Polarization and Correlation in MIMO Channels

Inhalt:
This paper reports results of field measurements of MIMO propagation channels from a typical mobile base-station deployed for radio access service provision using LTE and NR air interface technologies. The purpose of the paper is to illustrate sample behaviour of cross-polarization discrimination (XPD) and radio link correlation coefficients that are considered important for assessment and modeling of MIMO systems. The measurements conducted in sample line-of-sight and non-line-of-sight conditions show that signals transmitted from antenna arrays with ±45 deg slants experience materially different propagation conditions resulting in an asymmetrical wideband XPD. Within the wideband channel, both XPD and link correlation coefficients experience a considerable frequency selectivity, potentially due to the differences in power delay profiles for transmissions in the orthogonal polarities. The net effect of the MIMO channel on spatial multiplexing capability is demonstrated using singular value decomposition of the channel, highlighting possible further research directions such as adoption of polarization-specific power delay profiles, and integration of arbitrary XPD and MIMO link correlation conditions in performance models.