A number of approaches for capturing and processing location information of mobile users have been proposed in the past; however, only with the latest advances in the handset technology, a terminal-based positioning approach, using overlay SIP signaling on top of a packet switched bearer and area notification as basic functionality becomes feasible for mass applications. Especially in electronic commerce scenarios, in which users often interact with non-trusted services and shops, any location-based solution has to consider privacy aspects as well. The terminal-centric model presented in the paper leads to a simple and efficient way to achieve tunable privacy: mobile users define own "zones" and selectively disclose them to their buddies and to external services. As a result, localization can be performed only in the allowed places and by the allowed watchers, both parameters being configured by the user herself on her mobile terminal. We describe the system architecture, protocols and present representative technical scenarios.
A System for Locating Mobile Terminals with Tunable Privacy
