Distributed antenna system (DAS) has been introduced to overcome high mobility issues and to extend signals into coverage-hole areas in high-speed rail communications system. In this paper, we discuss echo channel effect and define the corresponding criteria in a time division duplexing (TDD) DAS railway communications system. Furthermore, timing drift problem while applying moving antenna selection technique to solve the echo channel effect is illustrated. Compensation algorithms then are proposed. Simulation results show that the proposed techniques can not only solve the interference problem in TDD-DAS but also provide better scalability in system deployment.
- Railway communications
- distributed antenna system (DAS)
- high-speed rail (HSR) communications
- radio over fiber (RoF)