User Clustering and Power Allocation for Energy Efficiency Maximization in Downlink Non-Orthogonal Multiple Access Systems

Non-orthogonal multiple access (NOMA) has been considered a promising technique for the fifth generation (5G) mobile communication networks because of its high spectrum efficiency. In NOMA, by using successive interference cancellation (SIC) techniques at receivers, users with different channel gain can be multiplexed together in same subchannel concurrent transmission spectrum. The simultaneously achieves system throughput NOMA. However, it also leads to more energy consumption, limiting application many energy-constrained scenarios. As result, enhancement efficiency becomes critical issue NOMA systems. This paper focuses on efficient user clustering strategy and power allocation design downlink maximization systems is formulated as an NP-hard optimization problem under maximum power, minimum data rate requirement, SIC requirement. For approximate solution much lower complexity, we first exploit quick suboptimal method assign each subchannel. Given optimal solved two steps. By employing Lagrangian multiplier Karush–Kuhn–Tucker optimality conditions, calculated addition, then, inter-cluster dynamic programming model further developed achieve overall theoretical analysis simulations show that proposed schemes significant compared existing methods.