High-Speed Railway Antenna Systems: Propagation Environments, Integration Challenges, and Future Directions

Future high-speed railway systems rely heavily on secure and efficient wireless communication for train operation, passenger services, positioning, and safety-related functions. Antenna systems play a critical role in establishing these communication links; however, their design and implementation in high-speed rail environments present unique challenges compared to conventional vehicular and terrestrial platforms. Factors such as high mobility, large metallic train structures, aerodynamic constraints, harsh propagation conditions, and stringent reliability requirements impose significant demands on antenna integration and performance. This paper provides a comprehensive overview of antenna systems for high-speed railways from both engineering and deployment perspectives. Particular emphasis is placed on implementation challenges, including train-mounted and trackside antennas, with detailed discussion on practical integration aspects such as platform effects, radome design, electromagnetic compatibility, and maintenance. Key propagation scenarios in high-speed railway operations—such as open track, tunnels, viaducts, and stations—are analyzed in terms of their impact on antenna radiation behavior and overall system performance. Furthermore, state-of-the-art antenna designs are systematically classified based on radiation characteristics, frequency bands, and functional roles, ranging from omnidirectional and multi-antenna systems to dual-band and emerging high-frequency solutions. Beyond performance metrics, this review also examines validation methodologies, comparing simulation-based studies with real-world measurements from operational railway environments. Finally, future challenges and research directions are outlined in the context of next-generation railway communication standards and emerging technologies. Overall, this review aims to bridge the gap between theory and practice by providing practical insights for researchers and railway engineers involved in the design, integration, and deployment of antenna systems for high-speed railways.