  Mobile users are envisioned to exploit direct communication opportunities
between their portable devices, in order to enrich the set of services they can
access through cellular or WiFi networks. Sharing contents of common interest
or providing access to resources or services between peers can enhance a mobile
node's capabilities, offload the cellular network, and disseminate information
to nodes without Internet access. Interest patterns, i.e. how many nodes are
interested in each content or service (popularity), as well as how many users
can provide a content or service (availability) impact the performance and
feasibility of envisioned applications. In this paper, we establish an
analytical framework to study the effects of these factors on the delay and
success probability of a content/service access request through opportunistic
communication. We also apply our framework to the mobile data offloading
problem and provide insights for the optimization of its performance. We
validate our model and results through realistic simulations, using datasets of
real opportunistic networks.
