Enterprise wireless access networks: systems and applications
Songwu Lu, Petros Zerfos · 2005
This dissertation examines design and performance issues of systems and applications deployed in wireless access networks based on the 802.11 technology. In recent years, a substantial number of network protocols and router services have been proposed to improve wireless network performance under dynamic channel conditions and host mobility. However, a system support framework for the implementation and deployment of these network services is still missing. We present DIRAC, a software-based router system that enables the implementation and deployment of various channel-adaptive and mobility-aware protocols on access routers. DIRAC follows a distributed architecture with Router Agent software modules residing at each access point, which provide link-layer information feedback to the Router Core on the access network router. Link-layer mechanisms are also exposed, thus enabling two-way interactions between the Router Core and the Router Agents. In the context of this router system, we further describe wireless router services that we implemented - fast handoffs for MIPv6, channel-adaptive FEC scheduling, and link-layer enforced policing - that take advantage of this architecture, and present performance evaluation results from our testbed. Furthermore, in order to gain a better understanding on the impact of data traffic load and resource requirements on wireless access systems, we study two popular wireless services: wireless messaging and dynamic video adaptation. We present traffic models derived from the analysis of traces obtained from a wireless messaging service, and discuss the impact of transcoding parameters on consumption of resources such as CPU utilization, network bandwidth and energy.