Motes are also sometimes referred to as smart dust. One mote is composed of a small, low powered and cheap computer connected to several sensors and a radio transmitter capable of forming adhoc networks.

The computer monitors the different sensors in a mote. These sensors can measure light, acceleration, position, stress, pressure, humidity, sound, and vibration among others. Data gathered are passed on to the radio link for transmission from mote to mote until data reaches the transmission node. These radio links between motes have a transmission distance of 10-200 feet.

One of the limiting factors in the development of motes is the battery. Although a bigger battery would mean a longer life for the mote and farther transmission capabilities for its radio link, smaller motes with smaller batteries are usually more versatile and flexible.

Motes are a relatively new development in the field of wireless sensing networks but with further developments, they can become a central technology. There are motes capable of tapping into a power grid while motes capable of harnessing solar or vibration power are still being developed.

Applications and History of Motes

The application and use of motes in just about any field is limitless. They can be used in conjunction with power meters, water meters and other utility meters to transmit data automatically to a central node or to an electromagnetic truck capable of temporarily powering up the motes in a certain area. Moreover, they can be used in agriculture to give a clear picture of the temperature, humidity, water level, etc for a given location.

Motes can be embedded into structures to give constant or periodic reports on structural integrity such as salt content levels in concrete. Furthermore, motes can be used in traffic management and monitoring by placing these devices on major intersections and streets.

Motes can also be used in military applications for recon and SAD missions. In fact, one of the original developers of motes was DARPA or Defense Advanced Research Projects Agency. It was here that the potential of the mote as a battlefield sensor was originally developed. In conjunction with a remotely piloted vehicle, a GPS sensor, a magnetometer and a radio transmitter, battlefield commanders would have a clear picture of the field and enemy location and thus would be able to react accordingly without resorting to the use of mines.

The MICA Mote

One of the commercially available motes is the MICA. This is a mote that runs on an operating system called TinyOS. Its size and shape can range from 2.25 x 1.25 x 0.25 inches rectangular to 1 x 0.25 inches circular. The MICA mote utilizes an Atmel ATmega 8 bit microcontroller 128L running at about 4 MHz with 28 kilobytes of flash memory for the program. It alternates between sleep mode and running mode to conserve its power. With 8 milliamps power requirement when in operation and only 15 microamps in sleep mode, a MICA mote can run for two years using two AA batteries.