AoI-Aware Uplink CR-NOMA Schemes in Satellite Internet of Things Networks

This paper investigates uplink transmission in satellite Internet of Things (IoTs) networks, where a low earth orbit satellite having a uniform planar array provides services simultaneously for an earth station (ES) and multiple IoT devices (IoTDs). Specifically, we use the statistical channel state information and propose two age of information (AoI)-aware uplink access schemes, namely sleep threshold-based access (STA) and forcing update threshold-based access (FUTA), so that many IoTDs can share the same channel with the ES through cognitive-radio inspired non-orthogonal multiple access (CR-NOMA) technology. By assuming that the satellite channels obey \kappa - \mu shadowed distribution, we exploit the discrete-time Markov chain model and derive the average AoI closed-form expression to assess the information freshness of the proposed schemes. Simulation results are given to confirm the correctness of the theoretical analysis and the superiority of the schemes we have proposed. Moreover, it is shown that compared with STA scheme, the FUTA can achieve better average AoI performance, and exhibits robustness against fluctuations in the transmission probability of IoTDs, enabling it to consistently maintain a lower average AoI.