Location-aware services (LAS) adapt content and service execution to the users current physical location. In todays cellular networks, only reactive LASs are offered. The user has to explicitly request the service before the network determines her current location and starts service execution. However, in the future the user would like to see proactive LASs, which are automatically triggered as soon as she enters a pre-defined point of interest. In contrast to reactive LASs, this requires that the network performs a continuous user tracking, which entails expensive point-to-point signaling at the air interface.Full Text at Springer, may require registration or fee