Influence of Polarization on Keyhole Probability on a MIMO-OFDM Train-to-Wayside System on Tunnels

This letter presents a deep insight on a real implementation of a train-to-wayside broadband radio on subway tunnels that makes use of a 2 ×2 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 letter is to study in detail the influence of the polarization in the probability of having a keyhole on a MIMO-OFDM 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.