CSI Feedback for Distributed MIMO

In this paper, we consider a distributed multi-input-multi-output (D-MIMO) system wherein multiple radio remote heads (RRHs) distributed in a cell are connected with a single baseband unit. To enable coherent joint transmission from multiple RRHs in the D-MIMO system, we propose several channel state information (CSI) codebooks as candidates for enhancements in the context of 3rd Generation Partnership Project (3GPP) 5G New Radio (NR) standardization. The proposed codebooks are developed based on the 5G Release-16 Type-II CSI codebook framework. In addition, we propose dynamic RRH selection (DRS) methods that are able to obtain performance gain and reduce the amount of feedback by sending the CSI only for the selected RRHs having dominant channel qualities. System-level simulation (SLS) results under realistic scenarios are provided to validate the potential of the proposed CSI codebooks and DRS methods.