A novel hierarchical channel state information measurement and feedback scheme in massive MIMO systems

Massive multiple-input-multiple-Output (Massive MIMO) is recognized as a promising technology to improve the system spectral efficiency by exploiting the massive degrees of freedom in spatial domain. However, in Massive MIMO systems, accurate channel state information (CSI) is required at transmitter, which corresponds to huge overhead of CSI measurement and feedback. In this paper, we propose a novel CSI measurement and feedback scheme to reduce the overhead in massive MIMO systems. Specifically, we propose a hierarchical CSI measurement and feedback scheme, which is comprised of two stages. At the first stage, partial CSI is measured and fed back to the transmitter. At the second stage, with the partial CSI, precoded CSI is measured and fed back. With the proposed scheme, the overhead of both CSI measurement and feedback can be significantly reduced. In addition, the analyses of CSI overhead and CSI distortion of the proposed scheme are also provided and verified by the numerical results.