Age of Information Minimization for Short-Packet Communications RSMA in Satellite-based IoT

This paper aims to minimize the age of information (AoI) of downlink rate-splitting multiple access (RSMA) in satellite-based Internet of Things (S-IoT) network over shadowed-Rician fading channels, where a satellite multicasts with multiple user equipments (UEs) by timely transmitting short-packet status updates. First, the expressions for block error rate (BLER) and average AoI (AAoI) are derived in a closed-form for short-packet communications with finite blocklength bound. Then, we formulate an AAoI minimization problem based on the theoretical derivations for the downlink RSMA S-IoT network, and design an age-optimal stationary power allocation (ASPA) scheme to solve the problem by utilizing the particle swarm optimization (PSO) algorithm. We further propose an age-optimal dynamic power allocation (ADPA) scheme based on the Markov decision process (MDP), and solve it by two deep reinforcement learning (DRL) algorithms. Monte Carlo simulations verify the accuracy of our derivations of BLER and AAoI, and also show that our ADPA scheme outperforms the related schemes.