Champaign-Urbana Community Wireless Network

The Champaign-Urbana Community Wireless Network (CUWiN) is a special project of the Urbana-Champaign Independent Media Center (UCIMC). Started in 2000 by a group of developers wishing to take advantage of under-utilized Internet links purchased for public use (such as those in municipal offices, schools, and universities), it began a partnership with UCIMC in 2004, gaining its current special project status. CUWiN inherits UCIMC's not-for-profit status and is devoted to building a network architecture to cost-effectively and efficiently create a community wireless network.

The project has built a communications network using wireless networking equipment ranging from commodity personal computers to specialized Soekris miniaturized, fan-less computers with integrated networking. This is essentially the same "WiFi" equipment used in homes and offices, but CUWiN put it on rooftops to connect neighbors and form a high-speed community network. It is one of many localized community wireless network projects across the world and is developing a platform which can be reused by certain types of these projects, based on their community's geographic structure.

CUWiN's three-part mission is to:

The CUWiN platform intends to provide a meshed, ad hoc, non-hierarchical network topology based on commodity infrastructure and technology. Historically, in such ad hoc networks scaling problems have arisen as the overhead involved in processing the routing information and maintaining a consistent link state among peers grows beyond the ability of the individual nodes in the network to track and forward it. In effect, once a network of this type has reached a certain size, the routing information alone uses all of the available capacity on the network.

Research into routing protocols has uncovered algorithmic approaches to handle and manage this complexity. While starting up, CUWiN relies on Dijkstra's Open Shortest Path First (OSPF), though they are in the process of implementing a much more amenable routing protocol named (HSLS), and then, later, implementing a modification to it named Adaptive Hazy-Sighted Link State (A-HSLS). They estimate that the scaling properties of the hazy-sighted link state family of algorithms provide the ability to scale to thousands or tens of thousands of nodes in a densely packed metropolitan network.

As with the routing protocol, CUWiN is also experimenting with a new routing metric introduced by the Massachusetts Institute of Technology named Expected Transmission Count (ETX). ETX allows links to be weighted based on the performance of the link experienced over time. The ability to so weight wireless links is needed due to the dynamic nature of physical environments. Where a tree in the winter has no leaves, a wireless link passing through it will be strong. In the summer, the leaves will have grown back, causing the link to have a lower capacity.

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