Opportunistic networks are formed by people carrying mobile devices with wireless capabilities. When in mutual transmission range (or contact), nodes of such networks use device-to-device communication to automatically exchange data, without requiring fixed infrastructure. A few apps have already proven opportunistic networking to be a useful communication paradigm. While contacts have been studied theoretically, in practice, they depend to a large extent on the characteristics of the mobile

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... ices, typically smartphones. Up to our knowledge, no study has considered the radio characteristics of current smartphones acting as opportunistic nodes yet. In this paper, we hence investigate the WiFi radio performances of smartphones for opportunistic networking. We start by revisiting the classical link budget by adding the impact of the phone's carrier. We then perform extensive measurements to fully characterize all components of the link budget between two smartphones. We find that the Two-Ray propagation model is the best fit as a smartphone propagation model. Eventually, to assess the capacity of opportunistic networking we evaluate a simple scenario of two pedestrians crossing on a path. In this scenario, we show that a maximum range of more than 400m can be achieved and that during the resulting contact opportunity a total of 171 MB goodput can be transferred.