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A Grand Challenge

CSL Plays Key Role in Major Effort on Ad Hoc Networks

By Doug Peterson

January 2007

As firefighters battled a blaze in an auto parts store in Chesapeake, Virginia, the roof suddenly collapsed, killing two firefighters. One key problem leading to the tragedy, authorities later reported, was that fire operations “were conducted on the same radio channel as the routine dispatch and transfer of additional units,” hampering communication during the early stages of the fire.

In the future, such communication breakdowns might be solved with mobile “ad hoc networks” -- wireless networks that can be deployed quickly and with no infrastructure by the military and first responders, such as firefighters.

With this goal in mind, CSL is playing a major role in a $6.5 million, five-year research project on mobile ad hoc networks, funded by the Defense Advanced Research Project Agency (DARPA) and involving three other institutions -- Stanford, MIT and the California Institute of Technology.

Dubbed the “DARPA Grand Challenge,” the project involves five CSL professors -- Ralf Koetter, Todd Coleman, Sean Meyn, Pierre Moulin and Ada Poon.

Ad hoc networks have many advantages over the old-style, “over and out” system in which only one person can talk at a time, says Koetter. In fact, some day ad hoc networks may even be able to transmit visuals back to a firefighting commander, as well as vital information such as temperature and oxygen levels.

However, mobile ad hoc networks still have a long way to go before they can be used safely and reliably.

“Wireless ad hoc networks are characterized by energy and delay constraints, interference between transmitted signals and rapidly changing conditions,” says Coleman. “The result has been networks that, while quickly deployable, are not nearly as reliable, fast or secure as they could be.”

An important goal of the DARPA project, Koetter and Coleman say, is to create an “intelligent” ad hoc network, which could treat certain messages, such as distress calls, as higher priority than other messages on the network when the system is near capacity. This might prevent debacles such as the one in Virginia in which routine dispatches interfered with the more urgent communication among firefighters.

In addition to creating an intelligent ad hoc network, CSL researchers will be designing secure networks, creating architectures that can adapt to many applications, developing practical coding algorithms and finding ways to prolong the lifetime of networks, which operate on batteries that cannot be recharged.

They will also bring network coding into play, a relatively new approach in information theory. Koetter, a pioneer in network coding, says classical information theory is built on a transportation model, in which bits of information are transferred from point A to point B like trucks transporting goods on the interstate. If one “truck” encounters another truck at an intersection, it must wait for the other information stream to pass by on the data highway.

“The difference with network coding,” Koetter says, “is that people realized there was no reason to keep the trucks separated. The bits coming down one pipe can be combined with bits coming down another pipe to form a new set of bits.”

This approach, in which information diffuses through a network, has the potential of offering more delay tolerance and more robustness to a network -- “almost anything you can imagine,” he adds.

In addition, Koetter and Coleman say, the lessons learned through the DARPA project could be used for any number of applications, such as smart highways that track road conditions, smart homes that improve energy use and systems that assist the elderly and disabled.

They point out that the project is very basic research, which was why it drew a large number of proposals from the information theory community all across the United States.

“Stanford is taking the lead, but nearly half of the team of 11 comes from Illinois,” Koetter points out. And with so many institutions vying for the project, he says that’s “quite a distinction for Illinois.”

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