FreeMobility: Dynamic Localization Using GIS

This paper presents the design, implementation and evaluation of the FreeMobility location determination system. FreeMobility is a distributed system that allows Access Points (AP) or cellular towers to dynamically determine the location of a mobile user using the received signal strength and the mobility information (the direction and traveled distance) from the mobile. FreeMobility does not require the database calibration nor does it require special infrastructure or installation, and it is readily applicable to commodity mobile devices like laptops, PDAs and cell phones. Using both actual measurements (from the University of South Carolina Beaufort and a residential neighborhood in Columbia, South Carolina) and online data resources (from the war-driving community and other research groups), this paper presents detailed analysis and experimental results that explore practical issues in implementing the FreeMobility system. The results demonstrated that FreeMobility provides reliable location estimates and the best localization error is to within 1.0 meter. With the assistance of the Geographic Information System (GIS), FreeMobility is able to provide meaningful location attributes in addition to basic coordinates from most other systems. Also with GIS, FreeMobility does not require dense tower deployment in order to pinpoint a mobile's location.