In this paper the coverage of outdoor public WiFi hotspot and its radiation safety are studied through full-wave electromagnetic simulation. The simulation model includes both the WiFi antennas and the nearby building structures. In order to get a good balance between accuracy and computational efficiency, the simulation is based on the Method of Moments (MoM) with higher-order basis functions (HOBs), parallel computation and out-of-core technique. Good agreement is obtained between the simulation and localized measurement, and thus the effectiveness of the simulation approach is verified.