Open Mesh

Open Mesh

by / June 6, 2005
In 1876, Alexander Graham Bell altered communications history when he invented the telephone. Just four years later, there were approximately 47,900 telephones in the United States.

But telephone service was expensive, and not everyone had the financial means to obtain it, creating an analog divide between the haves and the have-nots. Working to get around this, telephone companies offered party lines that gave customers the option of sharing a phone line for a reduced price.

Today's society also struggles with a divide, but of a digital nature -- between those who can afford broadband Internet access and those who cannot.

Affordable Mesh Networks
An Illinois group is working to bring wireless mesh networking to communities at a price they can afford.

Sascha Meinrath founded the Champaign-Urbana Community Wireless Network (CUWiN) initiative. He and his team have been working on wireless, ad hoc mesh network technology using open source software free to the public.

CUWiN hopes to gain cooperation from organizations that want to pool bandwidth for their communities in an effort to bridge the digital divide while moving toward a digital future. Meinrath explained that a lot of flat-rate, prepurchased bandwidth goes underutilized by entities such as businesses, municipalities and schools -- especially after business hours.

"There's a tremendous amount of bandwidth right now that people are paying for and not using," said Meinrath. "Our goal is to create a way to efficiently use this bandwidth in addition to introducing the idea of communitywide networks."

CUWiN's software utilizes the unlicensed 2.4 GHz frequency band to communicate via rooftop antennas in direct line of sight with one another. Because this frequency range is optimized for shorter distances, inexpensive, lower-powered antenna/radio combinations can be used to transmit the signal.

Radios convert digital data to wireless signals so information can be sent to nearby antennas, forming a network of available connections called a local area network (LAN).

Communications are made possible through nodes composed of an antenna/radio combination, a computer, a wireless card and the CUWiN software.

Weaving the Nodes
Each node joins the network automatically. Mesh topology allows the node to send data through multiple routes to multiple neighbors. For this reason, the network provides redundant connections with several paths for data transport. In addition, data sent directly to neighbors within the LAN without accessing the Internet travels at faster speeds -- much faster than a T1 line, according to Meinrath.

Mesh topology also allows for decentralization, which is beneficial in two ways.

"With mesh topology, there is no need for a central server system or centralized administration of the network," he explained.

The CUWiN software uses the Hazy Sighted Link State (HSLS) protocol so each node can choose the best path for data to travel the network. The chosen paths are based mainly on signal quality and the amount of nodes, or links, the data must travel through to reach a destination. Data is then sent using the shortest path with the best available signal strength, taking into account each link's established reliability over time.

The HSLS protocol essentially becomes the eyes of the network, with the ability to "see" when direct links go down and are no longer available. When this happens, the HSLS protocol sends updates to neighboring nodes, signifying the change.

By only sending this information to direct links instead of the entire network, and by only sending it when a change occurs in the network versus sending it at regular intervals, the protocol reduces the overall amount of updates sent out to the network. These updates are considered overhead, as they are not part of the original data sent by network users.

Minimizing overhead lets the network grow without being overwhelmed by demand for bandwidth as additional nodes populate the network and require routing updates of their own.

CUWiN's software runs on NetBSD, an open source operating system that can be customized as needed. Since NetBSD is nonproprietary, the network can function on non-vendor-specific hardware, minimizing costs.

Interested communities can deploy a network using off-the-shelf hardware or legacy equipment deemed obsolete -- nodes can be created using systems with processors as old as an Intel 486 or Pentium I.

"The idea is that you can take those old computers gathering dust in the garage and build a communications infrastructure out of them," Meinrath said.

The system must contain a wireless network interface card (NIC) compatible with CUWiN's software. A list of compatible NICs is offered on CUWiN's Web site, where people can also go to download the software for free and burn it to a CD. The Web site includes easy-to-follow instructions on how to set up a node.

Most of the process is automated.

"The system boots from our software, opening up the operating system, which then sends out beacons to find other nodes nearby. Once it finds them, the node assimilates into the network automatically," Meinrath explained.

Active Deployment
Several communities used CUWiN's software to set up wireless networks.

The Center for Neighborhood Technology (CNT), a 27-year-old nonprofit based in Chicago, is working on projects targeting the digital divide throughout the nation. CNT's overall goal is to reduce cost of living and improve conditions of communities and neighborhoods.

CNT's Community Wireless Networks project was created to look at how access could be made affordable to communities, said Project Manager Nicole Friedman.

The issue was highlighted by the need for Chicago-area community organizations to use the Neighborhood Early Warning System, a Web-based system that supplies the organizations with up-to-date information, including building occupation status, assessor's data and the building footprint of Chicago and surrounding areas. The purpose is to help communities combat detrimental neighborhood changes and revive areas in need of help.

Friedman said CNT recognized that not everyone had access to the tool, and without that access, community organizations and citizens were left in the dark.

Paul Smith, technology director of CNT's Community Wireless Networks, explained that CNT's original intent was to use existing Wi-Fi hardware to create rooftop-to-rooftop wireless networks. But because Wi-Fi was primarily designed for small, contained networks in locations like coffee shops, hotels and airports, Smith said, the technology wasn't really meant to supply an outdoor network.

"CUWiN solved a lot of the technical hurdles that plagued Wi-Fi technology, and the programmers overcame the limitations inherent in the wireless protocols to make them suitable for large, outdoor LANs and mesh networking environments," he said.

CNT currently uses CUWiN software for multiple projects, including creation of a large communitywide LAN in North Lawndale, an urban community four miles from downtown Chicago. Smith said a number of schools and businesses are already on board, and people in the community are donating their time to help establish the low-cost network.

A Digital Future
This is a unique time in history -- when technology, demand and public policy can all come together to connect people to the Internet for very low cost, Smith said.

"It's one of those opportunities you don't want to see slip by, or become legislated out of existence," he said, noting that getting students online after school hours is especially important. "The natural next step is high-speed access into the home so education doesn't just end at 3:00 when students go home."

Wireless networks can significantly benefit educational institutions, Meinrath added, citing schools that create inexpensive wireless networks so staff and students can communicate, and so parents can access information regarding their children's education as examples.

By creating a modern-day digital party line reminiscent of the party lines that bridged the economic divide in the telephone's early days, CUWiN's software solution and ad hoc mesh networking technology is bridging a new divide and getting people connected for low cost.
Sherry Watkins Contributing Writer