Resource allocation for SWIPT-enabled energy-harvesting downlink/uplink clustered NOMA networks

In this paper, the problem of network sum-rate maximization in energy-harvesting clustered non-orthogonal multiple-access (NOMA) networks with simultaneous wireless information and power transfer (SWIPT) is considered. The aim is to maximize the network sum-rate in the downlink (DL) and uplink (UL) directions via joint subcarrier assignment, time-switching and power allocation (J-SA-TS-PA), while ensuring users' quality-of-service (QoS). Particularly, each user cluster is to be assigned a subcarrier for data transmission in both link directions. However, problem J-SA-TS-PA happens to be non-convex, and NP-hard, and thus is computationally-intensive. Alternatively, a near-optimal low-complexity iterative solution procedure is devised to solve problem J-SA-TS-PA by splitting it into two sub-problems: (1) joint time-switching and power allocation per (user cluster, subcarrier) pair, and (2) one-to-one subcarrier assignment. Simulation results are presented to evaluate the proposed solution procedure, which is shown to yield comparable network sum-rate to the J-SA-TS-PA scheme (solved via a global optimization package), and superior to its OMA-based counterpart, while satisfying QoS constraints in both link directions.