Design, modeling, and analysis of user mobility and its impact on multi-hop wireless networks

Due to the readily deployable and self-organizing nature of mobile ad hoc networks (MANETs), various demanding military and civilian applications are expected to be widely implemented in MANETs. The fundamental issue in MANETs is that performance degrades dramatically as the increase of path failures due to the complexity of user mobility. Therefore, understanding the impacts and implications of user mobility is essential to the system design, topology control, and routing optimization in MANETs.In this doctoral study, by observing the limitations of both transient and stationary behaviors in existing random mobility models, we first propose a novel Semi-Markov Smooth (SMS) model. We showed that the proposed SMS model captures the transient user mobility according to the physical law of a smooth movement, and achieves the necessary stationary properties regarding stable average speed and uniform node distribution. Second, based on the SMS model, we investigate the MANET link properties by considering the joint effects of radio channel environments and node mobility. We showed that radio channel characteristics dominate the link performance for slower mobile nodes, while node mobility dominates the link performance for faster mobile nodes. In addition, the link lifetime distribution can be effectively approximated by an exponential distribution with the parameter, characterized by the ratio of average node speed to the transmission range. Third, we studied the impact of human diffusive behaviors on the properties of contact-based metrics, such as inter-meeting time. By investigating the empirical human mobility traces, we demonstrated that both human pause time and trip displacement exhibit a cutoff-power distribution. Furthermore, we showed that the human diffusive rate r effectively characterizes the joint temporal-spatial effect of human mobility regarding pause time and trip displacement on inter-meeting time. Especially, the higher the diffusive rate r is, the longer the power law head is in the distribution of inter-meeting time. Finally, we studied the inherent properties of group mobility in MANETs. We suggested that the group member correlation degree is jointly characterized by the human social correlation degree and the similarity of the users' relative movements and geographic locations. In addition, we showed that the group evolution behaviors and stability of group structures are based on the group user pair correlation degree. At the end, we propose a novel birth-to-death group mobility (BDGM) model for group mobility based studies in MANETs.