Radio-over-Fiber Distributed Antenna System for WiMAX Bullet Train Field Trial

Wireless broadband access for mobile applications is an area of increasing growth. An international collaboration, led by the Taiwan Industrial Technology Research Institute (ITRI), has been working to implement a dedicated WiMAX network for a user field trial on the Taiwan High Speed Rail (THSR) bullet train system. Continuous wireless coverage at train speeds up to 300 km/hr is challenging due to a number of critical issues, including handover at high speeds and coverage in challenging terrain such as tunnels. A radio-over-fiber (RoF) distributed antenna system (DAS) was developed by Corning Incorporated to address the critical issue of handover and increase the coverage for each WiMAX basestation. For a DAS deployment consisting of multiple discrete antennas, proper signal strength management is required because the maximum delay spread allowed by the WiMAX protocol is easily surpassed at realistic fiber ranges up to 9 km. This paper reviews some of the initial results of the RoF DAS experiments in SongShan tunnel in Taipei. Error-free signal transmission was achieved when the difference in received power from two consecutive antennas was greater than 10 dB.