Monitoring with Minimum Power

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, according to a University of Southern California statement.

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 monitor wildlife activity, explains the university statement. Sensornets are also being explored for industrial applications, such as in oil-field monitoring and management, where ordinary wireless methods, such as Wi-Fi, aren’t feasible. The units are battery powered, so minimum power consumption is critical—but at the same time, continuing coverage is essential.

The units’ activities 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.

Previous protocols, says the university, required individual units to be active for approximately 2-3 percent of monitoring time—that is, active about 29-45 minutes of every day of sensornet activity. SCP-MAC reduced the monitoring time to less than two minutes each day.

In February, the new protocol, written in the TinyOS operating system optimized for Mica2 individual sensor modules, was made available for download by Sensornet users and developers.

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