In this lesson, we discuss an experiment we conducted on our engineering building for the feasibility of using WiFi system for location verification. We investigated how to utilize our campus WiFi system as a third party trustworthy location verification system. A secure web app was written to retrieve the signal records for specific users from the campus WiFi system. The document distribution server can request this signal record from a particular user by presenting the proper credential. This is changing privacy preserving research topics, in terms of how to specify and impose the security and privacy policies. Possible services including a secure 911, where the policy and EMS person are trying to locate a specific user may be in danger. We assumed a mobile user has a registered account with the campus and their mac address show up in the signal record kept up by the campus system. We use a WiFi system in our engineering building to conduct the location by location experiments. Here is the floor map and the location of the install WiFi base stations. In this experiments, by walking around the building with a android laptop, we collected all the WiFi signal from all the installed base station that can be observed. With a campus ID system, we obtained the laptop signal the observed from the base stations. We verify if the connected access point matching those reported and configure in campus WiFi system. We also analyze the access point reported at different locations throughout the building and report the maximum and minimum number of access point reports throughout the building. Here are our finding in this WiFi signal experiments. First, the average signal difference is about 5.90 dBm. Second, the maximum number of the surrounding API discover is 12. The minimum number of the surrounding access point discover is seven. The location resolution is about five meter. Consider that as an arrow margin, not very good. Possible, this is possible due to the multiple pairs of wireless signal interference. It bounced back around the wall and the surrounding. We also find the time needed to for the campus WiFi system to update the user's information is along two minutes, that should be improved. Apple prevents apps from getting a list or WiFi access point around a users. This hinder is usage in location verification application, because we'll find as many information as possible. We have send a request to Apple to see if we can be granted with more privilege so that we can open the API to receive more base stations signal. The request for the experiment was denied because they are very concerned about the privacy of the user. With a high location resolution and arrow, the WiFi system can only help pinpoint which side of the building is a east wing or west wing, which part of the hallway within the wing, first floor and second floor, but not precise enough in terms of determining which room all the present device inside the room or outside room, inside the room outside the window of the room. We need different techniques or technologies for this. See you in the next lesson.
