Design And Implementation Of Emergency Communication System Based On Wi-Fi Direct

The emergency communication system is of great significance in disaster recovery and rescue operations.When disasters occur(for example,Wenchuan earthquake in China in2008 and Fukushima earthquake in Japan in 2011),communication infrastructure is usually destroyed or unavailable,and the tool that can provide communication in disaster relief is usually the smart phone that people use daily and often carry with them.Smartphones can use their short-range wireless communication technologies(such as Wi-Fi,Bluetooth,etc.)to build a temporary,emergency communication system for disaster relief,such as trapped survivors discovering rescuers through their smartphones and sending them distress messages.Although smartphones have the potential to form an emergency communication system,there are still some problems and challenges: 1)the system lacks emergency message distribution capabilities to deliver emergency messages from trapped people to nearby rescuers;2)the system cannot adapt to changing network topologies,which can change frequently due to the mobility of rescuers,and many smartphone-based emergency communication networks can be paralyzed as a result.In this paper,we design and implement an emergency communication system.Specific work includes: 1)To address the problem of lacking an emergency message distribution,we propose to use the service discovery feature of Wi-Fi Direct to complete the design and implementation of a public alert distribution protocol.The device distributes alerts in a publish/subscribe manner.The system can distribute alert coordinates location to search devices efficiently.2)To address the problem that Wi-Fi Direct technology itself does not support multi-hop communication and cannot adapt to network topology changes,we propose a connection scheme based on Wi-Fi Direct's role switching method.The smallest unit of the communication system based on this connection scheme is a single device in the network,so it supports devices to join or leave the network group dynamically,which is better to cope with the changing situation of network topology.Based on the role-switching connectivity scheme,an automatic connection design based on structured device names is completed,which allows smartphones to act as relay nodes to receive and forward messages without manual authorization.In this paper,the implemented emergency communication system is experimented with location alert distribution and peer-to-peer message sending functions.The experimental results show that the system carries a public alert distribution protocol that operates properly and efficiently,and that the role-switching connection scheme and automatic connection design can cope with changes in network topology.