Spatial dispersion and performance evaluation of indoor MIMO channels at 2.25 GHz†

Channel capacity of a MIMO system is dependent not only on the signal-to-noise ratio (SNR) but also on spatial correlation among antenna elements. Therefore, the system design must rely on good propagation predictions. By using a ray tracing simulator, which considers reflections, penetrations and diffractions in 3-D space, we predict channel properties and evaluate capacity of 4× 4 indoor MIMO channels for both line-of-sight (LOS) and non-line-of-sight (NLOS) cases. Before extensive simulations, the predictions of the simulator are verified by comparing results of wideband channel measurement and simulation. The comparison shows that path loss and RMS delay spread can be well predicted by simulation. Based on simulated results, we investigate the spatial dispersion of the channel and its impact on channel capacity. Data analysis shows that spatial dispersion can be better characterized by using both the azimuth spread and elevation spread than by only one of them. Moreover, the reduced capacity in the NLOS region due to lower signalto-noise can be partially compensated by an increase in capacity due to lower signal correlation.