Multiple-Input-Multiple-Output (MIMO) systems are being used in the majority of communication systems because of the capacity advantages that they provide. The correlation value between signals is a parameter that should be carefully considered while planning multi-antenna systems. In this paper, we emphasize the correlation between antenna elements in a multi-antenna system which has the minimum interelement spacing of 0.02 lambda. The spatial correlation value is studied with simulation and measurements while the transmission channel is modeled with optical ray-tracing method. Based on our simulation and measurement results, we demonstrate that even when the distance between antennas are larger than lambda, high spatial correlation can be obtained between signals in indoor propagation environments, when a few optical ray components are effective.