Design and evaluation of iMesh: An infrastructure-mode wireless mesh

Wireless mesh networks are multihop networks of wireless routers typically used for wireless coverage over a large community. Applications include community-scale peer-to-peer networking or sharing of a limited number of high-bandwidth wired gateways. In this work, we design and evaluate iMesh, an infrastructure-mode 802.11- based mesh network. Here, 802.11 access points double as routers making the network architecture completely transparent to mobile clients, who view the network as a conventional wireless LAN. Layer-2 handoffs between access points trigger routing activities inside the network, which can be thought as layer-3 handoffs. We describe the design rationale, including address assignment, hand-off and routing techniques. We also describe a testbed implementation of iMesh and analyze the handoff performance, as well as UDP and TCP performance when frequent handoffs are present. The results demonstrate excellent handoff performance with the overall latency varying between 50-100ms depending on different layer-2 techniques, even when a five-hop long route update is needed. Various performance measurements also demonstrate the clear superiority of a flat routing scheme relative to a more traditional, mobile IP-like scheme to handle layer-3 handoff. Overall, the iMesh architecture demonstrates the feasibility of supporting seamless mobility in a wireless mesh network even in presence of frequent handoffs.