ROME: Road monitoring and alert system through Geocache

We present a road monitoring and alert system implemented using a novel Geocache concept to enable efficient spatial monitoring in a mobile distributed sensing scenario. Technology trends have led to the integration of positioning, communications, and sensing capabilities into mobile entities such as cars and cellular phones, enabling them to monitor and report on their surroundings. We consider scenarios where events of interest must be detected from aggregated readings of multiple devices. For example, road monitoring could infer road defects from increased vibrations or road hazards from repeated emergency braking at the same location. This raises the challenge of aggregating sensor data from multiple mobiles that have passed the same location with efficient usage of communication resources. We introduce the Geocache concept, which allows anchoring sensor information at specific spatial coordinates, rather than storing it in a designated node. The Geocache protocol in either its relayed or delayed variant will then opportunistically determine a storage vehicle near the Geocache and hand the data off as vehicles pass by. We show through simulations with synthetic and realistic automotive position traces that relayed Geocache reduce messaging overhead by 66% compared to a baseline periodic broadcasting scheme and a Boomerang Geocache can provide a further 71% reduction when only few of the passing cars are able to sense the event.