Experimental results on 4x4 MIMO precoding in E-UTRA

This paper presents experimental results on MIMO multiplexing and MIMO diversity using precoding for OFDMA radio access in the Evolved UTRA downlink. In the evaluations, we compare throughput performance of 4x4 MIMO with 1 to 4-stream transmission for various modulation and channel coding scheme (MCS) set to clarify the selection criteria for the number of streams on rank adaptation as the function of received E-s/N-0 and fading correlations between antennas. Based on the evaluations, we concluded that throughput is maximized by using 3 or 4-stream transmission at the almost all region of received E-s/N-0 excepting the low received E-g/N-0 region less than 2 dB. Furthermore, the optimum combinations of the number of streams and MCS are identical when the antenna correlation is lower than 0.7. However, the switching points of received quality (E-s/N-0) on the combinations of the number of streams and modulation scheme is shifted by 2 to 5 dB in case of fading correlation, rho = 0.5 and 4 to 8 dB in case of rho = 0.7 are compared to those in rho = 0.