Opportunistic mobile social networks: From mobility and Facebook friendships to structural analysis of user social behavior

In the last few years, several real-world mobility traces for opportunistic networks have been collected in order to explore node mobility and evaluate the performance of opportunistic networking protocols. These datasets, often including online social data of the mobile users involved, are increasingly driving the research towards the analysis of user social behavior. Within these challenged infrastructureless networks where connectivity is highly intermittent and contact opportunities are exploited to allow communication, node mobility is basically driven by human sociality. As such, understanding node sociality is of paramount importance, especially for finding suitable relays in message forwarding. This paper presents a detailed analysis of a set of six different mobility traces for opportunistic network environments including nodes' Facebook friendships. Using a multi-layer social network approach and defining several similarity classes between layers, we analyze egocentric and sociocentric node behaviors on the two-layer social graph constructed on offline mobility and online social data. Results show that online and offline centralities are not significantly correlated on most datasets. Also online and offline community structures are different. On the contrary, most of the offline strong social ties correspond to online social ties and in some cases, online and offline brokerage roles show high similarity. (C) 2016 Elsevier B.V. All rights reserved.