| This Ph.D. dissertation focuses on design and analysis of efficient networking protocols in wireless local area networks and ad hoc networks. Known as WI-FI technology, wireless local area networks have become very popular today as an easy way of wire less access to the Internet. Wireless ad hoc networks also find a lot of applications which need wireless access or require a low cost or an immediate deployment of networked systems, like battlefield communications, public safety networks, disaster rescues, and wireless metropolitan area networks. However, it is a very challenging task to design efficient networking protocols to provide quality of service (QoS) and reliability in these networks. Compared to wired networks, in wireless networks links are not independent any more; bandwidth, power and processing ability are limited; channel errors happen frequently; network topology is subject to constant change; and the network is often self-organized and distributed. These challenges lead to close coupling among various layers in the protocol stack and a complete different medium access control (MAC) layer, and hence call for a cross-layer design between the MAC layer and other layers.; The dissertation conducts a thorough theoretical study on a contention-based MAC standard, IEEE 802.11, and investigates the close coupling between various protocol layers and the MAC layer, features of which have been used to provide QoS and reliability, and design efficient MAC, routing and transport protocols. The theoretical results discover that the contention-based IEEE 802.11 MAC standard can well support Quality of Service and at the same time achieve maximum aggregate throughput by regulating the access traffic. Guided by the theoretical studies, the protocol design demonstrates various novel ways of cross-layer design and their great benefit in improving performance of wireless networks. Unlike prior research on cross-layer design approach in wireless networks which focused on pure theoretical studies and either are too complicated to solve or the resulting solutions become too simple to be practical because of many unpractical assumptions, the theoretical studies and protocol design in this dissertation are based on the widely used IEEE 802.11 standard and hence can achieve immediate impact on products and revolutionize the way that people design networked systems. |
