Performance of MIMO spatial multiplexing in indoor line-of-sight environments

Spatial multiplexing in a MIMO system can achieve high speed transmission in i.i.d. Rayleigh channels. However, actual communications can be conducted in LOS environments where we have higher received signal power, whereas channels may be correlated. Although many MIMO measurement campaigns have been conducted so far, conventional investigations are not considered to be sufficient from wireless engineering viewpoint. In this paper, we examine bit error rate (BER) of spatial multiplexing as a function of total transmit power in indoor LOS environments. This: consideration is done using 4 x 4 MIMO channel measurements. We compare the BER performance with the one in NLOS environments. Then, we investigate also the BER performance for a case where the channel state information is available also at a transmitter. It has been shown that the BER performance is generally better in the LOS environments than in the NLOS ones despite higher fading correlations, and that the performance in the LOS environments tends to change largely depending on a MIMO system configuration. We have also considered the effect of mutual coupling in antennas to the performance, and relations between eigenvalue distributions and the performance.