Measurements and performance of large MIMO systems at 2.4 GHz for indoor WLAN

Large MIMO is a new and promising technique for boosting wireless link capacity. Currently, the research of large MIMO focuses on the theoretical aspects while work on the practical implementations and analysis are very limited. In this paper, we present some critical investigations on the behaviors of large MIMO in real propagation environment based on extensive channel measurements. On the one hand, our analysis has verified the advantages that the MIMO channel vectors between users tend to be orthogonal and the optimal capacity approximates the theoretical upper bound as the antenna array size grows. On the other hand, we observe that the practical limitations of allowable antenna array size and achievable spatial degrees of freedom in the physical channel have significant impacts. Furthermore, in order to enable the utilization of linear precoding techniques in such high-dimensional MIMO systems to achieve close-to-optimal capacity, a large ratio between the antenna array size of the large MIMO system and the number of simultaneously served users should be maintained.