Achievable Rate Maximization in Active RIS-Assisted High-Speed Railway Terahertz Communication Systems

The terahertz (THz) band provides gigahertz-level bandwidth, demonstrating significant potential for achieving ultra-high-speed data transmission in 6G communications, while also facilitating numerous promising applications. However, in complex environments, the system faces the challenge of blocking the line of sight. The emergence of Reconfigurable Intelligent Surface (RIS) technology provides a novel optimization approach for THz communication systems by dynamically adjusting reflection properties to enhance signal propagation paths, thereby improving communication quality. In high-speed railway scenarios, the stringent demand for achievable communication rates becomes even more critical. This paper investigates rate maximization in active RIS-assisted THz communications for high-speed railway environments. To better reflect real-world conditions, we incorporate a device-to-device (D2D) communication pair into the system model, focusing solely on RIS-reflected paths. A power allocation optimization scheme is proposed. Finally, numerical simulations validate the performance of this scheme, demonstrating its effectiveness in achieving higher communication rates.