This Mote's for You
"Smart dust" wireless sensor networks are on the cusp of revolutionizing monitoring and control systems
July 21, 2008
by Charles Waltner
A big part of making buildings smart is giving them a way to gather information about the physical world. But creating a network of ubiquitous sensors has proven difficult.
Though miniature sensors of all stripes are now widely available, the challenge has been in connecting these devices together. Standard wired and "Wi-Fi" networks have proven cumbersome and expensive for linking hundreds or thousands of sensors that could be in walls, ceilings, windows, desks, security badges, or virtually anywhere in an office building, manufacturing facility, or outdoor area.
So for the past few years researchers have been working on new kinds of low-power, low-bandwidth wireless "mesh" networks, but the technology has been slowed by dependability issues. Now, however, these networks could be ready to revolutionize how buildings and other facilities monitor what's going on inside them.
One of the leaders in this field is Kris Pister, a professor of electrical engineering at the University of California at Berkeley and chief technology officer for Dust Networks, a Hayward, Calif., start-up he launched in 2002.
More than a decade ago Pister helped coin the concept of "smart dust" to describe a network of miniature wireless sensors called "motes" (now about 12 millimeters square but likely to become as small as a pinhead). These devices can run on micro-batteries for up to 10 years. The idea is to be able to sprinkle these sensors throughout a building, home, industrial facility, or even a forest or field and have them easily form a pervasive monitoring system.
"It's been a long slog, but we've turned the corner, and now it's getting exciting."
But developers of this technology have struggled with the notoriously fickle radio waves that carry wireless signals. Physical barriers such as concrete walls, metal pipes, and interference from other electrical devices can greatly degrade such communication systems. And because these motes use only a fraction of the power of standard wireless devices for transmitting their messages, the challenges are even greater.
Pister says he has spent the last five years sorting through these problems and looking for ways to make wireless sensor networks easy to use and rock-solid reliable in virtually any environment.
After much research and field testing, he says wireless sensor networks are now able to provide the same dependability as a wired network for a fraction of the installation and maintenance costs. He says he has successfully addressed reliability issues by using short digital messages that have multiple time, frequency and travel paths. If one way is blocked, there are many other options for the signals.
The company has initially focused on selling its products to industrial automation companies for improving such tasks as monitoring pipelines, valves, and tanks for oil refineries, natural gas plants, and production facilities. Such places have been unforgiving environments for Dust Networks' technology. But the systems have proven extremely reliable in these rigorous tests, Pister says.
As proof, he says many industrial automation vendors, including market leaders Emerson and General Electric, are now using Dust Networks' products. "It's been a long slog, but we've turned the corner, and now it's getting exciting."
While Dust Networks has focused on industrial automation, smart dust can be equally useful for improving how buildings function. Pister says Dust Networks' wireless technology can now support virtually any kind of micro-sensor.
For example, building owners could add a network of smart dust heat sensors to each room of an office floor rather than relying on the temperature reading from just one thermostat. A matrix of such micro-devices could also monitor the sunlight entering a room, providing feedback to the building to lower or increase artificial lighting as needed.
Also, a mote network could tell who is in a room by picking up signals from the person's employee badge. By feeding this information into the environmental system, a building's heating, cooling or lights could be activated for specific areas.
And according to a recent article in The New York Times, technology companies are now developing wireless micro-sensors for the home to create "magic carpets" and other ways for healthcare providers and relatives to remotely monitor the activities of the elderly who are living alone.
Pister expects dust sensor technology to become mainstream as wireless sensor networks gain popularity and are used for such broader applications as healthcare or smart building controls. Motes now cost $10 to $100 each, but Pister says prices should drop rapidly.
Pister says Dust Networks uses a communications protocol that is "like IP but a little different." The company is now working with the main Internet standards body, the Internet Engineering Task Force (IETF), to develop an IP-based standard for wireless sensor networks. He says Cisco Systems is actively supporting this effort. Also, Cisco has been working with Dust Networks and others to develop comprehensive wireless network systems for industrial production facilities.
Currently, sensors on Dust Networks' wireless systems can easily link to Internet-based networks through translation gateways, and the data collected by the motes are formatted in Extensible Markup Language (XML), a common Internet protocol.
While it is still early days for wireless sensors systems, smart dust is already making a difference for major companies. Dust Networks' technology is now used by the likes of Shell Oil, British Petroleum, PPG Industries, K-V Pharmaceutical, and brewer Anheuser-Busch. As Pister notes, "The beer you drink might have been sensed by a mote along the way."
Charles Waltner is a freelance writer in Piedmont, Calif.