Enhancing energy efficiency in MC-NOMA systems through optimized channel and power allocation

Abstract

Non-orthogonal multiple access (NOMA) has quickly become popular due to its higher spectral efficiency (SE) and is crucial in extending future networks’ capacity. This paper presents an innovative approach to enhancing energy efficiency (EE) in downlink (DL) multi-carrier (MC) NOMA systems, in which a single base station (BS) supports a group of users across multiple sub-channels. A novel least user sum gain-based user assignment (LUSGUA) algorithm is proposed in this paper, which prioritizes users with the lowest channel gains for optimal sub-carrier allocation. Additionally, a novel power allocation (PA) scheme is developed across sub-carriers to further improve energy efficiency (EE), throughput, and fairness. Since the PA optimization problem (OP) is constrained and non-convex, to tackle this problem, a penalty approach (PTA) is proposed, which is then addressed by particle swarm optimization (PSO) with sequential optimization of the inter/intra-level PA. Power is allocated across sub-carriers at the inter-level using PSO, while at the intra-level, power is distributed among users via the Bisection Method (BM). Simulation results demonstrate that the proposed algorithm achieves significant enhancements in EE, with improvements ranging from 13.04% to 48.67% compared to existing resource allocation (RA) schemes techniques, while also improving system throughput, fairness, and outage percentage. These results highlight substantial advancements over traditional methods.