隧道環境的電波傳播通道模型

無線行動通訊的目標為提供使用者高品質、無中斷的通訊服務，無論所在的環境為何。隧道因其封閉、狹長的特性，成為一種特殊環境。近年來高速鐵路日漸發展為交通系統中的重要角色，對於隧道中通訊的需求與要求也因之提高。對於通訊系統設計而言，瞭解隧道環境中之電波傳播是一重要課題。在本篇論文中，我們討論了隧道中電波傳播之機制，並使用射線追蹤(Ray tracing)來分析在隧道中電波的直接波或多重路徑成份。考慮在不同型態隧道中的電波傳播，分別可以得到典型的通道參數如時間延遲及其擴散(spread)、發射到達角度及其擴散、衰弱、路程損耗。由於類似波導的效應，隧道中路程損耗之衰減指數小於空氣中福利斯傳輸方程式(Friis transmission equation)之衰減指數。然而在實際狀況中，鐵路軌道、纜線和變電箱等可能造成隧道上下表面的不平滑，隧道兩側也有作為逃生出口、維護的小月台而對電波產生捕捉效應，這些因素不利於隧道中之電波傳播。我們在新竹的高鐵隧道中進行了一次量測實驗。最後提出一指數模型來描述隧道中電波傳播之延遲分佈。

關鍵字

隧道；射線追蹤；電波傳播；通道模型

並列摘要

Tunnel is a special kind of communication environments. While high speed trains (HST) are being more popular in future, seamless communication in tunnel is thus required for commercial and entertainment needs. We investigate wave propagation in smooth tunnels which are constructed of simple plates geometrically. The ray tracing technique is applied to track all multipath components transmitted directly or through multiple reflections in the tunnel. Typical channel parameters such as time delay spread, angular spread, fading and path loss are obtained with different types of tunnels considered. The decay exponent of path loss is below 2 due to the guiding effects of tunnel structure. In spite of the behavior of guiding effects, real tunnels are not perfectly smooth because of cables, rails and platforms. We discuss these characteristics as well. A measurement was carried out in a tunnel located at the north of Hsin-Tsu City of Taiwan. An exponential model is used to model the power delay profile for wave propagation in tunnels.

並列關鍵字

tunnel ； ray tracing ； wave propagation ； channel model

參考文獻

[1] Zhi Sun and I. F. Akyildiz, “Channel Modeling of Wireless Networks in Tunnels”, in Proceedings of IEEE GLOBECOM 2008, p.p. 1 – 5, 2008.

[3] M. Lienard and P. Degauque, “Propagation in wide tunnels at 2 GHz: a statistical analysis,” IEEE Transactions on Vehicular Technology, Volume: 47, Issue: 4, p.p. 1322 – 1328, 1998.

[4] C. Zhang and Y. Mao, “Effects of Cross Section of Mine Tunnel on the Propagation Characteristics of UHF Radio Wsave,” in Proceedings of IEEE ISAPE '06, p.p. 1 – 5, 2006.

[5] Y. Yamaguchi, T. Abe, T. Sekiguchi and J. Chiba, “Attenuation Constants of UHF Radio Waves in Arched Tunnels,” IEEE Transactions on Microwave Theory and Techniques, Volume: 33, Issue: 8, p.p. 714 – 718, 1985.

[6] Y. P. Zhang and H.J. Hong, “Ray-optical Modeling of Simulcast Radio Propagation Channels in Tunnels,” IEEE Transactions on Vehicular Technology, Volume: 53, Issue: 6, Part 2, p.p. 1800 – 1808, 2004.

國際替代計量

隧道環境的電波傳播通道模型

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