Effectiveness of implicit beamforming using calibration technique in massive MIMO system

This paper describes the effectiveness of implicit beamforming which enables the transmission without the channel state information (CSI) feedback in massive MIMO system. First, we explain the CSI feedback scheme from the terminal stations to base station gives a very large overhead. The calibration technique, which compensate the difference of complex amplitudes between transmitters and receivers for the implicit beamforming, is next introduced. Finally, the throughput by the IEEE802.11ac based massive MIMO transmission with and without CSI feedback is clarified when considering Medium Access Control efficiency.