Smart railway systems integrate advanced information technologies into operational frameworks to enhance efficiency, safety, and reliability. While the advent of fifth-generation (5G) networks has significantly improved railway services, future smart railways demand capabilities such as ultra-high speed, ultra-low latency, enhanced security, seamless coverage, and precise positioning—requirements that 5G alone cannot fully satisfy. Consequently, sixth-generation (6G) networks are envisioned to support green and efficient all-day operations, robust information security, fully autonomous driving, and cost-effective intelligent maintenance. To address these needs, we propose an integrated network architecture that combines communications, computing, edge intelligence, and caching within railway systems. Our study investigates key enabling technologies for reliable transmission and comprehensive wireless coverage. For high-speed mobility scenarios, we introduce an AI-enabled cross-domain channel modelling approach alongside an orthogonal time–frequency space–time spread multiple access mechanism, designed to mitigate the challenges of limited spectrum resources and massive user connectivity. Furthermore, we evaluate the roles of blockchain, edge intelligence, and privacy-preserving technologies in establishing intrinsically secure railway communications.
Beyond connectivity, we explore emerging paradigms such as integrated sensing and communications (ISAC), AI-assisted Internet of Things (IoT), semantic communications, and digital twin networks. These technologies hold promise for advancing railway maintenance, monitoring, predictive analytics, and accident prevention. Finally, we outline potential research directions to guide the evolution of next-generation smart railways, highlighting the critical role of AI-driven solutions in achieving resilient, intelligent, and sustainable railway operations.
