On the Road with the Mobile Mesh
Military technology could help alleviate traffic problems.
October 22, 2003 2:55 AM
On a sunny but cold September morning, seven scientists met at the parking lot near Lawler Ranch Road and Sand Hill Road in Palo Alto to prepare for the second experiment of a so-called wireless mesh network, a communication system designed primarily for mobile communication.
Unlike point-to-point communication networks requiring central distribution, a mesh network relies on a relay system that creates a direct connection to any other available device, or node, configured for the network. That day's test would add a significant wrinkle--the relay laptops would be in cars traveling north on Highway 280.
The experiment is the brainchild of Information Systems Department professors Dr. Paul Beckman and Sameer Verma, and Ramesh Rao, a former lecturer in the department.
“[The] mobile mesh is a multipoint to multipoint network of mobile devices, like laptops, where the structure of the network changes based on distance, location and radio power,” Verma said. He added that the idea of a mesh network came from the military and that the technology has been used in actual combat.
“There is no predetermined network structure. The challenge in mobile meshes comes from the fact that devices move around, thereby changing the network paths continuously,” explained Verma.
The scientists decided to do something more exciting then carrying laptops and walking around to test the network. “We want to do the experiment in a car because it’s different and no one has done it before,” said Beckman.
Verma said they encountered unexpected problems with the technology in their first test drive. The laptops they used for the experiment were old and the batteries ran out midway through, bringing the test to a premature end.
Yet they had enough to prove that a mesh network could be established while driving on the highway. This time, to make sure they had enough power for the experiment, they brought power inverters to run the laptops off car batteries by plugging into the cigarette lighters.
When everything was set to go, the four cars, each with an operational laptop ready to be connected via wireless card to the mesh network, merged onto Highway 280 and drove north.
Leading the pack was Jason Stone of the Department of Information Technology and Dan Wong, an Information Technology Consultant from the College of Humanities. Verma and his former student Robin Lo were in the second car. Rao drove alone in the third car, with Beckman and his wife in the last car.
The cars stayed in single file on the highway. Once a stable network was established, Beckman and his wife, in the last car, sped up and 'leap-frogged' the other three to take the lead position. This was to test the network’s ability to adjust and to reestablish itself after its original stable connections were broken.
Beckman said that the cars drove close to one another during the first experiment so that computers could communicate with no problems. The leap-frogging of the cars in the second experiment was to test how the network would react to sudden changes. In addition to the leap-frogging, the cars stayed further apart - over 300 feet, about the length of a football field - while maintaining the speed limit. This was designed to find out if data could really 'hop' from one mobile computer to another through a third one located in the middle.
The test ended after 20 minutes when all the cars exited at Trousdale Drive. Beckman checked that the experiment data had been recorded before collecting all disks for later analysis. Later analysis proved that the experiment was a success; hoppings were recorded.
Verma estimates that it will take a few years before the technology is mature enough to go on the market. One problem, he said, is that there is no control over data transmission bandwidth. “Another problem is concerning privacy because while using the mesh network, a message sent through the network can be read by someone who is not the intended receiver,” he added.
Even with its current flaws, there are some real-world applications of the technology, according to Beckman.
“Drivers on the highway could use the technology to communicate with each other without using a cell phone,” he said. “If many cars are equipped with mesh network, the government could set up a roadside radio receiver to find out the traffic flow of a place.”
Beckman presented his findings at the Institute of Electrical and Electronics Engineers, Inc., semiannual Vehicular Technology Conference in Orlando, Florida. A future test drive is scheduled for later this month, which could involve the transmitting of more complex data, like music.
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