Dissemination in opportunistic mobile ad-hoc networks: The power of the crowd

Opportunistic ad-hoc communication enables portable devices such as smartphones to effectively exchange information, taking advantage of their mobility and locality. The nature of human interaction makes information dissemination using such networks challenging. We use three different experimental traces to study fundamental properties of human interactions. We break our traces down in multiple areas and classify mobile users in each area according to their social behavior: Socials are devices that show up frequently or periodically, while Vagabonds represent the rest of the population. We find that in most cases the majority of the population consists of Vagabonds. We evaluate the relative role of these two groups of users in data dissemination. Surprisingly, we observe that under certain circumstances, which appear to be common in real life situations, the effectiveness of dissemination predominantly depends on the number of users in each class rather than their social behavior, contradicting some of the previous observations. We validate and extend the findings of our experimental study through a mathematical analysis.