Refracting Reconfigurable Intelligent Surface Assisted URLLC for Millimeter Wave High-Speed Train Communication Coverage Enhancement

• Published in: IEEE transactions on vehicular technology Vol. 74; no. 1; pp. 953 - 967
• Main Authors: Liu, Changzhu, He, Ruisi, Niu, Yong, Mao, Shiwen, Ai, Bo, Chen, Ruifeng
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.01.2025; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Alternating optimization; Beamforming; Cellular communication; Communication; Constraints; Control systems; Data transmission; Decoupling; Design optimization; High speed rail; high-speed train (HST) communication; Industrial development; Information systems; Millimeter wave communication; Millimeter waves; millimeter-wave; MISO (control systems); Network latency; Optimization; Rail transportation; Railways; Reconfigurable intelligent surfaces; refracting RIS; Reliability; Simulation; Ultra reliable low latency communication; ultra-reliable and low-latency communications; Wireless communication; Wireless communication systems; Wireless networks
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2024.3457032

High-speed train (HST) has garnered significant attention from both academia and industry due to the rapid development of railways worldwide. Millimeter wave (mmWave) communication, known for its large bandwidth is an effective way to address performance bottlenecks in cellular network based HST wireless communication systems. However, mmWave signals suffer from significant path loss when traversing carriage, posing substantial challenges to cellular networks. To address this issue, reconfigurable intelligent surfaces (RIS) have gained considerable interest for its ability to enhance cell coverage by reflecting signals toward receiver. Ensuring communication reliability, a core performance indicators of ultra-reliable and low-latency communications (URLLC) in fifth-generation systems, is crucial for providing steady and reliable data transmissions along railways, particularly for delivering safety and control messages and monitoring HST signaling information. In this paper, we investigate a refracting RIS-assisted multi-user multiple-input single-output URLLC system in mmWave HST communications. We propose a sum rate maximization problem, subject to base station beamforming constraint, as well as refracting RIS discrete phase shifts and reliability constraints. To solve this optimization problem, we design a joint optimization algorithm based on alternating optimization method. This involves decoupling the original optimization problem into active beamforming design and packet error probability optimization subproblem, and discrete phase shift design subproblems. These subproblems are addressed exploiting Lagrangian dual method and the local search method, respectively. Simulation results demonstrate the fast convergence of the proposed algorithm and highlight the benefits of refracting RIS adoption for sum rate improvement in mmWave HST networks.