DVB-S Gap Fillers for Railway Tunnels

Broadband connectivity to passengers of high speed trains by means of a satellite link requires the realization of gap fillers (GFs) to extend the service coverage inside railway tunnels. In this paper we investigate the performance of GFs based on the digital video broadcasting-satellite (DVB-S) technology in a reference railway tunnel whose propagation characteristics have been derived by means of the ray tracing technique. The channel impulse response has been investigated in order to derive DVB-S performance in terms of bit error rate at different train position along the tunnel. Then, the statistical properties of the received power inside the tunnel has been assessed, showing a log-normal distribution with a strong correlation in time. Finally, based on the statistical behavior of the fading, an analytical expression of the system outage is provided and the transmitted power required to guarantee a given coverage has been derived.