Systems and Networking

Wireless Technology Hits the Road

highway traffic
Direct radio communication between vehicles, as well as with roadside infrastructure, promises to improve both traffic flow and safety.

Communications technology is transforming the driving experience. Automatic toll collection, crash reporting, and satellite-based navigation with traffic updates—as well as the widespread use of cell phones—provide drivers with much better information, as well as more distractions. But many researchers think that car travel is poised for an even bigger transformation as technology allows communications directly between vehicles.

In future Vehicular Ad-Hoc NETworks, or VANETs, such vehicle-to-vehicle (V2V) communication would complement—not replace—communication between vehicles and roadside infrastructure (V2I). Programs like the U.S. Department of Transportation’s Intelligent Transportation Systems (ITS) have long studied how intelligent infrastructure can modify traffic flow to reduce pollution, energy, and productivity costs, for example.

But VANET research, which arose from over a decade of research into more general Mobile Ad-hoc NETworks, or MANETs, is becoming part of the mainstream, for example in the Department’s IntelliDrive program. "VANET is the new kid on the block," says computer scientist Stephan Olariu of Old Dominion University in Norfolk, VA. "The acceptance of VANET by ITS was in question for a long time," he says, but research has demonstrate the power of V2V.

On July 15, the IEEE issued final approval of the 802.11p protocol, which operates in the licensed 5.9-GHz frequency band, as part of Wireless Access in Vehicular Environments (WAVE). This protocol aims to establish connections faster than the related 802.11a/b/g protocols used for Wi-Fi, which is critical in the rapidly changing highway environment.

One area where direct communications could yield clear benefits is safety. Cars could, for example, send nearby vehicles information about their position, lane, and speed to improve automated evasive actions. Other vehicles could also share information about upcoming road hazards or relay requests for emergency assistance to the roadside infrastructure or to other communications networks.

Francisco Martinez, of the University of Zaragoza, Spain, and his collaborators simulated the communication of safety information over an ad-hoc 802.11p network. "In vehicular networks, the nodes move frequently and you often cannot get the correct path to reach the end of the communication," Martinez says. "We think that combining vehicle-to-vehicle with vehicle-to-infrastructure we can solve these issues."

But reaping the safety benefits will require widespread adoption, Martinez notes. "To avoid accidents, a lot of vehicles must have this kind of communication hardware." Reaching this high penetration level is a key challenge. The first step, he believes, "is to finish the standardization process," so that companies can be confident investing in new products.

But Olariu is not so worried. "In general, premature standards kill research," he says. Although it will take time, he expects systems to appear first in high-end vehicles, much as antilock brakes and collision-avoidance systems have. Among the selling points for vehicle networking systems, he says, might be peer-to-peer applications that allow gaming or entertainment. "For some applications, a low penetration rate is good enough," Olariu says, and might open the way for wider adoption.

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