Multi-Modal Foundation Models for Space-Air-Ground Integrated 6G and Beyond Networks: A Survey and Tutorial

作者：Wali Ullah Khan, Muhammad Adil, Jahanzaib Malik, Chandan Kumar Sheemar, Symeon Chatzinotas, Salman A. AlQahtani, Khalid Yahya · 发表于：IEEE Open Journal of the Communications Society · 年份：2026 · DOI：10.1109/ojcoms.2026.3687570 · 被引用次数：1 · 研究领域：Advanced Wireless Communication Technologies、Satellite Communication Systems、Advanced MIMO Systems Optimization

Space-air-ground integrated networks (SAGINs) are emerging as a key architectural paradigm for 6G and beyond wireless systems, enabling seamless connectivity by integrating terrestrial radio access networks with aerial platforms and non-terrestrial networks (NTNs). The operation of SAGINs, however, departs significantly from conventional terrestrial assumptions due to high mobility, Doppler dynamics, intermittent connectivity, long and variable round-trip times, gateway bottlenecks, and strong cross-layer coupling. These characteristics motivate intelligence frameworks that leverage heterogeneous contextual information beyond traditional radio frequency (RF) measurements. This paper presents a comprehensive survey and tutorial on multi-modal foundation models (FMs) for SAGIN-centric 6G systems. The survey first introduces a structured taxonomy of SAGIN data modalities, including RF/channel state information (CSI), topology graphs, trajectories and ephemeris, telemetry and traffic traces, weather and atmospheric context, and sensing signals enabled by integrated sensing and communication (ISAC). It then reviews representation and tokenization strategies for heterogeneous wireless modalities and surveys emerging architecture families for multi-modal FMs, including early, late, and hybrid fusion designs, cross-attention mechanisms, mixture-of-experts models, hierarchical multi-timescale architectures, and retrieval-augmented frameworks. The paper further summarizes training para...