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Power allocation optimization for uplink non-orthogonal multiple access systems

Non-Orthogonal Multiple Access (NOMA) is a promising multiple access technique for 5G wireless communication networks due to its higher spectral efficiency and user fairness. Power allocation is the key to improve the performance of NOMA systems. In this paper, we focus on a certain NOMA group of a hybrid NOMA system. We formulate a sum-throughput maximization problem for uplink under the constraints of the total transmission power within a NOMA group and the minimum rate requirements of the users, which is a convex optimization problem. The closed-form solution of the optimal power allocation within a NOMA group is derived using the Karush-Kuhn-Tucker (KKT) conditions. According to the numerical results, the throughput performance of a certain NOMA group with our proposed power allocation scheme is much better than its OMA counterpart.