An Experimental Study of MIMO Performance Using Leaky Coaxial Cables in a Tunnel

This letter presents a 2 × 2 multiple-input-multiple-output (MIMO) measurement campaign using leaky coaxial cables (LCXs) in tunnel environment at 1.8 GHz according to the LTE-M standard. Emphasis is given to understand the effect of polarization and LCX spacing on the condition number and capacity of the radio MIMO channel in the tunnel. The analysis of the measured results reveals two important findings: the MIMO system using LCXs in the tunnel has a favorable performance, especially in the case of LCX cross polarization; the MIMO performance is not highly dependent on the LCX spacing. Therefore, it is believed that these results provide a prospective guidance for employing MIMO technology in tunnels.