A Decade of Research in Opportunistic Networks: Challenges, Relevance, and Future Directions.

Opportunistic networks are envisioned to complement traditional infrastructure-based communication by allowing mobile devices to communicate directly with each other when in communication range instead of via the cellular network. Due to their design, opportunistic networks are considered to be an appropriate communication means in both urban scenarios where the cellular network is overloaded, as well as in scenarios where infrastructure is not available, such as in sparsely populated areas and during disasters. However, after a decade of research, opportunistic networks have not yet been ubiquitously deployed. In this article we explore the reasons for their absence. We take a step back, and first question whether the use cases that are traditionally conjured to motivate opportunistic networking research are still relevant. We also discuss emerging applications that leverage the presence of opportunistic connectivity. Further, we look at past and current technical issues, and we investigate how upcoming technologies would influence the opportunistic networking paradigm. Finally, we outline some future directions for researchers in the field of opportunistic networking.