Fast Handover Mechanism for High Data Rate Ground-to-Train Free-Space Optical Communication Transceiver for Internet Streaming Applications

Kosuke MORI  Masanori TERADA  Daisuke YAMAGUCHI  Kazuki NAKAMURA  Kunitake KANEKO  Fumio TERAOKA  Shinichiro HARUYAMA  

Publication
IEICE TRANSACTIONS on Communications   Vol.E99-B   No.5   pp.1206-1215
Publication Date: 2016/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2015EBP3326
Type of Manuscript: PAPER
Category: Terrestrial Wireless Communication/Broadcasting Technologies
Keyword: 
free-space optical communication,  ground-to-train communication,  fast handover,  

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Summary: 
There is a strong demand to enjoy broadband and stable Internet connectivity not only in office and the home but also in high-speed train. Several systems are providing high-speed train with Internet connectivity using various technologies such as leaky coaxial cable (LCX), Wi-Fi, and WiMAX. However, their actual throughputs are less than 2Mbps. We developed a free-space optical (FSO) communication transceiver called LaserTrainComm2014 that achieves the throughput of 1 Gbps between the ground and a train. LaserTrainComm2014 employs a high-speed image sensor for coarse tracking and a quadrant photo-diode (QPD) for accurate tracking. Since the image captured by the high-speed image sensor has several types of noise, image processing is necessary to detect the beacon light of the other LaserTrainComm2014. As a result of field experiments in a vehicle test course, LaserTrainComm2014 achieves handover time of 21 milliseconds (ms) in the link layer at the speed of 60km/h. Even if the network layer signaling takes time of 10 milliseconds, the total communication disruption time due to handover is short enough to provide passengers with Internet connectivity for live streaming Internet applications such as YouTube, Internet Radio, and Skype.