Lasso: A device-to-device group monitoring service for smart cities

Many smart city applications involve groups of individuals that wish to remain together as they move throughout the city. For example, a group of tourists may be monitored by a tour operator to keep the group together and on schedule. Alternatively, a group of elementary school children in transit to school should be closely supervised by an adult to ensure the children stay safe. This paper presents \lasso, a smartphone-based service that exploits wireless devices carried by each group member to provide infrastructure-free group formation and monitoring. We show how smartphones equipped with Bluetooth Low Energy (BLE) can be used as personal beacons in a device-to-device group monitoring protocol to allow each user to join a group and see a distributed view of group membership in real time. While \lasso is general purpose in nature, we demonstrate it and evaluate its performance through a prototype application used by a tourist guide to monitor tour participants.