Design and implementation of a Witness Unit for opportunistic routing in tsunami alert scenarios

Some earthquakes generate tsunamis in the ocean or coastal regions. An early alert is essential for the coastal population to prevent loss of human life. The propagation of the alert is made through a range of communication means: radio, television, sirens, landlines and cell phones, social media including Twitter, and, if electrical power and communications utilities are blacked-out, through an alternative opportunistic network. In this article, a special device, named Witness Unit (WU), designed to work with a satellite network is presented as an alternative communications means in a temporarily degraded disaster environment. A greedy heuristic algorithm for the placement and deployment of the WUs is introduced and its interaction with emergency managers and citizens is discussed.