Using physical layer emulation to understand and improve wireless networks

Researchers and developers have long faced a fundamental tension between the experimental realism of wireless testbeds on one hand, and the control and repeatability of simulation on the other hand. This thesis introduces physical layer wireless net work emulation---a new approach to wireless network experimentation that balances the stark tradeoff of traditional alternatives by enabling both realistic and repeatable experimentation. The design and implementation of a functional wireless emulator are presented along with a discussion of how this implementation overcomes the challenges necessary to meet operational requirements. In particular, solutions to the problems of developing a hardware architecture for emulation, and software control of that architecture will be presented. To illustrate the power of physical layer wireless network emulation, case studies are presented. First, physical layer emulation is used to analyze several aspects of wireless LAN link-level behavior. Physical layer emulation is then used to investigate wireless LAN access point selection performance, and to develop improvements. This thesis shows that---compared to traditional approaches---physical layer wireless network emulation provides a better understanding of real-world wireless network performance, shortens the development cycle of wireless networking software, and facilitates the deployment of research into operational wireless networks without sacrificing a controlled experimental environment.