QoS issues and QoS constrained design of wireless sensor networks.

摘要

Most existing research in wireless sensor networks (WSNs) has been focused on proposing protocols to facilitate either energy efficient communication or sensing operation in WSNs. We believe that there exist fundamental limits in the operations and the parameters of WSNs. Characterizing these fundamental limits, establishing the relationships between the parameters and the WSN performance, and identifying the tradeoffs among different performance measures can provide us insights in designing sensor networks.; In this dissertation, the QoS properties of WSNs, including the coverage, reachability, and delay, are analyzed in an analytical framework. How the network parameters, such as the node density, sensing range, transmission range, impact the aforementioned QoS properties are investigated by abstracting the randomly deployed WSNs as random geometric graphs. Both homogenous and heterogenous sensor networks are addressed. Based on the analytical model, optimal sensor network parameters can be chosen to improve the network performance while achieving pre-specified QoS constraints.; Besides this abstraction, practical issues affecting the QoS performance of WSNs are also examined by doing extensive simulations in this dissertation. Specifically, results are obtained for the QoS properties in the flooding of WSN when a cross-layer approach is adopted, and other practical issues such as channel fading and MAC layer contention are taken into account. The results show that exchanging more information across the layers can help improve efficiency of the protocol. It is further shown that wireless fading helps to reduce the hop count, although it makes the transmission range less predictable and limits the improvement in the performance of such cross-layer design in WSNs.