Simulations are an essential tool for studying wireless networks, yet great care must be taken when choosing the simulation parameters, in order to have results reflecting what would happen in a real network. Thanks to extensive traces containing scan results collected by pedestrian users in an urban setting, we select the parameters of different NS-3 modules so that the results obtained match what we observed in a real setting, contrary to what happens if one uses the default values of these modules. We extend the NS-3 simulator in order to faithfully simulate the scanning phase and in order to dynamically change the IP address assigned to Mobile Stations. Finally, we use the simulation parameters that have produced realistic results to analyze what happens when the Access Point density changes.