The system solves a constraint on previous wireless networks—battery life—by mounting each node on a municipal streetlamp, where it draws power from city electricity. Researchers plan to install 100 sensors on streetlamps throughout Cambridge by 2011, using a grant from the National Science Foundation. Each node will include an embedded PC running the Linux OS, an 802.11 Wi-Fi interface and weather sensors, says Matt Welsh, assistant professor of computer science at Harvard.

For the sensors, the streetlamp approach opens up a new range of uses—for example, performing long-term experiments like real-time environmental monitoring, correlating microclimates with population health or tracking the spread of biochemical agents, according to BBN.

A large challenge was how to design a network that allows remote nodes to communicate with the central servers at Harvard and BBN. CitySense will do that by letting each node form a mesh with its neighbors, exchanging data through multiple-hop links. This strategy allows a node to download software or upload sensor data to a distant server hub using a small radio with only a 1-kilometer range, Welsh says.

People have built such networks on smaller scales before, but for private purposes, or to provide wireless Internet links in towns such as Madison, Wis., and Champaign, Ill., Welsh says. In contrast, CitySense will let academic researchers worldwide log on to the project website and submit their own research programs to run on the network.