Smartphone ad hoc networks (SPANs; also smart phone ad hoc networks) are wireless ad hoc networks that use smartphones. Once embedded with ad hoc networking technology, a group of smartphones in close proximity can together create an ad hoc network. Smart phone ad hoc networks use the existing hardware (primarily Bluetooth and Wi-Fi) in commercially available smartphones to create peer-to-peer networks without relying on cellular carrier networks, wireless access points, or traditional network infrastructure. Wi-Fi SPANs use the mechanism behind Wi-Fi ad-hoc mode, which allows phones to talk directly among each other, through a transparent neighbor and route discovery mechanism. SPANs differ from traditional hub and spoke networks, such as Wi-Fi Direct, in that they support multi-hop routing (ad hoc routing) and relays and there is no notion of a group leader, so peers can join and leave at will without destroying the network.
SPANs are useful under circumstances when the regular network is overloaded or unavailable, such as conferences, music festivals, or natural disasters, and have been popular in Australia and Latin America. They are popular with youth in the United States as a way to save money, as data sent directly from device to device is free.
