Performance Considerations on MIMO Spatial Multiplexing from the Viewpoint of Antennas and Propagation

MIMO channel characteristics and spatial multiplexing are investigated from the viewpoint of antennas and propagation in this paper. We conducted 4x4 MIMO channel measurement campaigns in an indoor propagation environment. Using the measured data, we examined the detail of the MIMO channels. The MIMO channels and eigenvalues are largely different for MIMO array orientations in an LOS environment. This is due to the effect of mutual coupling between antenna elements. Then, the bit error rate (BER) of eigenbeam space division multiplexing (E-SDM) in a quasi-static environment is examined using the measured MIMO channel data. It is shown that the BER performance in an LOS environment is affected by the mutual coupling. Furthermore, we obtained time-varying MIMO channel data, and calculated the channel auto-correlation and Doppler spectrum. The BER performance is evaluated for different maximum Doppler frequencies and different (LOS/NLOS) environments.