In this era of Facebook, Twitter and the iPhone, it is easy to take for granted our ability to connect to the world. Yet communication is most critical precisely at those times when the communications infrastructure is lost. In Haiti, for example, satellite phones provided by aid agencies were the primary method of communication for days following the tragic earthquake earlier this year. But even ordinary events such as a power outage could cripple the cell phone infrastructure, turning our primary emergency contact devices into glowing paperweights.
In situations such as these, an increasingly attractive option is to create an “ad-hoc” network. Such networks form on their own wherever specially programmed mobile phones or other communications devices are in range of one another. Each device in the network acts as both transmitter and receiver and, crucially, as a relay point for all the other devices nearby. Devices that are out of range can communicate if those between them are willing to help—passing messages from one to the next like water in a bucket brigade. In other words, each node in the network functions as both a communicator for its own messages and infrastructure for the messages of others.