CSIT estimation and feedback for FDD multi-user massive MIMO systems

To fully utilize the spatial multiplexing gains or array gains of massive MIMO, the channel state information must be obtained at the transmitter side (CSIT). However, conventional CSIT estimation approaches are not suitable for FDD massive MIMO systems because of the overwhelming training and feedback overhead. In this paper, we consider multi-user massive MIMO systems and deploy the compressive sensing (CS) technique to reduce the training as well as the feedback overhead in the CSIT estimation. We propose a distributed compressive CSIT estimation and feedback scheme to exploit the hidden joint sparsity structure in the user channel matrices and we obtain simple insights into how the joint channel sparsity can be exploited to improve the CSIT recovery performance.