A comprehensive survey of Edge-Fog-Cloud-IoT architectures: Intelligence, Security, and Sustainability

Abstract

The rapid expansion of IoT devices has resulted in a paradigm shift from centralized cloud computing models to highly distributed computing continua that incorporate IoT devices, edge gateways, fog nodes, regional cloudlets, and hyperscale cloud data centers. In this survey, we provide an overview of Edge-Fog-Cloud-IoT architectural models and the technologies that have driven them during 2020–2026. In contrast to previous surveys that treat edge computing, security, artificial intelligence, and sustainable computing as independent topics, we present a holistic framework and a five-layer reference model that encompass the functional, performance, and trust aspects of distributed systems. The paper systematically discusses the state-of-the-art approaches related to AI-based resource management and task offloading (including deep reinforcement learning, multi-agent reinforcement learning, and federated learning), Zero Trust security architectures, privacy-preserving techniques, and sustainable computing solutions. Open research challenges are highlighted, and future directions are outlined, especially in light of advances in 6G communication systems, digital twins, and self-management and orchestration paradigms. Our survey follows the PRISMA methodology and analyzes 97 papers selected from IEEE Xplore, ACM Digital Library, SpringerLink, ScienceDirect, Wiley Online Library, and arXiv.