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

TL;DR

This paper derives closed-form approximations for uplink MU-MIMO systems considering spatially correlated Ricean fading with unequal correlation matrices, LoS components, and link gains, providing insights into their combined effects on spectral efficiency.

Contribution

It introduces a novel analytical model that accounts for unequal correlation matrices and LoS components, extending previous work on MU-MIMO system performance analysis.

Findings

Unequal correlation matrices improve SINR and spectral efficiency.

Strong LoS components decrease spectral efficiency.

Approximations are robust across system parameters.

Abstract

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 demonstrate the aggregate impact of line-of-sight (LoS) and unequal correlation matrices. Numerical results show that while unequal correlation matrices enhance the expected SINR and ergodic sum spectral efficiency, the presence of strong LoS has an opposite effect. Our approximations are general and remain insensitive to changes in the system dimensions, signal-to-noise-ratios, LoS levels and unequal correlation levels.