Propagation statistic characteristic of 3D MIMO channel in outdoor-to-indoor scenario with different antenna heights

Three-dimensional multiple-input multiple-output (3D MIMO) is one of the most promising techniques for the fifth-generation (5G) mobile communication systems. In order to catch the the propagation characteristics of the 3D channel, extensive measurements have been carried out. Although outdoor to indoor (O2I) scenarios is one of the main propagation of 3D MIMO channel, it remains too much work to do. In this paper, we present the results of the 3D MIMO measurement in urban micro-cellular (UMi) O2I scenario at 6 GHz with bandwidth of 100 MHz. The antenna height is a key factor which can significantly effect the characteristic of 3D MIMO channel. Thus, the measurement is focused on the different heights of receiving antenna. The 3D MIMO channel impulse response (CIR) at different antenna heights is extracted from measured data in UMi O2I scenario. Also, delay spread (DS) and angular spread (AS) are calculated using space-alternating generalized expectation-maximization (SAGE) algorithm. We compare the DS, AS and channel capacity both in the line of sight (LoS) and non-line of sight (NLoS) cases by taking the antenna heights into consideration. There is a tendency that the DS of LoS area show bigger dispersion when the receiving ends are near the base station in vertical direction while the NLoS on the contrary. After that, the elevation and azimuth AS are provided to reveal the relation between AS and antenna heights. Also, the reflecting path is observed at time and spatial domain from our results. Finally, the channel capacity of the LoS and NLoS cases are displayed at different floors. It is found that the tendency which channel capacity turn out to be is in accord with other analyzed parameters and it shows that the closer to the base station, the lower channel capacity.