Cell-Free Massive MIMO with Imperfect Channel State Information and Hardware Impairments

Cell-Free massive MIMO (CF-mMIMO) systems are an exciting technology to meet the increasing need for faster data rates in 6G and beyond networks. Instead of traditional cell-based structures, these systems rely on multiple distributed access points working together to communicate with users using coherent transmission. However, deploying these large networks cost-effectively requires affordable transceivers. Yet, these budget-friendly devices can be prone to hardware imperfections and errors in estimating channel state information. Therefore, before implementing CF-mMIMO systems, it's crucial to conduct realistic evaluations that consider these factors. In this paper, we investigate the efficiency of linear precoding strategies in CF-mMIMO systems. By leveraging Gaussian random noise with diverse error variances, we emulate the presence of channel estimation error and gauge the robustness of precoding schemes against hardware impairments induced by power amplifiers. Intriguingly, the numerical results reveal the significant impact of these factors on the spectral efficiency of CF-mMIMO systems.