Shuttle Bus System Goes Wireless

Winter 2007

Hopkins Shuttle Route
An innovative mobile, wireless network created by computer scientists Herbert Rubens and David Holmer allows Hopkins Security to track the university’s shuttle buses at all times. What’s more, riders can now connect wirelessly to the Internet.

Six years ago, then undergraduates Herbert Rubens ’01 and David Holmer ’01 teamed up to work on a problem that today seems simple. They wanted to connect their computers wirelessly to the Internet from any spot in Shaffer Hall. “We were trying to figure out how to extend the Internet from here to there without plugging into a wire in the wall,” says Rubens.

That small endeavor has led the team to breakthrough discoveries in the area of wireless, mobile computer technology. To date, Rubens and Holmer, now graduate students with the computer science department have published with their advisor, computer science Professor Baruch Awerbuch, 15 academic papers on wireless network engineering. What’s more, the pair has set up one of the only known mobile, wireless networks in the nation, using the Johns Hopkins Shuttle Bus system.

The project, called Wave Relay, is the culmination of six years of research on how to create a secure computer network using mobile, wireless routers, rather than stationary routers fixed on buildings. “This is their baby,” says Awerbuch, “Many universities are trying to create a network like this. But to our knowledge, no one has been successful yet. This is a very impressive product result.”

Last year, Rubens and Holmer placed mobile, wireless routers and GPS receivers on the roofs of 12 Hopkins shuttle buses. They also put stationary routers on about 50 Hopkins buildings. Each router, equipped with a proprietary software algorithm, creates a secure, wireless network across the campus.

To envision the wireless network, think of a large, invisible, interconnected mesh across campus where data passes wirelessly, jumping or hopping from wireless router to wireless router, until it finally reaches a router physically connected to the Internet by a wire.

What’s more, the network continues to work while the vans are moving in an everchanging urban environment. For example, the network is constantly calculating the most efficient way to send data, even if wireless signals are obstructed by buildings as the buses move.

On the second floor of the New Engineering Building, Rubens demonstrates the network. Using Google Earth, Rubens views a map of the Hopkins campus on his computer with the real-time location of each shuttle bus. He calls the driver of the Stieff Shuttle on the phone. He asks her to drive across campus. On the computer, he watches the bus move. Then it starts driving down the road. With a click of his mouse, he sends the bus data files to test the network. It works.

For Hopkins, the project has had two immediate payoffs: It currently allows Johns Hopkins Security to track the location and speed of all 12 shuttle buses at all times; and it also enables faculty and students riding on buses to connect wirelessly to the Internet without a phone or cable line.

More importantly, note Rubens and Holmer, the project demonstrates the longterm potential of wireless networks created by mobile routers. This concept moves away from the conventional idea of using stationary routers to create wireless networks, such as those being set up by municipalities nationwide.

Instead, this approach extends the invisible mesh network to the moving users, in this case, buses. This increases the interconnectivity of the network, strengthening and extending its reach. “Dealing with mobility is going to become a big issue in the future,” says Rubens, “especially if you want to connect fire, police, and first responders across an entire city or municipality.”

Awerbuch says he is encouraged by the work of his students. “Other people have written papers about this idea,” he says. “But we don’t know of other networks that show this performance in real life. In this sense, we are dealing with something potentially revolutionary.”