AoI-Aware Multi-User Downlink Transmission Scheme for LEO Satellite Systems

Due to the increasing demands of users for information freshness and constrained power resources of low-earth orbit (LEO) satellite, this paper proposes a multi-user downlink transmission scheme to achieve a trade-off between age of information (AoI) and transmit power for LEO satellite systems. To this end, a constrained optimization problem is first formulated to minimize the weighted sum of long-term average AoI and transmit power, subject to the constraints of the maximal time-averaged AoI, the limited number of scheduled users, and the transmit power budget. Then, with the help of the drift-plus-penalty minimization method, the long-term optimization problem is transformed into a single-slot problem, so that the complex problem is mathematically tractable. Moreover, an angular-based joint beamforming and multi-user scheduling strategy is proposed to address the optimization problem. Finally, simulations verify that the proposed transmission scheme can achieve a trade-off between AoI and transmit power compared to the benchmarks.