20. Architecture and Evaluation of an Unplanned 802.11b Mesh Network

This paper describes an experimental 37-nodes wireless network in Cambridge, Massachusetts. Users volunteer to install an antenna on their roofs and either connect it to a home broadband connection or not. Average throughput of the Rooftop network is 627 Kbps with averaging 3 hops.

Roofnet uses a unique addressing system on top of IP addresses. A special routing protocol, Srcr, was also introduced to automatically update the routing table among different wireless access points. Since most of the links in between are rather weak, the routing must find an optimum throughput itself. This is called Estimated Transmission Time (ETT).

Roofnet also uses its own algorithm, SampleRate, to determine the bit rates of 1, 2, 5.5, 11Mbps in 802.11b network. The decision is based on actual data speed rather than periodic probes.

Comments:

• The beauty of this system is that, you don't need elaborate planning ahead where to put the wireless hops. The antenna is omni-directional, and software is self-configured.
• I'm not sure if this is ever popular in the States, but there's this thing called FON, which basically gives you an almost-free wireless AP if you agree to share your existing Internet access, whether charging your users or not. And when you are out of your own FON AP, you can access others' depending on your sharing mode. This is/was very, very, very popular in Spain. Would it be possible to apply similar techniques to the FON firmware and give it a try?