A community sensing framework for threat detection in metropolitan area

In this paper, a community sensing framework is proposed for detecting potential threat such as a dirty bomb in a metropolitan area. In wake of the recent bombing during the Boston marathon, it is clear that the task of detecting a potential threat in an open area is extremely difficult, since there does not exist a single choke point(s) for such social events in an unconstrained area. In this study, we propose a novel framework of a threat detection system using a community-based approach. Leveraging on the high penetration of smart phones and low cost and small form factor of certain sensors, such as the radiation sensor that can be carried on a key chain that has a Bluetooth module, critical measurements such as the nuclear radiation level can be measured by each sensor carried by a member of a community (such as an employee at an airport or a mall), and be sent to that person's smart phone, and eventually uploaded to a web portal using a corresponding app installed on the smart phone. The proposed system should be used as an augmented system in addition to the fixed detection system installed. Several challenges and issues of the proposed framework are identified, and a joint belief propagation and quickest detection method is proposed to detect and locate the potential threat with minimum delay while keeping the false alarm rate low. Simulation results demonstrate the effectiveness of the proposed framework.