Realistic channel models with proper accuracy - complexity trade-off are indispensable for some typical 5G scenarios, such as massive MIMO channels and high-mobility channels (e.g., high-speed train channels and vehicle-tovehicle channels).
Conventional MIMO channel models cannot be directly applied to massive MIMO channels in which different antennas may observe different sets of clusters.
Massive MIMO channel models should take into account specific characteristics that make them different from those in conventional MIMO channels, such as the spherical wavefront assumption and non-stationary properties. Also, 3D massive MIMO models, which jointly consider azimuth and elevation angles, are more practical but more complicated.
Some existing massive MIMO channel models are briefly summarized and classified in Table 1