ABSTRACT
A growing number of mobile users demand seamless access to their services while they move across heterogeneous wireless infrastructures, spanning from IEEE 802.11 and Bluetooth to cellular 3G and beyond. Even if device and network capabilities are growing, the development of mobile locationbased services (LBS) applications over this fully integrated wireless provisioning infrastructure remains a very challenging task because of the ‘hard’ service requirements of quality of service (QoS) and high scalability. For instance, disaster recovery scenarios, such as earthquakes and natural disasters, require prompt and scalable retrieval of user location information about many citizens to be timely delivered with soft real-time QoS constraints to many different information systems (e.g., emergency response team systems, fi re fi ghters systems, etc.). In addition, high user mobility further stresses service requirements by producing frequent location update notifi cations, thereby forcing consideration of innovative solutions for scalable location data dissemination. In the last years, presence services (PSs), traditionally exploited to keep only the online status of users in the traditional wired Internet, are gaining the ambitious role of maintaining and disseminating the whole context of users/services in IP-based mobile networks, including location information (Shacham et al. 2007).
