Networks of Small Sensors (Motes): Their Function and Applications


Function:

Motes are autonomous microcomputers which combine to form networks of: probes that gather information about their environment, analyze it internally, and send it back to a central station. They can be set in fixed locations, or actually attached to animals. At first glance, this seems simple, but certain considerations turn the motes into a more complex problem. They must be small; how will the power source function over an extended period of time? They must be cheap, because many motes must be used in order to monitor a large population or area. They must also be adaptable to new situations and missions because of the cost and difficulty associated with individually reprogramming each mote. They need to be resistant to rough handling and able to continue functioning as a network after a mote fails, as is practically inevitable in any real-world situation. Finally, they need to be able to present the data they gather in a format that can be easily accessed and analyzed by researchers.

Fortunately, Intel Labs and The University of California – Berkeley have formulated solutions to these questions. In order to conserve power, the motes will flip on and off for a millisecond or less to take their measurements, and then return to their dormant state to conserve power. UC Berkeley students and faculty designed a streamlined operating system specifically for motes, which they dubbed “TinyOS.” (TinyOS was written in NesC, the programming language developed by Intel and Berkeley specifically for motes.) TinyOS can be coupled with TinyDB, a database management tool for motes, which shows data and allows queries. When the data from the probes reaches the central data storage station, the station posts the results online via satellite. This gives researchers easy access to the information from anywhere in the world. Even the way in which the data is sent back to the data center is power-saving. When motes find information that needs to be sent back to the data center, they use an algorithm to find the closest mote and send the data to that mote, which then relays it to the next closest mote and etc. until the data reaches its destination. Ingenuities in programming also solve the issue of reprogramming. In order to reprogram a mote, programmers only reprogram one mote. Because the motes communicate among one another, the mote with the new instructions can send them computer-virus-style to each mote that comes in contact with it. This process repeats itself until all of the motes have the new instructions. Ingenious programming also accounts for the motes’ ability to continue to function as a network, even after several units are no longer functioning. However, this programming is not the solution to everything. A hard (but still cheap) casing and redundant systems are used to increase the chances of the motes survival after mishaps in the wild. The total cost (per unit) is currently $50 to $100, though it is hoped that it will soon be down to near $5.


Applications:

Networks of motes can be used in a variety of environment-related situations:


Hopefully, by using this data, long-term trends will be observed and scientists will have a greater understanding of the living systems that comprise the Galapagos archipelago.


Sources


Intel Exploratory Research: Smart Sensors to Network the World
An explanation of sensor networks in the wild.
http://www.intel.com/research/exploratory/smartnetworks.htm
Originally Published:
SCIENTIFIC AMERICAN
www.sciam.com
Smart Sensors to Network the World
By David E. Culler and Hans Mulder

Intel Exploratory Reserach: Instrumenting the World
http://www.intel.com/research/exploratory/instrument_world.htm

The Real World as One Giant Database
UC (Berkeley, Davis, Merced, Santa Cruz) CITRIS Newsletter - December 2003
Vol. 2, No. 5
http://www.citris-uc.org/newsletter/2003_Newsletters/december_2003/feature.htm