Users Mobility Models for Opportunistic Networks: the Role of Physical Locations; The Power of Autonomic

Opportunistic networks are pervasive networks built exclusively by users' devices. With respect to legacy multi-hop ad hoc networks (MANETs), opportunistic networks are much more resilient to disconnections, long network partitions, and dynamic reconfigurations. Therefore, they are suitable for challenged scenarios, such as disaster areas, or rural environments. While in MANET nodes' mobility is an issue, in opportunistic networks mobility is an opportunity for communication, therefore mobility models are a key component in opportunistic networks' research. Improved (with respect to MANETs) users mobility models are rapidly becoming reference tools for studying opportunistic networks, thanks to their accuracy in matching statistical features observed in real traces. A very interesting approach is defining mobility patterns based on social relationships between users. In this paper we argue that, while being a fundamental building block, social relationships alone cannot be the only driver for the mobility process. Users movements are also driven by the attraction of physical locations (e.g., the house, the working place) on users. We analyse from this standpoint the Communitybased Mobility Model (CMM), which is the reference point for social-aware community models. We show in detail that CMM is not able to capture locations' attractions on users. Therefore, we propose the Home-cell Community-based Mobility Model (HCMM), which retains the social-aware features of CMM and, in addition, permits to easily control the relationships between users and their preferred physical locations.