台灣高鐵無線通訊之通道量測與系統設計

Channel Measurements and System Design for Taiwan High Speed Rail Wireless Communication

陳昱超(Yu-Chau Chen)

指導教授 ： 李學智

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.03016

摘要

在本篇論文中，我們利用一正交分頻多工之通道量測系統在台灣高速鐵路的戶外與隧道環境下進行量測。此量測系統並非昂貴且笨重的通道探測機，而是由一般的實驗儀器組成，因此在量測訊號上可以依據量測目的而設計。通道特性包含通道頻率響應、角擴散、功率延遲擴散、都卜勒頻譜與傳播損失都是我們量測的重點，此外並針對高鐵車頂已有的兩支間隔14.5 公尺的天線進行分集增益的分析。由量測分析的結果，我們可以觀察出高鐵環境相當單純，其通道大部分都含有很強的直視波，且其傳播損失也很接近Friss formula 所計算出來的值。我們亦根據量測的結果來探討台灣高鐵上WiMAX基地台的佈建，並使用光載無線通信(RoF)技術來增加整個基地站涵蓋的範圍。此部分我們將量測結果配合台灣所使用的WiMAX 系統參數來模擬實際通訊傳輸時會產生的現象，並提出一個功率控制的機制來避免系統效能的降低。此模擬結果可做為未來台灣高鐵寬頻通訊系統建立的參考。
另一部份，我們將目前單一天線傳送單一天線的量測系統擴展到多輸入多輸出正交分平多工(MIMO-OFDM)的量測系統。目前台灣高鐵寬頻通訊系統在未來亦將採用多天線技術來提升通訊品質，此量測系統將會應用於未來的多天線通道量測。於現階段，我們會針對戶外的實際環境進行量測及數據分析。

關鍵字

通道量測 ； 正交分頻多工 ； 多輸入多輸出 ； 光載無線通信 ； 台灣高速鐵路

並列摘要

In this thesis we employed an OFDM-based channel sounder to measure the channel characteristics of Taiwan High Speed Rail (THSR) environment at the 2.5GHz band. This measurement system consists of general-purpose commercial equipments.
The OFDM signal format can be flexibly designed according to the requirement of channel measurement. The channel characteristics to be measured are the frequency responses, delay spread, angular spread, Doppler spectrum and propagation loss. We also study the diversity effect when two antennas are mounted on the rooftop but separated with a distance of 14.5m. From the measurement result, a strong line of sight (LOS) component is usually observed and the measured path loss is close to the prediction by the Friss formula. And we discuss the cell design for WiMAX system on
THSR based on link budget calculation. In order to extend the service range, the radio over fiber (RoF) technique is applied. The obtained channel characteristics are used in
the transmission simulation of the WiMAX-RoF system by channel emulator. From the simulation, we can figure out which part of the system needs the improvement for the
robust wireless communication. The simulation result can contribute to the THSR wireless communication system.
On the other hand, we establish a measurement system for MIMO-OFDM system. Since there are two antennas mounted on the rooftop with a separation of 14.5m, a study of improving the throughput performances by MIMO techniques may be needed in the future. This measurement system could be the basic study of the MIMO-OFDM measurement systems and used to verify algorithms designed for the OFDM systems.

並列關鍵字

OFDM ； THSR ； WiMAX ； MIMO ； RoF ； PDP ； Doppler Spectrum

參考文獻

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