June 6, 2005 By Sherry Watkins
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
You may use or reference this story with attribution and a link to