Millimeter wave directional channel modeling

A combination of extreme cell densification, more bandwidth, and higher spectral efficiency is needed to support the data traffic requirements for 5G cellular communications. In this paper, Kirchhoff approximation (KA) is integrated with a 3D ray-tracing (RT) algorithm to develop a directional channel model for urban millimeter-wave (mmW) small cells. We study the spatial correlation and coverage distance in line-of-sight (LOS), obstructed LOS (OLOS), and non-LOS (NLOS) scenarios. Using both the physical optics (PO) and geometric optics (GO) solutions, closed form expressions are derived for multiuser correlation of co-located receive antennas. Availability of LOS, carrier frequency, and surface roughness scale are all found to have a substantial impact on the diversity of spatial dimensions for signaling. It is found that using antenna arrays of moderate gain at both sides of the link, even under NLOS propagation condition, a typical urban cell size of 200m is achievable.