| This thesis considers the two special sensor networks for future sensor network design: mobile sensor networks and hybrid network of sensors and robots. To investigate two types of networks, we abstract two most important aspects that are ingrained in them: mobility and communication. We are especially interested in the interaction between communication and mobility, how they assist and enhance each other in a sensor network. On one hand, mobility can help with communication because mobility allows node to move to deliver information when wireless communication is not available or of poor quality; on the other hand, communication can help with mobility, which is the underlying support for robot actuation, because communication can provide information to direct comparably expensive mobility.; To explore the mobile and hybrid sensor networks, we built an infrastructure for sensor network. We focused on two problems: power-aware communication and clock synchronization. We gave several communication protocols to conserve the energy in sensor network communication, both on the scale of the whole network and on a single node. We showed that by carefully designed routing protocol and fine-tuned sleep/wakeup node schedule, much energy can be conserved. We also designed several protocols for global clock synchronization. The most interesting one is diffusion-based clock synchronization, which is a fault-tolerant and localized protocol.; The duality between communication and mobility was shown as follows. First, we showed that communication can be achieved by controlled mobility and natural mobility. We used active trajectory change to obtain guaranteed message delivery. Then we demonstrated that natural mobility can be used to help communication to conserve energy and overcome disconnection. Second, we showed in navigation application that communication can assist mobility. We gave communication protocols to support user guidance in a sensor network, refined the protocols by considering reducing network searching space, and explored a mobility coordination problem: task assignment in first responder applications. |
