On file sharing over a wireless social network

We consider the problem of broadcasting a large file over a wireless network (e.g., students in a campus). If each user who wants the file must download it from the carrier's WAN, dissemination time scales linearly. Two often-occurring facts suggest we can do better: (a) the demand for the file often spreads via a social network (e.g., Facebook); and (b) the devices predominantly used are GPS enabled, and equipped with a peer-to-peer (ad hoc) transmission mode. The premise of this paper is that (a) and (b) are often the case. Starting from here, we consider this coupled-network problem (demand on the social network; bandwidth on the wireless network) and taking advantage of the fact that 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 the number of users.