Uplink Performance of Cell-Free Massive MIMO Over Spatially Correlated Rician Fading Channels

We consider a practical cell-free massive multiple-input-multiple-output (MIMO) system with multi-antenna access points (APs) and spatially correlated Rician fading channels. The significant phase-shift of the line-of-sight component induced by user equipment movement is modeled randomly. Furthermore, we investigate uplink spectral efficiency (SE) maximum ratio (MR)/local minimum mean squared error (L-MMSE) combining optimal large-scale decoding based on phase-aware MMSE, element-wise MMSE linear (LMMSE) estimators. Then new closed-form SE expressions MR are derived. Numerical results validate our derived show that benefits from spatial correlation. It important to observe performance gap between L-MMSE increases number antennas per AP LMMSE estimator lower than other estimators due lack phase-shifts knowledge.