A MU-MIMO CQI Estimation Method for MU-MIMO UEs in LTE Systems

This paper addresses a method to estimate the multi user channel quality indicator (CQI) from the reported rank 1 single user CQI in LTE systems. We investigate the relationship between the multi user CQI and the channel condition. Based on that, we propose an updating mechanism where the estimated multi user CQI is varied according to the reported channel condition i.e. the rank 1 single user CQI. System performance of the proposed scheme is compared with the conventional fixed offset single user CQI estimation. System level simulation results show the efficiency of our proposed scheme with respect to both the enhancement in the system level performance and uplink overhead reduction. Using the statistic metrics derived from the system level simulation, we highlight the importance of having an accurate multi-user CQI estimation. The results illustrate how the multi user CQI information influence the packet scheduling and link adaptation decisions and ultimately the overall system performance.