9. Conclusions and future work
In this paper, we have presented a novel and detailed methodology for analyzing a set of real mobility traces for opportunistic networks using a multi-layer network approach. The aim of this study has been to better understand user social behavior in terms of egocentric and sociocentric behaviors that can be derived not only from mobility data (encounters’ social network) but also from the available additional information provided by the social network layer built on Facebook friendships. Our results have shown that online and offline social behavior computed in terms of centrality measures like betweenness, ego betweenness, closeness, degree and eigenvector centrality are not significantly correlated on most datasets. In other words, node popularity changes signifi- cantly on the online and offline social worlds. Also online and of- fline community structures are different. Analyzing the two-layer social network constructed on mobility data and Facebook friendships we have also shown that in some cases, online and offline brokerage roles show high similarity. However, the correlation between online and offline brokerage roles varies significantly from one dataset to another and it is not possible to extract a common trend with respect to this kind of similarity analysis. Finally, we have shown that in five of the six datasets considered, most of the strong ties in the social layer built on wireless encounters correspond to Facebook friendships.