Channel Model for Train to Train Communication using

Channel Model for Train to Train Communication using the 400 MHz Band Cristina Rico García, Andreas Lehner, Thomas Strang and Korbinian Frank cristina. ricogarcia@dlr. de, andreas. lehner@dlr. de, thomas. strang@dlr. de, korbinian. frank@dlr. de German Aerospace Center (DLR) A direct train to train communication is affected by the conditions of the railway environment. Research of the specific characteristics require a railway channel model, in particular: Fast fading. Doppler d. B Signal -Path Loss -Doppler -Fading -Delay Spread Slow fading Path loss: 10 n log 10(d) +C; n=2 -4 4, 8 m Free Space loss applicable the first d≤ 120 m (unobstructed first Fresnel zone). Distance m Train Station Scenario Shunting Yard Scenario Regional Network Scenario • Area smaller than 1 km 2. • Open areas, smaller than 1 km 2. • Covers areas larger than 1 km 2. • Formed by parallel „streets“ separated by platforms with or without roofs that may interfere the communication but that are situated either well above the antenna level or under it. Therefore, train stations allow line of sight. They are similar to wide avenues or parallel streets in urban areas • Grouping parallel rails and usually close to train stations and delimited by cuttings. Most of the structures in the shunting yards are metallic and under the train antenna level. Thus, line of sight is possible. • Narrow clean area ≥ 11, 6 m with curve radius down to 160 m that do not always allow line of sight. It might be surrounded by structures in both sides like tunnels, cuttings, and forest which may have a guiding effect. Bridges are not a source of shadowing since they are above the antenna level. Mountains may cause severe shadowing. • The maximum speed is typically between 25 km/h and 40 km/h. • The train speed is typically under 20 km/h. • Speeds up to 200 km/h are possible. Channel Model Path Loss: Kaji and Akeyama microcell model in wide avenues with low antenna levels applicable. Path Loss: Two ray model for microcells is applicable. Path Loss: Rural Hata-Okumura Model (Suburban in presence of mountains). In tunnels the attenuation is 15 -20 db/km plus 15 -20 db at the entrance and exit. Shadowing caused by narrow structures like bridges is negligible, in the order of 2 -5 d. B. Doppler: Speed < 20 km/h Maximum Doppler shift: Few Hz Doppler: Speed = 20 km/h - 40 km/h � Maximum Doppler shift: Few Hz Doppler: Speed < 200 km/h Maximum Doppler shift: 148 Hz Line of Sight Ricean Doppler spectrum (COST 207). Line of Sight Ricean Doppler spectrum. (COST 207). No Line of Sight is guaranteed Jakes Doppler spectrum. Fading: Line of Sight Rice fast fading channel. K = -1. 2 d. B Fading: No Line of Sight is guaranteed � Rayleigh fast fading. σ = 6 d. B Delay Spread: 1. 6 – 5 μs. Delay Spread: 9 μs Delay Spread: Open area: 0. 4 - 0. 6 μs Mountainous area: 20 μs. Institute of Communications and Navigations