In this work, we propose a modeling framework which captures the most fundamental behavioral and structural properties of mobile opportunistic networks from mobility to structural level. First, we introduce STEPS -- a simple parametric mobility model which can cover a large spectrum of human mobility patterns. STEPS abstracts the fundamental spatio-temporal behaviors of human mobility, i.e., preferential attachment and attractors, by using a power law to drive nodes' movement. We show that the model makes it possible to express key peer-to-peer properties of opportunistic networks such as inter-contact/contact time distributions. Leveraging on the expressive and modeling power of STEPS, we analyze how fundamental structural properties can emerge from the combination of elementary node's mobility behavior. Specifically, we bring out one sufficient condition of the emergence of the famous small-world structure in opportunistic networks. We also show that this special dynamic network structure improves significantly the communication capacity of opportunistic networks
