Architecture and evaluation of an unplanned 802.11b mesh network

This paper evaluates the ability of a wireless mesh archi-tecture to provide high performance Internet access while demanding little deployment planning or operational man-agement. The architecture considered in this paper has un-planned node placement (rather than planned topology), omni-directional antennas (rather than directional links), and multi-hop routing (rather than single-hop base stations). These design decisions contribute to ease of deployment, an important requirement for community wireless networks. However, this architecture carries the risk that lack of plan-ning might render the networks performance unusably low. For example, it might be necessary to place nodes carefully to ensure connectivity; the omni-directional antennas might provide uselessly short radio ranges; or the ine±ciency of multi-hop forwarding might leave some users e®ectively dis-connected. The paper evaluates this unplanned mesh architecture with a case study of the Roofnet 802.11b mesh network. Roofnet consists of 37 nodes spread over four square kilo-meters of an urban area. The network provides users with usable performance despite lack of planning: the average inter-node throughput is 627 kbits/second, even though the average route has three hops. The paper evaluates multiple aspects of the architecture: the e®ect of node density on connectivity and throughput; the characteristics of the links that the routing protocol elects to use; the usefulness of the highly connected mesh a®orded by omni-directional antennas for robustness and throughput; and the potential performance of a single-hop network using the same nodes as Roofnet.