Field trial results for integrated WiMAX and radio-over-fiber systems on high speed rail

As high speed rails become more and more popular, providing broadband Internet access on high speed rails is not widespread due to the large inter-carrier interference, terrestrial obstacles and inherent carriage shielding. In this paper an integrated Worldwide Interoperability for Microwave Access-Radio over Fiber (WiMAX-RoF) system is proposed and deployed along Taiwan High Speed Rail (THSR) rail tracks. Field trial and laboratory experiment results are presented. According to the field trial results, excessive delay induced by unequal fiber length deteriorates the throughput performance and can be overcome by equalizing the fiber length. On the other hand, rate adaptation for maximum throughput is challenging at high mobility. Careful calibration is needed to tradeoff the throughput gain against robustness to signal fluctuations. Laboratory experiments distinguish the impact of echo channel and remote antenna unit (RAU) distance from others. The results give insights in the analysis of field trial results.