MU-MIMO system performance analysis in LTE evolution

It has been recognized that a primary method of further enhancing the spectral efficiency of LTE Release-8 is to improve support for multi-user (MU) MIMO transmission in the downlink in an efficient manner. This paper investigates the performance improvements due to the enhanced support of single-cell MU-MIMO within the framework of LTE evolution (specifically LTE Release-9 and Release-10 also known as LTE-Advanced) considering a 4Tx-2Rx system. A realistic estimate of achievable MU-MIMO full-buffer throughput performance is provided with respect to variations in the propagation environment, feedback accuracy, antenna polarizations, antenna calibration as well as receiver type. It is observed that a closely spaced uniform linear array (ULA) at the base station and interference rejection capability at the mobile is essential to maximize MU-MIMO gains. Further, channel reciprocity based spatial channel feedback in a TDD scenario can provide significantly higher MU-MIMO throughput compared to codebook based feedback.