this paper is to present a user association and resource block (RB) allocation scheme in NOMA-based cellular HetNet for maximization of Jain's fairness index and spectral efficiency. The maximization problem is decomposed into two sub-problems. At first, the number of RBs that each small cell base station (SBS) can allocate for connection requests, is obtained. Then, the NOMA groups and RB allocation are optimized to increase the spectral efficiency. The results indicate the efficiency of the proposed scheme in enhancing the fairness index and spectral efficiency in HetNets compared to the conventional scheme.