Disaster Information Collection with Opportunistic Communication and Message Aggregation

When a large-scale disaster strikes, the communications infrastructure is usually unavailable. However, accurate and timely information of the disaster area is important because first responders rely on this information to assess the situation in the affected area and to provide an effective and immediate assistance. In this paper, a data collection method from an area of interest (AoI) within the disaster zone is proposed that uses the mobile phones of the people to serve as sensing nodes. In order for maximum AoI coverage to be achieved while minimizing delay, we propose a disruption tolerant network (DTN)-based data aggregation method. In this method, mobile phone users create messages containing disaster-related information and merge them with their respective coverage areas resulting in a new message with the merged coverage. The merging or aggregation of multiple messages will reduce message size and minimize the overall message collection delay. However, simply merging the messages can result in duplicate counting thus, to prevent this, a Bloom filter is constructed for each message. Also, to reduce further the message delivery time, the expected reaching time of a node to its destination is introduced as a routing metric. Through computer simulation with a real geographical map, the proposed method achieved a 9.7% decrease in information collection delay confirming that the proposed method achieved a smaller delay with a smaller number of total exchanged messages in collecting disaster information covering the AoI than epidemic routing.