Age-Optimal Power Allocation Scheme for NOMA-based S-IoT Downlink Network

In this paper, we consider a non-orthogonal multiple access (NOMA)-based satellite-integrated internet of things (S-IoT) network, where a satellite transmits timely status updates to multiple user equipments (UEs). To keep the freshness of status updates in this network, we formulate an age of information (AoI) optimization problem subject to long/short-term power and throughput constraints. We leverage tools from Lyapunov optimization to transform the optimization problem into a sequence of online power allocation problems. Since the original optimization problem is non-convex and hard to find the optimal solution, we utilize the particle swarm optimization (PSO) algorithm to obtain an optimal solution within a linear computational complexity. Simulation results show that our proposed NOMA-AoI scheme outperforms the benchmark schemes with regard to AoI performance. Furthermore, we also discuss the impact of importance weight V on the AoI and power consumption and validate the tradeoff.