| A fundamental evolution is witnessed in recent research and development of wireless sensor networks: the capabilities of the sensor nodes have gone broader beyond a static sensing device; and now they include node mobility. In this thesis, we present our current research status on exploiting node mobility in wireless sensor networks. We first investigate the impact of node mobility on localization which is the fundamental issue in mobile sensor networks. By leveraging different types of relative distance constraints, we propose a distributed and range-free Mobile Inequality Localization (MIL) algorithm, which is quickly re-localizable when all sensors are moving uncontrollably. With location awareness, we further analyze several unique issues in mobile sensor networks. One issue is about the coverage with mobile sensor nodes. By introducing the concept of probabilistic coverage, we develop a basic platform to provide the realtime coverage status for a given region. In addition, we address a double-mobility problem in coverage and propose a distributed protocol SSC to collaborate between controllable and uncontrollable mobility to maintain the coverage. The other issue is about the event collection. By leveraging the spatial-temporal correlation of events, we propose an online scheme for mobile nodes to selectively collect event information. We also present an intelligent approach to design feasible path for mobile sinks. To further understand the link feature in wireless sensor networks with real trace-data, we conduct several comprehensive measurement studies to investigate the interference tolerability in 802.15.4 networks. We also analyze and model the link feature with node distance and nearby environment. These measurement results provide potential direction to better design the related upper-layer algorithms and protocols for sensor applications. |
