Wide range wireless
networks often suffer from annoying service deterioration due to ever-changing wireless
environment. This is especially the case with passengers on long distance train
(LDT, such as inter-city, inter-provincial and international commuter trains)
to connect onto the Internet. To improve the service quality of wide area
wireless networks, we present the DragonNet system and protocol with practical
implementations. The DragonNet system is a chained gateway which consists of a
group of interlinked DragonNet routers running DragonNet protocol for node
failure amortization across the long stretching router chain. The protocol
makes use of the spatial diversity of wireless signals that not all spots on a
surface see the same level of radio frequency radiation. In the case of a LDT
of around 500 meters, it is highly possible that some of the routers in the
gateway chain still see sound signal quality, when the LDT is partially blocked
from wireless Internet. DragonNet protocol fully utilizes this feature to
amortize single point router failure over the whole router chain by
intelligently rerouting traffic on failed ones to sound ones. We have
implemented the DragonNet system and tested it in real railways over a period
of three months. Our results have pinpointed two fundamental contributions of
DragonNet protocol
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