Impact of Line-of-Sight and Unequal Spatial Correlation on Uplink MU-MIMO Systems

Closed-form approximations of the expected per-terminal signal-to-interference-plus-noise-ratio (SINR) and ergodic sum spectral efficiency of a multiuser multiple-input multiple-output system are presented. Our analysis assumes spatially correlated Ricean fading channels with maximum-ratio combining on the uplink. Unlike previous studies, our model accounts for the presence of unequal correlation matrices, unequal Rice factors, as well as unequal link gains to each terminal. The derived approximations lend themselves to useful insights, special cases and show the combined impact of line-of-sight (LoS) and correlated components. Numerical results show that while unequal correlation matrices enhance the system performance, the presence of strong LoS has an opposite effect. The approximations are general and remain insensitive to changes in the system dimensions, signal-to-noise-ratios, LoS levels, and correlation levels.