  We consider the problem of broadcasting a viral video (a large file) over an
ad hoc wireless network (e.g., students in a campus). Many smartphones are GPS
enabled, and equipped with peer-to-peer (ad hoc) transmission mode, allowing
them to wirelessly exchange files over short distances rather than use the
carrier's WAN. The demand for the file however is transmitted through the
social network (e.g., a YouTube link posted on Facebook).
  To address this coupled-network problem (demand on the social network;
bandwidth on the wireless network) where the two networks have different
topologies, we propose a file dissemination algorithm. In our scheme, users
query their social network to find geographically nearby friends that have the
desired file, and utilize the underlying ad hoc network to route the data via
multi-hop transmissions. We show that for many popular models for social
networks, the file dissemination time scales sublinearly with n; the number of
users, compared to the linear scaling required if each user who wants the file
must download it from the carrier's WAN.
