Analysis of outdoor propagation and multi-cell coverage from ray-based simulations in sub-6GHz and mmwave bands

This paper analyses the outdoor small-cell millimeter-wave (mmW) propagation using ray-based simulation tools. The main characteristics of the wireless channel, i.e. pathloss, delay and angular spreads, are characterized through various small-cell scenarios, and by comparison between several frequency bands. The 2.4 GHz and 5 GHz bands represent the traditional sub-6GHz frequencies in public radio-communication networks, while 28 GHz and 60 GHz stand for the mmW 5G candidate frequencies. A first analysis compares the downlink Signal-to-Noise Ratio (SNR) in an urban small-cell network, showing how severely the coverage beyond building or vegetation blockage is degraded at mmW. Then, the shadowing and channel scattering created by a small house is studied; the delay and angle spreads behind the house are divided by respectively 5.8 and 2.8 when going from 5 GHz to 60 GHz. Finally, the paper makes recommendations for representation of small objects, trees in particular, to achieve accurate channel or coverage simulations.