Investigating the overestimation of base station exposure in urban environments due to assumption of free space propagation

Safety assessment of exposure caused by cellular base stations based on calculation methods is often performed using free space propagation in order to include the worst case. For prospective technologies (e.g. small cells in the vicinity of people), this approach might lead to a high exploitation of exposure limits. This paper investigates the overestimation of downlink exposure being predicted with a free space propagation model in comparison to a deterministic 2D knife edge diffraction model in an exemplary urban environment for a rooftop mounted base station. The results show that overestimation is quite low in the vicinity of the base station, particularly in LOS regions. In a distance between 100 and 200 m the overestimation is constantly rising, whereas for distances larger than 200 m it stays nearly constant.