Tracking mobile users in wireless communications networks

Tracking strategies for mobile wireless networks are studied, assuming a cellular architecture where base stations interconnected by a wired network communicate with mobile units via wireless links. The cost of utilizing the wireless links for the actual tracking of mobile users is investigated. A tracking strategy in which a subset of all base stations is selected and designated as reporting centers is proposed. Mobile users transmit update messages only upon entering cells of reporting centers, while every search for a mobile user is restricted to the vicinity of the reporting center to which the user last reported. It is shown that for an arbitrary topology of the cellular network (represented by the interference graph), finding an optimal set of reporting centers is an NP-complete problem. Optimal and near-optimal solutions for important special cases of the interference graph are given