  High-speed railway is playing an important role in mass transportation, due
to its lower energy consumption, less environmental pollution, larger capacity
and higher safety features. The development of high-speed railway makes
people's life more and more convenient. Meanwhile, providing high quality of
service broadband communications for fast-moving users still remains unsolved,
despite the fact that new solutions of incremental improvements are keeping up
with this unprecedented communication requirement growth. This article proposes
a communication system infrastructure based on airborne relay for high-speed
trains in the further Cyber-Physical Systems. Comparisons and feasibility
analysis are provided as well as discussions of key wireless technologies and
obstacles in this system.
