Spatial Correlation and MIMO Capacity at 2.4 GHz

Multiple-Input Multiple-Output (MIMO) systems are commonly used methods in order meet the increasing capacity need in wireless communication systems. However, the channel capacity in the multi-antenna architecture depends not only on signal-to-noise ratio (SNR) but also the spatial correlation between antenna elements. Therefore, detailed information is required about the transmission medium during the system design. We used the ray tracing method for the radio propagation channel modelling during this study. In multi-antenna systems, measurements were made for 0.02λ receiving antenna spacing in a laboratory consisting of a full anechoic room, and the spatial correlation between far-field signals was observed. We also examined the impact of correlation on the channel capacity in a 2 x 2 MIMO system. The test results showed high level of correlation between received signals in cases where one and two beams were effective as reflections even though the distance between the antennas was bigger than the wavelength. Furthermore, we observed that the channel capacity increased as the correlation between sub-channels increased.