Spatial and Temporal Channel Characteristics of 5G 3D Channel Model with Beamforming for User Mobility Investigations

High carrier frequencies are an integral part of the upcoming 5G mobile networks due to the available larger transmission bandwidths that offer high data rates and increase the quality of experience. To compensate for the high path loss at these frequencies, beamforming is applied, resulting in users connecting and switching between beams of the same or different cells. The current 3D channel models proposed for 5G are complex and have high computational complexity when used in user mobility investigations, which typically require long simulation time for collecting a statistically sufficient number of mobility events. From that perspective, simplified and computationally efficient channel models need to be developed that capture the relevant spatial and temporal correlations. Hence, the characteristics of the channel at these frequencies are investigated in this article for 28 GHz with respect to fast fading power envelope distribution, temporal variations, and spatial correlations among beams of the same cell. The investigations are carried out by simulating the 3GPP channel model defined in TR 38.901. Results reveal that for non-line-of-sight scenarios the beam signals follow, to some extent, similar statistical distribution and properties as conventional channel models (e.g., Jakes Doppler spectrum and Chi-square distribution for fast fading power envelope [1, 2]). Nevertheless, the distribution of the fast fading power envelope and autocorrelation function need to be adapted to consider the diversity gain resulting from multi-path and the increase in coherence time. The latter is caused by applying sectorization and beamforming that distort the uniform distribution of angle of arrival for the received ray, which may result in a reduced Doppler spread. Moreover, it has been shown that there is a spatial correlation between beams of the same cell, especially among those that are candidates for serving a user.