Influence of polarization on keyhole probability on a MIMO-OFDM train-to-wayside system on tunnels

This paper presents a deep insight on a real implementation of a train-to-wayside broadband radio on subway tunnels that makes use of a 2x2 MIMO-OFDM setup. A keyhole is a phenomenon that usually happens in tunnels and that seriously degrades channel?s capacity, even if both transmitter and receiver antennas are uncorrelated. The main purpose of this paper is to study in detail the influence of the polarization in the probability of having a keyhole on a MIMOOFDM train-to-wayside communication system on a tunnel. MIMO keyholes are studied in four different polarization setups, six different tunnels cross-sections and, finally, capacity results are provided