A Study of Disaster Notification Wireless Mesh Network Applying Plumtree

In a huge earthquake, disaster notification system may cease to function due to the damage of communication cables, etc. Therefore, in this study, we assume a wireless mesh network using LPWA that operates independently from existing infrastructures such as the Internet. Disaster notification to first responders must be delivered reliably and with low latency. Flooding is a possible way to obtain redundancy. However, flooding increases the number of messages, and there is concern that increased latency due to time slot control. In this study, we focus on Plumtree that is a fault-tolerant and message-reducing algorithm and consider its application to the disaster notification wireless mesh network. Specifically, we propose a method to enable unicast notification to the first responder node by extending Plumtree. In the proposed method, each node has an additional routing table to keep the direction of the first responder node. Experimental results show that the number of hops in the proposed method is sufficiently small for message loss rates up to 5 %. Even when the loss rate is 50 %, the number of hops is less than approximately two and a half times compared to the shortest path tree.