On Nodal Encounter Patterns in Wireless LAN Traces

In this paper, we analyze multiple wireless LAN (WLAN) traces from university and corporate campuses. In particular, we consider important events between mobile nodes in wireless networks-encounters. We seek to understand encounter patterns in the mobile network from a holistic view, using a graph analysis approach. Such an analysis sheds light on the diverse, nonhomogeneous nature of users in the given environments in terms of their encounter events with other nodes. Furthermore, we evaluate the feasibility of forming an infrastructureless network to reach most of the nodes utilizing time-varying internode connectivity through encounters, and the robustness of such an ad hoc communication network. Our analysis shows that while the encounter events are “sparse” (i.e., any given node does not encounter with many other nodes), the connectivity of the whole network is well-maintained, and a Small World pattern of nodal encounter emerges for the observation periods longer than one day. More interestingly, the encounter events collectively form a robust communication network, in which store-carry-forward message dissemination can be successful even with over 20 percent noncooperative nodes or removal of short-lived (up to minutes) encounter events.