Architecture and Evaluation of an Unplanned 802.11b Mesh Network

Summary

This paper evaluated the architecture and performance of Roofnet, an unplanned 802.11b Mesh Network. It explored the effect of node density on connectivity and throughput, the links that the routing protocol uses, performance of a highly connected mesh and comparison to a single-hop network using the same nodes as Roofnet.

Roofnet is primarily characterized by the following design decisions:

• unconstrained node placement
• omni-directional antennas
• multi-hop routing
• optimization of routing for throughput in a slowly-changing network

Roofnet is organized such that a few nodes act as gateways to the internet. Each node needs a Roofnet address as well as an IP address, both of which it obtains automatically. Roofnet's routing protocol, Srcr makes use of Dijkstra's algorithm to find the highest-throughput route between any pair of nodes. Srcr also makes use of an "estimated transmission time" to chose routes. Finally, Roofnet has its own algorithm to choose the optimal transmit bit-rate.

Then, the authors use 4 sets of measurements on Roofnet to evaluate many characteristics of Roofnet.

The authors conclude that Roofnet works. Throughput and latency are comparable to that of a DSL link. The average throughput was measured to be 627 kbits/second. Roofnet is shown to be robust as it does not depend on a small number of nodes. It also shown that multi-hop forwarding performs better than single-hop forwarding.

Criticism & Questions

This paper was very well organized and easy to follow. Their evaluation considered many characteristics and they made sound arguments when analyzing their data. The charts and graphs were very helpful in understanding their points.

Feedback

I would vote to keep this paper in the syllabus.