Joint Power Allocation and Subcarrier Assignment for Network‐Coded Uplink Clustered Multicarrier Nonorthogonal Multiple‐Access Networks: Models and Performance Comparisons

ABSTRACT Recently, nonorthogonal multiple access (NOMA) has been proposed as a key enabler and candidate to overcome the spectral‐inefficiency of the conventional orthogonal multiple‐access (OMA) techniques, and meet the pressing demands for massive connectivity in 5G and beyond cellular networks. Despite the numerous merits of NOMA, power allocation must be optimized. In addition, the scarcity of the frequency spectrum is still a major bottleneck, and thus, bandwidth must also be carefully utilized. This paper investigates the problem of joint power allocation and subcarrier assignment (J‐PA‐SA) in uplink clustered multicarrier NOMA networks. Specifically, the objective is to maximize the network sum‐rate subject to users' minimum rate requirements. Two novel network‐coded single and multiple subcarrier assignment schemes are proposed to improve bandwidth utilization over the conventional single and multiple subcarrier assignment schemes. In general, the J‐PA‐SA problem is nonconvex and NP‐hard (i.e., excessively complex). To effectively solve it, it is decomposed into two subproblems: (1) power allocation per (user cluster, subcarrier) combination, and (2) subcarrier assignment. Solution procedures are proposed to solve the J‐PA‐SA problem for the conventional and network‐coded SA schemes. Simulation results revealed that the proposed solution procedures yield the optimal network sum‐rate solutions with low‐complexity, while satisfying the users' minimum rate requirement. Lastly, the network‐coded SA schemes are shown to significantly outperform to the conventional SA schemes for the NOMA and OMA networks.