| Summary: | 博士 === 國立交通大學 === 電信工程研究所 === 103 === It has attracted much attention to provide broadband wireless services in railway transport systems in recent years. In this dissertation, we aim to analyze and overcome some issues in railway communication systems, including train-to-ground communications, in-train communications and in-station communications.
For the train-to-ground communications, we discuss echo channel effect and define the corresponding criteria in a Time Division Duplexing (TDD) DAS railway com-munications system. Furthermore, timing drift problem while applying moving an-tenna selection technique to solve the echo channel effect is illustrated. Compensation algorithms then are proposed. Simulation results show that the proposed techniques can solve not only the interference problem in TDD-DAS, but also provide better scalability in system deployment.
In the in-train and in-station communications, we consider a central-controlled D2D architecture, in which a cellular operator can decide whether mobile devices can connect to each other directly. We aim to maximize system throughput while also achieve fairness in resource allocation. An algorithm that separates resource frame into resource-dedicate area and resource-contention area for fairness and throughput improvement is proposed. The algorithm dynamically adjusts the boundary of the resource-dedicate area and resource-contention area. Criteria based on Proportional Fair (PF) metric are formulated. Simulation results show that the proposed algorithm can maintain good fairness level and increase system throughput by exploring radio resource spatial reuse gain among D2D communication pairs.
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