Analysis of CQI prediction for MU-MIMO in LTE Systems

The aim of this paper is to get an insight of multiuser multiple-input and multiple-output (MU-MIMO) channel quality indicator (CQI) prediction for long term evolution (LTE) systems. MU-MIMO CQI predictions have been investigated for LTE Release 8 (rank one, Transmission Mode 5) and for LTE Release 9 (adaptive rank, Transmission Mode 8) at the link level. The relationship between CQI reporting and channel conditions is analytically analysed and demonstrated. The tradeoff between the performance gain and the feedback overhead w.r.t. MU-MIMO CQI prediction is investigated as well. The results have shown how MU-MIMO CQI prediction is influenced by channel correlation and that significant improvements can be achieved through rank adaption and receiver choice. The results have also shown the potentially most efficient system configuration (feedback design and CQI prediction scheme) to facilitate MU-MIMO transmission for practical LTE systems.