The need for disaster relief communications has been recognized by the United Nations Foundations as one of the great
challenges of the early 21st century: ‘‘When disasters strike, people need food, shelter, blankets, and medicine but without
an effective communications network, supplies are left undelivered, and relief workers are unable to do their jobs’’ [1].
During social gatherings or disaster events, traditional communication networks such as cellular ones operate with
difficulty, due to increased congestion levels and possible damage. Indeed, during such events, tremendous stress is placed
on networks due to the sudden rise in traffic demand for both usual and emergency calls. This effect is shown inFig. 1, which
reports the density of mobile phones engaged in calls in Rome both during an ordinary weekday and right after a metro