Optimizing Information Freshness in Satellite-UAV IoRT Networks: A Heterogeneous Multi-Agent Approach
In satellite-UAV assisted communication networks, jointly optimizing the UAV’s trajectory and the multi-agent scheduling decisions to minimize the age of information (AoI) is a notoriously challenging problem. The complexity is compounded by the fundamental heterogeneity between the satellite and UAV agents, including their disparate action spaces, partial observations, and differing energy-consumption and communication-cost penalties. To address this, we formulate the problem as a decentralized partially observable Markov decision process (Dec-POMDP) and propose a novel heterogeneous multi-agent compound-action proximal policy optimization (HMACPPO) algorithm. HMACPPO leverages a centralized training with decentralized execution (CTDE) framework, using role-specific decentralized actors together with agent-specific centralized critics conditioned on the global state. Specifically, the UAV employs a compound PPO (CPPO) actor for its hybrid action space, while the satellite uses a PPO actor for discrete scheduling. Extensive simulations show that HMACPPO outperforms the compared baselines, and that the resulting coordinated policy effectively manages the trade-off between AoI, UAV energy consumption, and operational cost.