The global deployment of high-speed railway (HSR) systems has revealed significant limitations in current 5G-Railway (5G-R) technologies, particularly under high-mobility conditions. This survey presents a systematic examination of how sixth-generation (6G) wireless technologies can transform HSR communications. The study analyzes eight interconnected domains: (1) architectural evolution from 5G-R to 6G-R systems, (2) advanced channel modeling for diverse HSR environments, (3) antenna designs for high-speed scenarios, (4) robust waveform development, (5) multidimensional network architectures, (6) AI-driven optimization, (7) IoT-enabled monitoring systems, and (8) high-capacity optical solutions. Drawing from extensive experimental studies and commercial trials, we demonstrate that 6G-R systems fundamentally differ through three paradigm shifts: the integration of communication and sensing functions, native AI implementation for operational efficiency, and hybrid satellite-terrestrial connectivity. The paper further identifies critical research challenges in deploying these technologies for next-generation intelligent railways.
Ai et al. (Mon,) studied this question.