In typical urban wireless channels with large delay spreads, the conventional TDoA (Time Difference of Arrival)-based mobile-WiMAX (Worldwide Interoperability for Microwave Access) positioning systems hardly satisfy the FCC (Federal Communications Commission)'s E-911 (Enhanced-911) detection criteria. In this paper, we propose a simple yet very effective TDoA-based position tracking algorithm for mobile-WiMAX systems when the user moves into GPS (Global Positioning System)-shadowed areas such as indoors or dense urban environments.