Geofence Index: A Performance Estimator for the Reliability of Proactive Location-Based Services

An ever-increasing number of today's mobile applications take advantage of location-based services (LBS) in order to proactively notify mobile users about location-dependent content or to execute location-dependent actions once the user enters or leaves a dedicated zone. The proactive LBS are thereby responsible to track the user's position energy-efficiently in the background and to continuously match the position against a set of zones for which geo-triggered actions are defined, better known as geofences. Unfortunately, proactive LBS suffer from a highly erratic reliability. Sometimes, location-dependent actions are not triggered although a user entered a geofence while in other situations location-dependent actions are executed even though a user did not enter any geofence. The reasons are manifold, ranging from an imprecise positioning technique over a lack of cellular network coverage to an inadequate configuration. This paper discusses the technical and environmental factors that have an influence on the reliability of proactive LBS. To make the reliability predictable, it introduces an estimator for the probability that a location-dependent action - as defined for a given geofence - gets triggered by a proactive LBS in case a user crosses the respective geofence. As a proof-of-concept, a prototypical implementation of the estimator is presented together with the outcome of comparing the computed estimations against the real world experiences with an exemplary proactive LBS.