Fair performance comparison between CQI- and CSI-based MU-MIMO for the LTE downlink

We compare the performance of the downlink of a 3GPP UTRAN Long Term Evolution (LTE) system with multi-user (MU) multiple input multiple output (MIMO) support and channel state information (CSI) feedback to a standard MU-MIMO LTE system utilizing channel quality indicator (CQI) feedback only. For the latter case, we propose an efficient method for estimating the appropriate MU-MIMO transmission parameters based on the LTE Release 8 feedback, which is not providing any additional MU-MIMO feedback information. In order to facilitate a fair performance comparison, we spend approximately the same number of feedback bits for both feedback methods and we evaluate which method performs better in the considered scenario for various cases by means of extensive system-level simulations, assuming a low-rate feedback channel. It is shown that significant performance gains may be realized with both proposed feedback methods compared to conventional LTE Release 8 networks without MU-MIMO support.