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WLAN propagation measurements in Railway tunnels. Case study: Madrid metro

In this work, we do an empirical approach to identify 802.11n technology Train to Ground communication specifics in underground applications from an industrial point of view. The equipment for the measurements was located aboard and along a track. The experiments consisted on measuring signal to noise ratio levels and beacon loss along a standard train cycle for physical layer performance assessment. Due to fading effects found, a break-even point should be found for Signal to Noise Ratio (SNR) Averaging level, crucial for fast handover in Dynamic Frequency Selection (DFS) environments.