Throughput and coverage improvement in wireless mesh networks
Saha, Amit Kumar
Johnson, David B.
Doctor of Philosophy thesis
In a wireless mesh network, nodes known as transit access points (TAPs) cooperatively forward traffic from users that may be multiple wireless hops apart. A limited number of TAPs also have a connection directly to the Internet, serving as gateway nodes that provide Internet connectivity to the entire mesh network. Wireless mesh networks are gaining in importance as an alternative to cable and DSL and are envisioned to provide fixed, nomadic, portable, and---eventually mobile---wireless broadband connectivity. In this thesis, I provide solutions to two important problems in wireless mesh networks and evaluate these solutions through simulation experiments. The two solutions, improving throughput and coverage, can simultaneously coexist and can complement each other in a single mesh network. Nevertheless, both the techniques can also exist independent of each other in a wireless mesh network and can individually prove advantageous. First, I present two novel traffic-aware routing metrics that take into account existing user traffic flows in the network. Previous routing metrics have been traffic-unaware, often causing routes with poor throughput to be selected when other better routes are available. These new traffic-aware metrics use information captured through measurements at the medium access control (MAC) layer, which is then exposed to the routing layer. I compare these traffic-aware metrics with existing traffic-unaware metrics under different network scenarios. Second, I present the design and analysis of a new technique for increasing the coverage of a wireless mesh network through deployment of small, low-cost booster TAPs (bTAPs). These bTAPs are strategically deployed and controlled by the system operator to wirelessly forward traffic between users and TAP nodes. This deployment model is especially suitable for wide area wireless access networks that use centralized management of radio resources. I analyze the use of bTAPs across different frequency reuse patterns typical of those used in multi-cell wireless environments for efficient management of costly radio spectrum. The bTAP architecture provides dramatic improvements in outage performance and a sufficient capacity gain to compensate for the radio resources required for forwarding user traffic via bTAPs.