Small army of sensors invades city

Rosario's got the ball, she passes it to Josh Bers . Then Racing has the ball and passes it to Bers. In this field, the ball is actually data, and Rosario and Racing -- named for two Argentine soccer teams -- are wireless sensors on the roof of BBN Technologies in Cambridge.

The sensors are part of the world's first high-powered, fixed, outdoor, wireless sensor network, called CitySense. Right now the network senses only weather data, but researchers expect that to change once the entire 100-node network is in place throughout Cambridge.

Bers, a senior engineer at BBN Technologies, heads the project with Matt Welsh, an assistant professor of computer science at Harvard University. Via the Internet, they can log on to the CitySense site and check the information being detected and transmitted by the two nodes atop BBN: wind speed and direction, temperature, humidity, and barometric pressure. Eventually, anyone will be able to log on to the site and not only check data, but also run their own experiments.

"We don't need 100 weather sensors in Cambridge," Welsh said, "but we are really researching how such an urban network will work that can then have later practical applications."

"There are lots of possible applications for the future," said Bers. "Urban pollution monitoring in Cambridge for one."

He hopes the network could be used by developing countries to help study, for instance, whether new emissions regulations in those countries are working.

With the help of the city electrician, George Fernandez, 20 new nodes will be mounted on street lights, hopefully by the end of the summer, said Bers. The sensors will then tap into the lamps' electricity for power and data messages can hop from one node to another to transmit information.

"It works like walkie-talkies do," he said. "Across radio waves. Each radio has a range to send data."

Bers, a fan of Argentina's soccer teams, named the five BBN nodes after several of them: Rosario, Racing, River, Boca, and San Lorenzo. Welsh's team of student researchers at Harvard named their five nodes for characters from the "Family Guy" cartoon.

A third researcher on the project, Majid Ezzati, a professor at the Harvard School of Public Health, plans to study air quality using particulate sensors that will later be mounted on some of the nodes Bers and Welsh put up.

The National Science Foundation provided the grant money to fund CitySense. Welsh and Bers are especially excited about the project being an open test bed, meaning that any researcher around the world could run an experiment on this Cambridge network.

"An open test bed lets people reprogram the network to run their own experiments," Welsh said. Each node contains a tiny computer that can upload programs. "Researchers can then have access remotely over the Internet," he said.

Welsh said most research into sensor networking is being done in remote locations using battery-powered sensors that have a limited longevity.

"This is an entirely different system; it can be more powerful over a long period of time and we could use more sophisticated embedded PCs to do data collection and computations."

Welsh, considered an expert in remote sensing networks, said the Cambridge project comes out of his interest in building large-scale networks of systems. He has created networks to monitor volcanic activity in Ecuador and is working on another for medical use, called CodeBlue. In that project, he places sensors on patients, with approval, to monitor heart rate and blood oxygenation levels. If the sensor detects a dangerous change, it can transmit a message directly to a doctor's pager.

Regarding CitySense, though, he said, "Putting this together opens up more questions than answers. We hope that others will get funding to add other sensors atop these.

"My hope is that the really juicy applications haven't even been thought up yet."