tes to the long-term propa- gation characteristic of the wireless channel and can be modeled as part of the large-scale propagation model. As for the small-scale fading model of a MIMO channel, the correlation of signals between antenna elements also needs to be considered and can be modeled by a spatial channel model that was used to evaluate performance of the previous generations of cellular standards. Although electromagnetic beam patterns generated by base station antenna arrays are 3D in nature, they were usually modeled as linear horizontal arrays, and elevation angles of signal paths have been ignored for simplicity. The 3D spatial channel models non-zero elevation angles associated with signal paths as well as azimuth angles SO that the small-scale fading effect on each antenna element of the 2D antenna grid and the correlation between any two pair of antenna elements on the 2D antenna grid can be modeled. New Radio Access Physical Layer Aspects (Part 1) 305 While the increase in average mutual information (capacity) of a MIMO channel with the number of antennas is well understood, it appears that the variance of the mutual informa- tion can grow very slowly or even shrink as the number of antennas increases. This phe- nomenon is referred to as channel hardening in the literature, which has certain implications for control and data transmission [31]. For a three-sector macrocell, the horizontal and vertical antenna patterns are commonly modeled with a 3 dB beam-width of 70 and 10 degrees, respectively, with an antenna gain of 17 dBi. The vertical antenna pattern is also a function of electrical and mechanical antenna downtilt, where the electrical downtilt is a result of vertical analog beamforming, generated by applying common and static phase shifts to each vertical array of 2D antenna elements. For instance, the electrical downtilt is set to 15 and 6 degrees for a macrocell deployment scenario with inter-site distance of 500 m and 1732 m, respectively, in 3GPP evaluation methodology [4]. In order to m