An Adaptive Power Allocation for NOMA-Based Multi-Layer Satellite System

Multilayer satellite networks (MLSNs) incorporating non-orthogonal multiple access (NOMA) offer a wide range of applications and enable seamless connectivity for various user demands. However, the effects of co-channel interference, complicated fading facts, and the dynamics of satellite networks limit further practical applications of NOMA in MLSNs. In this paper, we propose a NOMA-based MLSN system with an adaptive power allocation scheme. In order to accurately model the mobility of satellites, we derive a closed-form expression for the probability density function of the elevation angle observed by the terrestrial users for a low-Earth-orbit satellite, based on which detailed theoretical discussions are given about the statistical properties and channel capacities of satellite-terrestrial and inter-satellite links. Finally, we establish a novel adaptive power allocation scheme for the NOMA-based MLSNs to enhance user fairness by applying a particle swarm optimization (PSO) algorithm. The simulation results confirm the correctness of our theoretical results and the superiority of the adaptive power allocation scheme for user fairness of the NOMA-based dynamic MLSNs considered in this work.