Radio propagation measurement of subway tunnel for CBTC systems

In order to design wireless communication systems for CBTC use in subways, radio propagation characteristics inside tunnels are important. This paper describes 2.5 GHz and 5.7 GHz propagation loss measurements using dipole and patch antennas in a 1200 m section of a newly constructed tunnel which included some slopes and curves. Line-of-sight between transmitter and receiver does not exist after 180 m and reflections from the wall surface are the main propagation mechanism. The attenuation constant of propagation loss in the non line-of-sight region ranges from 0.026 to 0.03 dB/m.