Page 157 - 捷運技術 第35期

捷運技術半年刊 第 35 期 95 年 8 月 149

新一代數位無線電系統在臺北捷運之應用

王肇興

摘 要

既有台北捷運無線電系統為一雙向、調頻、UHF 頻段、中央控制式傳統無線電系統，提
供捷運路網控制中心與列車或攜帶手機之捷運人員通訊，傳統無線電系統基本上會碰到幾個
問題：頻道容易阻塞而沒效率、一個頻道故障時功能即受影響、沒有私密性等等。目前無線
電系統之發展已邁向數位式無線電系統，數位式無線電系統訊號品質更佳，無上述之缺點，
可同時傳輸接收語音及數據訊號，可加密使有保密功能，更能彈性運用。所以臺北捷運系統
開始全面轉換為 TETRA 數位無線電系統。

本文章主要介紹 TETRA 數位無線電系統，TETRA 為歐洲電信標準協會（ETSI）於 1990
年開始發展訂定之標準，現在除歐洲外已廣為世界各國所用。TETRA 數位無線電系統採分時
多工擷取之方式，頻寬為 25 KHz，單一頻寬可有四個通訊頻道，每一個通訊頻道可自由傳輸
語音或數據資訊，每一通訊頻道之傳輸最高可達 7.2 Kbits/sec，TETRA 系統調變採 Pi/4 QPSK
方式，編碼採 ACELP 方式。臺北捷運自新莊、蘆洲線開始無線電系統即以 TETRA 數位無線
電系統規設，並全面更新既有營運路線之傳統式無線電系統。

關鍵詞：調頻、分時多工、調變

The Current Trend of the Digital Radio System

on the Taipei MRT

Tsao-Sing Wang

The existing radio system for the Taipei Rapid Transit System is a traditional two-way,
frequency modulated, UHF, and centrally controlled radio system. The system permits central
control to communicate with trains and hand-held radios via a half-duplex operation in the Transit
Network. Basically, the traditional radio system has some problems: the audio channels are easy to
block and are not efficient; functionality will be affected when any one channel fails; it is also easy
to listen to so it is not secure and so on. Radio systems are moving towards the use of digital
systems in recent times. Digital radio systems have better signal quality, none of the above
shortcomings, are capable of transmitting both audio and data signals, are encryption capable and
have elasticity of demand. Because of these benefits, the Taipei Rapid Transit System radio system
is being updated to the TETRA radio system.
The purpose of this article is to introduce the TETRA digital radio system. TETRA is a
standard from the European Telecommunications Standards Institute（ETSI）since 1990. In addition
to Europe, this system standard has been widely used all around the world. The TETRA radio
system adopts time division multiple access, 25 kHz carrier spacing, 4 communication channels per
25 kHz carrier, and voice or data can be transmitted freely by any one channel. The maximum bit
rate for each channel can reach 7.2 Kbits/sec. The modulation for the TETRA system adopts Pi/4
QPSK, encoded by ACELP. The radio system for the Taipei Rapid Transit System will be TETRA
digital radio system beginning with the Hsinchuang and Luchou lines, and the old traditional radio
system will be changed and updated.

Key Words：frequency modulated, time division multiple access, modulation

臺北市政府捷運工程局，副工程司，電子郵件：10886@trts.dorts.gov.tw