Routing in Hierarchical Hybrid Satellite Networks: A Survey

With the deep evolution of satellite communication technologies and hierarchical hybrid networks (HHSNs), modern communication satellites have transformed from single-function relay nodes into core hubs enabling global interconnectivity. The dynamic topology, open-channel environment, and resource limitations inherent to HHSN expose satellite routing protocols to the challenges of the Reliability-Security-Efficiency (RSE) trilemma. In this paper, we provide a systematic review of advancements in HHSN routing research, analyzing core technical challenges through the lens of typical application scenarios while highlighting the divergent performance of various solutions under the RSE trilemma. To the best of our knowledge, we are the first to analyze the performance of HHSN routing protocols within the framework of the RSE theory. Existing reviews either treat routing merely as a component of broader surveys or lack analysis based on the RSE trilemma framework. Building on our review of HHSN routing protocols, we discuss the topology description and security aspects of HHSN and propose potential directions for future HHSN routing research.