A new communication protocol for wireless sensor networks just released by the Viterbi School's Information Sciences Institute is the most efficient yet with more than a tenfold improvement on previous versions.
Sensor networks, or sensornets are an emerging way to monitor inaccessible and unwired places. They depend on placing numerous sensor units across a wide area. The units communicate with each other, and send the information they gather at intervals to human operators.
In wilderness parks, for example, such networks are used to monitor activity by wildlife. Sensornets are also being explored for industrial applications in oilfield monitoring and managment, for example. Ordinary wireless methods, such as WiFi wont work for this purpose.
The units are battery powered, so minimum power consumption is critical but at the same time, continuing coverage is essential.
The activities of the units are orchestrated by special operating rules called Media Access Control (MAC) protocols. More than three years of ISI research supported by the National Science Foundation, Intel and other funders produced a new protocol, SCP-MAC, which produced a dramatic improvement in energy efficiency.
The protocol combines two techniques: low power listening in which units switch on for only very brief periods; and scheduled channel polling which synchronizes and schedules the listening.
"The basic approach of SCP-MAC is to let units alternate periods of sleeping with very brief periods of listening, as shown in the figure," says Wei Ye, an ISI research scientist. "Such a sleep pattern is found on birds, who need to keep vigilance while sleeping. To minimize the listening cost, SCP-MAC utilizes 'low-power listening,' which detects channel activity very quickly.
"It further reduces the transmission cost by synchronizing the listening schedules of nodes, so that a unit can wake up its neighbors by transmitting
Contact: Eric Mankin
University of Southern California