Extending Network Coverage by Using Static and Mobile Relays during Natural Disasters

During natural disasters, such as earthquakes, apart of the Internet access infrastructure can be damaged, leaving many users disconnected. At the same time, many peopleneed to communicate to find their relatives and receive officialnotifications about the current situation. This paper presents anevaluation of different techniques for extending network coveragein such scenarios. We use real-world data to model the poweroutage probability of cellular base stations in Tokyo area andcombine it with information about batteries/power generatorsto create accurate maps of network coverage for different timeperiods after an earthquake. In our simulation, we use a realmap of evacuation sites, provided by Japanese government. Wefirst considered mobile nodes, moving between evacuation sites, and investigated their impact on network coverage. Then, wedeveloped an algorithm to determine the optimal locations forstatic relays ensuring different levels of network coverage. Ourresults show that even a small number of fixed relays, carefullyplaced between the evacuation sites, can outperform a muchhigher number of mobile nodes in terms of network coverage.