Interference Suppression Multiuser MMSE Multiplexing Combined with Optimal Joint Transmit/Receive Diversity for a Cellular Distributed MU-MIMO System

In a cellular distributed multiuser MIMO (MU- MIMO) system, inter-cluster interference suppression is a challenge because user-cluster-wise distributed MU-MIMO is performed using the same radio resources in all user-clusters in each cell. Recently, we proposed the interference suppression multiuser minimum mean square error (IS-MU-MMSE) multiplexing for the single-antenna users case. In this paper, we extend IS-MU-MIMO multiplexing to the multiple-antenna users case. As the number of antennas per user increases, each user can transmit multiple streams using eigenmode transmission, however, the number of distributed antennas required increases and the antenna degrees of freedom for inter- cluster interference suppression decreases. We propose the IS- MU-MMSE multiplexing combined with optimal joint transmit/receive diversity (JTRD), where the concept of a virtual single antenna user is introduced, the number of required minimum distributed antennas at the base station is reduced to equal to the number of users, and the remaining antenna degrees of freedom are used for inter-cluster interference suppression. Through computer simulations, we evaluate the uplink user capacity and confirm that, in a high user-density environment, IS-MU-MMSE multiplexing combined with optimal JTRD is superior to that combined with eigenmode transmission.