ABSTRACT
As people increasingly use location-aware devices for various applications including wayfi nding (Arikawa et al., 2007; Navitime, 2009) and safetyenhancement (Enhanced 911, 2009), there is a tangible need for better infrastructural support of location-based services. Localization has been and is one of the most prominent areas of ubiquitous networking research. Early location systems (e.g., the Active Badge Location System [Want et al., 1992]) were built to allow people in closed experimental environments to access location-relevant information and services, and, since then, there has been a great increase in the number of global positioning system (GPS)-enabled devices, including location-aware mobile phones, in our everyday environments. Today, location-based services can be deployed on these devices to support various activities in everyday life.
